Formation of Guaiacol by Spoilage Bacteria from Vanillic Acid, a Product of Rice Koji Cultivation, in Japanese Sake Brewing

Microbial Community Affects Daqu Quality and the Production of Ethanol and Flavor Compounds in Baijiu Fermentation

Daqu is a traditional starter for Baijiu fermentation and is produced by spontaneous fermentation of ground and moistened barley or wheat. The quality of Daqu is traditionally evaluated based on physicochemical and subjective sensory parameters without microbiological analysis. Here, we compared the physicochemical characteristics of qualified (QD) and inferior (ID) Daqu, their microbial communities based on plate counting and PacBio SMRT sequencing of rRNA gene libraries, and their impacts on Baijiu fermentation. The results showed that the glucoamylase and α-amylase activities of QD were significantly higher than those of ID. The counts of yeasts and relative abundances of functional microbes, especially the amylolytic bacterium Bacillus licheniformis and fungi Saccharomycopsis fibuligera and Lichtheimia ramosa, were significantly higher in QD than in ID. The laboratory-scale Baijiu fermentation tests showed that the relative abundances of the amylolytic microbes were higher in the QD than the ID fermentation set, resulting in more efficient fermentation, as indicated by more weight loss and higher moisture content in the former. Consequently, more glycerol, acetic acid, ethanol, and other volatile compounds were produced in the QD than in the ID fermentation set. The results suggest that Daqu quality is determined by, and can be evaluated based on, its microbial community.

Quality relationship between smoked and air-dried bacon of Sichuan-Chongqing in China: Free amino acids, volatile compounds, and microbial diversity

The quality formation of Chinese bacon is closely related to flavor compounds and microbial composition; however, the contribution of microbial to flavor has not been fully explored. Previous studies have focused on the differences in microorganisms and flavor substances in smoked bacon. Thus, this study aims to investigate the relationship among microorganisms, free amino acids (FAAs), and volatile compounds (VOCs) in bacon produced by different drying processes. We analyzed the microbial composition by sequencing the V3-V4 region of the 16S rDNA gene and the fungal ITS2 region and flavor substances using an amino acid analyzer and chromatography-mass spectrometry (GC-MS). Results of taste activity values (TVA) and partial least squares discriminant analysis (PLS-DA) revealed that the flavor components of the two types of bacon had general and specific characteristics, with the key FAAs (glutamic acid, lysine, and alanine) being comparable and the key VOCs being dissimilar. Based on non-metric multidimensional scaling (NMDS) and linear discriminant analysis effect size (LefSe), bacteria had more biomarkers than fungi. Correlation analysis demonstrated that microorganisms, particularly bacteria (Staphylococcus and Salinivibrio), are crucial in regulating and shaping the flavor of bacon. Some sub-abundance of bacteria such as Kocuria enrich the flavor of bacon. These findings indicate that the simultaneous fermentation of multiple microorganisms is conducive to the recreation of the artisan flavor of Chinese bacon.

Diversity of Bacillus Isolates from the Sake Brewing Process at a Sake Brewery

We collected 92 isolates belonging to the genus Bacillus from the sake brewing process at Shiraki Tsunesuke Sake Brewery in Gifu, Japan to determine whether there is strain specificity at individual sake breweries. After distributing the isolates into seven groups, we observed that at least two groups (68 isolates) were kuratsuki bacteria at Shiraki Tsunesuke Sake Brewery. The kuratsuki Bacillus isolates were collected from different samples at the early and late stages of sake brewing in 2021 and 2019, respectively. These results showed that kuratsuki Bacillus entered the sake brewing process at this location. These kuratsuki Bacillus isolates had a high ethanol tolerance. Our previous paper showed the existence of kuratsuki Kocuria at Narimasa Sake Brewery in Toyama, Japan, but this study demonstrated that it is not found at Shiraki Tsunesuke Sake Brewery. Therefore, each sake brewery has specific kuratsuki bacterial strains, which are isolated with high frequency and contribute a specific flavor or taste to each sake brewery.

Heat resistance and genomics of spoilage Alicyclobacillus spp. Isolated from fruit juice and fruit-based beverages

Alicyclobacillus acidoterrestris is a spore-forming bacterium of importance to the fruit juice industry due to its remarkable heat resistance and production of guaiacol taint. Whole genome sequencing analysis reveals species demarcation corresponds to the two major genotypic groups to which A. acidoterrestris isolates belong. Heat resistance was significantly different between genotypic groups 1 and 2 with D₉₀ values of 15.5 and 9.3 min, respectively (p < 0.01). Comparison of squalene-hopene cyclase (shc) encoding sequences reveals non-synonymous changes and the alteration of glutamine residues. Glutamine absence may link to the stability reinforcement of the enzyme structure against thermal denaturation. Genomic islands harbouring heavy metal resistance genes are found in the majority of genotypic group 1 genomes (63%) but occurs in only one genome (5%) of genotypic group 2. Distribution of the genomic islands in the genotypic groups 1 and 2 is also consistent with phylogenetic trees and ANI and dDDH values. Subsequently, we propose genotypic group 1 as a new species closely related to A. acidoterrestris that possesses enhanced heat resistance.

Multiplexed Paper Microfluidics for Titration and Detection of Ingredients in Beverages

Food safety and access to systematic approaches for ensuring detection of food hazards is an important issue in most developing countries. With the arrival of paper-based analytical devices (µPADs) as a promising, rapid, easy-to-use, and low-cost analytical tool, we demonstrated a simple microfluidic-based titration study for the analysis of packaged fruit juices. Similar, to the titration experiments using traditional glassware in chemistry laboratories, in this study the titration experiments were developed using paper microfluidics for the analysis of several analytes such as pH, vitamin C, sugars, and preservatives present in the packaged fruit juices. The allergen found commonly in dairy based mixtures and the non-pathogenic biochemical component responsible for food spoilage in cider based fruit juices were also determined. The results obtained using paper microfluidics were compared with those obtained using a conventional spectrophotometric technique. Finally, a paper microfluidics based multiplexed sensor was developed for the analysis of common nutritional ingredients, an allergen, and a non-pathogenic byproduct present in packaged fruit juices on a single platform. Overall, the results presented in this study reveal that the proposed paper microfluidic assisted colorimetric multiplexed sensor offers a quick and reliable tool for on-spot routine analysis for food safety applications.

Smoke from simulated forest fire alters secondary metabolites in Vitis vinifera L. berries and wine

The exposure of Vitis vinifera L. berries to forest fire smoke changes the concentration of phenylpropanoid metabolites in berries and the resulting wine. The exposure of Vitis vinifera L. berries (i.e., wine grapes) to forest fire smoke can lead to a wine defect known as smoke taint that is characterized by unpleasant "smoky" and "ashy" aromas and flavors. The intensity of smoke taint is associated with the concentration of organoleptic volatile phenols that are produced during the combustion-mediated oxidation of lignocellulosic biomass and subsequently concentrated in berries prior to fermentation. However, these same smoke-derived volatile phenols are also produced via metabolic pathways endogenous to berries. It follows then that an influx of exogenous volatile phenols (i.e., from forest fire smoke) could alter endogenous metabolism associated with volatile phenol synthesis, which occurs via the shikimic acid/phenylpropanoid pathways. The presence of ozone and karrikins in forest fire smoke, as well as changes to stomatal conductance that can occur from exposure to forest fire smoke also have the potential to influence phenylpropanoid metabolism. This study demonstrated changes in phenylpropanoid metabolites in Pinot noir berries and wine from three vineyards following the exposure of Vitis vinifera L. vines to simulated forest fire smoke. This included changes to metabolites associated with mouth feel and color in wine, both of which are important sensorial qualities to wine producers and consumers. The results reported are critical to understanding the chemical changes associated with smoke taint beyond volatile phenols, which in turn, may aid the development of preventative and remedial strategies.