The Growth of Yeast and Fungi, the Formation of β-Glucan, and the Antibacterial Activities during Soybean Fermentation in Producing Tempeh

Microbiological, sensory, and chemical properties of high-quality tempeh made with instant Mosaccha tempeh inoculum powder

The combination of Saccharomyces cerevisiae and Rhizopus oligosporus liquid inoculum has been successfully used to ferment soybeans into tempeh that contains β-glucan. However, using the liquid inoculum of these two microbes as a starter is impractical; so, developing an instant tempeh dry inoculum in powdered form, called the Mosaccha inoculum powder, for ease of use is necessary. This study aimed to determine the best concentration of instant Mosaccha inoculum powder to produce high-quality Mosaccha tempeh. The study used a Complete Randomized Block Design with seven different levels of instant Mosaccha inoculum powder percentage, ranging from 0.3% to 1.8% (w/w). A commercial tempeh inoculum, RAPRIMA, amounting to 0.2%, was used as control. Then, the microbiological (total mold and total yeast) and sensory (color, aroma, texture, and taste) properties were evaluated. The data obtained was analyzed statistically using analysis of variance (ANOVA) and Honestly Significant Difference (HSD) tests at the 5% level. The results showed that the percentage of instant Mosaccha inoculum powder significantly affected the microbiological and sensory properties of Mosaccha tempeh. A concentration of Mosaccha inoculum powder between 0.6% to 1.8% could produce good quality Mosaccha tempeh, but the best Mosaccha tempeh was produced with 1.5% instant Mosaccha inoculum powder, which met the Indonesian National Standards (SNI) 3144:2015, had a very favorable taste, and contained 0.49% β-glucan. Therefore, Mosaccha inoculum in powdered form can be developed and used as a starter in making high-quality tempeh that contains β-glucan.

Soybean fermentation: Microbial ecology and starter culture technology

Fermented soybean products, including Soya sauce, Tempeh, Miso, and Natto have been consumed for decades, mainly in Asian countries. Beans are processed using either solid-state fermentation, submerged fermentation, or a sequential of both methods. Traditional ways are still used to conduct the fermentation processes, which, depending on the fermented products, might take a few days or even years to complete. Diverse microorganisms were detected during fermentation in various processes with Bacillus species or filamentous fungi being the two main dominant functional groups. Microbial activities were essential to increase the bean's digestibility, nutritional value, and sensory quality, as well as lower its antinutritive factors. The scientific understanding of fermentation microbial communities, their enzymes, and their metabolic activities, however, still requires further development. The use of a starter culture is crucial, to control the fermentation process and ensure product consistency. A broad understanding of the spontaneous fermentation ecology, biochemistry, and the current starter culture technology is essential to facilitate further improvement and meet the needs of the current extending and sustainable economy. This review covers what is currently known about these aspects and reveals the limited available information, along with the possible directions for future starter culture design in soybean fermentation.

Enhancing food safety in soybean fermentation through strategic implementation of starter cultures

Fermented soybean products have played a significant role in Asian diets for a long time. Due to their diverse flavours, nutritional benefits, and potential health-promoting properties, they have gained a huge popularity globally in recent years. Traditionally, soybean fermentation is conducted spontaneously, using microorganisms naturally present in the environment, or inoculating with traditional starter cultures. However, many potential health risks are associated with consumption of these traditionally fermented soybean products due to the presence of food pathogens, high levels of biogenic amines and mycotoxins. The use of starter culture technology in fermentation has been well-studied in recent years and confers significant advantages over traditional fermentation methods due to strict control of the microorganisms inoculated. This review provides a comprehensive review of microbial safety and health risks associated with consumption of traditional fermented soybean products, and how adopting starter culture technology can help mitigate these risks to ensure the safety of these products.

Sustainable production and pharmaceutical applications of β-glucan from microbial sources

β-glucans are a large class of complex polysaccharides found in abundant sources. Our dietary sources of β-glucans are cereals that include oats and barley, and non-cereal sources can consist of mushrooms, microalgae, bacteria, and seaweeds. There is substantial clinical interest in β-glucans; as they can be used for a variety of diseases including cancer and cardiovascular conditions. Suitable sources of β-glucans for biopharmaceutical applications include bacteria, microalgae, mycelium, and yeast. Environmental factors including culture medium can influence the biomass and ultimately β-glucan content. Therefore, cultivation conditions for the above organisms can be controlled for sustainable enhanced production of β-glucans. This review discusses the various sources of β-glucans and their cultivation conditions that may be optimised to exploit sustainable production. Finally, this article discusses the immune-modulatory potential of β-glucans from these sources.

Comparative study of solid-state fermentation with different microbial strains on the bioactive compounds and microstructure of brown rice

The effects of solid-state fermentation (SSF) with Lactiplantibacillus plantarum, Saccharomyces cerevisiae, Rhizopus oryzae, Aspergillus oryzae, and Neurospora sitophila were determined on the bioactive compound content and grain microstructure of brown rice (BR). After SSF, the β-glucan, arabinoxylans, γ-oryzanol, thiamine, riboflavin, phenolic, and flavonoid contents increased by 147, 11.2, 30.5, 16.9, 21.1, 76%, and 49.6%, respectively, indicating a marked increase in bioactive compound content. In addition, the water-soluble dietary fiber and arabinoxylan contents, and free phenolic and flavonoid contents significantly increased (p < 0.05). These changes were consistent with the microstructural changes observed after SSF, i.e., the outer cortex was rough, cracked, porous and separated from the starch endosperm, which was also cracked and porous; this should increase the dietary bioavailability of the bioactive compounds. SSF, especially with A. oryzae and Lb. plantarum, greatly enhanced the bioactive compound content in BR and has great potential in BR processing.

Nutrition and Sensory Evaluation of Solid-State Fermented Brown Rice Based on Cluster and Principal Component Analysis

Consumption of brown rice (BR) contributes to the implementation of the grain-saving policy and improvement of residents’ nutrient status. However, the undesirable cooking properties, poor palatability, and presence of anti-nutritional factors limit the demand of BR products. To enhance its quality, BR was solid-state fermented with single and mixed strains of Lb. plantarum, S. cerevisiae, R. oryzae, A. oryzae, and N. sitophila. Effects of solid-state fermentation (SSF) with different strains on the nutrition and sensory characteristics of BR were analyzed by spectroscopic method, chromatography, and sensory assessment. Contents of arabinoxylans, β-glucan, γ-oryzanol, phenolic, and flavonoid were significantly increased by 41.61%, 136.02%, 30.51%, 106.90%, and 65.08% after SSF, respectively (p < 0.05), while the insoluble dietary fiber and phytic acid contents reduced by 42.69% and 55.92%. The brightness and sensory score of BR significantly improved after SSF. Furthermore, cluster analysis (CA) and principal component analysis (PCA) were employed to evaluate BR quality. Three clusters were obtained according to CA, including BR fermented for 30 h and 48 h, BR fermented for 12 h, and the control group. Based on PCA, the best SSF processing technology was BR fermented with Lb. plantarum (0.5%, v/w) and S. cerevisiae (0.5%, v/w) at 28 °C for 48 h (liquid-to-solid ratio 3:10).