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      • Open Access Article

        1 - Diversity of Bacillus species isolated from biofilm of raw milk tankers and dairy processing equipments
        َA. Ansari S. Hanifian
        Bacillus is the dominant genus encloses gram-positive spore-formers that some are considered as a threat to the quality of foods and consumers’ health. This study aimed to explore the occurrence of Bacillus species in raw milk tankers and dairy processing equipmen More
        Bacillus is the dominant genus encloses gram-positive spore-formers that some are considered as a threat to the quality of foods and consumers’ health. This study aimed to explore the occurrence of Bacillus species in raw milk tankers and dairy processing equipments as well as to examine the biofilm-forming ability of the isolates. For this reason, a total of 80 samples consisting of 30 samples obtained from raw milk tankers, 30 samples of dairy processing equipments and 20 samples from various surfaces of the production plant was collected. According to the results, 16.66% of the samples obtained from raw milk tankers, 20% of dairy processing equipments and 40% of surface samples were found positive for Bacillus species. Various species of the Bacillus were found; amongst B. cereus with 36% and B. aloe and B. pumilus with 4% occurrence rate, were the most and least abundant species, respectively. Results of biofilm production revealed that 96% of the isolates were capable of producing biofilm. Eventually, it was concluded that conventional CIP procedure is unable to entirely remove the biofilm of Bacillus species from dairy plant surfaces. Hence, there is a need for a new approach to conquer the problem. Manuscript profile
      • Open Access Article

        2 - Contamination rate and biofilm formation by psychotrophic bacteria from bulk milk tanks and dairy processing equipments
        Rasoul Rezapour Shahram Hanifian
        Psychorotrophs are the heterogeneous group of bacteria that can grow at refrigerator temperatures. Most of these bacteria produce extracellular proteases and lipases which decompose lipids and proteins in milk that leads to undesirable defect in milk. These defects do n More
        Psychorotrophs are the heterogeneous group of bacteria that can grow at refrigerator temperatures. Most of these bacteria produce extracellular proteases and lipases which decompose lipids and proteins in milk that leads to undesirable defect in milk. These defects do not disappear even after pasteurization and sterilization. This study aimed to investigate the occurrence rate and diversity of psychotropic bacteria in raw milk tankers and dairy processing equipments as well as the biofilm-forming ability of the isolates. A total of 80 samples including 30 samples of raw milk tanks, 30 samples of dairy product processing equipments and 20 samples from different surfaces of the production line were collected. According to the results, 26.25% of the samples were found contaminated with psychrotrophic bacteria. Amongst, 65% of the surface samples of production line, 23.33% of the raw milk tanks and 3.3% of the processing equipment were positive for psychrotrophic bacteria. Out of 31 isolates, Bacillus genus had the highest contamination rate (32.25%), whilst Alcaligenes showed the lowest rate (3.2%). The results of biofilm formation revealed that 21 isolates (67.75%) were able to produce biofilm. It was concluded that in some cases, current CIP procedure is not efficient for the entire removal of biofilm from the processing equipments. It seems that it is necessary to apply complementary physical/chemical approaches along with the current CIP procedure to complete obliteration of biofilms from dairy industry. Manuscript profile