Xu Ning

Bio: Xu Ning is an academic researcher from Hubei University of Technology. The author has contributed to research in topics: Fermentation & Cordyceps. The author has an hindex of 11, co-authored 198 publications receiving 527 citations.

Effects of mixed cultures of Saccharomyces cerevisiae and Lactobacillus plantarum in alcoholic fermentation on the physicochemical and sensory properties of citrus vinegar

Abstract: Alcoholic fermentation is an essential step in producing high-quality vinegar and typically involves the use of pure yeast to initiate fermentation. In this study, two kinds of citrus vinegars were prepared with a pure culture of Saccharomyces cerevisiae and mixed cultures of Saccharomyces cerevisiae and Lactobacillus plantarum , respectively. During the alcoholic-fermentation stage, the contents of formic, lactic, and total organic acids were higher in the mixed cultures than in the pure culture. Mixed cultures citrus vinegar (MCCV) showed higher antioxidant activity than pure culture citrus vinegar (PCCV). The contents of sweet and umami free amino acids in MCCV were higher than those in PCCV. Meanwhile, flavor groups such as esters, alcohols, and aldehydes in MCCV also significantly improved. According to sensory analysis, MCCV showed higher intensity for sweet and umami attributes, as well as flowery and fruity attributes. Thus, mixed cultures of Saccharomyces cerevisiae and Lactobacillus plantarum in alcoholic fermentation can effectively improve the flavor and quality of citrus vinegar, thereby indicating additional economic benefits of fermentation.

Effect of a halophilic aromatic yeast together with Aspergillus oryzae in koji making on the volatile compounds and quality of soy sauce moromi

Abstract: Summary Koji making is an essential step in the production of high-quality soy sauce. In this study, we inoculated koji with a halophilic aromatic yeast (Zygosaccharomyces rouxii) and Aspergillus oryzae and investigated the effects on the volatile compounds and quality of soy sauce moromi. Our results suggest that the optimal yeast inoculation was approximately 1.5 × 106 yeast per gram of koji, and excessive yeast greatly decreased A. oryzae enzyme activity. In comparison with the control group, there were no significant changes in the concentrations of amino nitrogen, total titratable acids, total soluble nitrogen and reducing sugar by extending the fermentation time during the first fermentation month, whereas the concentration of glutamate in the yeast-inoculated sample increased by 46.16% and the arginine concentration decreased by 61.07%. After the second fermentation month, 17, 38 and 38 volatile components were identified by GC–MS in C1, C2 and C5, respectively. Moreover, a large number of volatile components, such as 2-Methoxy-4-vinylphenol, ethyl acetate and 1-Octen-3-ol were found in C2 and C5. And the total contents of volatile compounds in C2 were obviously higher than C5. This work furthers our understanding of the traditional multistrain koji making and provides a new method for enhancing the quality and flavour of soy sauce.

Effect of citrus peel on phenolic compounds, organic acids and antioxidant activity of soy sauce

Abstract: Soy sauce contains a number of bioactive components, which have been shown to possess strong antioxidative properties. Citrus peel (CP) possesses a complex mixture of flavonoids and has also show good antioxidant activity. In this study, we investigated the effect of CP on the dynamic changes of enzymatic activities in the koji and the changes in the phenolic compounds, organic acids, and antioxidant activity of soy sauce during moromi fermentation. The results show that adding CP in koji-making is helpful to increase the β-glycosidase activity and not effect on the activities of other enzymes in the koji. Moreover, the total flavonoid content (TFC), total phenolic content (TPC), contents of aglycone-form isoflavones, polymethoxylated flavones and organic acid, and the antioxidant activity of soy sauce brewed with CP were found to be higher than those of soy sauce brewed without CP during moromi fermentation, which showed strong positive correlation with antioxidant activities. This study suggests that adding CP in koji-making is a simple and effective method to improve functional and bioactive properties of soybean products, which can also avoid the waste of resources.

Screening and characterization of ethanol-tolerant and thermotolerant acetic acid bacteria from Chinese vinegar Pei

Abstract: Acetic acid bacteria (AAB) are important microorganisms in the vinegar industry. However, AAB have to tolerate the presence of ethanol and high temperatures, especially in submerged fermentation (SF), which inhibits AAB growth and acid yield. In this study, seven AAB that are tolerant to temperatures above 40 °C and ethanol concentrations above 10% (v/v) were isolated from Chinese vinegar Pei. All the isolated AAB belong to Acetobacter pasteurianus according to 16S rDNA analysis. Among all AAB, AAB4 produced the highest acid yield under high temperature and ethanol test conditions. At 4% ethanol and 30-40 °C temperatures, AAB4 maintained an alcohol-acid transform ratio of more than 90.5 %. High alcohol-acid transform ratio was still maintained even at higher temperatures, namely, 87.2, 77.1, 14.5 and 2.9% at 41, 42, 43 and 44 °C, respectively. At 30 °C and different initial ethanol concentrations (4-10%), the acid yield by AAB4 increased gradually, although the alcohol-acid transform ratio decreased to some extent. However, 46.5, 8.7 and 0.9% ratios were retained at ethanol concentrations of 11, 12 and 13%, respectively. When compared with AS1.41 (an AAB widely used in China) using a 10 L fermentor, AAB4 produced 42.0 g/L acetic acid at 37 °C with 10% ethanol, whereas AS1.41 almost stopped producing acetic acid. In conclusion, these traits suggest that AAB4 is a valuable strain for vinegar production in SF.

Fermenting liquid vinegar with higher taste, flavor and healthy value by using discarded Cordyceps militaris solid culture medium

Abstract: Cordyceps militaris has entered a large-scale artificial cultivation, and the solid culture medium of Cordyceps militaris are usually discarded. In this study, two kinds of liquid vinegars were prepared with discarded solid culture medium of Cordyceps militaris and rice, respectively. The contents of tartaric, methanoic, lactic and total organic acids were higher in cordyceps vinegar than in rice vinegar. Cordyceps vinegar showed higher antioxidant activity than rice vinegar. Moreover, cordyceps vinegar contained higher cordycepin and adenosine. The contents of sweet and umami free amino acids in cordyceps vinegar were higher than those in rice vinegar. Meanwhile, flavor groups such as esters and acids in cordyceps vinegar also significantly improved. According to sensory analysis, cordyceps vinegar showed higher intensity for sweet and umami attributes, as well as fruity attributes. Thus, discarded solid culture medium of Cordyceps militaris can be used to ferment liquid vinegar and improve the flavor and quality of vinegar, thereby indicating additional economic benefits of fermentation.

Lactobacillus plantarum with Functional Properties: An Approach to Increase Safety and Shelf-Life of Fermented Foods.

Abstract: Lactobacillus plantarum (widespread member of the genus Lactobacillus) is one of the most studied species extensively used in food industry as probiotic microorganism and/or microbial starter. The exploitation of Lb. plantarum strains with their long history in food fermentation forms an emerging field and design of added-value foods. Lb. plantarum strains were also used to produce new functional (traditional/novel) foods and beverages with improved nutritional and technological features. Lb. plantarum strains were identified from many traditional foods and characterized for their systematics and molecular taxonomy, enzyme systems (α-amylase, esterase, lipase, α-glucosidase, β-glucosidase, enolase, phosphoketolase, lactase dehydrogenase, etc.), and bioactive compounds (bacteriocin, dipeptides, and other preservative compounds). This review emphasizes that the Lb. plantarum strains with their probiotic properties can have great effects against harmful microflora (foodborne pathogens) to increase safety and shelf-life of fermented foods.

Oxidative stress tolerance and antioxidant capacity of lactic acid bacteria as probiotic: a systematic review.

Abstract: Lactic acid bacteria (LAB) are the most frequently used probiotics in fermented foods and beverages and as food supplements for humans or animals, owing to their multiple beneficial features, which appear to be partially associated with their antioxidant properties. LAB can help improve food quality and flavor and prevent numerous disorders caused by oxidation in the host. In this review, we discuss the oxidative stress tolerance, the antioxidant capacity related herewith, and the underlying mechanisms and signaling pathways in probiotic LAB. In addition, we discuss appropriate methods used to evaluate the antioxidant capacity of probiotic LAB. The aim of the present review is to provide an overview of the current state of the research associated with the oxidative stress tolerance and antioxidant capacity of LAB.