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1. Introduction
1.1 Changes in diet tendencies. A short overview.
During the last decades deep changes in society and in behavioural patterns of communities have been observed. Globalization, with its focus on free movement of capital, technology, goods, and services, has had deep effects on lifestyles that are in relation with diet. As result our diet has been influenced by many kinds of factors: growing industrial technologies, new electric appliance in our kitchen, new faster and more extensive way of transport that provide our shops and foreign food are just some of the various aspects involved.
The eating habits of our latest generation would be completely unrecognizable to many of us today.
The development of transnational supermarkets usually belonged to larger chains, global food advertising and promotion, liberalization of international food trade, joined by commercialization of domestic agricultural markets and cultural influences drive changes in the food supply and in the way we consume food. Furthermore, fast food and sweet products availability are made more desirable day by day thanks to the use of advertising and promotion. World is changing quickly, lifestyle is running on rapidly and the time we usually spend for a meal is decreasing constantly.
These are the basis for the so called “Junk Food”.
Increased consumption of more energy-dense drinks, nutrient-poor food with high levels of sugar and saturated fats, reduced physical activity combined with the spread of fast food, modernization, urbanization and globalization of food markets are just some of the forces thought as the causes of the growing obesity status.
In debates about food, social inequities and globalization, the latter tends to be presented as a process that affects national food security and poverty, with nutritional outcomes relegated to the status of subsequent consequence. In doing so, marketing, especially television advertising, encourages more consumers to consume certain kinds of products, and more producers to produce them, thus advancing the cycle of global market exchange and integration. And just as marketing facilitates globalization, globalization facilitates marketing. Researches on how people set and pursue their dietary goals have shown that mental representations of goals can also be triggered by
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environmental cues without a consciously choice, so that subsequent behaviour is then guided by these goals. Food globalization have influenced our attitude towards table manners, foreign foods and trends.
There is an enormous variability in eating patterns globally, but the main themes seem to be retained in most countries. In fact although we are able to see a great amount of different trades for the same product in lots of countries, we can easily find that these different trades belong to the same multinational food companies. Furthermore, the choice of the average consumer is not influenced by the nutritional value of goods but derives from the strategic advertising through television, trends and drivers carried on by multinational food companies. The result is a series of nutritional inequities in many nations, communities, and households that affect both the nutrition of developed countries and the under-nutrition of non developed ones.
The food amount discrepancy between rich countries and poor ones is steady increasing. Poor nations have got less and less food quantities available while rich countries can count on more food than what they need with serious problematic matters associated: wastefulness and obesity.
Although organs and enzyme profile involved in the digestive process are the same for each person, it could be different from one to one another. This lead to a simple consideration: consumers could handle rapid changes in diet in different ways. Obesity results from the interaction of genetic susceptibility characteristics and modifiable environmental factors, with genetic variations influencing a person's susceptibility to environmental changes. If genes are important in determining a person's susceptibility to gain weight, energy balance will be determined by calorie intake and physical activity. Busy schedules, sedentary lifestyle, increased automation of work, and decreased transport-related physical activity in modern societies, contribute to the increasing physical inactivity trend. The linkage between a sedentary way of living without a regular diet and the consumption of enriched fat food lead to a major probability to get an “obesity status”. Public opinion usually links physical exercise with trying to lose weight, particularly for women. This is consistent with the model of general action and inaction aim, which proposes that general action aims need more determination and consistency to give evident results. Supporting this argument, lowering food intake is seen as the better way to achieve the purpose of weight loss than
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physical activity alone or a combination of the two. People realize that although exercise burns off calories, a lot of exercise is needed to burn off a relatively small number of calories. Moreover, individuals trying to lose weight have not adopted regular physical activity as part of their good weight loss practice.
By this purpose it is noteworthy that diets rich in fruits and vegetables, as the Mediterranean diet, have historically held a place in dietary guideline. The term Mediterranean diet was coined during the 60s, observing the dietary habits adopted by the population residing near the Mediterranean Sea and noticing a reduced incidence of chronic illnesses and higher life expectancy when compared to other regions of the world. Defining the term, Mediterranean diet is a great challenge given the broad geographical distribution of the Mediterranean countries and the ethnic, cultural, religious, and economic variations among them. However, despite this, there is a dietary pattern characteristic of the Mediterranean diet. This includes a diet rich in fruit, vegetables, bread, cereals, olive oil as the major source of fat, from low to moderate amounts of fish and poultry and alcohol, and little quantity of red meat.
1.1.2 Changing habits, changing laws.
Generally, nutrition has positive connotations and implications, because it is usually linked to a pleasure feeling. This means that often our choices are influenced by our mood and desires. The link between health and nutrition was not a spontaneous connection by the average consumer.
From the middle of the ‘90s some scandals as dioxine and BSE have shifted the attention of people. Due to a number of food-related incidents and reported outbreaks worldwide, consumer confidence has begun to vacillate. Public opinion began to ask themselves, which are the various steps of the industrial process that are able to guarantee an appropriate safety about the food we buy. During the last decades panic situations sequences have upset the consumer trust about food products.
In European Union all these worries had been the major force in the proclamations of food safety laws and in the creations of infrastructures able to re-establish the trust in food chain, also using slogan as “from farm to fork”.
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European Union safety procedures regard all the food chain addressed to human and animal consumption. Currently EU provides a detail legislation and point out the producers and suppliers responsibility in order to guarantee safety and quality of food chain. To make clearer and scientific the food chain sector, at the end of the ‘90s a complex review of the all institutional and regulatory framework has been started. The 1997 Green Paper on Food Law, preceding the major food scares of the late 1990s, gave a new impetus to the foundation of European Food Law. This document set a number of important principles for the revision of EU Food Law and was followed by the 2000 White Paper on Food Safety. In particular, it foresaw the establishment of a General Food Law Regulation, laying down the principles of food law and the creation of an independent Food Authority, endowed with the task of giving scientific advice on issues based upon scientific risk assessment with clearly separated responsibilities for risk assessment, risk management and risk communication.
Beyond the Directive and Scientific Committee, in 2002 it has been created the European Food Safety Authority (EFSA), independent organism able to work in a strictly connection with lots of companies and scientific institutes, providing an independent scientific opinion of all food matters, discussions and issues that directly or indirectly influenced the food chain safety. EFSA supervises all the production and supplier steps about food chain, from the primary sector to the supermarket distributions in order to guarantee the highest quality for the consumer. Furthermore, the institution is in charge with the risks linked to the food chain and usually provides scientific reviews about issues regarding supplier food safety, both directly and indirectly, with remarks about animal and plants health point of view. Our food system is currently regulated in many different ways. Laws control the production and sale of food, but at the same time consumer attitude and tendencies are able to influence the way food is produced, sold and consumed.
1.2 Nutraceutical food
1.2.1 Nutraceutical and functional food, meaning
Over the past few years, there has been a great effort to study the relationship between dietary patterns and human health. Despite a multiplex of available diet and physic
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exercise programs for losing and maintaining weight, over the past years, interest in the use of complementary and alternative medicine for obesity and for other diseases treatments have greatly increased. People across the world have become conscious of the need of a healthy diet against “Globesity”.
For this purpose the term nutraceutical, derived from the mixture of the words “nutrition” and “pharmaceutical”, was coined in 1989 by Stephen De Felice, founder and chairman of the foundation for innovation in medicine located in Cranford, New Jersey. It was defined as “a food or part of food, that provides medical or health benefits including the prevention and treatment of disease”.
Nutraceutical demonstrated to affect beneficially one or more target functions in the body beyond adequate nutritional effects, in a way that is relevant to either improved state of health and well being or reduction of risk of disease.
Nutraceuticals may range from isolated nutrients, dietary supplements, and diets to genetically engineered “designer” food, herbal products and processed products such as cereals, soups, and beverages.
The functional food concepts is different from the nutraceutical one and can be defined as food products to be taken as part of the useful diet in order to have beneficial effects that go beyond what are known as traditional nutritional effect (Esteghamati et al., 2015).
European legislation does not consider functional foods or nutraceuticals as specific food categories. That means an inexistent specific regulatory framework for functional foods or nutraceuticals in EU Food Law, while the rules of the General Food Law Regulation, including responsibility for food safety, traceability, recall and notification, definitely applicable to all foods are numerous and depend on foodstuff nature itself (Coppens et al., 2005).
In the last two decades many studies have already focused on consumer awareness and acceptance of functional foods and Nutraceuticals, like evaluation of functional food consumers perception of these products and their efficacy, characterization of functional food consumers and regulations of functional food and health claims (Cardello et al., 2003; Cox et al., 2004; Dejong et al., 2003).
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1.3 The antioxidants
1.3.1 Antioxidants, meaning and action mechanism
The most common definition is provided by Halliwell in 1995 who suggested that the “antioxidant is a substance able to prevent or put back the oxidation process of the substrate, even if its presence is lower than the substrate itself”. The antioxidant’s requisite is that once it is oxidise, its radical form will not be reactive towards other chemical substances.
The antioxidants working way could be distinguished in two behaviours: the chain breakers and the metal scavengers.
The chain breakers are able to deactivate the radical form in two ways, with the Hydrogen Atom Transfer (HAT) or with the Single Electron Transfer (SET). HAT-based methods measure the classical ability of an antioxidant to quench free radicals by hydrogen donation (AH = any H donor) (Prior et al., 2005)
X*+ AH XH + A*
HAT reactions are solvent and pH independent and are usually quite rapid, typically completed in seconds to minutes. The presence of reducing agents, including metals, is a complication in HAT assays and can lead to erroneously high apparent reactivity. SET-based methods detect the ability of a potential antioxidant to transfer one electron to reduce any compound, including metals, carbonyls, and radicals. Antioxidants, as tocoferol and phenol compounds, belonging to the SET group can give the electron to a free radical and also to a prooxidant metal.
The metal scavengers prevent the free radicals birth because they can bind, with the chelation mechanism, metal ions. Metals such iron and copper are prooxidant elements able to decrease the activation energy of the lipid oxidation process (1), making new free radicals or promoting the singlet oxygen formation (2). Then the concentration of these metals contribute directly in the free radicals generation during the Fenton reaction (Prior et al., 2005).
Fe3+ + RH Fe2+ + R• (1) Fe2+ + 3O 2 Fe 3+ + O2 - • 1O2* + e - (2)
10 Fe2+ + H2O2Fe3+ + OH• + OH- (3)
1.3.2 Antioxidants, role in human diet
Antioxidants are well-established as an important part of how healthful eating can lower our risk of heart disease and cancer, and possibly other conditions that may develop in old age. Evidence, although indirect, of their absorption through the gut barrier is provided by the increase in the antioxidant capacity of the plasma after the consumption of polyphenols-rich foods. Although the analysis of plasma provides valuable information on the identity and pharmacokinetic profiles of circulating metabolites after supplementation, it does not provide accurate quantitative assessments of uptake from the gastrointestinal tract (Cruzier et al., 2010).
Much of the protective effect of fruits and vegetables has been attributed to phytochemicals, which are the non-nutrient plant compounds such as the carotenoids, flavonoids, isoflavonoids, glucosinolated and phenol acids. Polyphenols historically have been considered as antinutrients by nutritionists, because some, as tannins, have adverse effects such as decreasing the activities of digestive enzymes, energy, protein and amino acid availabilities, mineral uptake and having other toxic effects (Prakash et al., 2012).
Different phytochemicals have been found to possess a range of activities, which may help in protecting against chronic disease. Because of their concentrations of vitamins, phytochemicals, such as carotenoids and phenol compounds, are associated with a reduced risk of diseases such as certain types of cancer, chronic inflammations, cardiovascular and neurodegenerative diseases. These findings have led to the US National Research Council to recommend consuming five or more servings of fruits and vegetables a day, as part of an overall healthy diet and well-balance life concerning with an active way of living.
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Figure 1: Oxidative stress-induced diseases in humans, (Huy et al., 2009).
Endogenous metabolic processes, especially in chronic inflammations, are important sources of free radicals, which can react with and damage all types of biomolecules as lipids, proteins, carbohydrates and DNA. If damaged DNA is kept unrepaired, and the mutated cell gains the ability to survive and divide atypically, it may become cancerous. Thus, an increase in antioxidants, which can scavenge free radicals, may be a strategy to prevent cancer cell initiation, an important beginning stage of carcinogenesis. So, we can easily defined antioxidants as compounds in fruits and vegetables that may be helpful in avoiding chronic disease because of their role as a defence system against oxidative damage in our bodies. Some chemical features could summarize their antioxidant activity:
Reactivity as hydrogen or electron donor, because of their low oxidation-reduction potential.
The ability of the radical form to turn out to be stable thanks to the electronic delocalization present in the aromatic ring in phenol compounds.
Ability to bind metals in order to prevent their skill to become catalysts during oxidant reactions.
1.3.3 The Phenol group
The importance of bioactive compounds synthesized by plant secondary metabolism lies in their ability to protect plant cells from biotic and abiotic stress. Phenol compounds constitute one of the main classes of secondary metabolites. They display a
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large range of structures and they are responsible for the major organoleptic features of plant derived foods and beverages, particularly colour and taste properties, and they contribute to the nutritional qualities of fruits and vegetables.
Chemically the phenol group is characterized by an aromatic ring with at least one addiction of an hydroxyl group, it derives from L-phenylalanine and from tyrosine (Petty et al., 2009). The differentiation in the number and position of hydroxyl groups and in the way the carbonic skeleton appears allow distinguishing the phenol compounds on the bases of the molecular weight in low, intermediate and high weight. Generally phenols can be classified in two groups, depending on their affinity to the flavonoids.
Not belonging to the flavonoid group there are:
Hydroxycinnamic acids. They derive from p-cumaric acid or p- hydrossicinnamic acids, its molecular formula is C6-C3, caffeic, ferulic, sinapic and chlorogenic acids, a caffeic acid derivative, belong to this group. Inside the plant they play an antibiotic action and many roles linked to growth and germination inhibition.
Hydroxybenzoic acids. Derived from Hydroxybenzoic acid, the most distributed compounds of this group inside the plant reign are the gallic, vanillic, ellagic acids. Gallic acid is the basic structure of hydrolyzed tannins.
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Stilbenes: low molecular weight phenol compounds, they have two aromatic rings separated by ethane. So far the most important stilbene found is resveratrol, in trans and cis form has got chemotherapeutic, cardiovascular and antioxidant properties and it’s still studied by many authors.
Two aromatic rings linked by an eterocycle structure compose the flavonoids. Depending on the eterocycle type, number and position of the substitutes and type of the aromatic rings substitute, this group includes:
Antocianidins. Very important plant metabolites, are responsible for pigmentation and colour of fruits and flowers because they show different colours, red, blue or yellow, depending on the pH where they are. As other phenols group they are not found free in nature but as glucosydes. This explains why antocianidins can be hydrolised with acid and are soluble in water. They are constituted by two aromatic rings joined by an oxygenated, unsaturated and with a positive charge eterocycle.
Flavonols. They have C6-C3-C6 formula. Usually glycosilated, occur as 3-glucoside, 3-galactoside, 3-ramnoside and 3-glucoronide. The most important are: quercetin, kamferol and miricetin.
Flavanols. Class of flavonoids containing a ketone group, belong monomers such as catechin, epicathechin and dimers as teaflavine, proantocyadinins, Flavanones. Usually referred to citrus fruits. In the other plants are less common than citrus and usually glycosilated form are more frequent. Belonged to this group are naringenin, naringin and hesperetin.
Flavons. Apigenin, luteolin are the phenol class less represented in plant reign. Isoflavonoids. Belonged to leguminous family, they are characterized by the B ring in 3-position and not in 2 position as the other flavonoids. The most important are genistein, genistin, daidzedin and formononetin.
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Figure 3: Structure and examples of flavonoid derivatives (Zenebe et al., 2001).
Particular attention is attributed to the tannin group. They are a group of phenol compounds with a high molecular weight (between 500 and 3000 Da) able to confer important colloidal properties to the plant. Usually are divided into two class, hydrolyzed and condensed tannins. The first group contains compounds derives from hydrolysis such as gallic and ellagic acid while the latter, known also as proanthocyanidins represent a group of compounds such as procyanidins, prodelphinidins and propelargonidins, deriving from the condensation or oxidative polymerization of flavan-3-ols and 3,4 flavandiols with covalent bonds. Proanthocyanidins can be found in many plants and are responsible for wine and tea astringency, loss of the typical colour and participate in the oxidative, enzymatic and condensation reaction during ageing.
1.3.4 Phenol compound biosynthesis
The phenols are synthesized via two routes: the shikimic acid and the malonic acid way both able to generate complex phenols. The biosynthesis, through the shikimic pathway starts with the condensation of phosphoenolpyruvate with eritrose-4-phospate in order to get the 3-deoxi-D-arabine-eptulsonate 7-phospate (DHAP) with the enzyme DHAP
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synthase. Then the 3-dehydrochinate synthase determines the 3-dehydrochinic acid, substrate for the shikimate dehydrogenase. This enzyme carries out the reaction of the shikimate kinase in order to get in the final step with the action of chorismate synthase, that allows to remove the inorganic phosphate to get the chorismic acid.
Figure 4: Amino acid biosynthesis, through the shikimic pathway (Hiroko Mori et al., 2009). The following step for the specific generation of phenylalanine (Phe) and tyrosine (Tyr) is the formation of prephenic acid through the chorismate mutase. The prephenic acid can launch two different ways to get phenylalanine and tyrosine, the former foresees the formation of arogenic acid and then, with arogenate dehydratase and arogenate dehydrogenase action, build the phenylalanine and tyrosine. In the second one the prephenic acid with the prephenate dehydratase and dehydrogenate generate the phenilpiruvate and 4-hydroxyphenilpiruvate, respectively able to produce phenylalanine and tyrosine with a transamination.
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Figure 5: Tyrosine, phenyalanine and trypthopan production by the shikimic acid pathway (Ghosh et al., 2015).
Through its deamination it is transformed in trans-cinnamic acid by the phenylalanine ammonia-lyase (PAL) while the tyrosine ammonia-lyase can get to the trans-p-cumaric acid with the same pathway.
Figure 6: PAL enzyme action on phenylalanine.
From the trans-cinnamic acid the main hydroxicinnamic acids are synthesized.
The flavonoid biosynthesis consists initially in the condensation of three molecules of malonyl-CoA (derived from Acetyl-CoA through the enzyme acetil-CoA decarboxylase) with a 4-cumaroil-CoA through the chalcone sintase (CHS). The
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enzyme chalcone isomerase (CHI) catalyses the closure of the eterocyclic central ring, particularly the isomeric shift from the 4,2,4,6-tetraidroxychalcone to the naringenin.
Figure 7: Hydroxycinnamic acids and flavonoids biosynthesis (L. Marín, et al., 2015).
Then, the flavanon-3-hydroxylase (F3H) converts the naringenin in dihydrokaempferol (DHK), the substrate for the flavonols and antocyanidins synthesis. The enzymes flavonol syntetase (FLS) produces the kaempferol, the flavonoide 3’-hydroxilase (F3’H) and flavonoide 3’-5’-hydroxilase (F3’5’H) are able to synthesize dihydroquercetin and dihydromyricetin, respectively, then converted in quercetin and myricetin trough FLS. Dihydroflavonols are a class of colourless compounds, therefore the transformation in coloured anthocyanidins and anthocyanin need of three further enzymes: the first one is the dihydroflavonol 4-reductase (DFR), that catalyses the dihydroflavonols reduction in leucoanthocyanidins, then through the action of the anthocyanidin sintetase (ANS) and finally the UDP glucose flavonoide 3-o-glucosyltransferasi (3GT) leucoanthocyanidins (LDOX) are glycosilated in coloured anthocyanins.
18 Figure 8: Naringenin pathway (H. E. Khoo et al., 2013).
At this point the flavonoid methyltransferase carries on the various tasks through esterifications, glycosylations and methylations in order to get each of the 6 classes of flavonoids.
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2 State of art
2.1 Flavonoids in vitro and in vivo research
The body has several mechanisms to counteract oxidative stress by producing antioxidants, either naturally generated in situ called endogenous antioxidants, or externally supplied through foods, the exogenous antioxidant ones. The roles of antioxidants are to neutralize the excess of free radicals generated by enzymatic or non enzymatic reactions, to protect the cells against their toxic effects and to contribute in disease prevention. The continuous intake of antioxidant compounds turn out to be important, because of, when an antioxidant destroys a free radical, this antioxidant becomes oxidized. Therefore, the antioxidant resources must be constantly restored in the body (Huy et al., 2008). Associations between polyphenol intake or the consumption of polyphenol-rich foods were examined in several epidemiological studies. An abundant literature has shown that polyphenols can inhibit oxidation of LDL in vitro; this type of oxidation is considered to be a key mechanism in atherosclerosis (Fuhrman et al., 1995; Ishikawa et al., 1997; Kondo et al., 1994; Aviram et al., 2000; Osakabe et al., 2000). They are, therefore, polar and, most probably, largely eliminated during the isolation of LDL preceding the ex-vivo oxidation test. This opinion could explain the lack of protection in some studies (Sharpe et al., 1995; De Rijke et al., 1996; Van het Hof et al., 1999). Anticarcinogenic effects of polyphenols are well documented in animals. Polyphenols, when given to rats or mice before and/or after the administration of a carcinogenic agent or the implantation of a human cancer cell line, are most often protective and induce a reduction of the number of cancers or of their growth (Yang et al., 2001). These effects have been observed in various sites, mouth, stomach, duodenum, colon, liver, lung and are played by numerous compounds such as quercetin, catechins, flavanones, isoflavones (Johnson et al., 1994). Polyphenols may act as blocking agents at the initiation stage or may also limit the formation of initiated cells by stimulating DNA repair. Secondly, polyphenols can act as suppressing agents, and inhibit the formation and growth of tumors from initiated cells proliferation in vitro (Kuntz et al., 1999). Such neurodegenerative diseases are dependent of oxidative stress, which particularly affects brain tissues, so, antioxidants might therefore contribute to their prevention (Halliwell, B. et al., 2001). Polyphenols perhaps play a role against diabetes too, in fact, they may affect glycemia through different mechanisms, including
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the inhibition of glucose absorption in the gut or of its uptake by peripheral tissues (Matsumoto et al., 1992). Then polyphenols could not only inhibit the glucose absorption in the small intestine, but they couldalso limit their absorption in the kidney, as has been shown for phlorizin (Dimitrakoudis et al., 1992). Rutin, is also studied with good results in rats to understand the possible impact on osteoporosis (Horcajada-Molteni et al., 2000).
Figure 9: Protection from Polyphenols (Pandey et al., 2009).
2.2 The apple fruit
2.2.1 Apple origins and spread
Plants producing apples belong to the genus Malus, which emerged about 12 million years ago in China and consist primarily of small trees and shrubs. A member of the flowering Rosaceae family, apples were among the first flowering plants on earth, found their first citation in Homer’s Odyssey. The Rosaceae have given rise to many fruits that humans commonly eat, including pears, plums, peaches, strawberries and raspberries. During the early 20th Century Nikolai Vavilov, famous Russian plant explorer and botanist, supposed that a lot of these fruits can be derived from a region belonged to the Kazakhstan called Tian Shan. Currently it is accepted that a lot of the apple varieties known today are direct descendants of the wild apples evolved in Kazakhstan. During the centuries, lots of travellers and animals have passed through the richest apple forest of Asia helping the apple to move overland. As humans and animals travelled, seeds were dropped, seedlings grew many of unique apple types that we can find today sprang up throughout Asia and Europe.
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Consumers around the globe love apples for their taste, flavour, nutritional value and convenience. They are considered one of the most important fruit crop all over the world, with citrus, grapes and banana because of their adaptability and possibility to make juices and purèe.
Apples market is spread across all Europe, the major producers are Poland, Italy and France. Regarding Italy the most important areas where the apples are traditionally produced are concentrated in the North with particular concentration in Valle D’Aosta.
Apple Production By Country
Country 2006 2007 2008 2009 2010 2011 2012 2013 2014 F2015 (1) (2) Austria 163 193 159 185 169 199 157 155 188 177 -6 6 Belgium 358 358 336 344 288 305 220 220 318 294 -8 16 Croatia 48 40 49 60 89 83 59 96 62 101 63 40 Czech Rep 160 113 157 145 103 79 118 121 131 141 8 14 Denmark 27 32 26 24 21 20 18 23 26 24 -8 7 France 1,585 1,676 1,528 1,651 1,579 1,701 1,169 1,576 1,444 1,674 16 20 Germany 948 1,070 1,047 1,071 835 953 972 804 1,116 903 -19 -6 Greece 267 236 231 224 254 305 242 236 245 238 -3 -1 Hungary 480 203 583 514 488 301 750 585 920 522 -43 -31 Italy 1,991 2,196 2,164 2,237 2,179 2,293 1,939 2,122 2,456 2,280 -7 5 Latvia 32 31 34 13 12 8 9 15 10 9 -10 -21 Lithuania 100 40 74 74 46 49 39 40 27 37 37 5 Netherlands 348 396 376 402 334 418 281 314 353 329 -7 4 Poland 2,250 1,100 3,200 2,600 1,850 2,500 2,900 3,170 3,750 3,635 -3 11 Portugal 258 258 245 274 251 265 221 284 272 291 7 12 Romania 417 362 329 379 423 412 351 387 382 350 -8 -6 Slovakia 31 10 42 48 32 33 36 42 46 40 -13 -3 Slovenia 71 80 68 64 66 73 45 56 68 71 4 26 Spain 547 599 528 470 486 507 391 464 505 487 -4 7 Sweden 20 16 18 18 20 17 14 17 16 21 31 34 UK 174 196 201 212 214 226 162 204 225 225 0 14
(1) Percentage difference between F2015 and 2014
(2) Percentage difference between F2015 and the average of 2012 - 2013 - 2014
Table 1: European apple amount production until 2015 (from Wapa, World And Pear Association).
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2.2.2 Major flavonoids and their amount in Apple
Regarding flavonoids, apple is one of the most important fruit on we can pointed out; the antioxidant power of flavonoids is one of the reason because apples are again in the spotlight. Being phytochemicals,
flavonoids cannot be synthesized by humans and animals, so the dietary intake of these phytochemicals might become fundamental. Apples have a widely profile of flavonoids that allow to think apple as a great source of this secondary plant metabolite compounds.
Lee et al. (2000) demonstrated that Fuji, McIntosh, Red Delicious, Granny Smith and Liberty apples have got over 100mg of total phenols per 100g. Many studies have been performed to better understand
both the amount of phenol compounds in different cultivars and the interactions between all the different classes of these compounds. Currently great amount of phenol compounds are associated to the major antioxidant activity, and many different essays are performed in order to link the phenolic content and the antioxidant activity. In literature, the relationship between antioxidant activity and food concentration of phenol compounds is highly discussed, the difference in antioxidant activity among various apple cultivars might be due to the difference in composition and concentration of phenol compounds and also due to unknown synergistic effects among phenols and other constituents (Lee et al., 2000). The complexity of the chemical profile and its variations are in relation with the growth period, the growing season, the geographical location, and most importantly, the genetic variations. The substantial differences between apples, confirmed that the cultivar is the main factor determining the composition of bioactive compounds in these fruits. In addition, the contribution of phenols to the antioxidant activity in both flesh and peel confirm their important role in the bioactivity of whole apples (Vieira et al., 2011).
Figure 10: Contribution of total phenolics from selected fruits as a percent of total phenolics from all fruits consumed by Americans (Wolfe et al., 2008).
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Figure 11: Total phenol and flavonoids content of apple varieties (mean ± SD, n = 3) (Boyer et al., 2004).
The different polyphenol compounds can be classified into several groups based on the class in which they belong. Generally, five major polyphenol groups are found in various apple varieties: hydroxycinnamic acids, flavan-3-ols/ procyanidins, anthocyanins, flavonols and dihydrochalcones. The flavan-3-ols can be found in their monomers, catechin and epicatechin, oligomers, and procyanidins; flavonols are often associated with sugar (predominant sugar is fructose, galactose, glucose, rhamnose, arabinose, and xylose), whereas dihydrochalcones are mainly associated with glucose and xyloglucose.
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Polyphenol Group Compound
Hydroxycinnamic acids Chlorogenic acid
p-coumarylquinic acid
Flavan-3-ols/ procyanidins Procyanidin monomer, dimer, trimers. (+)-Catechin
(-)-Epicatechin
Anthocyanins Cyanidin 3-glucoside, Cyanidin 3-galactoside
Flavonols Quercetin-3-O-rhamnoside Quercetin-3-O-rutinoside Quercetin-3-O-galactoside Quercetin-3-O-glucoside Quercitin-3-O-arabinoside Quercitin-3-O-xyloside Dihydrochalcones Phloretin-2′-O-xyloglucoside Phloretin-2′-O-glucoside
Table 2: Main phenol compound in apple. Adjustment by Polyphenol compounds and antioxidant activity of new and old apple varieties (Wojdylo et al., 2008).
Regarding the concentrations, Wojdylo et al. (2009) after the evaluations of 67 apple varieties express that the content of total polyphenols lies between 5230.2 and 27239.6 mg/kg dry matter with significance differences depending on the apple cultivar. Then they suggested that procyanidins are the most predominant group in apples and constituted more than 80% of the total polyphenol compounds. Among procyanidins monomers and dimers, (from 4622.1 to 2548.0 mg/kg dry weight) the most relevant compounds are procyanidins B2 (68.7 - 2000.0 mg/kg dry weight) followed by epicatechin (65.9 - 2760.0 mg/kg dry weight), while the content of catechin is the lowest (10.1 - 720.0 mg/kg dry weight).
Hydroxycinnamic acids correspond to the second polyphenol class in apples, and they accounted for 1.2 - 31.2% depending upon the variety with a range of 1000 - 3500
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mg/kg dry weight. Phloretin-2′-O-glucoside and phloretin-2′-O-xyloglucoside were the two major dihydrochalcones reported for apple; for all varieties the content of dihydrochalcones ranged from 0,5-4,9% of total polyphenols. Their importance lies also in the contribute of apple juice and cider production (Sanoner et al., 1999). In fact, as suggested by Oszmianski et al. (1991) phloretin-2′-O-glucoside with epicatechin may be involved in the formation of oxidation products which account for the juice colour, although apple processing for juice carries out to a significant decrease in terms of phenols profile (Boyer et al., 2004). Flavonols group presents the lowest concentration in apple and was constituted mainly by quercetin-galactoside > rhamnoside > 3-xyloside > 3-arabinoside > 3-glucoside > 3-rutinose in this decreasing proportion. Quercetin derivatives are not the major polyphenol components of apple, but they are very important for human health. Quercetin was found to inhibit human prostate and lung cancer cell growth and to reduce the incident of cardiovascular diseases (Knekt et al., 2002). Regarding anthocyanins usually authors share two common lines, first of all they agree that anthocyanins are the less amount among the all phenol compounds (Vieira et al., 2009; Lata et al., 2007), then the major anthocyanins is constituted by cyanidin-3-glycosides. Sometimes authors like Vrhovsek et al. (2004) found four different cyanidin glycosides: cyanidin-galactoside, cyanidin-glucoside, 3-arabinoside and 3-galactoside. Other differences regards the cultivar Wojdylo et al. (2009) discovered that Priscilla, Geneva Early, Florina, Cortland, and Jonathan are the cultivar with major quantity of anthocyanins, while Łata et al. (2007) demonstrated that the richest sources of anthocyanins were Idared, Gloster, and Starking Delicious. The reasons for this difference in anthocyanin concentrations in apple skins might be attributed to the combination of low overnight temperatures and high level of sunshine hours during ripening (Reay et al., 1999) as well as to the genotype of apple. In Shampion Arno variety, which is a new variety, the content of anthocyanin was 0.0 mg/kg dry weight because this apple had typically green skin and probably the growing season is too short for it to develop a red colour of skin (Wojdylo et al., 2009).
Many consumers usually take off the peel before starting to eat their apple. In terms of flavonoids there is nothing worst. The major part of the studies of the last two decades shows how the phenol content inside the apple is very distant to be equally divided between flesh and peel. Peel has more and more phenols than flesh without any concern
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to the apple cultivar. These results reflect that the peel shows significantly higher antioxidant values than the flesh for all cultivars (Vieira et al., 2011).
Not only the amount of phenol compound changes between peel and flesh. We can easily underline how different flavonoids can be found in peel, flesh and seeds. Duda Chodak et al. (2011) report in the seeds of apples that phloridzin is the predominating polyphenol compound, whereas Chlorogenic acid, Epicatechin, and Procyanidin B2 are in the apple flesh. Quercetin glycosides are a significant fraction of polyphenols in the apple peels, but, as for seeds and flesh, they are either found in trace amounts only or they are not found at all. The analysis of composition of the polyphenols were performed by HPLC method on two-apple cultivar Sampion and Idared. The phloridzin predominated and its amount ranged from 72% to 84% of all assayed antioxidants, and the chlorogenic acid amounted to 15% and 10%, respectively. No quercetin glycosides were found in seeds, although they were a significant fraction of the polyphenols in apple peels. As for the Idared cultivar, quercetin galactoside (20%), quercetin fructoramnoside (18%), and epicatechin (13%) predominated, whereas in the Šampion apple peels, the most abundant were: procyanidin B2 (33% of all the polyphenols assayed), quercetin galactoside and quercetin fructoramnoside (15 and 11%, respectively). In the flesh of the apple cultivars examined, the following compounds prevailed: chlorogenic acid (14% and 53%, respectively), (–)epicatechin (29% and 10%), and procyanidin B2 (28% and 14%). In that part of the apples, none, or only trace amounts of quercetin glycosides were detected. These results show the importance of the all part of apple fruit, not only one fraction.
2.3 Health-promoting effects of apple flavonoids
Since most of the polyphenols in apples function as antioxidants, it's not surprising to see so many health benefit studies focusing on the antioxidant benefits from apple. Based on studies showing the concentrations of this all compounds, it appears that apples may play a large role in reducing the risk of a wide variety of chronic disease and in maintaining a healthy lifestyle. Apples are one of the most common fruit associated with reduced risk of cancer, heart disease, asthma, and type II diabetes when compared to other fruits and vegetables and other sources of flavonoids. Apple consumption was also positively associated with increased lung function as we can see from Feskanich et
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al. (2000) in a study linking apple consumption with a reduced risk for lung cancer. In this study, involving over 77,000 women and 47,000 men, fruit and vegetable intake was associated with a 21% reduced risk in lung cancer in women but only with an higher fruit and/or vegetable intake every day. Very few of the individual fruits and vegetables examined had a significant effect on lung cancer risk, but apples were one of the individual fruits associated with a decreased risk in lung cancer. In many studies that focused on a great number of people involved apples are usually gained a positive trend regarding health benefits. In a Finnish study performed by Knekt et al. (2002) involving 10,000 men and women, a strong inverse association was seen between flavonoid intake from different foodstuff and lung cancer development. The total cancer incidence was significantly lower at higher quercetin intakes and especially breast cancer risk tended to be lower at higher quercetin intakes. The authors conclude that as apples are the main source of flavonoids in the Finnish population, they are most likely responsible for the decreased risk in lung cancer.
Good outcomes in terms of epidemiological evidence are well supported by in vitro studies. Apples and especially apple peels, have been found to have a potent antioxidant activity and can greatly inhibit the growth of liver cancer and colon cancer cells as a result of their non proliferation ability (Eberhardt et al., 2000).
The positive correlation between apples and lung function have an impact also on Asthma disease, as it has been demonstrated by Shaheen et al. (2001) and Butland et al. (2000). They have found evidence to suggest that a higher consumption of apples may protect against asthma in adult. This effects can be interpreted as a part of the role that apple may provide to the all breathing system and that are able to protect humans from chronic obstructive pulmonary disease (Tabak et al., 2001).
Apples seem to be influential on cardiovascular disease too. Phenol intake was strongly correlated with a decreased mortality from heart disease in elderly men and also negatively correlated with myocardial infarction. Apple intake contributed to the total ingested flavonoids and was also associated with a reduced risk of death from coronary heart disease in men, even if the relationship was not statistically significant (Hertog et al., 1992). Some of these effects against cardiovascular disease may also come from its potential cholesterol decrease ability. Studies performed on rats show how there is a significant drop in plasma and liver cholesterol concentration and in the meanwhile an
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increase both in high-density lipoprotein and in the cholesterol excretion (Aprikian et al., 2001).
All these positive results both in epidemiological and in vitro studies are not able to explain if the potential health benefit derived from one main class of flavonoids or is a result of interactions between the phytochemicals. Most of the authors have already shown how the antioxidant activity may be seen as a result of the interactions between all the phytochemicals, due to their variety in the mechanism of action.
However, the interactions among nutritional components are complex, and it is unclear when these dietary components are most effective in relation to the onset of disease. The interaction of the many apple phytochemicals warrants more study as researchers attempt to further explain the mechanism behind the apple's ability to reduce risk of chronic disease.
2.4 Bioavailability
2.4.1 Flavonoids bioavailability
Both animal and cell culture studies show that there is an association between the polyphenol compounds found within apples and a wide variety of effects that may help the prevention of chronic diseases. This support the hypothesis that it is the phytochemicals found in fruits, especially apples, that impart healthy benefits. More research is still needed to clarify the effects of these compounds in vivo. In order to examine the effects of these compounds in vivo, it is necessary to understand the bioavailability of the specific compounds, and the bioavailability of these compounds within the fruit matrix.
All these bioactive compounds have received a great deal of attention in the last decades because lots of authors have underlined their possible helpful role in human health, they are not perceived as medicine but many studies highlight a protective effect.
Hence the question is: are these phytochemicals bioavailable?
Concentrations and bioavailability are key issues to evaluate when describing the effects of dietary phytochemicals on human health. Bioavailability can be defined in different ways. The commonly accepted definition is the proportion of the nutrient that is
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digested, absorbed and metabolised through normal pathways, by humans (Pandey et al., 2009; D’archivio et al., 2007).
Most flavonoids, except for the subclass of catechins, are present in plants bound to sugars as -glycosides. This structural feature establish if the flavonoids can be absorbed from the small intestine or if they have to move onto the colon before absorption can take place. Generally, glucosides are the only glycosides that can be absorbed from the small intestine, where the aglycones are usually absorbed. Glycosides were considered too hydrophilic for absorption by passive diffusion in the small intestine, thus only aglycones were likely to be taken in. Consequently once absorbed, two compartments are involved in the metabolism: First, organs as small intestine, liver and kidneys and then the colon. The polyphenols that are not absorbed in the small intestine reach the colon, where the microflora hydrolyze glycosides into aglycones and extensively metabolize the aglycones into various aromatic acids. So flavonoids introduced in form of esters, glycosides or polymers that cannot be absorbed in their native form from the small intestine, will be hydrolyzed by intestinal enzymes or degraded in the colon by microorganisms, which will break down the flavonoid ring structure. During the transport to the first section flavonoids go into conjugation process, that mainly includes methylation, sulfation, and glucuronidation and represents a metabolic detoxification process, common to many xenobiotics, in order to facilitates their biliary and urinary elimination by increasing their hydrophilicity. The conjugation mechanisms are highly efficient, and free aglycones are generally either absent, or present in low concentrations in plasma after consumption. Evidence is found regarding quercetin intake, quercetin glucoside is absorbed from the small intestine, whereas quercetin rutinoside is absorbed from the colon after deglycosylation (Hollman et al., 1999).
Catechins are quite rapidly absorbed, suggesting absorption from the small intestine, as well as anthocyanins are quite rapidly assimilated, but their bioavailability seems to be the lowest of all flavonoids. It is not clear yet whether the problematic quantification of anthocyanins in plasma and urine causes these low values. Proanthocyanidins differ from most of other plant polyphenols because of their polymeric nature and high molecular weight, this particular feature should limit their absorption through the gut barrier.
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Hydroxycinnamic acids, when ingested in the free form, are rapidly absorbed by the small intestine and are conjugated as the flavonoids. However, these compounds are naturally esterified in plant products compromising their absorption because intestinal mucosa, liver and plasma do not possess esterases capable of hydrolyzing chlorogenic acid to release caffeic acid. Hydrolysis can be performed only by the colonic microflora slowing the absorption.
Polyphenol metabolites circulate in the blood bound to proteins, especially albumin and the affinity of polyphenols for albumin varies according to their chemical structure, Dufour et al. (2007) demonstrated that the albumin-bound polyphenols can exert biological activity.
Hence, the forms reaching the blood and tissues are different from those seen in food and it is very difficult to identify all the metabolites and to evaluate their biological activity because it is not necessarily true that the predominant compound in the matrix food will be the highest one in the target tissues, as a consequence the most abundant ones in our diet are not automatically those that have the best bioavailability profile. Polyphenols are able to penetrate tissues, particularly those in which they are metabolized such as intestine and liver. Determination of the bioavailability of polyphenol metabolites in tissues may be much more important than what the knowledge of their plasma concentrations is, because of this will be the concentration biologically active for exerting the effects of polyphenols.
2.4.2 Post harvest apple treatment
Apples are one of the most distributed fruit worldwide, they are rich in flavonoids, phenol acids, vitamins, and fibers, that confer important antioxidant properties. Originally the main health claims for polyphenols were based on their properties as scavengers of free radicals and reactive oxygen species (ROS), but the bioactive compound content depends on some factors as cultivar, harvest, storage conditions, and processing (Carbone et al., 2011; Duda-Chodak et al., 2011).
At the harvest time, the generally accepted commercial practice is to pick apples before the onset of the respiratory climacteric, while apples ready to be commercialized are harvested during the high climacteric stage. The issue of changes in the chemical
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composition during storage of the fruit is still very important from fruit processing industry point of view.
Apples picked too early are susceptible to shrivel, scald and bitter taste. They also may not ripen appropriately after harvest. Apples picked too late may begin the respiratory rise, which will decrease their shelf life and lead to disorders such as flesh browning and breakdown, especially higher concentrations of CO2, resulted from the respiratory process, perform a greater incidence and severity of internal browning. Because internal browning is not detectable externally, except in very severe cases, affected fruit can be discovered by buyers or consumers only at the consumption moment, thereby will influence future confidence in the product.
Controlled atmosphere storage has allowed industry to grow to its current level and to be able to provide many kind of fruits during the different seasons. Apple is one of the predominant horticulture commodity stored under controlled atmosphere conditions (Leja et al., 2003). The objective of controlled atmosphere storage is to low oxygen and increase carbon dioxide concentrations to levels that will maintain fruit quality by decreasing respiratory metabolism and reducing ethylene production and action, but not to levels that induce fermentation or other damaging events (Bishop, 1996; Watkins, 2003).
Optimal postharvest treatments for fresh produce seek to slow down physiological processes of senescence and maturation and try to reduce development of physiological disorders and minimize the risk of microbial growth and contamination.
The fruit demand rises continuously and food industries are always looking for to new ways to provide fruit during all the seasons. These alternatives must satisfy the consumers and maintain a balance between sensory and quality. For this reason exploration and enhancement of new alternatives are essential. There is a real need to find alternatives for preservation of fresh-cut fruit and vegetables in order to improve the efficacy of washing post-harvest treatments.New techniques for maintaining quality and inhibiting undesired microbial growth are demanded in all the steps of the production and distribution chain.
Harvested products are metabolically active, so undergoing ripening and senescence processes must be controlled to prolong postharvest quality. Inadequate management of
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these processes can result in major losses in quality and nutritional attributes, such as bioactive compounds.
2.5 UV
2.5.1 UV, the love/hate relationship among plant and light.
UV is a solar radiation portion able to reach the earth surface.Whereas UV-C is entirely absorbed by the stratospheric ozone layer, UV-A and some UV-B radiation reach the Earth’s surface and thus can affect the biosphere. Nevertheless, UV-B radiation is an integral component of sunlight that has got wide-ranging effects on organisms, it is the most energetic part of the daylight spectrum and has the potential to damage macromolecules such as DNA and proteins, generate reactive oxygen species (ROS) and impair cellular processes.
Plants are able to specifically perceive UV-B photons. In doing so, a perception mechanism is required to distinguish UV-B from other light qualities.
The love/hate relationship among plant and light is enhanced by the evidence that plants are sessile organisms that depend on sunlight as the energy source for photosynthesis. For conventional reason UV spectrum is divided in three parts: UV-A from 320 to 400nm, UV-B from 280 to 320nm and UV-C with sub 280nm wavelength.
Figure 12: UV portions at different wavelengths https://www.bioscience.org
With the advent of molecular genetics, it was discovered that plants use a multitude of sensory proteins to create a link between environmental incentive and physiological responses. In the case of light, plants use a wide variety of highly sensitive and
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sophisticated photoreceptors. The increase of phenol compound concentration inside plant may be seen as a plant response from abiotic stress such as wounding or pathogen attack. In several studies the protective effects of UV-B were correlated with changes in biochemical composition of leaf tissue that resembled the plant’s defence responses to insect attack.
2.5.2 The UV-B and plant physiology
With the aim to understand if the secondary plant metabolites synthesis and collection would be enriched without using molecular and genomic ways, in the last years authors focus their attention to some environmental features as temperature and light exposure, that, with an optimal use, could modify content and profile of these phytochemicals. However, UV-B is not only an agent of damage and has an important role as a regulatory signal. UV-B radiation is able to manage several aspects about plant physiology, one of them, regards the ability to improve the plant defence system against UV itself with the stimulation of gene expression able to codify for enzymes that are linked to the phenol synthesis (Jenkins and Brown, 2007). These secondary metabolites, mainly phenolic compounds, flavonoids, and hydroxycinnamic acids are accumulated in the vacuoles of epidermal cells in response to UV-B irradiation in order to attenuate the penetration of the UV-B range of the solar spectrum into deeper cell layers. They have got a crucial physiological relevance as UV-B sunscreens.
This phytochemical class can be collected on plant epidermal layer to protect plant from UV-B damaging consequences with the absorption of the radiation itself.
During the last few years a lot of authors focus their attention on the molecular signal UV-B pathway. Using Arabidopsis thaliana, recent achievements have led to identification and mechanistic characterization of key players in UV-B perception and signaling. Specifically, mediated UV-B perception and the subsequent UVR8-COP1 interaction have emerged as a central, primary mechanism for UV-B signaling (Tilbrook et al., 2013; Rizzini et al., 2011; Jenkins et al., 2014).
UVR8 is a seven-bladed β-propeller protein of 440 amino acids, that in light conditions devoid of UV-B exists as homodimer.
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UVR8 homodimer is monomerised by UV-B, with UV-B absorption proceeding using a tryptophan-based chromophore. The UVR8 monomer interacts directly with COP1 (Constitutively Photomorphogenic 1) to initiate UV-B signal. UVR8 monomer is redimerized through the action of RUP1 and RUP2 (repressor of UV-B photomorphogenesis), which disrupts the UVR8-COP1 interaction, inactivates the signaling pathway and regenerates the UVR8 homodimer again ready for UV-B perception (Tilbrook et al., 2013; Christie et al., 2012).
UVR8-associated responses help the plant acclimate to UV-B and therefore serve to prevent UV-B damage and stress.
2.5.3 Phenol compounds response after UV-B irradiation
UV-B induces a multitude of physiological responses influencing growth and development at various stages of the plant life cycle.
Recent advances in the science and engineering of UV-light irradiation have demonstrated that UV-B treatment holds considerable promise for shelf-life extension of fresh fruits and vegetables.
However, UV stress mediated changes in phenol profile and antioxidant activity are dependent on the duration of stress, adaptation time of plants to UV-B stress and physiological status of the plant at the time of UV-B exposure.
In apple fruits, strong solar radiation induces a remarkable increase in Flavonoids evidently to prevent the development of a phototooxidative damage.
Lots of studies already underline how the light is one of the most important and essential factor to affect apple anthocyanidin biosynthesis, because the transcription of genes involved are regulated by light exposure itself.
In general, it is well known the synthesis of phenol compounds can also be stimulated by UV exposure in postharvest, as it was already reported for example for quercetin in onion and strawberry, flavonoids in broccoli and black currant.
Regarding the different phenol compounds UV-B stress mediated increase of phenylalanin ammonia-lyase activity occurs leading to an acceleration of the biosynthesis of phenolic compounds. Hydroxycinnamic and hydroxybenzoic acids are
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the biochemical precursors of flavonols and anthocyanins in the shikimate pathway. Therefore, both precursors showed an early increased reaction to UV-B exposure demonstrating that the synthesis of phenolic compounds and associated antioxidant activity of black currant fruits is stimulated by a short term UV-B radiation in postharvest (Huyskens-Keil et al., 2007).
As suggested by Zhang et al. (2011), two anthocyanins, cy3-galactoside (cy3-gal) and cy3-arabinoside, were detected in the red ‘Granny Smith’ apple peels, with cy3-gal is chiefly responsible for red colour. In this study the expression analysis of anthocyanin biosynthetic genes showed that all of the selected genes in the anthocyanin pathway were markedly elevated in the re-exposed fruits, and their expression was highly correlated with anthocyanin accumulation. Anthocyanin accumulation in ‘Granny Smith’ apples is the result of interactions between multiple key enzymes in the anthocyanin pathway, and the colouring mechanism of ‘Granny Smith’ may be similar or identical to that of red-skinned cultivars.
2.5.4 Apple’s reaction after UV-B, differences between peel and flesh.
In literature there are a lot of studies showing how the apple peel holds much more phenol compounds than the flesh. The biosynthesis of phenol compounds was affected by UV-B radiation in postharvest, but not in the same way for peel and flesh.
Hagen et al. (2007) investigated the effect of postharvest irradiation of phenolic compounds, in the peel and flesh of red, sun-exposed and green, shade-grown “Aroma” apples,irradiated with a combination of visible light and UV-B radiation or visible light alone.
Apples with a high content of anthocyanins and quercetin glycosides, either because of previous light exposure or genetic background, the UV-B response may be “saturated” and a further increase of these compounds may then not be possible.
Postharvest irradiation with Vis +UV-B had a stronger influence on the peel concentration of chlorogenic acid than preharvest exposure to solar radiation. In contrast, the content of epicatechin, procyanidins and phloridzin in the present study was minimally influenced by the irradiation treatments, even though the peel concentration of these compounds was almost two-fold higher in the sun-exposed apples than in the shade-grown apples.
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The results suggest that postharvest irradiation in apples can be used to improve their health benefits and colour appearance without changing important taste-related parameters or causing damage to the fruit. A combination of visible light and UV-B radiation was the most effective irradiation treatment and the response was greatest for the peel of the shade-grown apples. The apple flesh showed no response to any of the irradiation treatments.
Furthermore, as irradiation has got more consequences in peel than in flesh, it’s easy to find changes also in general appearance and skin colour. The shade-grown apples treated with Vis +UV-B had developed a skin colour that was much redder, darker and less yellow than the other groups of shade-grown apples. The skin of shade-grown apples exposed to Vis alone became more yellow and less green during irradiation. The skin colour of the sun-exposed apples exposed to Vis +UV-B was not different from that of the start-samples, but was slightly darker and less yellow than the skin colour of the sun-exposed apples exposed to Vis alone or kept in the dark, (Hagen et al., 2007; Ribeiro et al., 2012).
Postharvest irradiation with Vis +UV-B enhanced the sum of flavonoids, sum of phenols and total phenols in the peel of shade-grown apples. The combination of visible light and UV-B radiation was found to be the most effective irradiation treatment and only the apple peel, not the flesh.
In order to make clearer how the post-harvest irradiation may be useful for phenol biosynthesis more studies are needed, especially it might be a crucial way of study the possibility to understand in which part of the post-harvest managing the irradiation should provide much success.
2.6 The biofilm and the edible coatings
2.6.1 The biofilm and the edible coatings in food industry.
Today, consumers and food industry increasingly have focused their attention on the safety and quality of food: growing demand by consumers of high quality food has suggested the industry to develop products aimed at maintaining, as far as possible, their appearance and their natural characteristics, as well as presenting a nutraceutical profile increased. In this context, it is gradually developing biodegradable packaging materials
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to preserve product quality and increase the stability (Garcia et al., 2001). The interest is directed towards the application of natural biopolymers as packaging materials and coating of foodstuffs. Such materials should therefore present both functional characteristics as to preserve the quality of the food, and the peculiarity of being edible. “Edible film" refers to a thin layer of edible material applied to a food product, which exert a positive influence during the shelf life of the food itself.
In food field, biofilms can act as a carrier of antimicrobial agents and antioxidants, playing a protective action on foodstuff, they can be used to control the spread of undesired substances from the surface inside the product, provide additional nutritional value to food and intensify the organoleptic properties thanks to the preservative effect of aromatic compounds. Such coatings can be made to prevent deterioration, then mechanical, chemical and microbiological damages and can also be arranged in multilayer packaging materials along with film not edible, representing in this case, the inner surface in direct contact with food.
The characteristics of the biofilm are affected by many factors, such as the type of material (composition and molecular weight) used as a structural matrix, the conditions under which this is preformed (type of solvent, pH, concentration of components and temperature), the type and concentration of additives added. The main benefit that derives from the biofilm in replacement to traditional packaging is the reduction of environmental pollution, especially for the ability to consume the biofilm together with the food itself as edible portion (Bourtoom, 2008).
2.6.2 Edible Coatings and Edible Films, how and why.
In addition to basic postharvest technologies of temperature management, the use of a biodegradable film is one way to focus on future studies. These coatings, that we can classify as active packaging, were developed in response to changes in current consumption and market trends and is designed to improve fresh product quality and safety.
The edible biofilm are distinguished between Edible Coating (EC) and Edible Films (EF).
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An EC is a thin layer of edible material applied directly and in liquid form as a coating on the foodstuff, dipped it into a solution consisted of a structural matrix.
An EF is a thin film of edible material that is applied to the food after being preformed: it is modelled as a solid sheet and then is applied to the product as a shell.
During the production of a biofilm, the basic components are dispersed and dissolved in a solvent (water, alcohol or a mixture). Then the solution of the film is stretched and dried under conditions of relative humidity and temperature required, in order to get the individual layers of the biofilm (Bourtoom, 2008). Edible biofilms should satisfy specific functional requirements (barrier effect, solubility, rheological and mechanical properties, edibility, biodegradation), and these properties depend on the composition of the film, by its structure, by the conditions of the process and application and by the addition of plasticizers, antimicrobial and structural agents, antioxidants, colourants and flavouring.
The Edible Coating acts as a barrier against external agents (humidity and steam) protecting the product and prolonging its shelf life. The functional characteristics required depend on the food matrix in which the EC must be applied and the processes of deterioration which apply to him the food itself (Guilbert et al., 1996).
To get the best coating it is necessary evaluate the permeability towards gas and water vapour, mechanical capacity of cohesion and adhesion, the microbiological stability, transparency and solubility (Falguera et al., 2011), in order to understand which are the interaction between the coating and food during the shelf-life.
2.6.3 Edible coatings properties.
Edible Coatings and shelf life
The coatings have got important properties that can influence the shelf-life in order to retard food deterioration by inhibiting the growth of microorganisms, due to their natural intrinsic activity or to the incorporation of antimicrobial compounds.
A possible application might be the interaction between MAP and coatings technology especially for fresh vegetables and fruits in order to restrict gas diffusion (ethylene, CO2, O2, and vapour) through the film wall (Vu et al., 2011).
