Contamination of Clostridium perfringens in soy sauce, and quantitative microbial risk assessment for C. perfringens through soy sauce consumption

Moromi mash dysbiosis trigged by salt reduction is relevant to quality and aroma changes of soy sauce

Health concerns related to excessive salt consumption have increased the demand for foods with reduced salt content. However, it is a challenge to perform low salt fermentation of high salt liquid-state (HSL) soy sauce due to the interplay between salt and microorganisms. In this study, ≤12 % (w/v) NaCl led to failed fermentation of HSL soy sauce. At 9 % (w/v) NaCl, amino acid nitrogen decreased to 0.31 g/100 mL, total acid increased to 10.1 g/L, and biogenic amines increased to 904.49 mg/L. With reduced salt, the total number of bacteria (1-2 orders of magnitude) and spoilage bacteria (Bacillus, Kurthia, Staphylococcus saprophyticus, and Lactobacillus pobuzihii) increased, and the total number of functional microorganisms (Weissella, Zygosaccharomyces, and Candida) decreased. Unacceptable volatiles contents were higher in reduced-salt soy sauce than in normal salt soy sauce. Most of the unacceptable volatiles were positively correlated with spoilage bacteria.

Enhancement of microalgal biomass productivity through mixotrophic culture process utilizing waste soy sauce and industrial flue gas

Wastewater treatment plants are indispensable facilities, which emit a massive amount of greenhouse gases. To boost CO₂ mitigation and wastewater treatment performance, mixotrophic microalgae cultivation using wastewater has recently been proposed. In this study, food industry wastewater (waste soy sauce) was applied to Chlorella sorokiniana UTEX 2714 cultivation. By using a medium with 20% (v/v) of 10-fold diluted soy sauce, the biomass and fatty acid methyl ester (FAME) productivity enhanced by 1.93 and 1.76 times, respectively. Biomass productivity increased up to 5.2 times when using medium with high soy sauce content under high-intensity light that inhibits cell growth in photoautotrophic environments. Furthermore, industrial flue gas treatment with wastewater was demonstrated by outdoor semi-continuous cultivation with 42% improved biomass production. Consequently, these results suggest that mixotrophic microalgal cultivation has great potential to address both climate change and water pollution while producing valuable products and can contribute to building a sustainable society.

Quantitative Risk Assessment of Hepatitis a Virus Infection Arising from the Consumption of Fermented Clams in South Korea

This study estimated the risk of hepatitis A virus (HAV) foodborne illness outbreaks through the consumption of fermented clams in South Korea. HAV prevalence in fermented clams was obtained from the Ministry of Food and Drug Safety Report, 2019. Fermented clam samples (2 g) were inoculated with HAV and stored at -20-25 °C. Based on the HAV titer (determined using plaque assay) in fermented clams according to storage, the Baranyi predictive models provided by Combase were applied to describe the kinetic behavior of HAV in fermented clams. The initial estimated HAV contamination level was -3.7 Log PFU/g. The developed predictive models revealed that, when the temperature increased, the number of HAV plaques decreased. The Beta-Poisson model was chosen for determining the dose-response of HAV, and the simulation revealed that there was a 6.56 × 10^-11/person/day chance of contracting HAV foodborne illness by eating fermented clams. However, when only regular consumers of fermented clams were assumed as the population, the probability of HAV foodborne illness increased to 8.11 × 10^-8/person/day. These results suggest that, while there is a low likelihood of HAV foodborne illness from consuming fermented clams across the country, regular consumers should be aware of the possibility of foodborne illness.

Predictive modeling and probabilistic risk assessment of Clostridium perfringens in hamburgers and sandwiches

This study aimed to develop a mathematical model for the survival of Clostridium perfringens in hamburgers and sandwiches and to evaluate their microbial risk. The primary model was developed in hamburgers using 4 strains of C. perfringens at 5, 10, 15, 25 and 37 °C, and the kinetic parameters of the primary model were fitted well with the Weibull model (R ² ≥ 0.95). The secondary model was developed and validated in hamburgers and sandwiches using the Davey model, which was evaluated by B _f , A _f , and RMSE values within the acceptable range. A probabilistic risk model was developed and simulated using @Risk program to estimate the probability of infection (P _inf ) of C. perfringens based on the data on prevalence (n = 100), time, temperature, and consumption of hamburgers and sandwiches (150.00 ± 20.96 g). Based on the simulation model, the mean C. perfringens exposure dose was 0.00976 CFU/g, and the estimated mean P _inf was 1.78 × 10^-13, which was very low in comparison with the current available data. The proposed model and the result can thus be useful to establish risk management options and microbial criteria for C. perfringens contamination in hamburgers and sandwiches.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-01000-z.