Microbial ecology of Australian commercial rice koji and soybean miso

Abstract

Background: Rice koji and miso are growing in popularity globally. This is because of both the unique sensory properties of the foods, and the belief that fermented foods may be beneficial for our health. This study aimed to increase the collective understanding of the physiochemical properties and microorganisms found in rice koji and miso. Results:The microbial communities within rice koji and soybean miso were analyzed using physiochemical, microbiological and metagenomic methods. Metagenomic analysis found Bacillus and Weizmannia were the dominant bacterial genera in rice koji samples, and Tetragenococcus, Staphylococcus and Bacillus predominant in the miso samples.Aspergillus was the predominant fungal genera in all three rice koji samples, and in five of the seven miso samples. Debaryomyces was the dominant genera in one miso sample, while no fungal microorganisms were identified in the other miso sample. The physiochemical analysis found rice koji water activity (A w ) between 0.90 and 0.91 and pH from 5.3 to 5.6. The miso samples showed A w ranging from 0.73 to 0.88, pH between 4.2 and 5.3, and salt concentration from 6.4% to 15.5%. Conclusion:The predominant genera detected and physiochemical properties in each sample varied according to supplier, length of fermentation and ratio of ingredients used.Details of the microorganisms identified in varieties of unpasteurised rice koji and miso can be used to assist producers with food safety processes, manipulate the flavor of the product and enable accurate labeling of the foods.

Population genomics ofAspergillus sojaeis shaped by the food environment

“…For instance, amplicon sequencing of miso samples matured for less than six months and greater than six months all showed the presence of Aspergillus sp. (Allwood et al 2023). Thus, phenotypic differences between AS and AP may not be apparent until later stages of fermentation, where AS may still be metabolically active.…”

Exploring the culinary and health significance of fermented foods: A comprehensive review

“…Miso, a cornerstone of Japanese cuisine, epitomizes the transformative alchemy of fermentation, yielding a savory paste imbued with umami richness. Its allure extends beyond its culinary applications, as miso harbors a constellation of probiotic organisms and bioactive compounds, bestowing upon it potential health-promoting properties [51,52]. The protracted fermentation process, lasting anywhere from several months to years, underscores miso's status as a product of patience and precision.…”

“…Once the miso reaches the desired level of fermentation, it can be transferred to clean jars and stored in the refrigerator to slow down further fermentation. Miso can be used as a seasoning or flavoring agent in soups, marinades, sauces, dressings, and other dishes, adding depth and complexity to the flavor profile [51][52][53][54].…”