الفهرس 
Introduction
Sensory, chemical and sanitary evaluation of creamOnly 14 pages are availabe for public view
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Abstract
A total of two hundred random samples of cream including raw, pasteurized, sterilized and whipped cream were collected from different dairy shops, farmers, houses, desserts shops and supermarkets in Assiut City. Each sample was put in ice box with thermometer to maintain temperature at 4-5C. The samples were dispatched to the laboratory with a minimum of delay where they were examined.
It is evident that 6(20%) samples of raw cream showed sourness. In the pasteurized one; it was appeared in 11.4% of the examined samples. Concerning bitterness flavor, raw cream samples had the highest incidence of bitterness (93.3%) followed by pasteurized cream 32.9% and 15.7% for whipped cream samples. Only 4 samples of sterilized cream showed bitterness. The cooked flavor was detected in 1(1.4%), 7(23.3%) and 6(8.6%) of pasteurized, sterilized and whipped cream samples, respectively, while raw cream lack it. About the rancidity, it appeared in two samples of pasteurized cream and one sample of sterilized cream. Body defects noticed in four and one out of 30 raw and sterilized cream samples, respectively. It was noticed also in nine and thirteen samples out of 70 pasteurized and whipped creams, respectively.
The fat % in the examined raw, pasteurized, whipped and sterilized cream samples had mean values of 38 ± 1.6 , 23.7 ± 0.9, 12.3 ± 0.7 and 18.4 ± 1.5%, respectively.
Only two samples of raw and whipped cream samples were positive for presence of inhibitory substances in percentages of 6.7 and 2.9%, respectively. In the contrary, all examined samples of pasteurized and sterilized cream were free from any inhibitory substances.
The data represented that the mean value of titratable acidity percentage of examined raw cream samples was 0.04± 0.003. Otherwise, it was 0.04± 0.005 in the whipped cream samples. The mean value of acidity % was 0.03 in both pasteurized and sterilized creams. In addition, results showed that nine samples out of 70 pasteurized creams, fifteen out of 30 sterilized and one sample out of 70 whipped creams proved to be excellent for resazurin reduction test .No samples were found to be of fair, bad or very bad quality in the examined sterilized cream. Only four samples were proved to be of very bad quality that belonged to raw cream.
Aerobic plate count of examined cream samples ranged between 1x105 to 2.2x107 with a mean value of 5 x 106 ± 1.1 x 106 bacteria /g in raw cream. While, in pasteurized cream 55.7% of the samples had counts ranged from 104 to less than 105 /g with a mean value of 7.7 x 104 ± 9 x 103 cfu/g . Moreover, aerobic counts of sterilized and whipped cream were ranged from 6 x 10 to 4.5 x104 and 1.5 x 104 to 2.3 x 107 /g with mean values of 7 x 103 ± 1.7 x 103 and 1.2 x 106 ± 4 x 105, respectively.
The results revealed that 93.3% of the examined raw cream samples contaminated by psychrotrophs with a mean value of 3 x 106 ± 7.9 x105 cfu /g.. Regarding the pasteurized samples, 56 out of 70 samples were contaminated by psychrotrophs with the mean value of 6.6 x 105 ± 1.9 x105 cfu/g. The positive psychrotrophic sterilized cream samples were 56.7%, likewise the mean value was 2.6 x 103 ± 6.9 x102 cfu/g. In whipped cream, psychrotrophs were detected in 70% of the samples and their mean value was of 5.2 x 105 ± 1.6 x105cfu /g.
The pasteurized, sterilized and whipped cream samples were highly contaminated with thermoduric bacteria: 95.7, 100 and 97.1%, respectively. While in raw samples, it could be found in 76.7% only. As well as their mean values were 9.3 x102 ± 1.8 x102 ,1.4 x105 ± 4.6 x104 , 6.4 x104 ± 1.7 x104 and 2.2 x105 ± 4.6 x104 cells/g, respectively, in the above cream samples.
Proteolytic bacterial count was excited in all examined cream samples, represented as 93.3% in both raw and sterilized cream, but with different mean values which reach 3.9 x106 ± 1.1 x106 in raw samples, while in sterilized cream was 2.8 x104 ± 5.9 x103 cfu/g. The incidence of proteolytic bacteria in the examined whipped cream was 91.4% and mean value of 3.9 x106 ± 1.6 x106 / g. Out of 70 pasteurized cream samples 60 were polluted by proteolytic bacteria; the mean of cell counts was 9.2 x105 ± 2.2 x105. The contamination rate of lipolytic bacterial count was very high and closely agreement (93.3, 97.1, 96.7 and 95.7%) in all the investigated cream samples.
By using MPN technique, all raw cream samples were contaminated with coliforms. 35 Out of 70 pasteurized cream samples contained coliforms. Concerning the sterilized cream samples, coliforms counts were in 23.3% of the samples. In the contrary, in whipped cream samples their incidence was 88.6% of the examined samples. Fecal coliforms were detectable in all the examined raw cream samples (100%). In pasteurized cream samples the contamination rate was 38.6%. Its population was high in whipped cream (88.6%). While in sterilized cream, fecal coliforms could be found in one sample only. Referring to E. coli, raw cream samples were the highly contaminated (53.3%) followed by the whipped (40%). However, sterilized cream samples were free from E. coli.
Enterococci were contaminated most of the examined cream samples, but in various percentages, the highest incidence was in raw cream (96.7%) with a mean value of 1.2 x106 ± 2.7 x105 cfu/ g followed by whipped cream in 84.3% and the mean value was 8.1 x104 ± 2.1 x104. In pasteurized samples, the incidence of enterococci was 54.3% and its mean value was 1.5 x104 ± 3.4 x103/g. Otherwise, 6.7% only of examined sterilized cream was polluted by enterococci and the mean value was 1 x102 /g.
The incidence of Staph. aureus was 46.7% in raw cream, 31.4% of whipped cream and 8.6% in pasteurized cream samples, while the examined sterilized cream samples failed detection of Staph. aureus.
Yeasts and molds were present in 76.7, 90, 80 and 94.3% of the examined samples of raw, pasteurized, sterilized and whipped cream, respectively. Both pasteurized and sterilized samples had minimum value of 10 cfu /g and in whipped cream was 20 cfu/g, while it was measured as 103/g in raw cream
The examined raw cream samples were the highly one contaminated with anaerobes (66.7%) followed descending by 60, 22.9 and 16.7% in whipped, pasteurized and sterilized samples, respectively.
E. coli O157 and non O157 using biochemical technique was detected in 70% of raw cream samples comprising 20% for E. coli O157 and 50% for non-157. The organisms found in 13 (18.6%) out of the 70 pasteurized cream samples including 5.7 and 12.9% for O157 and non-O157, respectively. In whipped cream, the incidence of E. coli group was 40%, the non-O157 group was 28.6%, while 8 samples (11.4%) yielded E. coli O157. However, none of the sterilized cream samples were found to harbour the organisms. Serological identification of the different isolates declared the absence of E. coli O157 in all examined cream samples but all the identified cultures were belong to E. coli non- O157.
Fourteen E. coli strains (that were characterized previously as E. coli non-O157 using serological test) were subjected to Multiplex PCR technique and all the strains proved to be negative as E. coli O157. Identification of enterotoxigenic E. coli in a single reaction tube using multiplex PCR could identify EPEC, EAEC, and ETEC strains and the virulence markers for these three categories are well defined.
Salmonella spp.were recovered only in raw and whipped examined cream samples in percentages of 26.7 and 8.6%, respectively. from these presumptive isolates, four (13.3%) and three (4.3%) strains, respectively, were excluded on the basis of serological identification. different identified strains of Salmonella via sero-typing technique were Salmonella typhimurium, S. enteritidis and S. haifa. By using PCR, six strains isolated from raw and whipped creams proved to be positive for Salmonella.
The study revealed that most of examined cream samples are considered in border line of quality, have high counts of most organisms examined and agree too little extent with the Egyptian Standards (in sterilized samples). So, it will be advised to consume this type of cream.
The safety of cream could be improved by the addition of Fennel honey at a concentration of 10% as it considered more active against S. enteritidis than potassium sorbate.
On the 1st and 2nd week of validity , statistical analysis using ANOVA (95%) denoted that there was no significant difference between aerobic plate counts and the three different honey concentrations while at the 3rd and 4th week , lower counts were significantly differ at the P value of < 0.05 among the different concentrations of honey. Very high positive correlation between the psychrotrophic counts of control and the samples of different honey concentrations (highly significance value measured at P value < 0.01). Comparing the counts obtained every week; there was statistical significant difference (P < 0.05) between the fungal survival and the honey cream mixture that declared mainly at the 4th week of storage time.
Regarding the role of fennel honey in improving the shelf life, it could be concluded that all concentrations of honey showing significant decrease of aerobic plate count from the 3rd week of storage of pasteurized cream at 4±1ºC and highly significant decrease from the 1st week for psychrotrophic counts while little effect has been noticed on yeast and mold counts and it significantly decrease at the 4th week of storage. These results proved that honey even at low concentration 1% can extend the shelf life of the examined cream samples a week over the suggested date of validity.
So, the present study advised addition of 1% honey to pasteurized cream samples to improve their microbial quality and extend their shelf life.