Microbial Starter Research Articles

An isolated salt-tolerant Tetragenococcus halophilus 2MH-3 improved the volatile flavor of low-salt fermented fish sauce by regulating the microbial community

The application of low-salt fish sauce is limited by its tendency to spoil easily and inadequate flavor generation. Herein, a salt-tolerant Tetragenococcus halophilus 2MH-3 strain with strong abilities of enzyme production and biogenic amine degradation was utilized as a starter for the production of low-salt fish sauce. Bacterial community analysis revealed discrepancies in microbiota between low-salt fish sauces fermented with (Th group) or without 2MH-3 (LF group). Staphylococcus was the primary genus in the Th group at 1 M fermentation (47.42 %), followed by Psychrobacter (10.82 %), while Tetragenococcus swiftly ascended to the dominant status with a relative abundance of 5.88 % after 3 M fermentation. Conversely, the abundance of Tetragenococcus throughout the LF fermentation period was no significant change. In Th group, 118 volatile components were detected with 21 high-concentration flavor compounds being the primary flavor components (OAV ≥ 1), which were basically produced by Alkaliphilus, Psychrobacter, Tetragenococcus, Bacteroides and Staphylococcus based on the co-occurrence heatmaps after PLS-DA evaluation. Furthermore, the co-occurrence network map demonstrated that the decrease in key biogenic amines such as histamine, putrescine, cadaverine and tyramine, the increase in bacterial diversity, as well as the increase in 21 core volatile flavor compounds (OVA ≥ 1.0), were mainly caused by the addition of T. halophilus 2MH-3 in the low-salt fish sauce. Therefore, T. halophilus 2MH-3 could be utilized as an underlying microbial starter in the industrialization of fish sauce.

Metabolite profiling highlights the effect of microbial intervention in the soaking step of tempe

SummarySoaking of soybeans is an essential step in tempe fermentation. Owing to the uncontrolled microflora, spontaneous soaking during tempe production leads to inconsistencies in tempe quality. Common methods to control it include the addition of acids or microbial starters. Despite knowing the benefits, their impact on tempe's composition was less understood. In this study, prior to tempe fungal fermentation, soybeans were soaked with Lactiplantibacillus plantarum NBRC 101978 and Pichia burtonii NBRC 0844. Tempe samples were subjected to comprehensive analysis using a widely targeted gas chromatography–mass spectrometry (GC–MS) metabolomics approach and evaluation of physical characteristics. A total of 100 metabolites of sugars, amino acids, fatty acids, and organic acids were annotated in all samples. Principal component analysis (PCA) explaining 47.6% of the variance showed that microbial interventions led to alterations in the metabolome of all samples, including the accumulation of amino acids in lactic acid bacteria (LAB)‐soaked soybean tempe and tyramine in yeast‐soaked soybean tempe. Unlike chemically added soaked soybean tempe, microbial intervention significantly reduced the relative intensity levels of several sugars by more than twofold. Furthermore, microbial interventions in the tempe‐soaking step significantly elevated the levels of bioactive metabolites more than twofold. The introduction of microbial interventions in the tempe‐soaking step also influences the physical characteristics of the end product. These findings merit further consideration for tempe development and the food industry.

Lactic and propionic acid bacteria starter cultures for improved nutritional properties of pea, faba bean and lentil

Increasing plant-based food consumption as a sustainable and health-oriented alternative to meat is pivotal. Pulses are rich in proteins, minerals, and vitamins; however, they also contain antinutritional compounds, impairing their nutritional value. This study addresses this challenge through the development and application of four distinct microbial consortia in pulse-based fermentations, featuring lactic acid bacteria or a combination of lactic and propionic acid bacteria. Microbial starters significantly reduced galacto-oligosaccharides in all pulse materials, concurrently degrading vicine and convicine in faba beans, while the impact on tannins in faba beans and lentil was moderate. Fermentation with lactic acid and propionic acid bacteria consortia exhibited notable vitamin B12 production, and the effect on the content of phenolic compounds of the studied pulses was also evidenced. Additionally, genomic analyses discerned distinctive profiles among the samples, elucidating the microbial community dynamics shaping fermentation outcomes. The results of this study proved how fermentation can advance the development of pulse-based products with improved nutritional and sustainability attributes.

Regulatory mechanisms of the microbial starter fortification on the community and flavor characteristics in Doubanjiang

Doubanjiang is a special Chinese seasoning paste produced by mixing broad bean paste with chili paste. Besides the antimicrobial substances, such as capsaicin contained in chili, the microbiota and metabolism are directly developed by the stress effect of abiotic factors that periodically change during the fermentation process. The microbial starter is a promising way to improve the quality of Doubanjiang production. In the present study, the regulatory mechanisms of the microbial starters (Tetragenococcus halophilus, Zygosaccharomyces rouxii, and Candida versatilis) were explored by comparing the microbial community, flavor characteristics and their correlation networks between the fortified and control groups. In comparison to the control group, the volatile compound content increased by 30.77%, with notable increases in phenylethyl alcohol, beta-ionone, etc. Conversely, there was a reduction in non-volatile compounds, including reducing sugar, acidity, amino acid nitrogen, and organic acids. The microbial structure underwent a shift, with an increase in the relative abundance of C. versatilis, while Z. rouxii demonstrated no variance and T. halophilus was not detected. The correlations of the specific microbes and certain flavor compounds were modified by the starter (p < 0.05). Notably, the correlation between Enterobacter/Malassezia and 3-furaldehyde was shifted from a negative to a positive conversion. The observed increase in beta-ionone, ethyl phenylacetate, etc., resulted from the synergistic effects, correlated transformations, and reduction of antagonistic interactions. These findings indicate that the starter powerfully regulates the interactions between microbial communities and metabolic networks, thereby provide valuable insights for the improvement of Doubanjiang quality.

Apple Blossom Agricultural Residues as a Sustainable Source of Bioactive Peptides through Microbial Fermentation Bioprocessing.

This study explored the impact of starter-assisted fermentation on apple blossoms to enhance their potential as a source of antioxidant and antifungal molecules. Fructobacillus fructosus PL22 and Wickerhamomyces anomalus GY1 were chosen as starters owing to their origin and promising ability to modify plant secondary metabolites. An initial assessment through microbiological and physicochemical analyses showed superior outcomes for starter-assisted fermentation compared to the spontaneous process. Enzymatic hydrolysis of proteins, primarily controlled by starters, orchestrated the generation of new low-molecular-weight peptides. W. anomalus GY1 also induced modifications in the phenolic profile, generating a diverse array of bioactive metabolites. These metabolic changes, particularly the release of potentially bioactive peptides, were associated with significant antioxidant activity and marked antifungal efficacy against three common mold species. Our results shed light on the potential of microbial starters to valorize agricultural wastes and convert them into a valuable resource for industry.

Reduction of aflatoxins and ochratoxin A by addition of commercial Koji during fermentation of the Korean traditional soybean paste, Doenjang

Contamination by aflatoxins and ochratoxin A of traditional Korean fermented soybean paste (Doenjang) is a serious food safety issue. In this study, we investigated the inhibitory effects of commercial Koji, a microbial starter culture used for fermentation, on mycotoxin contamination during Doenjang production at in vitro and scaled-up fermentation levels. A commercial Koji dominated by Aspergillus oryzae JI-4 exhibited strong antifungal and antimycotoxigenic activities against aflatoxigenic Aspergillus flavus and ochratoxigenic Penicillium verrucosum both in vitro and in situ. Furthermore, co-inoculation with Koji JI and mycotoxigenic fungi in the early stage of Doenjang fermentation significantly suppressed aflatoxins and ochratoxin A production by more than 93% (p < 0.05) and improved the nutritional properties and sensory qualities of the final product. These results suggest that the addition of commercial Koji could be an effective and practical approach to reduce aflatoxins and ochratoxin A contamination during the fermentation of soybean paste.

Study of the effects of pasteurization and selected microbial starters on functional traits of fermented table olives

Table olives are one of the most known fruit consumed as fermented food, being a fundamental component of the Mediterranean diet. Their production and consumption continue to increase globally and represent an important economic source for the producing countries. One of the most stimulating challenges for the future is the modernization of olive fermentation process. Besides the demand for more reproducible and safer production methods that could be able to reduce product losses and potential risks, producers and consumers are increasingly attracted by the final product characteristics and properties on human health.In this study, the contribution of microbial starters to table olives was fully described in terms of specific enzymatic and microbiological profiles, nutrient components, fermentation-derived compounds, and content of bioactive compounds. The use of microbial starters from different sources was tested considering their technological features and potential ability to improve the functional traits of fermented black table olives.For each fermentation assay, the effects of controlled temperature (kept at 20 °C constantly) versus not controlled environmental conditions (oscillating between 7 and 17 °C), as well as the consequences of the pasteurization treatment were tested on the final products. Starter-driven fermentation strategies seemed to increase both total phenolic content and total antioxidant activity. Herein, among all the tested microbial starters, we provide data indicating that two bacterial strains (Leuconostoc mesenteroides KT 5-1 and Lactiplantibacillus plantarum BC T3-35), and two yeast strains (Saccharomyces cerevisiae 10A and Debaryomyces hansenii A15-44) were the better ones related to enzyme activities, total phenolic content and antioxidant activity. We also demonstrated that the fermentation of black table olives under not controlled environmental temperature conditions was more promising than the controlled level of 20 °C constantly in terms of technological and functional properties considered in this study. Moreover, we confirmed that the pasteurization process had a role in enhancing the levels of antioxidant compounds.

Assessment of Microbial Interactions between Potential Lactic Acid Bacteria Starters and Major Microorganisms During in vitro Fermentation in a Medium Similar to Cocoa Pulp in Côte d'Ivoire

However, uncontrolled or random fermentations carried out in the country by farmers producing marketable cocoa beans of variable quality. The problem of variability in the quality of beans has led to significant economic losses in the country estimated at several billion CFA Francs. The objective of this work was to analyze the interactions between potential starter lactic acid bacteria and the major microorganisms selected during cocoa fermentations in Côte d’Ivoire. The work methodology began with the cultivation of yeast, lactic acid bacteria, acetic acid bacteria and Bacillus strains in their respective YPG, MRS, YEPG and BN media for 48 hours at 30°C. Then, the microbial load of each culture was determined and set at 105 cells/mL. The strains were subsequently placed in the similar interaction medium of cocoa pulp (PSM) alone (monoculture) or together (coculture) for the study of microbial interactions. This study took place over 5 days and samples were taken for analyzes after 0, 48 and 120 hours of incubation at 30°C. The interaction was monitored by assessing microbial growth using optical density and Thoma cell counts for monocultures and agar media for cocultures. Additionally, acid production and reduction in sugar intake were also measured over the 5 days. All crops showed good growth. Growth was greater in cocultures with values ​​ranging from 4.12 log (CFU/mL) to 9.21 log (CFU/mL). In addition, the cocktails acidified the environment much more than the monocultures with values ​​oscillating between 0.10 ± 0.00 and 0.21 ± 0.00. Also, the quantity of sugars in the different broths decreased significantly in the cocktails during the first 48 hours, going from 1.08 ± 0.08 to 0.20 ± 0.01. Microbial starters in monocultures and cocultures have shown their ability to adapt to the environment like cocoa pulp. The high microbial growth, sugar consumption, and acidification of the medium in the cocktails reflected a synergistic interaction between the strains during fermentation when they were together. In short, these strains could be used for a starter composition to control fermentation and obtain good quality beans.

The Common and Unique Microbiota in Sabah’s Traditional Rice Wine Starter Cultures (SASAD)

Rice wine is an alcoholic beverage produced through the fermentation of cereal grains, mainly rice, with microbial starters consisting of fungi and bacteria. However, the microbes in the rice wine starter cultures have never been documented comprehensively except for a few studies that looked into culturable microbes. Hence, their exact core microbiota contents especially those unculturable microbes remained unknown. Therefore, this research aimed to identify the fungal and bacterial communities in sasad through ribosomal amplicon-based next-generation sequencing and analysis that captured both the culturable and unculturable microbiota. The results showed that two fungal phyla (Mucoromycota and Ascomycota) with five genera (Mucor, Rhizopus, Saccharomycopsis, Wickerhamomyces, and Kodamaea) and two bacterial phyla (Proteobacteria and Firmicutes) with 10 genera (Kosakonia, Weissella, Enterobacter, Lactococcus, Pseudomonas, Bacillus, Chromobacterium, Paludibacterium, Enterococcus, and Gluconobacter) were identified as the core microbiota (relative abundance &gt; 1.00%) in the sasad samples. Some of these microbes have been reported in other starter cultures, but some are unique to the sasad (Chromobacterium and Paludibacterium). Hence, this research provides the first comprehensive report on the microbes in sasad and provides important insights into the potential roles of core microbiota. These data may be used to facilitate the development of starter cultures with defined microbial compositions for the consistent production of safe and high-quality rice wines in the future.

Fermentation of Texturized Pea Protein in Combination with Proteases for Aroma Development in Meat Analogues.

The potential use of texturized pea protein in meat analogues was investigated by comparing the effects of fermentation on pea and myofibrillar pork proteins in a model system including additives, microbial starters, and proteases. Model fermentation was controlled for 15 days by a pH decrease and microbial count and free amino acid increase. Besides, volatile production and sensory properties were evaluated at the end of fermentation. Protein type affected free amino acid generation and volatile profile. Models supplemented with proteases showed an increase in amino-acid-derived compounds (branched aldehydes and alcohols) and fruity odor notes. During fermentation, protease addition significantly reduced the production of linear aldehydes (pentanal, hexanal, and octanal) in vegetal models, while pyrazine compounds were not affected. This changes in the volatile profile reduced the legume beany odor but increased the perception of toasted cereal-like notes generated by the texturization process.

Новые биопродукты на молочной и растительной основах и их качественная характистика

Industrial starter cultures and probiotics are part of many functional dairy and plant bioproducts. Starter cultures affect the clot structure of fermented dairy and plant bioproducts. This article introduces new types of dairy and plant probiotic products with their biochemical, microbiological, and rheological properties. The research featured three microbial starter consortia fortified with propionic acid bacteria. Activated propionic acid bacteria Propionibacterium freundenreichii subsp. shermanii AC-2503 served as a control. Dairy, lactose-free, oat, and rice raw materials were used as foundations. The tests including an objective consistency assessment. The viable microbial cell count in the finished bioproducts was as high as 107–108 CFU/cm3. The dairy samples demonstrated the highest viscosity. The plant bioproducts had weak clots, but the starter consortia made them uniform.

Inclusion of autochthonous and allochthonous microbial starters in wet fermentation processes of Coffea arabica L.

All around the world, specialty coffees submitted to fermentation gain economic prominence in the coffee trading sector. This study used two cultivars of Coffea arabica L. growth by Agência Paulista de Tecnologia dos Agronegócios (APTA) on Marilia region (midwest region of São Paulo state, Brazil): cultivar yellow Topázio MG 1190 (YTPMG) and cultivar red Catuai IAC 144 (RCIAC). Both cultivars were submitted to wet fermentation processes in order to: 1) observe the influence of starter cultures and 2) to describe their microbiological and sensorial performances. Sensorial findings were respectively compared to their non-fermented and naturally fermented samples. Equal portions of YTPMG and RCIAC cherries were distributed into different buckets containing 20 L of potable water each, leading to two experiments with 5 treatments, of which T1 was natural fermentation and the others received different combinations of autochthonous or allochthonous yeasts, besides species of commercial lactic bacteria. Laboratorial evaluation included: pH, temperature, soluble solids and microbiological analysis. Sensorial analyses were conducted by experts and Q-graders. The sensory data were submitted to statistical analysis. After 46 h under wet fermentation, the counts of “good” micro-organisms (M.O.) enhanced (yeasts and lactic bacteria) and the “bad” M.O. reduced (enterobacteria), resulting in differentiated aroma among the coffees treatments. Lactic bacteria starters (SACCO Brasil) stimulated yeasts growth during fermentation, while Lactobacillus plantarum (LEMA) inhibited. All the fermented coffee were graded as specialty coffees, reaching more than 80 points, and the highest notes referred to the treatments that included lactic bacteria starters. YTPMG had better cupping notes than RCIAC. Cupping notes were lower than 80 for all non-fermented coffees, indicating that the technology of controlled fermentation including starter cultures is able to ensure exquisite sensorial values and a better placing in the highly competitive market.

The Effect of Variation of Types of Microbial Starters on The Physical Characteristics of Modified Cassava Flour (Mocaf) Rich in Beta-Carotene

&lt;p&gt;The development of beta-carotene-rich mocaf flour as a functional food aims to increase its nutritional content and functional properties as an antioxidant for health. The development of beta-carotene-rich mocaf flour can be optimized through good fermentation methods, especially with the use of starter. This study aims to further analyze the effect of using a type of starter on the mocaf characteristics of cassava species rich in beta-carotene through a comparison of several types of starter. In this study, three types of starter were used, namely the Bimo-CF starter, the Berhasil starter and thse BRIN starter. The results showed that the use of starter during fermentation affected the physicochemical properties of mocaf flour in the form of differences in solubility, increased viscosity and decreased syneresis. Scanning Electron Microscope (SEM) was used to analyze the microstrutural of mocaf flour using starter during fermentation resulted in a more massive reshuffling of starch granules and causes changes in the structure of starch granules that become irregular round in shape with increasingly non-uniform sizes. NIR (Near infrared) and proximate analysis of the content of mocaf flour, showed that the use of the Bimo-CF starter, the Berhasil starter and the BRIN starter during fermentation affected the decrease in moisture content, protein content, ash content, fiber content, phosphorus, and increased fat and dry matter content.&lt;/p&gt;

The Volatile Flavor Substances, Microbial Diversity, and Their Potential Correlations of Inner and Surface Areas within Chinese Qingcheng Mountain Traditional Bacon.

The objective of this study was to explore the microbial diversity, volatile flavor substances, and their potential correlations in inner and surface Chinese Qingcheng Mountain traditional bacon (CQTB). The results showed that there were 39 volatile flavor substances in inner and surface CQTB detected by headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS). Moreover, significant differences in volatile flavor substances between the inner and surface CQTB were observed. Sixteen key volatile flavor substances were screened (OAV > 1), including guaiacol, nonanal, ethyl isovalerate, and others. High-throughput sequencing (HTS) result indicated that Firmicutes, Proteobacteria, and Actinobacteria were the predominant bacterial phyla, and Ascomycota and Mucoromycota were the predominant fungal phyla. Staphylococcus, Psychrobacter, and Brochothrix were the predominant bacteria, and Debaryomyces, Penicillium, and Mucor were the predominant fungal genera. Spearman correlation coefficient analysis suggested that Apiotrichum and Lactobacillus were closely and positively correlated with the formation of key phenol compounds. The present work demonstrates the microbial diversity and related volatile flavor substances and their potential correlations in CQTB and provides a theoretical basis for the development of microbial starter culture and green processing of CQTB.

Production of functional Arabica and Robusta green coffee beans: Optimization of fermentation with microbial cocktails to improve antioxidant activity and metabolomic profiles

Currently, growing recognition of the health benefits associated with functional foods and beverages has increased the demand for products that offer more than just basic nutrition. Coffee is a widely consumed beverage, in which fermentation of green coffee beans contributes to the development of a special aroma and higher levels of antioxidants. The objectives of this study were to optimize the fermentation conditions and simultaneously improve antioxidant activity and metabolites. The conditions optimized by Box–Behnken design (BBD) suggested that the highest total esters, total phenolic content (TPC), and antioxidant activity (ABTS, DPPH, FRAP) could be reached by fermentation at 30 °C for 2 days with 13.25% sucrose (w/w) using a microbial cocktail. Two sets of selective microbial starters, Lactiplantibacillus plantarum TISTR 2265 (LP) and a cocktail of TISTR yeasts with LP (YC-LP), were further considered as powerful starters for solid-state fermentation (SSF) of Arabica and Robusta beans, enhancing antioxidant activity within the first 3 days of fermentation. Arabica beans fermented by LP reached 198.03% TPC, 44.21% ABTS, 90.35% DPPH, and 97.13% FRAP, while Robusta beans fermented by YC-LP showed 108.24% TPC, 204.19% ABTS, 170.71% DPPH, and 59.60% FRAP, higher than an uninoculated starter. The analysis of 41 fermented metabolites revealed the different metabolomic profiles for both coffee beans, offering valuable insight into the correlation between chemical constituents and functional characteristics. This study represents the first comprehensive comparison of the metabolomic profiles of fermented Arabica and Robusta green coffee beans.

GC–MS‐based metabolomics elucidates the impact of cereal‐based microbial starters on the metabolite profile of mahewu prepared from yellow maize

SummaryFermentation of yellow maize using different inocula yields mahewu products with varying compositions. Comprehensive analysis of the metabolites influencing distinctive characteristics of mahewu from sorghum malt (YMSM); wheat (YMW), malted millet (YMMM) and malted yellow maize (YMYM) inocula was investigated using an untargeted gas chromatography high‐resolution time‐of‐flight mass spectrometry (GC‐HRTOF‐MS)‐based metabolomics. Metabolites in mahewu from different inocula included phenols, fatty acid methyl ester (FAME), benzenes, amides, amines, cyclic compounds, fatty acid ethyl esters (FAEEs), esters, ketones and vitamins which differentiated metabolites identified in raw yellow maize (RYM). Principal component analysis (PCA) showed that the mahewu and related inocula were distinguished across PC1 and PC2. The OPLS‐DA result further intensifies the significant (P ≤ 0.05) metabolite causing variations among samples. This study serves as the first report into the metabolome of yellow maize mahewu from different inocula, serving as a foundation for the quality control of mahewu products for further research.

The facilitation between Staphylococcus carnosus M43 and Zygosaccharomyces rouxii Y-8, and as starter on the quality of broad bean paste

Zygosaccharomyces rouxii (Z. rouxii) and Staphylococcus carnosus (S. carnosus) are fundamental taxa in spontaneous bean-based food fermentation, playing a vital role in flavor generation and macromolecule degradation. The present study aimed to investigate the biological mechanisms underlying the interaction between Z. rouxii Y-8 and S. carnosus M43 in BBP (broad bean paste) moromi by mono- and co-culture. It was found that the biomass of Z. rouxii and S. carnosus was higher in co-culture than that in mono-culture (p < 0.05), indicating that a facilitation relationship among them. Moreover, the observed intensity of facilitation (OIF) peaked at 0.479 ± 0.002 under aerobic conditions, which was higher than that under anaerobic conditions (0.147 ± 0.014). Furthermore, the facilitative microbial interaction showed the stability and robustness during co-culture with different inoculum proportions (1:3, 1:5, 1:7, 1:10) and cell passage from 1 to 4 generations. Physical separation co-culture and acetic acid tolerance test revealed that acetic acid played a crucial role in regulating the interaction between Z. rouxii (R2 = 0.6955) and S. carnosus (R2 = 0.7097), with metabolic complementarity and inhibition alleviation as the underlying mechanisms. Additionally, Z. rouxii and S. carnosus as starter could enhance the accumulation of flavor compound, and accelerate the maturity of BBP fermentation. The dissection of interaction between Z. rouxii and S. carnosus provided valuable insights for revealing the complex web of relationships among microbiota and the development of microbial starter in BBP brewing ecosystem.

Autochthonous Microbes to Produce Ligurian Taggiasca Olives (Imperia, Liguria, NW Italy) in Brine

Table olives are considered high-quality food, and Italy has a wealth of varieties and typical features that are truly unique in the world (about eighty cultivars of table olives or dual-purpose olives, four of which are protected by the protected designation of origin—PDO), and it is the second largest European consumer, behind Spain. The Taggiasca olive does not have a PDO, but it is very appreciated not only in the region of production (Liguria), but also in all the Italian regions and abroad. Autochthonous microbes (bacteria, yeasts, and filamentous fungi) are essential in the fermentative processes for brine olive production. However, these microbial communities that colonised the olive drupes are affected by the environmental conditions and the fermentation treatments. Hence the importance of studying and comparing olive microbes from different farms and investigating the relationships between bacteria, yeasts, and filamentous fungi to speed up the deamarisation process. Our results showed that yeasts are dominant relative to lactobacteria in all three brines studied, and Wickerhamomyces anomalus was the most performant fungus for the oleuropein degradation. The latter represents the best candidate for the realisation of a microbial starter.

Microbiological Activity Affects Post-Harvest Quality of Cocoa (Theobroma cacao L.) Beans

Cocoa beans are the basic ingredient to produce chocolate and its derivatives, including cosmetics, foods, and pharmaceutical products. The quality of cocoa beans is greatly affected by post-harvest handling, especially by microbial activity involved in pre-conditioning after they are harvested, including fermentation, drying, and storage. This review aims to provide various factors that affect each stage of post-harvest cocoa beans, process mechanisms, and various latest technologies that can be used to improve the quality of cocoa beans. Microorganisms could be involved in each post-harvest stage and affect the cocoa beans’ quality. However, fermentation was one of the keys to determining the quality of cocoa beans because fermentation involved various microorganisms, such as yeast, lactic acid bacteria, and acetic acid bacteria, which were interrelated primarily to produce precursor flavor compounds. The drying and storage processes were decisive in maintaining quality, especially in preventing mold growth and other microbial contaminants. Various technologies could improve the quality of cocoa beans during post harvest, especially by adding microbial starters during fermentation. Using several technologies of vacuum drying and a controlled atmosphere during storage could maintain the quality of the cocoa beans. However, many challenges must be faced, especially those related to controlling microbial activity during post-harvest. Therefore, post-harvest technology needs to be continuously developed, especially in controlling microbiological activities to improve the quality of cocoa beans effectively.

Untargeted metabolomic profiling of Aspergillus sojae 3.495 and Aspergillus oryzae 3.042 fermented soy sauce koji and effect on moromi fermentation flavor

Aspergillus sojae 3.495 and Aspergillus oryzae 3.042 are essential microbial starters in fermented foods due to their high hydrolytic enzyme activities. However, their metabolic characteristics and differences during soy sauce fermentation are still unclear. This study identified 42 non-volatile differential metabolites based on UHPLC-MS/MS, among which 10 amino acids and derivatives and 4 non-volatile acids were high in A. sojae 3.495 koji, while 3 sugar alcohols, 5 flavonoids, and 4 fatty acids were prominent in A. oryzae 3.042. Further analysis revealed that higher acidic protease (1887.43 U/g) in A. sojae 3.495 and higher glucoamylase (2413.36 U/g) and cellulase (890.78 U/g) in A. oryzae 3.042 dominated the formation of differential metabolites. Metabolic pathway analysis showed that shikimate and phenylalanine metabolic pathways in A. sojae 3.495 were more active and enhanced 3-methyl-butanal and 2-phenylethanal in moromi fermentation. The more prominent pathways of sugar alcohol metabolism and flavonoid biosynthesis in A. oryzae 3.042 koji enhanced 2-methyl-butanoic acid and ethyl 3-methylbutyrate in moromi and significantly elevated reducing sugars (1.56 g/100 mL). Overall, comparative metabolomics elucidated the metabolic framework and flavor formation mechanisms of different inocula in soy sauce koji, providing ideas for scientific control of soy sauce fermentation and multi-strain koji-making for flavor enhancement.