Enhancement of saltiness perception by odorants selected from Chinese soy sauce: A gas chromatography/olfactometry-associated taste study

Odor-induced saltiness enhancement of volatile compounds screened from duck stewed with chili pepper

Odor-induced saltiness enhancement (OISE) is thought to be a unique salt reduction technique which capitalizes on olfactory-gustatory interaction. Volatile compounds of stewed duck obtained from orthonasal (no-treatment) and retronasal (saliva-treatment) pathways and their capacity on OISE were analyzed by GC-O-MS and molecular simulation in order to ascertain the role of odors in duck stewed with chili pepper on saltiness enhancement. Totally 17 unique volatile compounds were identified in retronasal pathways. Eight salty-congruent volatile compounds were screened from the stewed duck, one of which being E-2-decenal, specific to retronasal volatile compounds following oral enzymatic digestion. These volatile compounds' OISE in NaCl solution was confirmed, and the retronasal pathway effect outweighed the orthonasal one. Molecular docking revealed that volatile compounds interacted with saltiness receptors through hydrogen bonding and hydrophobic force, which may be responsible for its enhanced saltiness. These findings suggest that olfactory pathways and specific odors might simultaneously mediate OISE.

Dynamic effects of ultrasonic treatment on flavor and metabolic pathway of pumpkin juice during storage based on GC-MS and GC-IMS

In this study, the dynamic effects of ultrasonic treatment (0-400 W) on the volatile flavor compounds of pumpkin juice under different storage periods were investigated systematically using a combination of headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS) techniques. A total of 139 and 46 volatile organic compounds (VOCs) were identified by GC-MS and GC-IMS, respectively. The results indicated that complex changes in volatile components occurred during storage. It was found that the content of key volatile components, such as 2-ethylhexan-1-ol and 1-pentanol, decreased significantly, whereas the content of 1-nonanol and menthol increased in the early stage of storage, resulting in the gradual change of the aroma of pumpkin juice from an initial aromatic fruity aroma to an alcoholic and rancid aroma. In particular, it was noted that the 200 W ultrasonic treatment not only effectively promoted the release of volatile components, but also significantly slowed down the generation of undesirable flavor substances during storage, which had a positive effect on the retention of pumpkin juice flavor. Through multivariate statistical analysis and KEGG enrichment analysis, phenylalanine metabolism was found to play a key role in regulating the formation of volatile flavor compounds, further confirming the potential value of ultrasonic treatment in the preservation and processing of pumpkin juice. This provides important theoretical support and practical guidance for the commercial production and processing technology of pumpkin juice and other fruit and vegetable juices.

Research Progress in Saltiness Perception and Salty Substitutes

Salty taste in foods is a key sensory attribute for appetite enhancement, however, consumption of a high salt diet is associated with a high risk of hypertension, stroke, and heart diseases. To address this issue, the World Health Organization (WHO) has recommended reducing the global per capita salt consumption by 30% by 2025, with adults optimally consuming less than 5 g/day of salt. Therefore, the search for new salty substitutes to reduce salt intake in foods has become a research hotspot. Despite the ongoing endeavors of global research, multiple studies have focused on the application of a single category of salty alternatives or food processing quality (such as preservative effects and process characteristics), and there is still little comprehensive evaluation of these alternatives in terms of nutritional value, health impact, and consumer acceptance in the literature. This review will first outline the urgency of global salt reduction, followed by thorough discussion of salty substitutes and associated mechanisms from the perspective of human salty taste perception. Second, the present review will explore the potential application of salty substitutes and highlight the interaction between taste and odor in foods. Additionally, the potential impacts of salty substitutes on human health will be discussed. The present review will provide a scientific basis for the development of low salt products by food industry.

Dynamic changes in microbial communities during sweet flour sauce fermentation and their correlations with physicochemical properties and volatile compounds

Sweet flour sauce is a traditional fermented condiment in China, known for its distinct sweet and savory flavor profile. During the fermentation process, the dominant bacterial genera were Ralstonia and Bacillus, and the dominant fungal genera were Aspergillus, Issatchenkia, Clavispora, and Zygosaccharomyces. In addition, total acidity (TA) and amino acid nitrogen (AAN) in different fermentation stages were determined by the acidometer titration method, and reducing sugar (RS) was determined by the 3,5-dinitrosalicylic acid method. The correlation network revealed TA, RS, and AAN were closely related to multiple microorganisms. TA showed significant positive correlations with Gluconobacter, Candida, and Clavispora. RS was positively correlated with Geotrichum, and AAN was positively correlated with Methylobacterium-Methylorubrum and Zygosaccharomyces. Correlation network analysis was also conducted to show the significant correlations among 2 bacterial genera, 9 fungal genera, and 16 characteristic volatile compounds. In general, the relationships between fungus and volatiles were more significant, with a wide range of yeasts exerting significant functions in forming flavor compounds, whereas most bacteria were negatively correlated with volatiles. Among fungi, Clavispora and Meyerozyma were positively associated with furfural, methional, 5-methyl-2-phenyl-2-hexenal, 2-isopropyl-5-methylhex-2-enal, and benzeneacetaldehyde. Zygosaccharomyces exhibited strong correlations with acetic acid, 2-furanmethanol, phenylethyl alcohol, and 2-methyl-1-butanol. These findings can be used to better understand and manage the fermentation process, making it possible to improve the quality of sweet flour sauce by enriching key microorganisms. PRACTICAL APPLICATION: During the fermentation of sweet flour sauce, the metabolic activities of microbial communities exerted an important function in forming unique sensory and nutritional properties. These findings revealed significant correlations among microorganisms, vital physicochemical indices, and key volatiles, providing a theoretical foundation for regulating the fermentation process, enhancing product qualities, and developing functional strains.

The processing of shaking and standing improves the taste quality of summer black tea

Shaking and standing (SS) enhances the aroma intensity and quality of black tea (BT). However, its contribution to the taste remains unknown, and the interaction mechanism between the aroma and taste perception of black tea is also undisclosed. Here, the metabolomics and sensory evaluation-assisted flavor analysis were employed to investigate the changes in non-volatiles induced by SS, and the interaction mechanism between aroma and taste perception. SSBT exhibited considerable reduced bitterness and astringency intensities compared to BT. Notably, the concentrations of contributing compounds such as catechins, proanthocyanidins, theaflavins, anthocyanins, and flavonol glycosides were decreased in SSBT. Sensory experiments further revealed that nine floral and sweet odorants in SSBT exhibited odor-enhancing interactions. Molecular docking validated the binding affinity and interaction forces between mono/di-ligands and OR1G1/OR52D1. Furthermore, the presence of the nine odorants exerted inhibitory effects on the bitterness and astringency of SSBT. These findings provide a novel perspective on the formation of flavor in SSBT.

Computational approaches for decoding structure-saltiness enhancement and aroma perception mechanisms of odorants: From machine learning to molecular simulation

The unclear relationship between structure and saltiness enhancement limits the development and application of savory odorants. The structure characteristic-saltiness enhancement perception (SEP) mechanisms of savory odorants were investigated by machine learning, molecular docking, and site-directed mutagenesis simulations. The XGBoost model (R2 = 0.96) showed better prediction on the maximum saltiness-enhancement ability of odorants based on their structures. The important features of the odorants contributing to SEP were analyzed by Shapley additive explanations (SHAP). Results showed that phenyl and aldehyde groups had significant positive contributions to SEP, with SHAP values of + 2.94 and + 0.74, respectively. Molecular docking and site-directed mutagenesis simulations elucidated the interaction region, forces, and key sites between savory odorants and olfactory receptors. Results showed TM3, TM5 and TM6 were the main interaction regions of the savory odorants prioritize binding with OR1A1 and OR1D2, resulting in the characteristic aromas. Hydrogen bonding and hydrophobic interactions were the key driving forces. Phe203, Asn109, and Asn155 of OR1A1 were partially important residues involved in the interactions with savory odorants. These findings presented a quick screening approach for savory odorants and revealed their SEP mechanism, providing theoretical guidance to facilitate the application of odor-induced salt reduction in food industry.

Decoding of the enhancement of saltiness perception by aroma-active compounds during Hunan Larou (smoke-cured bacon) oral processing

The enhancement of saltiness induced by odrants perceived from the retronasal cavity during Larou oral processing was analyzed. During the oral processing of Xiangtan Larou, the smoky attribute was the dominant when chewing 0-15 times, followed by the savory (15-24 times) and meaty (24-42 times). Partial least squares analysis predicted 33 aroma compounds from the retronasal cavity significantly (p < 0.05) contributing to the aroma perception. A total of 12 aroma compounds with saltiness-enhancement ability were confirmed by odorant-NaCl mixture model experiments. Results revealed that 2-methoxy-4-vinylphenol (1.00-1000.00 μg/L) had the strongest enhancing effect on saltiness at NaCl (2969.85 mg/L), followed by diallyl sulfide (0.156-2.50 μg/L), 2,5-dimethylthiophene (0.156-50.00 μg/L), 2,6-dimethylphenol (1.00-100.00 μg/L), 2,5-dimethylpyrazine (0.391-50.00 μg/L), and 2,3-butanedione (0.50-100.0 μg/L). The sulfur-containing, nitrogen-containing, and phenolic odorants with savory, roasty, sulfide, meaty or smoky, attributes showed the better ability in saltiness enhancement.

Revealing metabolite profiles in soy sauce and exploring their correlation with umami taste using UPLC-Orbitrap-MS/MS and GC-Tof-MS derivatization

Soy sauce has a rich base of non-volatile substances, but existing studies are insufficient. This study analyzed the metabolites of 19 Chinese commercial soy sauces by UPLC-Orbitrap-MS/MS and GC-Tof-MS derivatization, and detected 674 and 230 kinds of substances, respectively, that could be grouped into 12 different classes of compounds, such as peptides, amino acid derivatives, organic acids, sugars, sugar alcohols, amino acids and so on. For the first time, 215 dipeptides and 91 amino acid derivatives in soy sauce were analyzed in detail and systematically from the perspective of composition and amino acid structure. The flavor profile of soy sauce was obtained by electronic tongue analysis, and orthogonal projections to latent structures (OPLS), random forest (RF), correlation were used to screen potential compounds associated with umami. The intersection of the three methods yielded 9 substances, including 4 reported umami-taste compounds, i.e., Glu, Fru-Glu, Inosine 5'prime-monophosphate (IMP) and Arg-Ser, as well as 5 others that may potentially contribute to umami or be associated with umami-taste producing microorganisms, including His-Asn and Homoserine lactone. This study will advance the understanding of soy sauce metabolites, and provide an in-depth reference for dipeptides and amino acid derivatives in soy sauce.

Chemometrics methods, sensory evaluation and intelligent sensory technologies combined with GAN-based integrated deep-learning framework to discriminate salted goose breeds

The authenticity of salted goose products is concerning for consumers. This study describes an integrated deep-learning framework based on a generative adversarial network and combines it with data from headspace solid phase microextraction/gas chromatography-mass spectrometry, headspace gas chromatography-ion mobility spectrometry, E-nose, E-tongue, quantitative descriptive analysis, and free amino acid and 5'-nucleotide analyses to achieve reliable discrimination of four salted goose breeds. Volatile and non-volatile compounds and sensory characteristics and intelligent sensory characteristics were analyzed. A preliminary composite dataset was generated in InfoGAN and provided to several base classifiers for training. The prediction results were fused via dynamic weighting to produce an integrated model prediction. An ablation study demonstrated that ensemble learning was indispensable to improving the generalization capability of the model. The framework has an accuracy of 95%, a root mean square error (RMSE) of 0.080, a precision of 0.9450, a recall of 0.9470, and an F1-score of 0.9460.

Effectively saltiness enhanced odorants screening and prediction by database establish, sensory evaluation and deep learning method

Odor-taste interaction has gained success in enhancing saltiness perception. This work aimed to provide candidate odorants for saltiness enhancement. Volatile compounds and their frequencies in salty foods were systematically analyzed. The compounds with higher frequency were incorporated into the savory aroma compounds database. The saltiness enhancement concentrations of representative aroma compounds at the NaCl solution (3.00 g/L) were detected by sensory evaluation. SELF-referencing Embedded Strings-based representation leaning and graph attention network combined with Backpropagation Neural Network classifier was utilized to predict the saltiness-enhancing ability of odorants. Results showed that ketones, pyrazine and sulfur-containing compounds showed higher saltiness-enhancing ability. Mushroom and fatty attributes contributed to the saltiness-enhancing ability of aroma compounds. Deep learning model showed excellent generalization ability and accuracy (95.93 %), which provided rapid screening method for selecting savory aroma compounds. This study would provide new pathways for food industry to achieve salt reduction goals.

Key aroma compounds associated with umami perception of MSG in fried Takifugu obscurus liver

Monosodium glutamate (MSG) is a basic representative of umami taste, but it exerts adverse effects as reported in several studies. Enhancing umami perception through aroma-taste interactions is a potentially useful approach as a flavor enhancer to reduce future MSG intake. We identified the aroma compounds in fried Takifugu obscurus liver, then studied the effect of aroma compounds on perceived umami taste using the sensomics approach. A total of 117 volatile compounds were identified from the fried liver. Thereinto, 30 volatile compounds related to five basic tastes were detected by gas chromatography/olfactometry-associated taste analysis. Aroma compounds associated umami, sweet and salty perception in the fried Takifugu obscurus liver showed the potential to enhance umami perception of MSG solutions. Three aldehydes, i.e. heptanal, (Z)-4-heptenal and 2-methylbutanal, significantly enhanced the umami intensity perception of an MSG solution (p < 0.05). The use of aroma compounds to enhance umami perception is considered as a promising tool, further broadening the research area of umami science for application as flavor enhancers in the food industry. In addition, this study also provides an insight into revealing aroma-taste interaction.

A comprehensive review of plant-derived salt substitutes: Classification, mechanism, and application

The diseases caused by excessive sodium intake derived from NaCl consumption have attracted widespread attention worldwide, and many researchers are committed to finding suitable ways to reduce sodium intake during the dietary process. Salt substitute is considered an effective way to reduce sodium intake by replacing all/part of NaCl in food without reducing the saltiness while minimizing the impact on the taste and acceptability of the food. Plant-derived natural ingredients are generally considered safe and reliable, and extensive research has shown that certain plant extracts or specific components are effective salt substitutes, which can also give food additional health benefits. However, these plant-derived salt substitutes (PSS) have not been systematically recognized by the public and have not been well adopted in the food industry. Therefore, a comprehensive review of PSS, including its material basis, flavor characteristics, and taste mechanism is helpful for a deeper understanding of PSS, accelerating its research and development, and promoting its application.

Synthesis, taste characteristics and taste mechanism of N-lactoyl leucine from soy sauce using sensory analysis and UPLC-MS/MS

Recently, amino acid derivatives gradually gained attention, but studies on N-lactoyl-leucine (Lac-Leu) and N-lactoyl-isoleucine (Lac-Ile) are limited. This study aims to explore the contributions of Lac-Leu and Lac-Ile to soy sauce. Lac-Leu and Lac-Ile were synthesized via enzymatic synthesis method catalyzed by Tgase. The mixed solutions containing Lac-Leu were found to have greater taste improvement than those containing Lac-Ile. Sensory evaluation indicated the sour, bitter, and astringent taste of Lac-Leu in water as well as its kokumi, astringent, and umami-enhancing taste in MSG solution. The taste threshold and umami-enhancing threshold of Lac-Leu measured by TDA and cTDA, respectively, were 0.08 mg/mL and 0.16 mg/mL. Molecular docking of Lac-Leu and Lac-Ile with the kokumi receptor CaSR and the umami receptors T1R1 and T1R3 indicated that Lac-Leu had higher affinities with receptors than Lac-Ile. These findings demonstrated the underlying contribution Lac-Leu made to soy sauce, indicating its potential to improve the flavor quality of soy sauce.

Umami and saltiness enhancements of vegetable soup by enzyme-produced glutamic acid and branched-chain amino acids

Introduction

One major challenge of reducing salt content in food is the risk of the overall taste becoming bland. Enhancing saltiness is an effective strategy for salt reduction, and the development of salt-reduced foods using these saltiness-enhancing flavorants as food additives is underway. However, an increasing number of consumers demand a reduction in additives in clean-label foods.

Objective

Enzyme processing of food is an attractive strategy for developing clean-label foods because enzymes are not considered additives. We aimed to improve the saltiness and umami intensity of vegetable soups by enzyme treatment while meeting clean-label requirements. We first optimized the enzymatic reaction conditions of a protease and glutaminase blend and then investigated the synergistic effects of this enzyme blend on the taste of vegetable soup.

Results

Sensory evaluations indicated that the reaction products (e.g., protein hydrolysates or amino acids) could enhance the umami, kokumi, and saltiness intensity of vegetable soup supplemented with 0.5% NaCl. Notably, the saltiness intensity ratio of the enzyme-treated soup with 0.50, 0.45, and 0.40% NaCl were increased by 1.31-, 1.16-, and 0.99-fold, respectively, when this ratio for the control soup with 0.50% NaCl was set to 1.0. This indicates a 20% salt reduction rate can be achieved by enzyme treatment. Moreover, we found that these enhancements were synergically caused by enzyme-produced glutamic acid and branched-chain amino acids.

Conclusion

Our findings suggest that using enzyme blends of bacterial and fungal proteases and glutaminase is an effective approach to enhancing the saltiness levels of vegetable soups while meeting clean-label requirements.

Effects of polyols at low concentration on the release of sweet aroma compounds in model soda beverages

This study investigated the effect of polyols erythritol, d-mannitol, and maltitol on the volatility of aroma compounds γ-butyrolactone, 3-methyl-1-butanol, and 2-phenylethanol in aqueous solution. Headspace solid-phase microextraction/gas chromatography and diffusion-ordered nuclear magnetic resonance techniques were used to obtain information on aroma-food matrix interaction. Results demonstrated that adding polyols at final low concentrations of 5% or 10% (w/w) to an aqueous solution of 2-phenylethanol reduced the release of vapor-phase aromas, except in the case of 3-methyl-1-butanol, which was not affected by the presence of polyols in the liquid matrix. Polyols also reduced the diffusion coefficients of all three aroma compounds, probably due to friction between the molecules. At low polyol concentrations, aroma compound volatility and diffusion coefficient values were altered compared to those of aromas released from pure water. This observation is related to the physicochemical properties of the aroma compounds. These insights may help guide the use of the combination of aroma compounds and polyols in the formulation of sugar-free and reduced-sugar beverages.

Chemical compounds

γ-butyrolactone (PubChem CID: 7302), 3-methyl-1-butanol (PubChem CID: 31260), 2-phenylethanol (PubChem CID: 6054), erythritol (PubChem CID: 222285), d-mannitol (PubChem CID: 6251), maltitol (PubChem CID: 493591).

Progress in Multisensory Synergistic Salt Reduction

Excessive salt intake, primarily from sodium chloride prevalent in modern food processing, poses a significant public health risk associated with hypertension, cardiovascular diseases and stroke. Researchers worldwide are exploring approaches to reduce salt consumption without compromising food flavor. One promising method is to enhance salty taste perception using multisensory synergies, leveraging gustatory, olfactory, auditory, visual, tactile and trigeminal senses to decrease salt intake while preserving food taste. This review provides a comprehensive overview of salt usage in foods, mechanisms of salty taste perception and evaluation methods for saltiness. Various strategies for reducing salt consumption while maintaining food flavor are examined, with existing salt reduction methods' advantages and limitations being critically analyzed. A particular emphasis is placed on exploring the mechanisms and potential of multisensory synergy in salt reduction. Taste interactions, olfactory cues, auditory stimulation, visual appearance and tactile sensations in enhancing saltiness perception are discussed, offering insights into developing nutritious, appealing low-sodium foods. Furthermore, challenges in current research are highlighted, and future directions for effective salt reduction strategies to promote public health are proposed. This review aims to establish a scientific foundation for creating healthier, flavorful low-sodium food options that meet consumer preferences and wellness needs.

Could the aroma of spices produce a cross-modal enhancement of food saltiness and contribute to reducing salt intake?

BACKGROUND

As a result of its correlation with cardiovascular diseases, salt intake must be reduced. According to multi-sensory integration, aroma plays an important role in saltiness enhancement; this could enable a food's salt content to be reduced without losing acceptance. We therefore studied the effect of three spices, Curcuma longa, Laurus nobilis L. and Petroselinum crispum L., on saltiness enhancement through sensory tests on consumers. This was followed by olfactometric analysis with the aim of relating the effect to the spices' aromatic composition.

RESULTS

According to the odour-induced salty taste enhancement (OISE) mean values, bay leaf and turmeric had the highest effect on saltiness enhancement, at a similar level to dry-cured ham aroma, wherwas parsley had a significantly lower OISE value. Only one odour-active compound (OAC), eugenol, showed a direct correlation with the spices' OISE values. Turmeric primarily had OACs with sweet aroma, whereas bay leaf had more OACs belonging to the spicy-aroma category.

CONCLUSION

The three spices, turmeric, bay leaf and parsley, investigated in the present study appear to enhance the salty taste of mashed potato with a low salt content. The results suggest that an interaction effect among OACs with different aromatic ranges may exist. Therefore, when the global OAC modified frequency value, grouped according to aroma range, was considered, the sweet range appears to counteract the effect of the spicy aroma on saltiness. © 2024 Society of Chemical Industry.

High-pressure processing enhances saltiness perception and sensory acceptability of raw but not of cooked cured pork loins-leveraging salty and umami taste

The salt (NaCl) content in processed meats must be reduced because of its adverse effects on cardiovascular health. However, reducing salt in meat products typically leads to a lower taste intensity and, thus, consumer acceptability. Industry interventions must reduce salt content while maintaining taste, quality, and consumer acceptability. In this context, high-pressure processing (HPP) has been proposed to enhance saltiness perception, though there are contradictory reports to date. The present work aimed to conduct a targeted experiment to ascertain the influence of HPP (300/600 MPa) and cooking (71°C) on saltiness perception and sensory acceptability of meat products. HPP treatment (300/600 MPa) did enhance those two sensory attributes (approx. +1 on a 9-point hedonic scale) in raw (uncooked) cured pork loins but did not in their cooked counterparts. Further, the partition coefficient of sodium (PNa+), as an estimate of Na+ binding strength to the meat matrix, and the content of umami-taste nucleotides were investigated as potential causes. No effect of cooking (71°C) and HPP (300/600 MPa) could be observed on the PNa+ at equilibrium. However, HPP treatment at 300 MPa increased the inosine-5'-monophosphate (IMP) content in raw cured pork loins. Finally, hypothetical HPP effects on taste-mediating molecular mechanisms are outlined and discussed in light of boosting the sensory perception of raw meat products as a strategy to achieve effective salt reductions while keeping consumer acceptability.

Mushroom alcohol(1-octen-3-ol)and other 7 aroma compounds selected from Chinese dry-cured hams can enhance saltiness perception

Reducing NaCl content in food while maintaining acceptability poses a significant challenge. Odor-induced saltiness enhancement (OISE) emerges as a promising solution. This study utilized gas chromatography-olfactory (GC-O) in conjunction with gas chromatography-mass spectrometry (GC-MS) to identify 37 key volatile compounds in three representative Chinese dry-cured hams. These compounds had an odor activity value (OAV) of ≥1 or a modification frequency (MF) of ≥30%. Subsequently, quantitative descriptive analysis (QDA) identified eight odorants associated with saltiness. These included 1-octen-3-ol, nonanal, heptanal, 2-methylbutanal, 3-methyl-butanal, benzaldehyde, octanal, and 2,6-dimethylpyrazine. Remarkably, these odorants significantly intensified saltiness (P < 0.05) when added to a low-concentration NaCl solution (0.3%), compared to zero or high concentrations (0.75% and 0.8%). As a result, traditional Chinese salty meat products offer a promising source of odorants for enhancing saltiness, compensating for reduced NaCl content through OISE.

Odorants Identified in Chinese Dry-Cured Ham Contribute to Salty Taste Enhancement

Jinhua dry-cured ham (JDH) is a traditional fermented Chinese meat product. We studied the dynamic sensory and emotional profiles of JDHs obtained by five preparation methods and the corresponding release of sodium ions (Na+), potassium ions (K+), and volatile organic compounds (VOCs) during oral processing. The VOCs with salty taste enhancement abilities were screened based on the correlations of VOCs with salty flavor and concentration of Na and K ions with salty flavor. A trained sensory panel evaluated the saltiness enhancements of selected VOCs by using static and dynamic sensory methods. The results revealed that Na+, K+, and selected VOCs were mainly released during 0-10 s of the chewing process. The release of Na+ and K+ in JDH residue samples exhibited consistently decreasing trends, while in saliva, their concentrations increased. The VOCs showing a high correlation with Na+ and K+ and salty flavor have saltiness enhancement abilities in both NaCl solutions and NaCl + MSG mixtures. Odor-induced saltiness was pronounced at low salt concentrations (0.2% NaCl). The investigation demonstrated 16 VOCs exhibiting saltiness enhancement abilities, including 4 pyrazines, 5 acids, 4 sulfur-containing compounds, and 3 other compounds. The sensory evaluation suggested pyrazines and sulfur-containing compounds as good saltiness enhancers. 2-Furfuryl mercaptan significantly enhanced the salty sensation in the NaCl + MSG solutions when compared with MSG alone (p < 0.05). This research provides evidence that certain odorants identified in JDHs exhibit salty-enhancing properties, indicating their potential for salt reduction at the industrial level.

The latest advances on soy sauce research in the past decade: Emphasis on the advances in China

As an indispensable soybean-fermented condiment, soy sauce is extensively utilized in catering, daily cooking and food industry in East Asia and Southeast Asia and is becoming popular in the whole world. In the past decade, researchers began to pay great importance to the scientific research of soy sauce, which remarkably promoted the advances on fermentation strains, quality, safety, function and other aspects of soy sauce. Of them, the screening and reconstruction of Aspergillus oryzae with high-yield of salt and acid-tolerant proteases, mechanism of soy sauce flavor formation, improvement of soy sauce quality through the combination of novel physical processing technique and microbial/enzyme, separation and identification of soy sauce functional components are attracting more attention of researchers, and related achievements have been reported continually. Meanwhile, we pointed out the drawbacks of the above research and the future research directions based on published literature and our knowledge. We believe that this review can provide an insightful reference for international related researchers to understand the advances on soy sauce research.

Exploring the core functional microbiota related with flavor compounds in fermented soy sauce from different sources

Flavor, the most important quality index of soy sauce, is mostly influenced by the microbiota in fermented food ecosystem, however, the association between microorganisms and soy sauce flavor is still poorly understood. Therefore, the bacterial and fungal profiles, physicochemical parameters, and flavor compounds (9 organic acids, 17 free amino acids and 97 volatile flavor compounds) of 5 different source soy sauce were investigated using high-throughput sequencing, HPLC, amino acid analyzer and SPME/LLE-GC-MS, and their correlations were explored. A total of 3 fungal genera and 12 bacterial genera were identified as potential flavor-producing microorganisms by multivariate data and correlation analysis. Notably, Lactobacillus and Tetragenococcus were strongly positively correlated with succinic acid and lactic acid, respectively. Moreover, not only fungi, but also bacteria were found to be closely correlated with volatiles. Finally, 5 screened potential flavor-producing microorganisms were validated using a rapid fermentation model, with multiple strains showing the potential to improve the soy sauce flavor, with Lactobacillus fermentum being the most significant. Our research will provide a theoretical basis for the regulation and enhancement of soy sauce flavor.

Sensory Flavor Profile of Split Gill Mushroom (Schizophyllum commune) Extract and Its Enhancement Effect on Taste Perception in Salt Solution and Seasoned Clear Soup

Edible mushroom has attracted increasing attention as a natural flavor enhancer. This research studied sensory flavor profiles and identified umami taste-related compounds in split gill mushroom extract (SGME) using descriptive analysis and chemical analysis, respectively. The effects of SGME on taste enhancement as perceived by trained descriptive panelists and general consumers were evaluated in salt solutions and clear chicken soups. The results showed that SGME had mushroom, bitter aromatic, dark brown, meaty, and musty flavor notes and salty and umami tastes. Glutamic acid, aspartic acids, adenosine 5'-monophosphate (5'-AMP), and guanosine 5'-monophosphate (5'-GMP) contributed to SGME's umami taste. As perceived by trained panelists, saltiness enhancement caused by SGME in aqueous solutions occurred only at relatively low salt concentrations (0.3 and 0.5%), while its umami enhancement effect was more pronounced. When SGME was added into reduced-salt seasoned clear chicken soups, it helped to enhance both the salty and umami tastes of the soups. The 20-31.25% reduced-salt soups with 12.5% of SGME were rated as salty as (p > 0.05) the control soup with regular salt content as perceived by both trained panelists and general consumers. The results suggest that SGME could be used as a natural flavor enhancer in the development of reduced-salt foods.

Flavor-food ingredient interactions in fortified or reformulated novel food: Binding behaviors, manipulation strategies, sensory impacts, and future trends in delicious and healthy food design

With consumers gaining prominent awareness of health and well-being, a diverse range of fortified or reformulated novel food is developed to achieve personalized or tailored nutrition using protein, carbohydrates, or fat as building blocks. Flavor property is a critical factor in the acceptability and marketability of fortified or reformulated food. Major food ingredients are able to interact with flavor compounds, leading to a significant change in flavor release from the food matrix and, ultimately, altering flavor perception. Although many efforts have been made to elucidate how food matrix components change flavor binding capacities, the influences on flavor perception and their implications for the innovation of fortified or reformulated novel food have not been systematically summarized up to now. Thus, this review provides detailed knowledge about the binding behaviors of flavors to major food ingredients, as well as their influences on flavor retention, release, and perception. Practical approaches for manipulating these interactions and the resulting flavor quality are also reviewed, from the scope of their intrinsic and extrinsic influencing factors with technologies available, which is helpful for future food innovation. Evaluation of food-ingredient interactions using real food matrices while considering multisensory flavor perception is also prospected, to well motivate food industries to investigate new strategies for tasteful and healthy food design in response to consumers' unwillingness to compromise on flavor for health.

A systematic review on the flavor of soy-based fermented foods: Core fermentation microbiome, multisensory flavor substances, key enzymes, and metabolic pathways

The characteristic flavor of fermented foods has an important impact on the purchasing decisions of consumers, and its production mechanisms are a concern for scientists worldwide. The perception of food flavor is a complex process involving olfaction, taste, vision, and oral touch, with various senses contributing to specific properties of the flavor. Soy-based fermented products are popular because of their unique flavors, especially in Asian countries, where they occupy an important place in the dietary structure. Microorganisms, known as the souls of fermented foods, can influence the sensory properties of soy-based fermented foods through various metabolic pathways, and are closely related to the formation of multisensory properties. Therefore, this review systematically summarizes the core microbiome and its interactions that play an active role in representative soy-based fermented foods, such as fermented soymilk, soy sauce, soybean paste, sufu, and douchi. The mechanism of action of the core microbial community on multisensory flavor quality is revealed here. Revealing the fermentation core microbiome and related enzymes provides important guidance for the development of flavor-enhancement strategies and related genetically engineered bacteria.

Sodium reduction in foods: Challenges and strategies for technical solutions

In many parts of the world, sodium consumption is higher than recommended levels, representing one of the most important food-related health challenges and leading to considerable economical costs for society. Therefore, there is a need to find technical solutions for sodium reduction that can be implemented by food producers and within food services. The aims of this review are to discuss the barriers related to sodium reduction and to highlight a variety of technical solutions. The barriers relate to consumer perception, microbiology, processing, and physicochemistry. Existing technical solutions include inhomogeneous salt distribution, coated salt particles, changing particle sizes and forms, surface coating, multisensory combinations, sodium replacements, double emulsions, adapted serum release by microstructure design, and adapted brittleness by microstructure design. These solutions, their implementation and the associated challenges, and applicable product categories are described. Some of these solutions are ready for use or are in their early development stages. Many solutions are promising, but in most cases, some form of adaptation or optimization is needed before application in specific products, and care must always be taken to ensure food safety. For instance, further research and innovation are required in the dynamic evolution of saltiness perception, consumer acceptance, the binding and migration of sodium, juiciness, microbiological safety, and the timing of salt addition during processing. Once implemented, these solutions will undoubtedly support food producers and food services in reducing sodium content and extend the application of the solutions to different foods.

Decoding of the Saltiness Enhancement Taste Peptides from the Yeast Extract and Molecular Docking to the Taste Receptor T1R1/T1R3

The development of saltiness or saltiness enhancement peptides is important to decrease the dietary risk factor of high sodium. Taste peptides in the yeast extract were separated by ultrafiltration and subsequently identified by UPLC-Q-TOF-MS/MS. The 377 identified peptides were placed into the umami receptor T1R1/T1R3. The results showed that eight taste peptides with higher binding energies were screened by molecular virtual docking, and the results revealed that Asp218, Ser276, and Asn150 of T1R1 play key roles in umami docking of peptides. The taste characteristic description and saltiness enhancement effect results suggested that PKLLLLPKP (sourness and umami, 0.18 mM), GGISTGNLN (sourness, 0.59 mM), LVKGGLIP (umami, 0.28 mM), and SSAVK (umami, 0.35 mM) had higher saltiness enhancement effects. The sigmoid curve analysis further confirmed that the taste detection threshold of the GGISTGNLN in the peptide and salt model (157.47 mg/L) was lower than 320.99 mg/L and exhibited a synergistic effect on saltiness perception, whereas SSAVK, PKLLLLPKP, and LVKGGLIP exhibited additive effects on the saltiness perception. This work also corroborated previous research, which indicated that the sourness and umami taste attributes could enhance the saltiness perception.

Insights into the flavor perception and enhancement of sodium-reduced fermented foods: A review

Salt (sodium chloride, NaCl) is a vital ingredient in fermented foods, which affects their safety, texture, and flavor characteristics. Recently, the demand for reduced-sodium fermented foods has increased, as consumers have become more health-conscious. However, reducing sodium content in fermented foods may negatively affect flavor perception, which is a critical quality attribute of fermented foods for both the food industry and consumers. This review summarizes the role of salt in the human body and foods and its role in the flavor perception of fermented foods. Current sodium reduction strategies used in the food industry mainly include the direct stealth reduction of NaCl, substituting NaCl with other chloride salts, and structure modification of NaCl. The odor-induced saltiness enhancement, application of starter cultures, flavor enhancers, and non-thermal processing technology are potential strategies for flavor compensation of sodium-reduced fermented foods. However, reducing sodium in fermented food is challenging due to its specific role in flavor perception (e.g., promoting saltiness and volatile compound release from food matrices, inhibiting bitterness, and changing microflora structure). Therefore, multiple challenges must be addressed in order to improve the flavor of low-sodium fermented foods. Future studies should thus focus on the combination of several strategies to compensate for the deficiencies in flavor resulting from sodium reduction.

The Enhancement of the Perception of Saltiness by Odorants Selected from Chinese Douchi in Salt Solution

Douchi is a traditional fermented soya bean product that is popular for its smelled saltiness and unique flavor. In order to look for the relationship between smelled saltiness of volatiles and their saltiness-enhancing properties, gas chromatography-olfactometry/associated taste was used to select odorants associated with saltiness in Yongchuan Douchi. The enhancement effects of saltiness intensity by selected odorants were further verified by sensory evaluation analyses of 2-alternative forced-choice and odor-induced saltiness enhancement in a follow-up study. A total of 14 odorant compounds were selected for their odor-associated saltiness perception. The compounds of 2-ethyl-3,5-dimethyl pyrazine, 2,5-dimethyl pyrazine, dimethyl trisulfide, 3-(methylthio) propanol and 3-(methylthio) propanal could significantly enhance saltiness perception in salt solution. Among them, 2-ethyl-3,5-dimethyl pyrazine was reported for the first time to be able to improve the salty taste. The study suggested that salty food is an ideal material for selecting saltiness-enhancing odorants, which could provide more direct theoretical support for salt reduction in the food industry.

Community structure of yeast in fermented soy sauce and screening of functional yeast with potential to enhance the soy sauce flavor

Yeast plays an important role in the formation of desirable aroma during soy sauce fermentation. In this study, the structure and diversity of yeast communities in seven different soy sauce residues were investigated by ITS sequencing analysis, and then the aroma characteristics of selected yeast species were examined by a combination of gas chromatography-mass spectrometry (GC-MS), headspace solid-phase microextraction (SPME) and liquid-liquid extraction (LLE). A total of 18 yeast genera were identified in seven soy sauce residues. Among them, Candid and Zygosaccharomyces were detected in all samples, followed by Millerozyma, Wickerhamiella, Meyerozyma, Trichosporon and Wickerhamomyces, which were found in more than two-thirds of the samples. Subsequently, eight representative species, isolated from soy sauce residues, were subjected to environmental stress tolerance tests and aroma production tests. Among them, three isolated species were regarded as potential aroma-enhancing microbes in soy sauce. Wickerhamiella versatilis could increase the contents of ethyl ester compounds and alcohols, thereby improving the fruity and alcoholic aroma of soy sauce. Candida sorbosivorans enhanced sweet and caramel-like aroma of soy sauce by producing 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) and 3-hydroxy-2-methyl-4h-pyran-4-one (maltol). Starmerella etchellsii could enhance the contents of 2,6-dimethylpyrazine, methyl pyrazine and benzeneacetaldehyde. This study is of great significance for the development and application of flavor functional yeasts in soy sauce fermentation.

Paving the Way for a Green Transition in the Design of Sensors and Biosensors for the Detection of Volatile Organic Compounds (VOCs)

The efficient and selective detection of volatile organic compounds (VOCs) provides key information for various purposes ranging from the toxicological analysis of indoor/outdoor environments to the diagnosis of diseases or to the investigation of biological processes. In the last decade, different sensors and biosensors providing reliable, rapid, and economic responses in the detection of VOCs have been successfully conceived and applied in numerous practical cases; however, the global necessity of a sustainable development, has driven the design of devices for the detection of VOCs to greener methods. In this review, the most recent and innovative VOC sensors and biosensors with sustainable features are presented. The sensors are grouped into three of the main industrial sectors of daily life, including environmental analysis, highly important for toxicity issues, food packaging tools, especially aimed at avoiding the spoilage of meat and fish, and the diagnosis of diseases, crucial for the early detection of relevant pathological conditions such as cancer and diabetes. The research outcomes presented in the review underly the necessity of preparing sensors with higher efficiency, lower detection limits, improved selectivity, and enhanced sustainable characteristics to fully address the sustainable manufacturing of VOC sensors and biosensors.

Human Oral Sensitivity to and Taste Modulation by 3-Mercapto-2-Methylpentan-1-ol

Introduction

3-Mercapto-2-methylpentan-1-ol (3 M) is a key onion flavor (aroma), but past sensory work has focused primarily on ortho-nasal presentation. A series of experiments was conducted to characterize human sensitivity to oral 3 M solutions, then determine how 3 M impacts perception of basic tastes.

Methods

Detection thresholds were measured for a food grade, racemic mixture using a forced-choice staircase procedure (n = 19). Recognition was measured by presenting a single stimulus per trial (3 M, vanillin, or water), with "onion," "vanilla," or "water" as responses (n = 18). Supra-threshold intensity (n = 20) was measured for various concentrations using the general labeled magnitude scale (gLMS). Odor-taste interactions were studied using mixtures of 3 M and exemplars of basic tastes. Participants rated the intensity of basic tastes, or both taste and aroma, using the gLMS (n ranged from 10 to 15). All stimuli were in aqueous solution.

Results

Participants detected oral 3 M at about 0.90 ppb and recognized 3 M as "onion" at about 5 ppb. Supra-threshold intensity increased roughly as a cumulative logistic function of concentration. 3 M enhanced the rated savory intensity of monosodium glutamate, but did not enhance the dominant qualities of exemplars of the other four basic tastes. Under a response-context more favorable to an analytic approach, savory enhancement was reduced but not eliminated. Savory enhancement was eliminated with nose-clips.

Conclusions

Oral sensitivity was lower than previous retronasal studies would suggest, but roughly consistent with concentrations in cooked allium varieties. Oral 3 M selectively enhanced savory intensity, an effect likely due to retronasal aroma rather than taste or mouthfeel.

Implication

3 M is a promising candidate aroma to enhance or impart a savory flavor.

Characterization of the Aroma-Active Compounds in Banana (Musa AAA Red green) and Their Contributions to the Enhancement of Sweetness Perception

"Hongmeiren" bananas are popular because of their red peel. Two extraction methods solvent-assisted flavor evaporation and headspace solid-phase microextraction, combined with gas chromatography-olfactometry and gas chromatography-mass spectrometry (GC-MS), were used to analyze the volatile components of "Hongmeiren" bananas. A total of 86 aroma compounds were identified by GC-MS, 62 of which were identified as the major aroma-active compounds with an odor activity value ≥ 1 or modified frequency ≥ 30%. Ethyl (E)-2-butenoate, 4-undecanone, and α-phellandrene were found in bananas for the first time. Sensory experiments showed that eight sweet-associated odorants could significantly achieve the sweetness enhancement effect at 30 g/L sucrose solution by odor-induced changes in taste perception. These experiments suggest that selected odorants can achieve sugar reduction, but with consideration of the sugar concentration. The study of the sweetness enhancement effect of individual compounds provides a more direct theoretical support for sugar reduction in the food industry.

Biocontrol Effect and Possible Mechanism of Food-Borne Sulfide 3-Methylthio-1-Propanol Against Botrytis cinerea in Postharvest Tomato

Botrytis cinerea is one of the most destructive fungal pathogens causing tremendous losses in fresh fruit or vegetables. 3-Methylthio-1-propanol (3-MP) is a naturally occurring food-borne sulfide, which is mainly used to increase the flavor in food. However, the potential application of 3-MP in the postharvest phase to manage fruit fungal diseases has not been explored. In this study, the antifungal activity of 3-MP against B. cinerea was evaluated, and the possible mechanism involved was explored. In vitro 3-MP treatment could effectively inhibit the mycelial growth, spore germination, and germ tube elongation of B. cinerea. 3-MP also impaired the spore viability and membrane integrity of B. cinerea as well as increased the leakage of nucleic acids, proteins, and malondialdehyde (MDA) in B. cinerea. In vivo 3-MP fumigation treatment inhibited the infection of B. cinerea on tomato fruits. Also, the fruits with 3-MP fumigation treatment exhibited higher antioxidant enzyme activity, lower MDA content, and a significant delay of induction of the expression of most of the stress-related genes when compared to the control group. Moreover, a cytotoxicity evaluation revealed that 3-MP had no toxicity to normal cells in a certain concentration range. Collectively, our research results will provide evidence for the development of food-borne sulfide 3-MP as a fungicide in food and agriculture and will provide an important reference for the formulation of B. cinerea biocontrol strategies.

Dysgeusia: A review in the context of COVID-19

Background

Taste disorders in general, and dysgeusia in particular, are relatively common disorders that may be a sign of a more complex acute or chronic medical condition. During the COVID-19 pandemic, taste disorders have found their way into the realm of general as well as specialty dentistry, with significance in screening for patients who potentially may have the virus.

Types of Studies Reviewed

The authors searched electronic databases (PubMed, Embase, Web of Science, Google Scholar) for studies focused on dysgeusia, ageusia, and other taste disorders and their relationship to local and systemic causes.

Results

The authors found pertinent literature explaining the normal physiology of taste sensation, proposals for suggested new tastes, presence of gustatory receptors in remote tissues of the body, and etiology and pathophysiology of taste disorders, in addition to the valuable knowledge gained about gustatory disorders in the context of COVID-19. Along with olfactory disorders, taste disorders are one of the earliest suggestive symptoms of COVID-19 infection.

Conclusions

Gustatory disorders are the result of local or systemic etiology or both. Newer taste sensations, such as calcium and fat tastes, have been discovered, as well as taste receptors that are remote from the oropharyngeal area. Literature published during the COVID-19 pandemic to date reinforces the significance of early detection of potential patients with COVID-19 by means of screening for recent-onset taste disorders.

Practical Implications

Timely screening and identification of potential gustatory disorders are paramount for the dental care practitioner to aid in the early diagnosis of COVID-19 and other serious systemic disorders.