1961/2011
LA MECCANICA_Layout 1 05/01/11 12.10 Pagina 1
TECNICA
MOLITORIA
10064 PINEROLO - ITALY - Tel. +39 0121393127 - Fax +39 0121794480 - e-mail: info@chiriottieditori.it Supplemento al n° 3 del 2013 di Tecnica Molitoria - Sped. in A.P. - D.L. 353/2003 (Conv. in L. 27/02/2004 n° 46) art. 1 comma 1 DCB TO - n. 1 anno 2013 - IP
CHIRIOTTI EDITORI
vol. 64 - n. 14/A yearly issue 2013
INTERNATIONAL
ISSN0040-1862
WITH SUPPLIER DIRECTORY
COP TM int 2013_Layout 1 12/03/13 14:21 Pagina 1
YOUNG-MASSA Srl - Via Santa Maria, 5 20873 - Cavenago Brianza (MB) - Italy Tel. +39 0295019613 - Fax +39 0295019413 info@youngmassa.it - www.youngmassa.it Young-Massa 2013_Layout 1 28/02/13 14:16 Pagina 1
yearly issue 2013
14/A
Whenever there is the opportunity to install a new plant, we can find the solution for any milling and storage requirement, with a tailor-made project, result of a totally Italian know-how. While trusting in a promising future, we are in position to provide the market innovation, experience and passion in order to optimize your milling production processes respectful of nature, human wellbeing and demanding international regulations.
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AC50 group for application of carton top cover
FCBS20 multihead combination weigher
RAN 241 automatic casepacker for short pasta
Trays loading device
VSB120 Packaging and automatic squaring unit
Packaging line for fragile products
VS120
vertical packer
IR9 automatic casepacker for long pasta
HS20 LD horizontal
flow-pack packaging
machine for long pasta
yearly issue 2013
14/A
Whenever there is the opportunity to install a new plant, we can find the solution for any milling and storage requirement, with a tailor-made project, result of a totally Italian know-how. While trusting in a promising future, we are in position to provide the market innovation, experience and passion in order to optimize your milling production processes respectful of nature, human wellbeing and demanding international regulations.
IF YOU CAN IMAGINE IT, WE CAN MAKE IT.
mill Service Spa
Via Pelosa, 78 Selvazzano Dentro, Padova / Italia Ph. +39 049 8978743 + 39 049 8978744 Fax +39 049 8978780
info@ms-italia.com - www.ms-italia.com Via U. Mariotti, 143 - S. Agostino - 51100 Pistoia ITALY
Tel. +39 0573 44571 - fax +39 0573 933223 e.mail: info@ricciarellispa.it - www.ricciarellispa.it
AC50 group for application of carton top cover
FCBS20 multihead combination weigher
RAN 241 automatic casepacker for short pasta
Trays loading device
VSB120 Packaging and automatic squaring unit
Packaging line for fragile products
VS120
vertical packer
IR9 automatic casepacker for long pasta
HS20 LD horizontal
flow-pack packaging
machine for long pasta
1961/2011
LA MECCANICA_Layout 1 05/01/11 12.10 Pagina 1
TECNICA
MOLITORIA
10064 PINEROLO - ITALY - Tel. +39 0121393127 - Fax +39 0121794480 - e-mail: info@chiriottieditori.it Supplemento al n° 3 del 2013 di Tecnica Molitoria - Sped. in A.P. - D.L. 353/2003 (Conv. in L. 27/02/2004 n° 46) art. 1 comma 1 DCB TO - n. 1 anno 2013 - IP
CHIRIOTTI EDITORI
vol. 64 - n. 14/A yearly issue 2013
INTERNATIONAL
ISSN0040-1862
WITH SUPPLIER DIRECTORY
COP TM int 2013_Layout 1 12/03/13 14:21 Pagina 1
YOUNG-MASSA Srl - Via Santa Maria, 5 20873 - Cavenago Brianza (MB) - Italy Tel. +39 0295019613 - Fax +39 0295019413 info@youngmassa.it - www.youngmassa.it Young-Massa 2013_Layout 1 28/02/13 14:16 Pagina 1
1 2
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GAMMA PRODUTTIVA
♦ Impianti completi di stoccaggio prodotti granulari e polverosi.
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♦ Elevatori a tazze: verticali, inclinati ed a zanca.
♦ Filtri autopulenti e statici.
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PRODUCTION RANGE
♦ Systems complete with granular and dusty product stockings.
♦ Systems complete with short format pasta ensilage and packaging machine feeding line.
♦ Systems complete with dosing and mixing units.
♦ Systems for scrap and waste pre-crumbling and grinding.
♦ Compression and suction pneumatic conveying lines.
♦ Mechanical conveyance: belt, chain and Archimedean screw conveyors.
♦ Vertical, sloped and Z bucket elevators.
♦ Static and self-cleaning filters.
♦ Control panels with P.L.C. and computer.
Via A. Diaz, 15
84018 Scafati (SA) - Italy Tel. +39 081 8631205 r.a.
Fax +39 081 8630301 e-mail: sircem@tin.it www.sircem.it macchine ed impianti
per industrie alimentari mangimistiche e chimiche
SIRCEM.qxp_Layout 1 25/01/12 14:36 Pagina 1
PERONTECNICI
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MOLITECNICA SUD snc di Giuseppe Pellicola & Figli Sede legale e stabilimento:
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IMMAC_Layout 1 19/02/13 10:41 Pagina 1
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C M Y CM MY CY CMY K
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54
PAPERS
Vol. 64 - March 2013
Supplement of the Italian
2013 yEARly ISSuE
DURUM WHEAT Phenolic acids in durum wheat
and derived products: role and perspectives
58
M.A. D’Egidio - D. Martini F. Taddei - A. De Rossi I. Nicoletti - D. Corradini
GLUTEN-FREE BREAD
Effectiveness of waxy rice and rice bran in delaying starch retrogradation during gel ageing
68
C. Cappa - M. Mariotti M. Lucisano
MYCOTOXINS
Mycotoxins and grain-quality monitoring of durum
and common wheat imports
76
R. De Pace - V. Menga - V. Vita C. Franchino - M.A. Dattoli - C. Fares
Tecnica Molitoria International is published once a year with a circulation of 6,000 free copies either sent by air mail or distributed at international exhibitions.
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Managing Editor Chiara Chiriotti Direttore Responsabile
Assistant Editor Chiara Mancusi Editorial Staff Elena Folco, Nadia Barotto Laura Sbarato, Cristina Quaglia,
Simonetta Musso
Copyright© 2013 by Chiriotti Editori srl - All rights reserved
Supplemento a Tecnica Molitoria n. 3, marzo 2013 - ISSN 0040-1862 - Spedizione in abb. postale Torino Autorizzazione n. 172 (5-5-1950) del Tribunale di Pinerolo - Printer: Tipolitografia Giuseppini - Pinerolo
YEARLY
IN ENGLISH ➠
MONTHLY
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Managing Director Giuseppe Chiriotti
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Luigi Voglino voglino@chiriottieditori.it Head of Advertising Strategies
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Raffaella Frigo - Triveneto
DEPARTMENTS
88 - TECNICA MOLITORIA
The Italian milling magazine Tecnica Molitoria, since 1950 90 - CEREAL CLEANING, DRYING & STORAGE
Complete storage plants for every type of requirement - Automatic management of ventilation for stored grain - Cle- aning and drying machines for maize and cereals
96 - SORTING
Bühler Sortex opens new customer service centre in London - Versatile and multiple-configuration sorting machines 100 - MILLING EQUIPMENT
Turnkey milling systems - Modern stone mill plants for grinding whole flour - Plansichter upgranding with tailor-ma- de new frames to fit existing machines - Versatile and hygienic rollermills
105 - FEED MILL EQUIPMENT
Sanitation plant for animal feed manufacturing 107 - MILLS
Turnkey flour handling plant for intake, storage, blending and load-out 109 - PASTA & COUSCOUS PRODUCTION
Multipurpose lines for different types of pasta, couscous, snack pellets - Machines and lines for couscous, dry pa- sta and special pasta - Automatic cutting groups and stamping machines for pasta and snacks
116 - FRESH PASTA PRODUCTION
Compact pasta laboratory for all kind of fresh pasta shapes - Dry and fresh pasta, couscous and ready meal pro- duction lines
122 - DOSING, MIXING & HANDLING
Conveying, dosing, mixing and packaging plants for powders - Raw material handling plants up to feeding the processing machines - Handling and conveying equipment at the new Ghigi pasta plant
127 - INGREDIENTS & FOOD STORAGE
Storage and handling plants for raw materials and finished products - Efficient and flexible storage and handling systems for foods
132 - PEST CONTROL
Real time and permanent rodent monitoring system 134 - PACKAGING
Filling and bagging machines for feed additives - Packaging machines and lines for granular and powdery pro- ducts
138 - ANCILLARY EQUIPMENT
Spare parts and accessories for flour and feed mills - Automatic continuous lubrication in a flour milling plant - Two- way diverting valves for pneumatic conveying lines
143 - SUPPLIER NEWS
New headquarters for Sea - Molitecnica Sud internationalization process - Italpack’s complete packaging solutions - Officine Loporcaro broadens its offer - Sustainability and energy-saving at the Golfetto Sangati production unit - Turnkey plants for mills, pasta and feed manufacturers - Mulmix Facco wins contracts all over the world - P.L.P. li- quid systems around the world
152 - EXHIBITIONS & MEETINGS
Powtech forum for milling, dosing, weighing and agglomeration - Calendar of international events in Italy and worldwide events - International symposium on durum wheat
155 - ITALIAN SUPPLIER DIRECTORY
168 - ADVERTISER INDEX – INDEX OF COMPANIES MENTIONED IN THIS ISSUE
2013 yEARly ISSuE
58 - Tecnica Molitoria International - Yearly issue 2013 58 - Tecnica Molitoria International - Yearly issue 2013
DURUM WHEAT
PHENOLIC ACIDS in durum WHEAT
and derived PRODUCTS:
role and perspectives
Keywords: phenolic acids, durum wheat, analytical methods, technological processes
M
ariaG
raziaD’E
GiDio1*- D
aniElaM
artini1,2- F
EDEricat
aDDEi1- a
ntonEllaD
Er
ossi3- i
sabEllan
icolEtti3- D
aniloc
orraDini31
Consiglio per la Ricerca e Sperimentazione in Agricoltura (CRA, Unità di Ricerca per la Valorizzazione Qualitativa dei Cereali) - Via Cassia 176 - 00191 Roma - Italy
2
Università Campus Biomedico - Via Alvaro del Portillo 21 - 00128 Roma - Italy
3
Consiglio Nazionale delle Ricerche - Istituto di Metodologie Chimiche - Via Salaria Km 29,300 - 00015 Monterotondo Stazione - Roma - Italy
*mariagrazia.degidio@entecra.it
Tecnica Molitoria International - Yearly issue 2013 - 59
DURUM WHEAT
INTRODUCTION
The growing interest for general health amelioration of chronic diseases and pre- vention of the effects of aging directed con- sumer’s interest towards phytonutrients and mainly natural antioxidants derived from plants. Antioxidants may be defined as compounds that inhibit or delay the oxidation of other molecules by inhibiting the initiation or propagation of oxidizing chain reactions.
Antioxidants are important both for food preservation and for the defence of human body against the oxidative stress. Oxidative stress seems to result from an imbalance in the body between oxidants and antioxidants due to a decrease in natural cell antioxidant capacity or an increase in the amount or overproduction of reactive oxygen species (ROS) in the organism. Consumption of food rich in antioxidants may lead to scav- enging of free radicals and ROS that could otherwise cause oxidative damage to bio- molecules such as lipids, proteins and nu- cleic acids.
Plants are known to contain a wide range of chemical classes with antioxidant activity.
Great attention has been traditionally de- voted to dietary antioxidants such as ascor- bic acid, carotenoids, tocopherols, but also other food antioxidants, such as phenolic compounds, play a significant role increas- ing the human body natural resistance to oxidative damage (Liyana-Pathirana and Shahidi, 2006). The antioxidant activities of phenolic compounds is mainly attributed to their redox properties, which allow them to act as reducing agents, hydrogen donors and quenchers of singlet oxygen. Increased consumption of plant-derived phenolics has been related to a reduced risk of degen- ABSTRACT
Food antioxidants, such as phenolic compounds, play a significant role for the defence of human body against oxidative stress, increasing the body natural resistance to oxidative damage. Cereals are known as a major source of a wide range of phenolic acids (PAs). In the wheat kernels the dis- tribution of antioxidant components is not ho- mogeneous and their concentration is greater in the external layers.
This study was focused on the optimization of analytical methods used for PAs extraction and identification in order to evaluate content and profile of these compounds in durum wheat and derived products obtained either by conventional or innovative technological processes.
The traditional milling process provides the re-
moval of external layers and peripheral tissues
determining a drastic reduction of PAs. The use
of whole-grain products or the application of
technological processes (i.e. debranning) could be
a useful tool for preserving the PAs natural pool
present in durum wheat.
60 - Tecnica Molitoria International - Yearly issue 2013
DURUM WHEAT
erative diseases (i.e. cardiovascular diseases, cancer, and other chronic diseases). Phe- nolic acids (PAs), generally recognized as po- tent antioxidants, are secondary metabolites widely distributed in the plants and in term of their dominance they are second only to flavonoids.
Cereals are known as a major source of a wide range of PAs belonging to hydroxycin- namic acids and hydroxybenzoic acids de-
oxidative stress. Adom et al. (2003) reported that ferulic acid was the major phenolic ac- id in wheat; Zhou et al. (2004) reported that approximately 57-77% of total phenolics in wheat were composed of ferulic acid, thus suggesting the use of ferulic acid as marker of wheat antioxidants.
In the wheat kernels the distribution of an- tioxidant components is not homogeneous and their concentration is greater in the ex- ternal layers (fig. 1). Wheat grains are tradi- tionally processed for the preparation of the most wheat-based food products and mostly refined flour/semolina is used. The milling process of wheat includes the removal of ex- ternal layers; peripheral tissues such as germ and envelopes are generally eliminated in the so-called bran fraction as by-products.
It has been demonstrated that the bran frac- tion alone has a higher antioxidant activity than that of other milling fractions. Zhou et al. (2004) pointed out that antioxidants, in- cluding PAs, are concentrated in the aleurone layer of the wheat bran; Mateo Anson et al.
(2008) showed that the higher the propor- tion of aleurone material in wheat fractions, the higher the antioxidant capacity observed for these fractions.
Moreover, numerous epidemiological stud- ies investigated the potential health ben- efits of consuming more wholegrain foods and the relative data indicated that in- creased consumption of whole grains may reduce the incidence of chronic diseases and certain types of cancer. Such beneficial effects have been ascribed to the presence of dietary fiber and a variety of phytochem- icals such as PAs.
PAs occur in wheat as soluble free and conju- gated forms and as insoluble bound forms.
The determination of the total amount of PAs is currently performed by spectropho-
Fig. 1 - Wheat kernel morphological features.
rivatives; these include ferulic, p-coumaric,
p-hydroxybenzoic, vanillic and syringic
acids. Naturally occurring antioxidants
such as ferulic acid have been recognized
as important therapeutic agents against
neurovegetative disorders such as Alzhei-
mer disease (Kanski et al., 2002) where the
oxidative stress plays a crucial role: ferulic
acid serves as potent inhibitor for hydroxyl
and peroxyl radicals thereby acting against
Tecnica Molitoria International - Yearly issue 2013 - 61
DURUM WHEAT
tometric methods based on the Folin-Cio- calteau reaction using ferulic acid as the standard (Hirawan et al., 2010), whereas re- versed phase high performance liquid chro- matography (RP-HPLC) is the technique of choice for the identification and quantifica- tion of individual PAs, using a variety of RP columns eluted by increasing the concentra- tion of either acetonitrile or methanol in the mobile phase containing an acidic additive (Hirawan et al., 2010; Wang et al., 2013). The qualitative and quantitative analysis by RP- HPLC is performed after the extraction of soluble free and conjugated PAs and insolu- ble bound forms of PAs, which are currently extracted in separated fractions by a combi- nation of multistep liquid-liquid extraction, cleanup procedures and alkaline hydroly- sis of either the supernatant or the residue from the initial liquid-liquid extraction (Li et al., 2008)
In this work PAs content and profile were studied in different milling fractions of du- rum wheat and derived products and com- pared with wholemeal products. A no tra- ditional technological approach such as debranning was also studied in order to en- hance the value of the resulting bran frac- tion as excellent source of raw material with potential application as nutraceuticals and functional food ingredients.
MATERIAL AND METHODS
Samples
A widespread Italian durum wheat cultivar (Duilio) was considered for this study. Du- rum wheat grains were ground by conven- tional milling process on a pilot plant with three breaking and three sizing rolls (Büh-
ler MLU 202) in order to obtain semolina and by-products. Semolina was processed by experimental press (Namad) to obtain spaghetti dried at low temperature by an experimental drier (Afrem, France). Grains were also processed by a micronization pi- lot plant (Separ Micro-System) to obtain a wholemeal used to produce pasta with the same technological conditions adopted for the traditional one. Durum wheat grains of cv Duilio were also subjected to the debran- ning process by using a laboratory machine with an abrasive stone element; debranning process was performed on kernels after hy- dration with 3% water and a resting time of 15 minutes, because the pre-hydration made the tegument layers less crumbly, allowing a more regular and homogeneous removal (Bottega et al., 2009). For debranning, 12 subsequent time intervals, each of 15 sec- onds, were applied.
Identification and quantification of PAs by RP-HPLC
The extraction of PAs (soluble free and con- jugated and insoluble bound forms) was performed in duplicate according to the procedure proposed by Li et al. (2008) with minor modifications (fig. 2). Separation, identification and quantification of PAs were carried out by RP-HPLC using a Shi- madzu LC-10A
VPsystem consisting of an SCL-10A
VPsystem controller, two LC-10AD-
VP
solvent delivery units, a SPD-M10A spec-
trophotometric photodiode array (PDA)
detector, a CTO-10AS
VPcolumn oven, a
DGU-14A on-line vacuum membrane degas-
ser, and a Rheodyne (Cotati, CA, Usa) Model
8125 semi-micro injection valve with a 5 µL
sample loop. Instrument control and data
acquisition and processing were performed
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by the Shimadzu Class VP 5.6 HPLC data system on a Pentium II 400 PC compatible computer. A Polaris C18A column (150 x 2.0 mm ID, 5 µm; Varian Inc. Lake Forest, CA) with a C18 (30 x 2 mm, 5 µm) guard cartridge column was employed at con- trolled temperature of 30°±1°C. PAs were separated by a multi-segments gradient of increasing concentration of acetonitrile in water acidified with 2.0% (v/v) formic acid, at a flow rate of 0.2 mL/min. UV-Vis spectra were recorded in the 210-600 nm range, and the chromatograms were acquired at 254, 280, and 320 nm.
The identification of individual analytes was performed on the basis of their retention times and collected UV spectra, compared with those of authentic standard solutions.
Stock solutions of each standard com- pound were prepared by dissolving weighted amounts of each standard in 80% (v/v) meth- anol-water mixture. These solutions were individually injected into the HPLC column and eluted using the above gradient elution programs to determining their chromato- graphic retention times and collecting UV spectra by the PDA detector. The identified PAs were quantified by the internal standard method using five points regression graphs of the UV absorption data collected at the wavelength of maximum absorbance of each identified PA, which were determined by the PDA spectra acquired in the wavelength range 210-600 nm. Calibration graphs of PA standards were constructed using authen- tic standards that had undergone the same extraction procedure to ensure that losses due to the extraction were accounted for. All samples were analyzed in triplicate, and the concentrations of individual PAs were ex- pressed in milligrams per kilogram (mg/kg) of dry matter (dm).
RESULTS AND DISCUSSION
Preliminary experiments were devoted to optimize the methods employed for the ex- traction of PAs from the different milling fractions of durum wheat and for their sub- sequent identification and quantification by RP-HPLC, using a narrow bore C-18 column operated under gradient elution mode with the starting eluent and the gradient former consisting of water and acetonitrile, respec- tively. Formic acid was incorporated at con- centration of 2% (v/v) into the starting eluent to control the protonic equilibrium at acidic pH value, in order to keep carboxyl and hy- droxyl groups of the analytes in their pro- tonated form. This in order to avoid peak broadening caused by the simultaneous pres- ence of protonated and ionized forms of the PAs and to improve their hydrophobic inter- actions with the C-18 stationary phase.
The developed method allowed the com- plete separation, in less than 40 min, of all PAs potentially present in our samples. The separation by RP-HPLC of 3,5-dichloro-4-hy- droxybenzoic acid (employed as the internal standard) and the soluble conjugated PAs p-hydroxybenzoic acid, vanillic acid, syringic acid, p-coumaric acid, sinapic acid and feru- lic acid extracted from wholemeal is shown in fig. 3.
In order to obtain accurate and reliable ana-
lytical data, the developed RP-HPLC method
was validated according to the International
Conference on Harmonization (ICH) guide-
lines (ICH 1997) and applied for the identi-
fication and quantification of the individual
PAs extracted as soluble free and conjugated
forms and as insoluble bound forms from dif-
ferent milling fractions and from traditional
and wholemeal dried pasta. The content of
the individual soluble free and conjugated
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Fig. 2 - Scheme of the PAs extraction method.
Fig. 3 - RP-HPLC separation of soluble conjugated PAs extracted from wholemeal. Column and experimental conditions as reported in the text; peak identity:
p-hydroxybenzoic acid (1), vanillic acid (2), syringic acid (3), p-coumaric acid (4), ferulic acid (5), sinapic acid (6) and 3,5-dichloro- 4-hydroxybenzoic acid (7). Compound (7) was incorporated into the sample of wholemeal as the internal standard.
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PAs and of the insoluble bound PAs extract- ed from the wholemeal sample is reported in tab. 1. As expected from previous findings (Li et al., 2008; Hirawan et al., 2010), PAs are mainly present in the bound form followed by conjugated form, whereas free form is pre- sent in a very small amount. Ferulic acid is the most abundant in the bound form, while in the conjugated form sinapic acid prevails.
Results of the quantitative analysis of solu- ble free and conjugated PAs and of insolu- ble bound PAs on the three milling fractions and the two dried pasta samples show that the content of each PA in the three differ- ent forms differs significantly among mill- ing fractions and type of dried pasta, as it is shown in fig. 4, which displays the observed differences in the PAs contents as the per- centage change of each PA compared to its content in the wholemeal; for this reason not all PAs are reported but only those revealed and quantified in the wholemeal. Changes in the content of PAs were compared with the amounts present in the wholemeal, repre- senting the reference material against which to compare the modifications induced by technological processes.
As regard the milling process, natural com- pounds present in the kernel are concentrat- ed in the bran, whereas in semolina are gener-
ally present in lower amount. Pasta-making process does not affect significantly the PAs content of semolina and pasta produced by wholemeal shows a level similar or slightly higher than that initially present in the ker- nel. Further RP-HPLC analyses were carried out to identify and quantify insoluble bound PAs in samples extracted from the differ- ent fractions obtained by debranning wheat grain at subsequent time intervals, as re- ported in the Experimental sections. Results of these analyses are reported in fig. 5 as histograms depicting the content of ferulic acid in the fractions corresponding to the different peripheral layers of wheat grain subjected to the debranning process. Ferulic acid represents a good marker of the aleu- rone layer in the kernel and therefore could be a useful index of the progressive removal of peripheral parts; as expected, this acid is the predominant one and maintains quite similar levels until sixth debranning time, after that a regular and consistent decrease is observed. Fig. 6 displays the percentage distributions of PAs in selected debranning fractions. Ferulic acid was the most abun- dant PA in all fractions, accounting for 91%
of the total PAs. The contents of the other five PAs varied proportionally to that of fer-
Table 1 - Content of free, conjugated and bound PAs in wholemeal - mg/kg, dm (±SD)*.
p-hydroxybenzoic acid vanillic acid syringic acid p-coumaric acid ferulic acid sinapic acid Total Retention time* 12.14 (±0.19) 15.99 (±0.18) 20.14 (±0.20) 29.39 (±0.16) 31.22 (±0.10) 31.81 (±0.07) min (±SD)
Free form nq 1.56 (±0.07) nd 0.69 (±0.05) 7.77 (±0.38) 1.18 (±0.04) 11.20 Conjugated form 5.00 (±0.35) 12.44 (±0.44) 1.72 (±0.23) 2.22 (±0.05) 35.42 (±1.29) 90.99 (±0.41) 147.79 Bound form nq 4.01 (±0.06) 1.83 (±0.07) 22.42 (±0.20) 752.56 (±5.14) 30.08 (±0.26) 810.90
*Average values of triplicate analysis; SD, standard deviation; nd, not detected; nq, not quantified.
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Fig. 4 - Variations in the content of soluble free (4a), conjugated PAs (4b) and of insoluble bound PAs (4c) in the different milling fractions and dried pasta. The histograms depict the percentage variation of each PA compared to its content in the wholemeal.
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ulic acid with the result that the percentage amount of each PA was almost the same in all fractions. These results are in accordance with Peyron et al. (2002) who found that the concentration in phenolic acids was at least 40 times higher in aleurone layer than in the starchy endosperm but, despite this large difference, the proportion of each compounds was roughly similar in the two botanical tissues.
CONCLUSIONS
The whole kernels of durum wheat repre- sent a good source of antioxidants, specifi- cally of phenolic acids. Along durum wheat chain, the traditional milling process is the
more critical step and PAs concentration is drastically reduced in the refined prod- ucts (i.e. semolina), while is much higher in the outer layers of the grains (bran). Whole grains and bran are a natural source of PAs and more generally of bioactive compounds, but in the most pheripheral layers also dif- ferent contaminants (i.e. mycotoxins, heavy metals, etc.) can be present, so debranning process can be successfully applied in order to obtain derived products rich in bioactive compounds and jointly of suitable hygienic- sanitary quality. Bran fraction obtained by debranning process may be also used as a value-added product in the preparation of functional food ingredients and/or for en- richment of semolina/flour for positive ef- fects on human health.
Fig. 5 - Content of ferulic acid in samples extracted from different debranning fractions. Each time (T) represents interval of 15 seconds of subsequent debranning.
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REFERENCES
Adom K.H., Sorrells M.E., Liu R.H. “Phytochemical pro- files and antioxidant activity of wheat varieties”. J. Ag- ric. Food Chem., 51: 7825-7834, 2003.
Bottega G., Cecchini C., D’Egidio M.G., Marti A., Pagani M.G. “Debranning process to improve quality and safety of wheat and wheat products”. Tecnica Molitoria International, 60, n. 10/A: 67-78, 2009.
Hirawan R., Ser W.Y., Arntfield S.D., Beta T. “Antioxidant properties of commercial, regular- and whole-wheat spaghetti”. Food Chem., 119: 258-264, 2010.
International Conference on Harmonization, “Q2B: Vali- dation of analytical procedures: methodologies; avail- ability”. Federal Register, 62: 27463-27467, 1997.
Kanski J., Aksenova M., Stoyanova A., Butterfield DA.
“Ferulic acid antioxidant protection against hydroxyl and peroxyl radical oxidation in synaptosomal and neu- ronal cell protection culture systems in vitro: structure- activity studies”. J. Nutr. Biochem., 13: 273-281, 2002.
Li L., Shewry P.R., Ward J.L. “Phenolic acids in wheat va-
rieties in Healthgrain diversity screen”. J. Agric. Food Chem., 56: 9732-9739, 2008.
Liyana Pathirana C.M., Shahidi F. “Antioxidant properties of commercial soft and winter wheats (Triticum aestivum L.) and their milling fractions”. J. Sci. Food Agric., 86:
477-485, 2006.
Mateo Anson N., Berg V.D.R., Havenaar R., Bast A., Hae- nen G.R.M.M. “Ferulic acid from aleurone determines the antioxidant potency of wheat grain (Triticum aesti- vum L.)”. J. Agric. Food Chem., 56: 5589-5594, 2008.
Peyron S., Surget A., Mabille F., Autran J.C., Rouau X., Abecassis J. “Evaluation of tissue dissociation of durum wheat grain (Triticum durum Desf.) generated by milling process”. J. Cereal Sci., 36: 199-208, 2002.
Wang L., Yao Y., He Z., Wang D., Liu A., Zhang Y. “Deter- mination of phenolic acid concentrations in wheat flours produced at different extraction rates”. J. Cereal Sci., 57:
67-72, 2013.
Zhou K., Laux J.J., Yu L. “Comparison of Swiss red wheat grain and fractions for their antioxidant properties”. J.
Agric. Food Chem., 52: 1118-1123, 2004.
Fig. 6 - Percenta- ge distributions of PAs in selected debranning fractions. Data related to T1 (6a), T3 (6b), T6 (6c) and T12 (6d) are shown.
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gluten-free bread gluten-free bread
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Effectiveness of WAXY RICE and RICE BRAN in delaying STARCH RETROGRADATION during gel ageing
Keywords: gel, rheology, starch retrogradation, gluten-free bread
c
arolac
appa- M
anuElaM
ariotti* - M
aral
ucisanoDepartment of Food, Environmental and Nutritional Sciences (DeFENS) - Università degli Studi di Milano - Via G. Celoria 2 - 20133 Milano - Italy
*manuela.mariotti@unimi.it
gluten-free bread
Tecnica Molitoria International - Yearly issue 2013 - 69
INTRODUCTION
Gluten-free baked products contain a large amount of starch, whose behaviour during process and storage greatly influences the final products quality and shelf-life. As re- ported by Lii et al. (1995), the formation of a gel or a paste is one of the main events that controls the texture and quality of starch- containing foods. Gel structure depends on many factors, such as starch source and con- centration, amounts and types of amylose and amylopectin leached out from starch granules, interactions among amylose, amy- lopectin and granules, besides heating and cooling conditions in terms of treatment temperature, length and rate (Mariotti et al., 2005). In particular, starch retrogradation is the major phenomenon involved in bread staling. Different actions can be taken to de- lay bread staling such as the use of enzymes (maltogenic α-amylase or lipase) or the ad- dition of monoglycerides that limit starch granule swelling and rupturing during bak- ing (Delcour and Hoseney, 2010). Also fibres may play a positive effect on quality param- eters related to bread staling, such as crumb softness and springiness (Wang et al., 2002), thanks to the increase of the water absorp- tion of the dough. Bread staling is also af- fected by the amount of protein and starch in the formulation (Kim and D’Appolonia, 1977) and by the total or partial replacement of regular wheat flour with waxy flours (Park and Baik, 2007; Morita et al., 2002; Hung et al., 2007).
The rheological properties provided by the starchy matrix to the final product appear to be of great importance in gluten-free (GF) breadmaking. Up to now, instruments such as the Rapid Visco Analyzer and the Brabend- er Viscoamylograph have been used as stand- ABSTRACT
Gluten-free baked products contain a high amount of starch that it is mostly responsible for their rapid loss of softness during ageing, mainly caused by starch retrogradation. The aim of this research was to evaluate the mechanical and rheological properties of gels obtained from corn starch (CS), rice flour (RF) and their mix- tures. Furthermore, the capability of waxy rice flour (WRF) and rice bran (RB) to reduce starch retrogradation, when added at different ratios (25 and 50%), was investigated in order to increase the shelf-life of starch-containing foods. Gels were prepared by means of the Brabender Micro- Visco-Amylograph (MVA) and their rheological properties, during a 7 days storage period at 4°C, were evaluated both through compression test (TA-HDplus Texture Analyzer) and strain and fre- quency sweep test (Physica MCR 300 Rheometer).
During ageing, gels stiffness increased at different
extents and rates. Samples containing CS showed
the highest consistency. On the contrary, WRF
originated very weak gels and resulted more effec-
tive than RB in delaying gel hardening. The pres-
ence of WRF or RB, both at 25 and 50%, strongly
reduced G’ values of the mixtures containing CS
or RF. For the same gels, G’ curves overlapped up
to 7 days storage, indicating a very slow hardening
kinetic. The results obtained in this research thus
highlighted the possibility to enhance the shelf-
life of gluten-free baked products, by including
WRF and/or RB among the other ingredients.
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ard analytical tools to assess the pasting char- acteristics of starch and flour suspensions during heating and cooling cycles (Shuey and Tipples, 1980; Tsai et al., 1997; Mariotti et al., 2009); whereas dynamic oscillatory rheom- etry has been frequently applied to study the viscoelastic properties of starch gels (Lii et al., 1995; Hsu et al., 2000).
The aim of this research was to evaluate the rheological properties of gels obtained from corn starch, rice flour and their mixtures, and the capability of waxy rice flour and rice bran to reduce starch retrogradation, when added at different ratios to the starchy ma- trix.
MATERIALS AND METHODS
In this study, corn starch (CS) and rice flour (RF) were chosen as principal ingredients, be- ing the main responsible for the texture of many GF products. Waxy rice flour (WRF) and rice bran (RB) were selected as potential alternative and/or additional raw materials to reduce GF bread staling.
CS was provided by Roquette Frères (Les- trem, France); RF, WRF and RB by Beneo- Remy NV (Leuven-Wijgmaal, Belgium).
Seven different mixtures (50CS-50RF;
50CS-50WRF; 50CS-50RB; 50RF-50WRF;
50RF-50RB; 50CS-25RF-25WRF; 50CS- 25RF-25RB) were prepared (Hobart mixer;
5 min mixing at 25°C). Ratios among the different flours were chosen to simulate the proportions existing among the different ingredients in the most common GF bread formulations.
The moisture content of the raw materials was determined according to the Official Standard Method AACC 44-15A (2000). The total nitrogen content was evaluated accord-
ing to the Official Standard Method AOAC 920.87 (1999), and the protein content was calculated adopting 5.95 as conversion fac- tor. The amount of total starch (TS) was de- termined using the Total Starch Assay Kit (Megazyme International Ireland Ltd., Bray Business Park, Bray, Co. Wicklow, Ireland).
All these determinations were made at least in duplicate (n≥2). The amylose content was assessed by the UNI ISO 6647 Method (1991) and expressed as the proportion by weight of amylose (g/100 g db).
The pasting properties of the raw materi- als and their mixtures were evaluated (n≥6) with a Brabender Micro-Visco-Amylograph (MVA; Brabender OHG, Duisburg, Ger- many): 12 g sample/100 mL H
2O (on a 14%
moisture basis); speed: 250 min
-1; measuring range: 300 cm•g
f; temperature increase/de- crease: 3°C/min; temperature profile: heat- ing from 30° up to 95°C, holding at 95°C for 30 min, cooling from 95° to 30°C. The following indices were considered: pasting temperature (PT, °C; temperature at which an initial increase in viscosity occurs), peak viscosity (PV, Brabender Units, BU; maxi- mum paste viscosity achieved during the heating cycle), final viscosity (FV, BU; paste viscosity achieved at the end of the cooling cycle), and setback (SB, BU; index of the vis- cosity increase during cooling, correspond- ing to the difference between FV and the minimum viscosity reached after the hold- ing period at 95°C).
The rheological properties of the gels (ob- tained from the MVA as previously reported) were evaluated after 30 min at 25°C (t0) and after 1 (t1), 2 (t2), 3 (t3), 4 (t4), and 7 (t7) days of storage at 4°C. Before each trial, gels were conditioned at 25°C for 30 min.
For texture analysis, 18 g of each gel were
submitted to compression with a cylindri-
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cal probe (diameter: 3.5 cm) at a crosshead speed of 1 mm/s (10N load cell), up to 30%
deformation by using a TA-HDplus Tex- ture Analyzer (Stable Micro Systems, Sur- rey, UK). Gel stiffness was calculated by the slope of the first linear trait of the compres- sion curve, as an index of gel hardness. At least five replicates (n≥5) were performed for each sample and for each storage time.
For dynamic rheological measurements, a Physica MCR300 Rheometer (Anton Paar GmbH, Graz, Austria) equipped with a cor- rugated parallel plate system (diameter: 2.5 cm), set at a gap of 1 mm, was used. After loading the sample, the excess of gel was trimmed off and the sample was allowed to rest for 5 min at 25°C, before starting the tests: strain sweep test (1Hz, 0.01-300%
strain), frequency sweep test (1% strain, 0.1- 10Hz frequency). Storage modulus (G’) and viscous modulus (G’’) of gels were measured.
All the measurements were performed in triplicate (n=3).
Analysis of variance (ANOVA) was performed using the Least Significant Differences (LSD) test to compare sample means; differences were considered significant at P<0.05 (Stat- graphic Plus for Windows 5.1).
RESULTS AND DISCUSSION Pasting properties of the different raw materials and mixtures
The viscoamylographic indices of the dif- ferent raw materials and mixtures, whose composition is shown in table 1, are re- ported in fig. 1. CS and RF presented the highest pasting viscosity (PV) values, and CS showed the highest potential retrogra- dation ability – underlined by the gel set back values (SB, 877±47BU) – indicating their tendency to form strong gels. On the contrary, WRF, characterized by an amylose content of 0.7 g/100 g db, exhibited a lower pasting temperature if compared with RF (65° and 74°C, respectively) and the low- est increase of viscosity during the cooling phase (SB, 370±11BU). The presence of WRF in the mixtures thus determined a SB reduction, dependent not only on the total starch amount of the samples but also on the properties of the raw material used. Rice bran – presenting the lowest total starch content and the highest level of fibre – did not form a gel in the experimental condi- tions adopted during the MVA test. Thus,
Table 1 - Raw material characterization.
Sample Moisture Protein Total starch Amylose
(g/100 g) (g/100 g db) (g/100 g db) (g/100 g db)
CS 11.05±0.03c - 97.97±1.30c 26.3
RF 9.24±0.01b 8.06±0.04b 86.94±1.97b 26.2
WRF 12.31±0.01d 7.22±0.03a 88.61±2.18b 0.7
RB 5.03±0.05a 14.44±0.05c 20.35±0.25a 1.5
Abbreviations used: CS, corn starch; RF, rice flour; WRF, waxy rice flour; RB, rice bran.
Note: values followed by different letters in the same column are significantly different (P<0.05).
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Fig. 2 - Stiffness of the gels stored at 4°C up to 7 days.
Fig. 1 - Pasting properties of the raw materials and their mixtures.
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gluten-free bread
when it was used in combination with CS or RF and embedded into the starchy matrix, an important decrease of viscosity was evi- denced, due to its physical interference dur- ing gel networking.
Gel hardness by compression tests
As evidenced in fig. 2, CS gel evaluated 30 min after production showed the highest consistency (1.20 N/mm), while WRF gel exhibited the lowest one (0.08 N/mm). A significant correlation was found between gel stiffness and viscoamylographic final vis- cosity (r=0.771, P<0.01), indicating that the gels formed into the MVA maintained their properties even when evaluated in different shear conditions. With regards to gel ageing, the consistency of the samples increased at different extents and rates. After 7 days of storage, CS gel was still characterized by the highest stiffness (3.34±0.11 N/mm), and the same was observed for 50CS-50RF gel among the binary mixtures (3.33±0.03 N/mm). CS and RF coupling, actually very frequent in the commercial blends used for gluten-free bread production, originated gels highly given to hardening. When terna- ry mixtures were tested (50CS-25RF-25WRF and 50CS-25RF-25RB), WRF resulted more effective than RB in delaying gel hardening;
in fact, the presence of WRF in the blend determined lower stiffness increase during ageing in comparison to RB, although RB was more effective against gel hardening at t0. Gel stiffness, evaluated after 7 days of storage, was positively correlated (r=0.806;
P<0.05) with the viscoamylographic SB val- ues, indicating how this parameter could usefully predict the retrogradation behav- iour of starchy systems during storage. As retrogradation is one of the main events in-
fluencing bread staling, the monitoring of the viscoamylographic properties of the in- gredients (raw materials and mixtures) used in the gluten-free recipes could represent a convenient tool for improving bread formu- lation.
Viscoelastic properties of gels
Small amplitude oscillatory measurements provide simultaneous information on the elastic (G’, storage modulus) and viscous (G’’, loss modulus) nature of the materials.
In the strain sweep curves, at lower level of strain, G’ exceeded G’’, suggesting a solid- like behaviour of the gels. The heating/
cooling treatments occurring during gel for- mation inside the viscoamylograph, in fact, have induced the networking of the gelati- nized starch. At higher strains, a cross-over point between G’ and G’’ was observed at every storage time for samples WRF, 50RF- 50WRF and 50RF-50RB, whereas for the other gels, characterized by slower retrogra- dation kinetics, the same phenomena was evidenced only after some days of storage, when gels increased their consistency and fractured under the higher strains applied (data not shown).
The highest G’ values were registered for CS
and 50CS-50RF gels, while WRF originated
very weak gels. The addition of WRF both
at 25% (data not shown) or 50% concentra-
tion strongly reduced G’ values of the mix-
tures containing CS or RF. The same effect
was observed also when RB was added to the
mixture, both at 25% (data not shown) and
50%. These data, even if recorded under dif-
ferent testing conditions, are in agreement
with those obtained from the compression
test. In fact, a significant correlation was
found between fresh made gel stiffness and
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G’ (r=0.925, P<0.0001) evaluated at 1Hz, suggesting that both these parameters can be used to monitor gel characteristics. Con- sidering the G’ curves obtained from the
frequency sweep tests at the different ageing times (fig. 3), it was evident how CS, RF and 50CS-50RF curves shifted progressively to- wards higher values, while WRF curves were
Fig. 3 - Storage modulus (G’) of selected gels stored at 4°C for 0 (■), 1 (●), 2 (
*
), 3 (♦
), 4(), 7 (▲) days.
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virtually overlapped, indicating once again the maintenance of constant characteristics over time.
CONCLUSIONS
The high amount of starch included in glu- ten-free baked products is mostly responsible for their quality decay, mainly due to a rapid loss of crumb softness. As highlighted in this study, CS and RF coupling, very frequent in commercial blends for gluten-free bread production, originated gels characterized by high values of stiffness and G’, but highly subjected to hardening, as demonstrated by the sharp increase of this parameter after 7 days of storage. On the contrary, WRF (that contains a limited amount of amylose) and RB (due to its low starch content and its high level of fiber) originated very weak gels and resulted very effective in delaying gel hard- ening. WRF, in particular, came out to be more effective than RB. Both WRF and RB, at 25 and 50% level of substitution, however, strongly reduced stiffness and G’ values of the mixtures containing CS or RF and, for the same gels, G’ curves overlapped up to seven days, indicating very slow hardening kinetics. Therefore, WRF and RB seem to be potentially effective in enhancing the shelf- life of GF baked products when included in the starchy matrix.
The next ongoing step is the identification of the proper amount of WRF and/or RB to be included in GF bread formulations, in order to allow both an appropriate workability of the dough – that may result too sticky, as re- ported by Morita et al. (2002) and by Yi et al.
(2009) – and the maintenance of the softness of the product during a prolonged storage, thus assuring a good consumer acceptability.
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Delcour J.A., Hoseney R.C. “Principles of Cereal Science and Technology”. AACC International, Inc., St. Paul, MN, Usa, 2010.
Hsu S., Lu S., Huang C. “Viscoelastic changes of rice starch suspensions during gelatinization”. Journal of Food Science, 65(2): 215-220, 2000.
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