الفهرس 
INTRODUTION
Effect of pottSsium sorbate on the keeping of raw milkOnly 14 pages are availabe for public view
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Abstract
Raw milk samples were collected from the experimental station of the depanment limal production, Faculty of Agriculture, Assiut University and dispatched to the atory. Potassium sorbate was added to produce concentrations of 0.00 (control), , 0.30, 0.60, 0.90 and 1.20%. The sample of each concentration was divided into rts, one was stored at 300 C and the other was stored in refrigerator (4 ± 2 0 C). Then raw milk samples of each concentration were examined chemically (C.O.B.test, .T., Acidity %, pH value and Resazurin test) at intervals of 0, 4, 8, 12, 16, 20 and ~ours and microbiologically (Aerobic plate, psychrotrophic, coliforms, enterococci, sts and moulds count) every day until the sample deteriorated.
from the obtained results, it was evident that addition of 0.60, 0.90 and 1.20% assium sorbate increased the shelf-life of raw milk samples stored at 300 C to 20, 24 1 24 hours, respectively. In addition, these samples showed a marked decrease in all crobial counts as compared with sorbate-free samples. The decreasing percentages were ,.00, 85.20, 92.00 and 94.80% (aerobic plate count), 91.40, 94.20, 95.00 and 95.80% sychrotrophic count), 35.14, 70.27, 96.76 and 99.19% (coliforms count), 30.00, 50.00, tOO and 50.00% (enterococci count) and 44.19, 51.16, 93.02 and 95.35% (yeasts & ouIds count) by the use of 0.30, 0.60, 0.90 and 1.20% potassium sorbate, respectively fter 24 hours storage at 300 C. In case of samples stored in refrigerator, the shelf-life rere prolonged to 9 days in sorbate containing samples. Additionally, the microbial aunts were sharply decreased before the deterioration of the raw milk samples to lD.detectable levels.
Another milk sample was sterilized and then divided into 4 groups, each group was inoculated with 24 hours old cultures of one of the followings: B. cereus, Salm. typhimurium, Staph. aureus and E. coli. Potassium sorbate was added in 5 concentrations of 0.00 (sorbate-free), 0.10, 0.30, 0.60, 0.90 and 1.20%. The sample of eachwas divided into 2 portions, the first one stored at 300 C and the second one in refrigerator (4 ± 20 C). The effect of potassium sorbate on the growth of these rganisms was determined daily and compared with sorbate-free samples (0.00%). found that the use of 0.30, 0.60, 0.90 and 1.20% potassium sorbate increased the -life and reduced the rate of B. cereus growth in samples stored at 300 C and
20 C. While, the inhibitory effect of potassium sorbate against Salm. typhimurium was
o
pronounced in samples stored at 30 C as these samples spoiled. At refrigerator
erature (4 ± 20 C), the numbers of Salm. typhimurium were sharply decreased and the ing quality was prolonged in sorbate containing samples as compared with the control
e (sorbate-free sample). Moreover, all sorbate concentrations had a good inhibitory the growth rate of Staph. aureus in samples stored in refrigerator. the numbers of E. coli diminished gradually along the storage days at 300 C til deterioration of samples. However, in refrigerator, E. coli count achieved a . •mum level at the 8 tb., 10th. 13th. 18th. and 25th. day of storage in samples containing 0.10, 0.30, 0.60, 0.90 and 1.20% added sorbate, respectively.
Domiati cheese samples were prepared in the laboratory from pasteurized milk containing 1, 5 and 10% added sodium chloride and to each different concentrations of sorbate were added (0.30, 0.60, 0.90 & 1.20%) besides a sorbate-free sample for each concentration of sodium chloride which is taken as a control. The sample of each concentration was divided into 2 parts, one was stored at 300 C and the other at refrigerator temperature (4±2 0 C). The samples were examined microbiologically every week upto 8 weeks. The obtained results revealed that, Domiati cheese prepared from milk contained different concentrations of added sodium chloride in combination with different concentrations of added potassium sorbate and kept at different storage temperatures had a great inhibitory effect upon the existing microorganisms
The use of 0.30% added potassium sorbate with 1 % sodium chloride contammg les and stored in refrigerator (4 ± 2 ° C) re~11lted in a high reduction rate (89.46 % ) obic plate count by the end of storage period. In case of psychrotrophs, the count
ly reduced to reach undetectable levels by the end of the 5th. week of storage of
added sorbate with 1 % sodium chloride and stored at 30 ° C. interesting to mention that addition of 0.30% sorbate with 1 % sodium chloride was y effective against coliforms, which could not be detected by the end of the 2nd.
of storage at 30 ° C, and by the end of the 6th. week of storage of samples kept at
°
2 C. Concerning yeasts and moulds, the reduction rate was 95.23% in samples
sorbate with I % sodium chloride by the end of storage
Cooking butter samples were purchased from Assiut City markets and divided into parts to which potassium sorbate was added in 5 different concentrations including 0.00
control), 0.30, 0.60, 0.90 and 1.20%. Each part was subdivided into 2 portions, one stored at refrigeration temperature (4±2°C) and the other at freezing temperature (_6°C), and then examined microbiologically every week upto 8 weeks. from the obtained
evident that the best decreasing percentages of total bacterial and psychrotrophic counts (95.48 & 96.88%), respectively were occurred in 0.30% sorbate¬treated samples stored at _6°C by the end of storage period (8 weeks). Furthermore, in samples containing 0.30% of added potassium sorbate, no coliforms, enterococci, yeasts and moulds could be recovered by the end of the 7th. & 3ut 4th. & 3r.d. and 5th. & 4th. weeks of storage at 4±2°C and _6°C, respectively.
Additionally, ice-cream powder was purchased from Assiut City Supermarkets and prepared in the laboratory according to the manufacturer (Egyptian Dairy & Food Company) with addition of 0.00 (control), 0.30, 0.60, 0.90 and 1.20Each sample was divided into 2 portions, one kept at freezing temperature ( _60 C) and the was kept in deep freezer (_180 C) and examined microbiologically weekly upto 8 The total bacterial, psychrotrophic, enterococci, yeasts and moulds counts to undetectable levels gradually upto _60 C and rapidly at _180 C. The rate of aerobic plate count were 98.98, 99.92, 99.97 and 99.98 and 99.57, 99.93, 99.98 and 99.99% in 0.30, 0.60, 0.90 and 1.20% sorbate containing samples stored at _60 C and _180 C, respectively. Psychrotrophic count were undetectable by the end of the 7tlL 6t1l., and 5th. and 5th.. 4th. and 3rd.. week of storage in 0.30, 0.60 and 0.90 & 1.20% sorbate containing samples stored at _60 C and _180 C, respectively. In addition, no enterococci could be detected by the end of the 2nd.- week in all sorbate concentrations stored’ at _60 C or _180 C (100% reduction rate) except 0.30% sorbate containing sample stored at _60 C where the reduction rate was 66.67 % by the end of the 3rd.. week. Also,
yeasts and moulds count was sharply decreased to undetectable levels by the end of the 8th. 7t!L 6th. & 6th. and 6th.. 5th.. 5th. & 5th. week of storage in freezer (_60 C) and deep freezer (_18°C) with added 0.30, 0.60, 0.90 and 1.20% potassium sorbate, respectively .
. So, the most effective concentration is 0.30% sorbate containing samples stored in freezer (_60 C) with longer storage time.
Addition of 0.10, 0.30, 0.60, 0.90 and 1.20% potassium sorbate to milk used for yoghurt manufacture, affect the yoghurt cultures. The yoghurt accepted its normal consistency by using of 0.10 and 0.30% potassium sorbate but the other concentrations (0.60, 0.90 & 1.20%) prevent the coagulation process. Moreover, psycbrotrophs, coliforms, enterococci, yeasts and moulds could not be detected in all sorbate containing samples as well as the control one (sorbate-free sample).
% potassium sorbate.
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