1. Introduction
4.3 CHALLENGE TEST OF DRY-CURED HAM
The aim of the study was to evaluate the growth of L. monocytogenes in dry-cured hams with and without preservatives (E252). The products were contaminated, sliced and stored at different temperatures (4°C, 10°C, 15°C and 20°C) for 120 days. The different dry-cured hams were analyzed for pH, Aw and L. monocytogenes after 0, 30, 60, 90 and 120 days (T0, T30, T60, T90 and T120).
The values of pH at 4°C are reported in the graphic n.1.
Gaphic n.1: Values of pH at 4°C
The values of pH at 10°C are reported in the graphic n.2.
Gaphic n.2: Values of pH at 10°C
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values 5,87 5,78 5,90 6,05 6,20 Average values 5,94 5,69 5,73 5,79 5,83
Maximum values 5,99 5,90 6,02 6,17 6,31 Maximum values 6,02 5,78 5,81 5,88 5,92
Minimum values 5,75 5,66 5,78 5,93 6,08 Minimum values 5,85 5,60 5,64 5,70 5,74
pH values in MAP dry-cured ham with E252 at 10°C pH values in MAP dry-cured ham at 10°C
5,0 5,5 6,0 6,5 7,0
0 30 60 90 120
Average values Maximum values Minimum values
pH values in MAP dry-cured ham at 10°C
Time(days)
pH
5,0 5,5 6,0 6,5 7,0
0 30 60 90 120
Average values Maximum values Minimum values
pH values in MAP dry-cured ham with E252 at 10°C
Time(days)
pH
80
The values of pH at 15°C are reported in the graphic n.3.
Graphic n.3: Values of pH at 15°C
The values of pH at 20°C are reported in the graphic n.4.
Graphic n.4: Values of pH at 20°C
The average values of pH in both dry-cured hams at 4°C and at 10°C were constant for all the 120 days, also considering a standard error of 0,10. The average values of pH decreased in both products stored at 15°C and at 20°C during the shelf-life. If we consider only pH, the values in the graphics n. 1, 2, 3 and 4 could allow the growth of L.
monocytogenes.
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values 6,04 5,75 5,75 5,75 5,74 Average values 5,94 5,75 5,67 5,67 5,62
Maximum values 6,20 5,91 5,91 5,91 5,90 Maximum values 6,02 5,83 5,75 5,75 5,70
Minimum values 5,88 5,59 5,59 5,59 5,58 Minimum values 5,86 5,67 5,59 5,59 5,54
pH values in MAP dry-cured ham with E252 at 15°C pH values in MAP dry-cured ham at 15°C
5,0 5,5 6,0 6,5 7,0
0 30 60 90 120
Average values Maximum values Minimum values
pH values in MAP dry-cured ham at 15°C
Time(days)
pH
5,0 5,5 6,0 6,5 7,0
0 30 60 90 120
Average values Maximum values Minimum values
pH values in MAP dry-cured ham with E252 at 15°C
Time(days)
pH
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values 5,82 5,62 5,50 5,49 5,46 Average values 5,99 5,80 5,72 5,72 5,72
Maximum values 5,91 5,71 5,59 5,58 5,55 Maximum values 6,08 5,89 5,81 5,81 5,81
Minimum values 5,73 5,53 5,41 5,40 5,37 Minimum values 5,91 5,72 5,64 5,64 5,64
pH values in MAP dry-cured ham at 20°C pH values in MAP dry-cured ham with E252 at 20°C 5,0
5,5 6,0 6,5 7,0
0 30 60 90 120
Average values Maximum values Minimum values
pH values in MAP dry-cured ham at 20°C
Time(days)
pH
5,0 5,5 6,0 6,5 7,0
0 30 60 90 120
Average values Maximum values Minimum values
pH values in MAP dry-cured ham with E252 at 20°C
Time(days)
pH
81
The values of Aw at 4°C are reported in the graphic n.5.
Graphic n.5: Values of Aw at 4°C
The values of Aw at 10°C are reported in the graphic n.6.
Graphic n.6: Values of Aw at 10°C
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values 0,911 0,912 0,912 0,912 0,912 Average values 0,906 0,904 0,902 0,904 0,898
Maximum values 0,928 0,928 0,928 0,928 0,928 Maximum values 0,920 0,918 0,916 0,914 0,912
Minimum values 0,895 0,895 0,895 0,895 0,896 Minimum values 0,893 0,891 0,889 0,887 0,885
Aw values in MAP dry-cured ham at 4°C Aw values in MAP dry-cured hamwith E252 at 4°C 0,700
0,750 0,800 0,850 0,900 0,950 1,000
0 30 60 90 120
Average values Maximum values Minimum values
Aw values in MAP dry-cured ham at 4°C
Time(days)
Aw
0,700 0,750 0,800 0,850 0,900 0,950 1,000
0 30 60 90 120
Average values Maximum values Minimum values
Aw values in MAP dry-cured ham with E252 at 4°C
Time(days)
Aw
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values 0,921 0,920 0,919 0,918 0,917 Average values 0,909 0,904 0,898 0,893 0,888
Maximum values 0,934 0,933 0,932 0,931 0,930 Maximum values 0,930 0,924 0,919 0,914 0,909
Minimum values 0,908 0,907 0,906 0,905 0,904 Minimum values 0,888 0,883 0,877 0,872 0,867
Aw values in MAP dry-cured ham at 10°C Aw values in MAP dry-cured ham with E252 at 10°C 0,700
0,750 0,800 0,850 0,900 0,950 1,000
0 30 60 90 120
Average values Maximum values Minimum values
Aw values in MAP dry-cured ham at 10°C
Time(days)
Aw
0,700 0,750 0,800 0,850 0,900 0,950 1,000
0 30 60 90 120
Average values Maximum values Minimum values
Aw values in MAP dry-cured ham with E252 at 10°C
Time(days)
Aw
82
The values of Aw at 15°C are reported in the graphic n.7.
Graphic n.7: Values of Aw at 15°C The values of Aw at 20°C are reported in the graphic n.8.
Graphic n.8: Values of Aw at 20°C
The values of Aw did not allow the growth of the pathogen. The average values of Aw in both dry-cured hams at 4°C and 10°C were constant for all the 120 days. The average values of Aw decreased in both products stored at 15°C and 20°C during the shelf-life.
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values 0,920 0,917 0,913 0,909 0,905 Average values 0,918 0,908 0,893 0,888 0,879
Maximum values 0,932 0,928 0,924 0,921 0,917 Maximum values 0,930 0,920 0,901 0,901 0,891
Minimum values 0,909 0,905 0,901 0,897 0,893 Minimum values 0,905 0,896 0,886 0,876 0,866
Aw values in MAP dry-cured ham at 15°C Aw values in MAP dry-cured ham with E252 at 15°C 0,700
0,750 0,800 0,850 0,900 0,950 1,000
0 30 60 90 120
Average values Maximum values Minimum values
Aw values in MAP dry-cured ham at 15°C
Time(days)
Aw
0,700 0,750 0,800 0,850 0,900 0,950 1,000
0 30 60 90 120
Average values Maximum values Minimum values
Aw values in MAP dry-cured ham with E252 at 15°C
Time(days)
Aw
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values 0,917 0,900 0,883 0,866 0,849 Average values 0,911 0,903 0,895 0,888 0,880
Maximum values 0,933 0,916 0,899 0,882 0,865 Maximum values 0,925 0,917 0,909 0,901 0,894
Minimum values 0,900 0,883 0,866 0,850 0,833 Minimum values 0,897 0,889 0,882 0,874 0,866
Aw values in MAP dry-cured ham at 20°C Aw values in MAP dry-cured ham with E252 at 20°C 0,700
0,750 0,800 0,850 0,900 0,950 1,000
0 30 60 90 120
Average values Maximum values Minimum values
Aw values in MAP dry-cured ham at 20°C
Time(days)
Aw
0,700 0,750 0,800 0,850 0,900 0,950 1,000
0 30 60 90 120
Average values Maximum values Minimum values
Aw values in MAP dry-cured ham with E252 at 20°C
Time(days)
Aw
83
The values of L. monocytogenes at 4°C are reported in the graphic n.9.
Graphic n.9: Values of L. monocytogenes at 4°C
The values of L. monocytogenes at 10°C are reported in the graphic n.10.
Graphic n.10: Values of L. monocytogenes at 10°C
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values log cfu/g 2,814 2,476 2,136 1,800 1,462 Average values log cfu/g 3,089 2,656 2,222 1,789 1,356
Average values cfu/g 651 299 137 63 29 Average values cfu/g 1228 453 167 62 23
L. monocytogenes values in MAP dry-cured ham at 4°C L. monocytogenes values in MAP dry-cured hamwith E252 at 4°C 0
1 2 3 4 5 6 7 8 9 10
0 30 60 90 120
Average values log cfu/g
L. monocytogenes values in MAP dry-cured ham at 4°C
Time(days)
Log cfu/g
0 1 2 3 4 5 6 7 8 9 10
0 30 60 90 120
Average values log cfu/g
L. monocytogenes values in MAP dry-cured ham with E252 at 4°C
Time(days)
Log cfu/g
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values log cfu/g 2,741 2,203 1,664 1,126 0,588 Average values log cfu/g 2,800 2,245 1,690 1,135 0,581
Average values cfu/g 551 160 46 13 4 Average values cfu/g 631 176 49 14 4
L. monocytogenes values in MAP dry-cured ham at 10°C L. monocytogenes values in MAP dry-cured ham with E252 at 10°C 0
1 2 3 4 5 6 7 8 9 10
0 30 60 90 120
Average values log cfu/g
L. monocytogenes values in MAP dry-cured ham at 10°C
Time(days)
Log cfu/g
0 1 2 3 4 5 6 7 8 9 10
0 30 60 90 120
Average values log cfu/g
L. monocytogenes values in MAP dry-cured ham with E252 at 10°C
Time(days)
Log cfu/g
84
The values of L. monocytogenes at 15°C are reported in the graphic n.11.
Graphic n.11: Values of L. monocytogenes at 15°C
The values of L. monocytogenes at 20°C are reported in the graphic n.12.
Graphic n.12: Values of L. monocytogenes at 20°C
The level of contamination of L. monocytogenes decreased during the shelf-life of dry-cured hams with and without preservatives (E252) at all the different temperatures of storage.
The values of the pathogen were similar for both products, there were no relevant differences between the samples.
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values log cfu/g 3,229 2,472 1,715 0,958 0,201 Average values log cfu/g 3,320 2,829 2,339 1,358 0,377
Average values cfu/g 1694 296 52 9 2 Average values cfu/g 2088 675 218 23 2
L. monocytogenes values in MAP dry-cured ham at 15°C L. monocytogenes values in MAP dry-cured ham with E252 at 15°C 0
1 2 3 4 5 6 7 8 9 10
0 30 60 90 120
Average values log cfu/g
L. monocytogenes values in MAP dry-cured ham at 15°C
Time(days)
Log cfu/g
0 1 2 3 4 5 6 7 8 9 10
0 30 60 90 120
Average values log cfu/g
L. monocytogenes values in MAP dry-cured ham with E252 at 15°C
Time(days)
Log cfu/g
Time (days) 0 30 60 90 120 Time (days) 0 30 60 90 120
Average values log cfu/g 3,460 2,430 1,400 0,371 Average values log cfu/g 3,790 2,740 1,690 0,640 0,010
Average values cfu/g 2885 269 25 2 Average values cfu/g 6170 550 49 4 1
L. monocytogenes values in MAP dry-cured ham at 20°C L. monocytogenes values in MAP dry-cured ham with E252 at 20°C 0
1 2 3 4 5 6 7 8 9 10
0 30 60 90
Average values log cfu/g
L. monocytogenes values in MAP dry-cured ham at 20°C
Time(days)
Log cfu/g
0 1 2 3 4 5 6 7 8 9 10
0 30 60 90 120
Average values log cfu/g
L. monocytogenes values in MAP dry-cured ham with E252 at 20°C
Time(days)
Log cfu/g
85