Bacterial diversity of the Thai traditional salt fermented fish with roasted rice bran (Pla-ra) was investigated using classical and molecular approaches. Bacterial population of Pla-ra ranged from 102–106 in solid-state (SSF) and 106–109 CFU/g in submerged (SMF) fermentation types. Halanaerobium spp. and Lentibacillus spp. were the main genera particularly detected when rRNA analysis was applied. Tetragenococcus halophillus were dominant during the final stage in sea salt-recipe samples while Bacillus spp. were found in those rock salt recipes. In contrast, cultural plating demonstrated that Bacillus spp., generally B. amyloliquefaciens, were the dominant genera. In addition, B. pumilus, B. autrophaeus, B.subtilis and B. velezensis shown some relations with rock salt-recipe samples. The main volatile metabolites in all samples were butanoic acid and its derivatives. Key factors affected bacterial profiles and volatile compounds of salt fermented fish were type of salt, addition of roasted rice bran, and fermenting conditions.
Bacterial diversity of the Thai traditional salt fermented fish with roasted rice bran or Pla-ra, in Thai, was investigated using classical and molecular approaches. Pla-ra fermentation could be classified into two types, i.e., solid-state fermentation (SSF) and submerged fermentation (SMF). Bacterial population ranged from 102-106 and 106-109 CFU/g in SSF and SMF, respectively. The rRNA detection revealed that Halanaerobium spp. and Lentibacillus spp. were the main genera present in all types and most stages of fermentation. Tetragenococcus halophillus were dominant during final stage of fermentation in the samples in which sea salt was used as one of the ingredients while Bacillus spp. were found in those that rock salt was used. In contrast, cultural plating demonstrated that Bacillus spp. were the dominant genera. B. amyloliquefaciens were the main species found in all types of Pla-ra whereas B. pumilus, B. autrophaeus, B.subtilis and B. velezensis were specifically associated with the samples in which rock salt was used. The main volatile metabolites in all Pla-ra samples were butanoic acid and its derivatives. Dimethyl disulfide was observed during earlier stage of fermentation under high salt condition with a long fermentation period. Key factors affected bacterial profiles and volatile compounds of salt fermented fish are type of salt, addition of roasted rice bran, and fermenting conditions.
Abstract-Soybean koji is an important ingredient for traditional fermented food in South-East Asia and East Asia. It provides large amount of enzyme from koji mold, Aspergillus oryzae S., to digest nutrients in substrates. This study aimed at production of certain enzymes in soybean koji and potential to be applied for accelerating fish sauce fermentation. Koji containing 60% soybean was used as substrate to investigate the enzyme production by A. oryzae S. The growth of this mold was enumerated by potato dextrose agar. The mycelium development of A. oryzae S. was observed by scanning electron microscope. During koji production, pH of soybean koji increased from 6.32 to 6.07. It was caused by extracellular proteins production. The highest neutral protease, alkaline protease and amylase activities were 84.38, 41.35 and 200 unit/g of dry weight, respectively. Moreover, growing of enzyme activities on soybean koji correlated with the growth of this mold. Electron micrograph showed that spores of A. oryzae S. were formed after 48 h of cultivation period. Additionally, the highest enzymes activities were also shown in this stage.
Safety of food consumption especially pork product is important for consumer in Thailand. This study aims to estimate the pathogenic ability of Salmonella Enteritidis and Salmonella Kentucky isolated from pork products by evaluation heat resistance and survival of these bacteria when exposed to simulated gastrointestinal system. D-value at 50º C of S. Enteritidis and S. Kentucky were 30.49 and 21.55 min, respectively. D 55 of these 2 strains were decreased to 6.49 and 8.22 min, respectively. While D 60 were 2.79 and 2.62 min, respectively. To evaluate the survival of these bacteria in simulated gastrointestinal system, S. Enteritidis and S. Kentucky were exposed to the acid broth system (pH 2.0) and the simulated small intestinal system (bile broth system, pH 6.5). After 110 min of incubation time in acid broth system, the survival rates of S. Enteritidis and S. Kentucky were 80.29% and 82.11%, respectively. Furthermore, the survival rate of S. Enteritidis and S. Kentucky in bile broth system demonstrated that these bacteria were able to resist in the simulated small intestinal system (pH 6.5) due to they showed high survival rate as 86.72% and 102.51%, respectively. As these results, if these bacteria contaminate in food products, it will increase the risk of foodborne disease to consumer. To prevent the risk from Salmonella spp. in these products, the food safety during handling and the appropriate thermal process for these products should be concerned.
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