Prevalence of Some Deteriorating Microorganisms in Some Varieties of Cheese

Aim: This work throws light on the deteriorating microorganisms in some varieties of cheeses [hard cheese (Ras cheese), and processed cheese]. Material and Method: Thirty Ras cheese and processed cheese samples were collected randomly and subjected to chemical & microbiological examination to determine its contamination with deteriorating microorganisms. Results: Chemical examination showed that the mean titratable acidity % of Ras and Processed cheese samples were 0.5 ± 0.073 and 0.93% ± 0.062%, respectively, while salt % were 3.4 ± 0.078 and 1.03% ± 0.05%, respectively. Most of samples were contaminated with high numbers of Coliforms, yeast, mold, proteolytic, lipolytic and Enterococci. Conclusion: There are poor hygienic measures during production, processing and handling of cheese.

riety of spoilage microorganisms in dairy foods due to practices used in production, formulation, processing, packaging, storage, distribution, and handling [1].
Fermentation of lactose lower pH acts as a preservative and allows desirable microflora to restrict undesirable microorganisms growth; adding salt to reduce the water activity (aw); packaging with less oxygen and freezing slow spoilage rate of dairy foods [1].
This work was planned to throw light on the deteriorating microorganisms in some varieties of cheeses [hard cheese (Ras cheese), processed cheese].

Sample Collection
Thirty each of hard cheese (Ras), and processed cheese was randomly collected as sold to consumers from dairy shops in Cairo and Giza governorates.

Chemical Examination
Titratable acidity percentage was measured according to [2] and NaCl content according to Volhard method [3].

Microbiological Examination
Preparation of decimal dilutions for the collected samples, Total coliform count with Completed test for E. coli, Total proteolytic count, Lipolytic microorganisms count, Enterococci count, Total Yeast and Total Mold count were examined according to [3] with bio chemical identification of the isolated Coliforms & Enterococci species were examined according to [4]. While yeast species were examined according to [5].

Chemical Examination
Titratable acidity percentage: Increase of titratable acidity is a monitor of freshness and the bacterial activity in milk [1] [6]. While lower pH of milk to less than 4.6 protects the fermented dairy products from contamination with pathogens and considers safe hygienically [7] [8]. Data recorded in Table 1 showed that the mean titratable acidity percentage of the examined Ras and Processed cheese samples were 0.5 ± 0.073 and 0.93% ± 0.062%, respectively. Nearly similar  [9]. Higher results of processed cheese were reported by [10]. Whereas, lower findings of Processed cheese were obtained by [ Nearly similar results in processed cheese were recorded by [9].
While lower obtaining of Ras cheese were recorded by [9].
The variation of salt content in the examined cheese samples is due to the added salt depends on individual dairies, and there is no standard in addition of salt to cheese and the amount of salt relies on discretion of cheese maker [12].
The high salt content in some examined samples can mask the poor bacteriological quality of the raw milk and prevent gas holes formation and off-flavor especially in summer [14].

Microbiological Examination
Coliforms contents (MPN/g): Coliform count is an indicator of possible fecal contamination, microbial quality and reflects the hygienic conditions in the food processing [15]. Regarding the results represented in Table 2, coliform could be detected in all of the examined samples of Ras cheese and Processed cheese, with mean values of 1.2 × 10 10 ± 3.3 × 10 9 and 2.5 × 10 9 ± 6.5 × 10 8 MPN/g in Ras and Processed cheese, respectively.
Lower results of processed cheese were reported by [9] [16] [17]. Lower results amined Ras cheese and processed cheese contain high numbers of coliform.
coli was found in Ras cheese and processed cheese with percentages of 1.61 and 20%, respectively. E. coli is due to fecal contamination, indicates that other pathogens of fecal origin may be found [19]. Results presented in Table 4 illustrated the serological identification of the suspected isolates of E. coli by slide agglutination test. In Ras cheese, the suspected isolates were negative, while in processed cheese one strain out of 14 strains was positive and classified as E. coli O 25 . Escherichia coli is present in the gastrointestinal tract of man and dairy animals. Milk can be contaminated either directly through animal feces or indirectly through contaminated surrounding environment, workers, and equipments. Most strains of E. coli are harmless commensals; some causes human gastrointestinal disease with mild to severe symptoms that may be fatal in high-risk individuals. Moreover, E. coli was reported for cases of pyelonephritis cystitis, pyelitis, peritonitis and appendicitis [20] [21].
Total yeast count: Yeast contamination is economically hazard as it causes Table 3. Incidence of isolated coliforms from the examined samples.
Nearly similar results of Ras cheese were recorded by [9] [17], while lower findings were recorded by [23]. Lower results of Processed cheese were obtained by [11] [24], while higher results were recorded by [9] [17]. According to the Egyptian standards the count of total viable yeast should not exceed 100 cfu/g in hard cheese [25], 100% of Ras cheese samples was disagreed with this standard. This high level may be due to poor hygienic measures during production or using raw materials of bad quality [26].
Total mold count: Presence of mold cause economic losses because it is accompanied by visible spoilage discoloration, off flavor, and rejection of the product, and may be a source of mycotoxins result in outbreaks of human food poisoning and many diseases as cancer, leukemia, and kidney toxicity [31] [32].
Nearly similar findings of Ras cheese were recorded by [17]. Higher obtaining of Ras cheese was recorded by [9], while lower outcomes were reported by [23]. It was found that 33.3 and 56.
67% of the examined Ras cheese and Processed cheese, respectively were highly contaminated with mold and disagree with the Egyptian standards [15] [33] because of the warm weather and inadequate refrigeration, increased species diversity [34]. The fungi contributed to poor cleaning and unhygienic measures during production and handling and post processing contamination [35] [36].
Total lipolytic count: Psychrophilic bacteria like Pseudomonas, Enterobacter, Alcaligenes and some spore-formers produce extracellular lipase enzyme  that is adsorbed on milk fat globules and concentrated in the manufactured cheese. These enzymes hydrolyze triglyceride fat constituents of short chain fatty acids, including butyric, caproic, caprylic, and capric acids resulting in unpleasant odors in milk and rancidity in cheese [39] [45]. Results detected in Table 2 revealed that lipolytic organisms were present in Ras and Processed cheese samples in percentages of 100% and 40%, respectively, with a mean count of 3 × 10 8 ± 1.2 × 10 8 and 16.8 × 10 3 ± 5.4 × 10 3 cfu/g, respectively. Lower results of Ras & Processed cheese were obtained by [11] [44].
Total Enterococci count: Enterococci are useful indicator to the hygienic conditions during food manufacture. The presence of specific virulence factors in some strains of Enterococcus faecalis and to a lesser extent in strains of Enterococcus faecium makes them pathogenic to human [46] [47]. Using contaminated water supply, equipment and unhygienic conditions during the production, handling, and milk processing are the causes for their presence [48] [49] [50]. The given results recorded in Table 2 illustrated that Enterococci were isolated from all examined cheese samples with a mean value of 7.7 × 10 8 ± 7.2 × 10 8 and 4.3 × 10 8 ± 2.7 × 10 8 cfu/g in the examined Ras and Processed cheese samples, respectively. Lower results of Ras cheese were recorded by [17].
Nearly similar findings of processed cheese were recorded by [17], whereas lower results were recorded by [51].