Thermal inactivation kinetics of Bacillus cereus in Chinese rice wine and in simulated media based on wine components

Effects of different lactic acid bacteria on the characteristic flavor profiles of Chinese rice wine

BACKGROUND

It has been well accepted that lactic acid bacteria (LAB) are the main bacterial genera present during the brewing of Chinese rice wine (CRW). LAB plays a decisive role in the flavor quality of CRW; however, its application in CRW has previously been overlooked. Therefore, effects of different LAB as co-fermenter on the flavor characteristics of CRW were investigated.

RESULTS

Co-fermentation of LAB increased the utilization rate of reducing sugar, concentration of lactic acid, amino acid nitrogen and total acidity, as well as the content of volatile flavor compounds. Different LAB doses had little effect on the flavor profiles of CRW, but the species of LAB greatly affected the flavor characteristic. The flavor of CRW co-fermented with Lactococcus lactis was characterized by long-chain fatty acid ethyl esters, while co-fermentation with Weissella confusa highlighted the ethyl esters of low molecular weight and short carbon chains in the resultant CRW. Alcohol compounds were dominant in the CRW co-fermented using Pediococcus pentosaceus.

CONCLUSION

The co-fermentation of LAB increased the number of volatile flavor compounds, especially esters. LAB exhibited great potential in the application of CRW industry to enrich the flavor characteristics and enhance the flavor diversity of the final product. © 2023 Society of Chemical Industry.

Research Progress on Flavor and Quality of Chinese Rice Wine in the Brewing Process

Chinese rice wine (CRW) is a traditional and unique alcoholic beverage in China, favored by many consumers for its rich aroma, unique taste, and complex ingredients. Its flavor is primarily composed of volatile and nonvolatile compounds. These flavor compounds are partly derived from grains and starters (Qu), while the other part is produced by microbial metabolism and chemical reactions during the brewing process. Additionally, ethyl carbamate (EC) in CRW, a hazardous chemical, necessitates controlling its concentration during brewing. In recent years, numerous new brewing techniques for CRW have emerged. Therefore, this paper aims to collect aroma descriptions and thresholds of flavor compounds in CRW, summarize the relationship between the brewing process of CRW and flavor formation, outline methods for reducing the concentration of EC in the brewing process of CRW, and summarize the four stages (pretreatment of grains, fermentation, sterilization, and aging process) of new techniques. Furthermore, we will compare the advantages and disadvantages of different approaches, with the expectation of providing a valuable reference for improving the quality of CRW.

Potential Use of Emerging Technologies for Preservation of Rice Wine and Their Effects on Quality: Updated Review

Rice wine, a critical fermented alcoholic beverage, has a considerable role in different cultures. It contains compounds that may have functional and nutritional health benefits. Bacteria, yeasts, and fungi commonly found in rice wines during fermentation can induce microbial spoilage and deterioration of the quality during its distribution and aging processes. It is possible to control the microbial population of rice wines using different preservation techniques that can ultimately improve their commercial shelf life. This paper reviews the potential techniques that can be used to preserve the microbial safety of rice wines while maintaining their quality attributes and further highlights the advantages and disadvantages of each technique.

Drinking tastes of Chinese rice wine under different heating temperatures analyzed by gas chromatography-mass spectrometry and tribology tests

Drinking tastes and lubrication properties of Chinese rice wine (CRW) under different heating temperatures were studied by tribology tests, gas chromatography-mass spectrometry (GC-MS) and sensory evaluations. CRW's drinking tastes were evaluated by taste panelists. Flavor compounds were detected by GC-MS. Lubrication properties of CRW were measured by tribometer. Drinking tastes changed under different heating temperatures and were the best at 60°C assessed by panelists. Four key compounds, furfural, benzaldehyde, butanedioic acid diethyl ester, and phenylethyl alcohol, were determined by GC-MS affecting drinking tastes of CRW. Their variation trends were consistent with the changes of CRW's tastes. The variation of CRW's lubrication properties had a positive correlation with that of CRW's taste, especially astringency. The lowest friction coefficient implied the best lubrication performance and taste at 60°C. Therefore, it was possible to rapidly evaluate drinking tastes of CRW using tribology technology based on the results. Reasons for temperatures influencing CRW's lubrication properties and drinking tastes were also analyzed in this study.

Flavor Formation in Chinese Rice Wine (Huangjiu): Impacts of the Flavor-Active Microorganisms, Raw Materials, and Fermentation Technology

Huangjiu (Chinese rice wine) has been consumed for centuries in Asian countries and is known for its unique flavor and subtle taste. The flavor compounds of Huangjiu are derived from a wide range of sources, such as raw materials, microbial metabolic activities during fermentation, and chemical reactions that occur during aging. Of these sources, microorganisms have the greatest effect on the flavor quality of Huangjiu. To enrich the microbial diversity, Huangjiu is generally fermented under an open environment, as this increases the complexity of its microbial community and flavor compounds. Thus, understanding the formation of flavor compounds in Huangjiu will be beneficial for producing a superior flavored product. In this paper, a critical review of aspects that may affect the formation of Huangjiu flavor compounds is presented. The selection of appropriate raw materials and the improvement of fermentation technologies to promote the flavor quality of Huangjiu are discussed. In addition, the effects of microbial community composition, metabolic function of predominant microorganisms, and dynamics of microbial community on the flavor quality of Huangjiu are examined. This review thus provides a theoretical basis for manipulating the fermentation process by using selected microorganisms to improve the overall flavor quality of Huangjiu.

Quantitative structure-activity relationships (QSAR) of aroma compounds in different aged Huangjiu

Huangjiu is a traditional wine in China with special taste and flavor. However, changes of aroma compounds during storage of Huangjiu remain unclear. In this study, aroma compounds in Jinse Nianhua Huangjiu of three different storage ages were qualitatively and quantitatively analyzed via headspace solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). Based on odor activity value (OAV), the most important aroma compounds were found to be esters, aldehydes, alcohols, acids, ketones, phenols, and lactones. Even though the types of the aroma compounds were similar in different-aged Huangjiu, the concentrations of some compounds varied. Some aroma compounds' thresholds and OAV in Huangjiu were obtained by AC'Scent Intl. Olfactometer. It showed the key aroma compounds in Huangjiu had a positive correlation with their OAV instead of concentration. Quantitative structure-activity relationship (QSAR) models were developed to predict the flavor thresholds for alcohols, acids, and esters in Huangjiu, with higher accuracy for alcohols (R² = 0.978) and acids (R² = 0.987). This study will provide valuable information to unveil the regulation of Huangjiu flavor from molecular basis. PRACTICAL APPLICATION: The built mathematical model enables to predict changes of aroma compounds in Huangjiu during storage, based on the relationship between the quantum structure parameters of those aroma compounds and the odor activity value of flavor chemicals. This research will contribute to simplifying the wine flavor analysis for wine industry and also help to identify the age of the Huangjiu for customers.

Inactivation kinetics of Bacillus cereus spores by Plasma activated water (PAW)

In recent years, plasma activated water has attracted more attention as a new disinfectant. The purpose of this study was to explore impact of variation of different treatment conditions on the inactivation kinetics of Bacillus cereus spores by PAW. All survival curves showed that the number of spores has decreased rapidly at first, followed by tailing results from the reduction inactivation rate. A linear and two nonlinear models (Weibull and Log-logistic model) were fitted to these data, and Log-logistic model fitted the inactivation of the B. cereus spores best. B. cereus spores in 10⁶ CFU/mL was reduced by 1.62-2.96 log CFU/mL by PAW at 55 °C due to the reactive species generated in PAW. Elevated temperature, lower initial spore concentration, lower bovine serum albumin content, and smaller activation volume of PAW considerably enhanced PAW inactivation of B. cereus spores. These results provide an approach to evaluate the inactivation efficacy of different treatment conditions for PAW.

Characterization of key aroma compounds in Chinese rice wine using gas chromatography-mass spectrometry and gas chromatography-olfactometry

To determine the key aroma compounds in Chinese rice wine (CRW), four types of CRW (YH, JF, SN, and XX) were analyzed by gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), and sensory evaluation. The contributions of the key aroma compounds to the flavor characteristics were determined by partial least squares regression. Sixty-one aroma compounds were detected. Twenty-five components were identified as odor-active compounds. On the basis of their odor active values, 18 odor-active compounds were determined as key aroma compounds. Ethyl isovalerate, ethyl butyrate, ethyl acetate, ethyl hexanoate, and phenylethyl alcohol were key aroma compounds in all four types of wine. The unique key aroma compounds of JF wine were isovaleraldehyde and isoamyl acetate; those of XX wine were 1-butanol, benzaldehyde, ethyl benzoate, ethyl phenylacetate, 2-octanone, and furfural; that of YH wine was ethyl 2-methylbutyrate; and those of SN wine were 1-butanol, 1-hexanol, 2-butenoic acid ethyl ester, and 3-methyl-1-butanol.

Effect of ultrasonication and thermal and pressure treatments, individually and combined, on inactivation of Bacillus cereus spores

Bacillus cereus spores are a concern to the food industry due to their high resistance to processing and their ability to germinate to vegetative cells under suitable conditions. This research aimed to elucidate the mechanisms of Bacillus cereus spore inactivation under ultrasonication (US) combined with thermal (thermosonication, TS) treatments, with pressure (manosonication, MS) treatments, and with thermal and pressure (manothermosonication, MTS) treatments. Electronic microscopy, dipicolinic acid (DPA) release, and flow cytometric assessments were used to investigate the inactivation effect and understand the inactivation mechanisms. The sporicidal effects of the US and thermal treatment were slight, and the MS and TS also showed little inactivation effect. However, ultrasonication promoted the detachment of the exosporium, thereby reducing the spore's ability to adhere to a surface, while the thermal treatment induced a decrease in the electron density in the nucleoid of bacterium, which retained a relatively intact exosporium and coat. MS caused 92.54% DPA release, which might be due to triggering of the germinant receptors or releasing of ions and Ca²⁺-DPA. In addition, the morphological changes such as core hydration and cortex degradation were significant after treatment with MS. The release of DPA and the morphological changes were responsible for the reduction in thermal resistance. The MTS showed a remarkable inactivation effect of 3.12 log CFU/mL reductions after 30 min of treatment. It was the most effective treatment and exhibited a large fraction of damage. In addition, the MTS had a significant impact on the intracellular structure of the spores, with the coat destroyed and the cortex damaged. These results indicated that ultrasonication combined with thermal and pressure treatments had a significant sporicidal effect on Bacillus cereus spores and could be a promising green sterilization technology.