mohammad bagher habibi

In this study, the effect of different inoculum concentrations of E. faecium subsp. faecium strains on chemical, microbial and sensory properties of doogh was evaluated during two months of storage at 4 and 25°C. As compared with the control samples, samples containingstrain 1 of E. faecium subsp. faeciumand strain 2 of E. faeciumsubsp. faeciumat concentrations of 106 and 108 cfu/ml showed that decreasing of pH and increasing of acidity in the first month of storage.Also, inoculated samples of doogh with E. faecium subsp. faecium strains showed a significant decrease (p˂0.05) in the enumeration of molds and yeasts, coliform and mesophilic microorganisms at both storage temperatures (4 and 25°C). Among the samples, inoculated doogh sample with strains of E. faecium subsp. faecium with concentration of 108 cfu/ml was more effective in reducing the unwanted microbial load. Samples of inoculated doogh with concentration of 108 cfu/ml at 4 °C had an acceptable shelf life up to 50 days, while it was 40 days for the same control sample counterpart. Sensory evaluation showed that inoculated doogh samples were more acceptable than control doogh samples stored at 4°C. Generally, the E. faecium subsp. faecium strains, due to more decreasing of pH and higher acidification, reduced microbial load, and have a positive effect on sensory properties then can be used as a co-culture in the production of fermentation dairy products.

In this study the effect of Biopolymer/Saqez resin (SR) particle composites which were prepared by incorporating micronized SR particles alone and in combination with egg white, inulin, WPC and sodium caseinate biopolymers in yogurt gel matrices was evaluated. Microscopic observations were conducted to determine the structural features of the SR composites. The findings were combined with data on textural properties, syneresis and pH values to discuss the physicochemical properties of the yogurt gels, which differed substantially depending on the type of biopolymer involved in gel network structure development. A mechanism is put forward to explain the role of SR particles as filler materials of biopolymer gel matrices that can improve physicochemical properties of yogurt and its stability during storage time if incorporated with adapted biopolymers and if applicated alone doesn’t have good interaction with yogurt network . Among all used biopolymers Inulin and Egg white biopolymers have best inetractions with saqez resin and inhibited from flocculation of resin, in comparison with control samples (INY & EGY) they increased hardness and consistency at least 10 and 13 % respectively, decreased seneresis at least 2% and pH maintained constant in storage time.

One of the pathogenic bacteria species in the genus of Lactococcus is Lactococcus garvieae. It causes human disease (endocarditis) and mastitis in dairy cows to appear. The presence of these bacteria in the raw milk products like Lighvan cheese was reported. Lighvan cheese is a traditional cheese which is made from raw sheep's milk.In this study, fresh milk, curd, Fresh cheese and ripe cheese, and fresh grass Lighvan area was used to isolate bacteria. Biochemical tests at 10°C and 45°C and grow in salt concentration 4% and 6.5 %, was performed. After extraction of DNA, PCR reaction with primers for genes of Lactococcus 16S rRNA performed and the products were sequenced by the company Source BioScience England, then in gene databases NCBI, the sequence of which more than 97% were similar in terms of genus and species were identified.At first, 1500 colonies similar to Lactococcal genera isolated from different sources such as fresh grass, fresh milk, curd, fresh cheese and ripened cheese according to colony morphology. Then, the 625 isolates were selected by gram stain. The biochemical tests carried out to select 60 isolates of Lactococcal genus and the PCR was used to determine the 16S rRNA gene sequence region to identify species. Based on molecular identification 50 species, were belonged to the Lactococcal genera and finally two species of Lactococcus were Lactococcus garvieae.According to the results, the presence of two species of Lactococcus garvieae (fresh milk and curd) was demonstrated in the early stages of Lighvan cheese production, But, there was no presence of the bacteria in fresh cheese and ripened cheese.