Water-in-oil-in-water double emulsion for the delivery of starter cultures in reduced-salt moromi fermentation of soy sauce

Effect of fermented soybean on metabolic outcomes, anthropometric indices, and body composition: a systematic review and meta-analysis of clinical trials

The aim of the current study was to systematically review and quantify the findings of randomized controlled trials (RCTs) assessing the effect of fermented soy products on anthropometric indices, body composition, and metabolic outcomes. PubMed, Scopus, and Web of Science were searched to identify the relevant articles from inception until March 2024. The weighted mean differences (WMD) and corresponding 95% confidence intervals (CI) were calculated as effect sizes and analyzed using the random-effects method. A total of 2205 records were found, of which 15 RCTs were eligible. Results demonstrated significant beneficial effects of fermented soy on body mass index (WMD = -0.14 kg m-2, 95% CI: -0.28, -0.01, P = 0.039), waist circumference (WMD = -1.50 cm, 95% CI: -2.94, -0.07, P = 0.04), visceral fat (WMD = -692.17 mm2, 95% CI: -1011.58, -372.77, P < 0.001), fasting plasma glucose (WMD = -6.39 mg dL-1, 95% CI: -10.38, -2.40, P = 0.002), and total cholesterol (WMD = -5.0 mg dL-1, 95% CI: -6.60, -3.39, P < 0.001) compared with controls. However, the responses of other parameters to fermented soy were not significant. Overall, fermented soy may confer health benefits on certain metabolic outcomes, anthropometric indices, and body composition.

Developing a High-Umami, Low-Salt Soy Sauce through Accelerated Moromi Fermentation with Corynebacterium and Lactiplantibacillus Strains

The traditional fermentation process of soy sauce employs a hyperhaline model and has a long fermentation period. A hyperhaline model can improve fermentation speed, but easily leads to the contamination of miscellaneous bacteria and fermentation failure. In this study, after the conventional koji and moromi fermentation, the fermentation broth was pasteurized and diluted, and then inoculated with three selected microorganisms including Corynebacterium glutamicum, Corynebacterium ammoniagenes, and Lactiplantibacillus plantarum for secondary fermentation. During this ten-day fermentation, the pH, free amino acids, organic acids, nucleotide acids, fatty acids, and volatile compounds were analyzed. The fermentation group inoculated with C. glutamicum accumulated the high content of amino acid nitrogen of 0.92 g/100 mL and glutamic acid of 509.4 mg/100 mL. The C. ammoniagenes group and L. plantarum group were rich in nucleotide and organic acid, respectively. The fermentation group inoculated with three microorganisms exhibited the best sensory attributes, showing the potential to develop a suitable fermentation method. The brewing speed of the proposed process in this study was faster than that of the traditional method, and the umami substances could be significantly accumulated in this low-salt fermented model (7% w/v NaCl). This study provides a reference for the low-salt and rapid fermentation of seasoning.

An Updated Comprehensive Overview of Different Food Applications of W1/O/W2 and O1/W/O2 Double Emulsions

Double emulsions (DEs) present promising applications as alternatives to conventional emulsions in the pharmaceutical, cosmetic, and food industries. However, most review articles have focused on the formulation, preparation approaches, physical stability, and release profile of encapsulants based on DEs, particularly water-in-oil-in-water (W1/O/W2), with less attention paid to specific food applications. Therefore, this review offers updated detailed research advances in potential food applications of both W1/O/W2 and oil-in-water-in-oil (O1/W/O2) DEs over the past decade. To this end, various food-relevant applications of DEs in the fortification; preservation (antioxidant and antimicrobial targets); encapsulation of enzymes; delivery and protection of probiotics; color stability; the masking of unpleasant tastes and odors; the development of healthy foods with low levels of fat, sugar, and salt; and design of novel edible packaging are discussed and their functional properties and release characteristics during storage and digestion are highlighted.

A novel strategy for simultaneous reduction of salt and animal fat in burger using a taste contrast system based on double emulsion

The work investigated a taste contrast strategy to reduce the salt content in burgers by a novel design of water in gelled oil in water double emulsion (DE) as an animal fat replacer. Oleogelation reduced the particle size and improved emulsion viscosity, resulting in more emulsion stability than conventional DE. Moreover, oil gelation enhanced the encapsulation efficiency of salt. The partial substitution of the optimized DE incorporating salt within the W1 and cinnamaldehyde within the oil phase with animal fat in the burger successfully reduced salt content by up to 25% while maintaining the desired level of saltiness. The presence of cinnamaldehyde also increased oxidative stability and decreased color changes during storage. The replacement of DE and oleogel in burgers diminished cooking loss, while negatively affected the textural properties. Therefore, further optimization of this strategy could lead to healthier food formulations with reduced fat and salt content.

Microfluidics potential for developing food-grade microstructures through emulsification processes and their application

The food sector continues to face challenges in developing techniques to increase the bioavailability of bioactive chemicals. Utilising microstructures capable of encapsulating diverse compounds has been proposed as a technological solution for their transport both in food and into the gastrointestinal tract. The present review discusses the primary elements that influence the emulsification process in microfluidic systems to form different microstructures for food applications. In microfluidic systems, reactions occur within small reaction channels (1-1000 μm), using small amounts of samples and reactants, ca. 102-103 times less than conventional assays. This geometry provides several advantages for emulsion and encapsulating structure production, like less waste generation, lower cost and gentle assays. Also, from a food application perspective, it allows the decrease in particle dispersion, resulting in a highly repeatable and efficient synthesis method that also improves the palatability of the food products into which the encapsulates are incorporated. However, it also entails some particular requirements. It is important to obtain a low Reynolds number (Re < approx. 250) for greater precision in droplet formation. Also, microfluidics requires fluid viscosity typically between 0.3 and 1400 mPa s at 20 °C. So, it is a challenge to find food-grade fluids that can operate at the micro-scale of these systems. Microfluidic systems can be used to synthesise different food-grade microstructures: microemulsions, solid lipid microparticles, microgels, or self-assembled structures like liposomes, niosomes, or polymersomes. Besides, microfluidics is particularly useful for accurately encapsulating bacterial cells to control their delivery and release on the action site. However, despite the significant advancement in these systems' development over the past several years, developing and implementing these systems on an industrial scale remains challenging for the food industry.

Effect of Sequential Inoculation of Tetragenococcus halophilus and Wickerhamomyces anomalus on the Flavour Formation of Early-Stage Moromi Fermented at a Lower Temperature

Microbial inoculation in moromi fermentation has a great influence on the physicochemical and flavour properties of soy sauces. This work investigated the effect of inoculating Tetragenococcus halophilus and Wickerhamomyces anomalus on the flavour formation of early-stage moromi (30 days) fermented at a lower temperature (22 °C) by determining their physicochemical and aroma changes. The results showed that single yeast or LAB inoculation increased the production of amino nitrogen, lactic acid and acetic acid, as well as free amino acids and key flavour components. Particularly, the sequential inoculation of T. halophilus and W. anomalus produced more free amino acids and aromatic compounds, and there might be synergistic effects between these two strains. More characteristic soy sauce flavour compounds, such as benzaldehyde, HEMF, guaiacol and methyl maltol were detected in the sequentially inoculated moromi, and this sample showed higher scores in savoury, roasted and caramel intensities. These results confirmed that sequential inoculation of T. halophilus and W. anomalus could be a choice for the future production of moromi with good flavour and quality under a lower temperature.

Raman Spectroscopy of Emulsions and Emulsion Chemistry

Emulsions are dispersed systems widely used in various industries. In recent years, Raman spectroscopy (RS), as a spectroscopic technique, has gained much attention for measuring and monitoring emulsions. In this review, we explore the use of RS on emulsion structures and emulsification, important reactions that use emulsions such as emulsion polymerization, catalysis and cascading reactions, as well as various applications of emulsions. We explore how RS is used in emulsions, reactions and applications. RS is a powerful and versatile tool for studying emulsions, but there are also challenges in using RS to monitor emulsion processes, especially if they are rapid or volatile. We also explore these challenges and difficulties, as well as possible designs that can be used to overcome them.

Metabolomics analysis of salt tolerance of Zygosaccharomyces rouxii and guided exogenous fatty acid addition for improved salt tolerance

BACKGROUND

Zygosaccharomyces rouxii plays an irreplaceable role in the manufacture of traditional fermented foods, which are produced in a high-salt environment. However, there is little research on strategies for improving salt tolerance of Z. rouxii.

RESULTS

In this study, metabolomics was used to reveal the changes in intracellular metabolites under salt stress, and the results show that most of the carbohydrate contents decreased, the contents of xanthohumol and glycerol increased (fold change 4.07 and 5.35, respectively), while the contents of galactinol, xylitol and d-threitol decreased (fold change -9.43, -5.83 and -3.59, respectively). In addition, the content of four amino acids and six organic acids decreased, while that of the ten nucleotides increased. Notably, except for stearic acid (C18:0), all fatty acid contents increased. Guided by the metabolomics results, the effect of addition of seven exogenous fatty acids (C12:0, C14:0, C16:0, C18:0, C16:1, C18:1, and C18:2) on the salt tolerance of Z. rouxii was analyzed, and the results suggested that four exogenous fatty acids (C12:0, C16:0, C16:1, and C18:1) can increase the biomass yield and maximum growth rate. Physiological analyses demonstrated that exogenous fatty acids could regulate the distribution of fatty acids in the cell membrane, increase the degree of unsaturation, improve membrane fluidity, and maintain cell integrity, morphology and surface roughness.

CONCLUSION

These results are applicable to revealing the metabolic mechanisms of Z. rouxii under salt stress and screening potential protective agents to improve stress resistance by adding exogenous fatty acids. © 2022 Society of Chemical Industry.

Reduction of sodium chloride: a review

Sodium chloride (NaCl) is an enjoyable condiment. However, evidence is accumulating to indicate that an excessive intake of Na⁺ in food may lead to an increased risk of cardiovascular and cerebrovascular diseases. Previous systematic reviews have focused on replacing NaCl with other metal salts (e.g. KCl). However, new salty flavor enhancers (yeast extract, taste peptides, and odor compounds) have yet to be reviewed. This systematic review evaluates the methods for, and feasibility, of NaCl reduction. It defines NaCl reduction and considers the methods used for this purpose, especially the use of flavor enhancers (yeast extract, taste peptides, and odor compounds). © 2022 Society of Chemical Industry.

Incorporation of Exogenous Fatty Acids Enhances the Salt Tolerance of Food Yeast Zygosaccharomyces rouxii

Fatty acids have great effects on the maintenance of the cell membrane structure, cell viability, and cell metabolisms. In this study, we sought to elucidate the effects of exogenous fatty acids on the salt tolerance of food yeast Zygosaccharomyces rouxii. Results showed that Z. rouxii can grow by using exogenous fatty acids (C12:0, C14:0, C16:0, C16:1, C18:0, C18:1, and C18:2) as the sole carbon source. Four fatty acids (C12:0, C16:0, C16:1, and C18:1) can improve the salt tolerance of cells, enhance the formation of the cell biofilm, regulate the chemical compositions, restore growth in the presence of cerulenin, regulate the contents of membrane fatty acids, and control the expression of key genes in the fatty acid metabolism. Our results reveal that Z. rouxii can synthesize membrane fatty acids from exogenous fatty acids and the supplementation of these fatty acids can override the need for de novo fatty acid biosynthesis.

Optimisation of bacterial release from a stable microfluidic-generated water-in-oil-in-water emulsion

Application of droplet microfluidics for the encapsulation of bacteria in water-in-oil-in-water (W/O/W) emulsion allows for production of monodisperse droplets with controllable size. In this study the release of bacteria from W/O/W emulsion, the effect of the double emulsion structure on bacterial growth and metabolic activity, and the stability and mechanism of bacterial release were investigated. W/O/W emulsions were formed using a double flow-focusing junction microfluidic device under controlled pressure to produce droplets of approximately 100 μm in diameter containing an inner aqueous phase (W₁) of about 40–50 μm in diameter. GFP-labelled Escherichia coli (E. coli-GFP) bacteria were encapsulated within the W₁ droplets and the stability of emulsions was studied by monitoring droplet size and creaming behaviour. The double emulsions were stabilised using a hydrophilic (Tween 80) and a lipophilic surfactant (polyglycerol polyricinoleate) and were destabilised by altering the osmotic balance, adding NaCl either in the inner W₁ phase (hypo-osmotic) or outer W₂ phase (hyper-osmotic). The release of E. coli-GFP was monitored by plating on agar whereby the colony form unit (CFU) of the released bacteria was determined while fluorescent microscopy was employed to observe the mechanism of release from the droplets. The release of E. coli-GFP was significantly increased with higher concentrations of NaCl and lower amounts of Tween 80. Microscopic observation revealed a two-step mechanism for the release of bacteria: double W/O/W emulsion droplet splitting to release W₁ droplets forming a secondary double emulsion followed by the collapse of W₁ droplets to release E. coli-GFP into the continuous aqueous phase.

Encapsulation enhanced viability and metabolic activity. Nutrients can cross the oil layer. Bacterial release increased while emulsion stability decreased at high osmotic pressure and low surfactant concentration. Two-step release mechanism observed.

Heat preadaptation improved the ability of Zygosaccharomyces rouxii to salt stress: a combined physiological and transcriptomic analysis

Zygosaccharomyces rouxii plays important roles in the brewing process of fermented foods such as soy sauce, where salt stress is a frequently encountered condition. In this study, effect of heat preadaptation on salt tolerance of Z. rouxii and the protective mechanisms underlying heat preadaptation were investigated based on physiological and transcriptomic analyses. Results showed that cells subjected to heat preadaptation (37 °C, 90 min) prior to salt stress aroused many physiological responses, including maintaining cell surface smooth and intracellular pH level, increasing Na⁺/K⁺-ATPase activity. Cells subjected to heat preadaptation increased the amounts of unsaturated fatty acids (palmitoleic C16:1, oleic C18:1, linoleic C18:2) and decreased the amounts of saturated fatty acids (palmitic C16:0, stearic C18:0) which caused the unsaturation degree (unsaturated/saturated = U/S ratio) increased by 2.4 times when compared with cells without preadaptation under salt stress. Besides, salt stress led to increase in contents of 5 amino acids (valine, proline, threonine, glycine, and tyrosine) and decrease of 2 amino acids (serine and lysine). When comparing the cells pre-exposed to heat preadaptation followed by challenged with salt stress and the cells without preadaptation under salt stress, the serine, threonine, and lysine contents increased significantly. RNA sequencing revealed that the metabolic level of glycolysis by Z. rouxii was weakened, while the metabolic levels of the pentose phosphate pathway and the riboflavin were enhanced in cells during heat preadaptation. Results presented in this study may contribute to understand the bases of adaptive responses in Z. rouxii and rationalize its exploitation in industrial processes.Key points• Heat preadaptation can improve high salinity tolerance of Z. rouxii.• Combined physiological and transcriptomic analyses of heat preadaptation mechanisms.• Provide theoretical support for the application of Z. rouxii.

Effect of aroma-producing yeasts in high-salt liquid-state fermentation soy sauce and the biosynthesis pathways of the dominant esters

Fermentation with excellent aroma-producing yeasts can enhance the flavour of soy sauce. In this work, Millerozyma farinosa CS2.23, Zygosaccharomyces rouxii CS2.42, and Candida parapsilosis CS2.53 were added to the high-salt liquid-state moromi to promote soy sauce fermentation. All three yeasts improved the TE of soy sauce, the highest of which reached 1.03 g/L with added CS2.42. Other quality indexes of soy sauce, including RS, TA, and AN, were not greatly affected. The volatile esters of soy sauce added to the three yeasts increased by 108.85%, 166.71%, and 113.61% compared with the control through GC-MS analysis. Obviously, CS2.42 had an excellent ability to produce esters. Studying the biosynthesis pathway of esters, CS2.42 has the best esterification ability, while CS2.53 has the advantage of alcoholysis ability. The exploration of the biosynthetic pathway of acetate and ethyl esters has laid a foundation for regulating esters in soy sauce fermentation.

Fermentation of high-salt liquid-state soy sauce without any additives by inoculation of lactic acid bacteria and yeast

Food additives are artificial or natural substances that are added to food to improve the color, aroma, taste, and other qualities, and to meet processing requirements. For the concern of food health and safety, brewed soy sauce without additives has attracted consumers' attention. Here, only four necessary raw materials including soybean, wheat, salt, and water were added. High-salt soy sauce fermentation was conducted for six months by sequential inoculation of lactic acid bacteria and yeast under different brine content (18%, 20%, and 22%). By analyzing the physicochemical indicators during moromi, three soy sauces (No. 1: 18% salt, inoculated with Tetragenococcus halophilus and Zygosaccharomyces rouxii, No. 5: 20% salt, inoculated with T. halophilus and Z. rouxii, No. 11: 22% salt, inoculated with T. halophilus and Candida versatilis) were selected and sterilized to produce finished products for further comparative investigation. Results showed that the flavor components of these three soy sauces were richer in variety than the commercial soy sauces and No. 11 soy sauce was detected to have the largest total amount of organic acids. Plate count agar analysis revealed that the free amino acid differences of soy sauces were distinct, among which the No. 11 soy sauce had the highest glutamate content of 19.64 g L^-1. Besides, it was found that the shelf life of these three soy sauces could reach two years at 4 ℃. This study suggests that the high-salt soy sauce made by rational application of lactic acid bacteria, yeast, and effective sterilization can have high quality and long shelf life without adding any additives.

Effects of Tetragenococcus halophilus and Candida versatilis on the production of aroma-active and umami-taste compounds during soy sauce fermentation

BACKGROUND

Soy sauce is a well-known condiment worldwide. However, the high salt content in soy sauce contributes to the high intake of sodium salt, which usually results in high blood pressure. High salt soy sauce usually has the better quality (aroma and taste) than low salt. Tetragenococcus halophilus and Candida versatilis are important starters for soy sauce fermentation. It is of urgent need to explore what the effect of these two strains on the aroma- and taste-attributes of soy sauce to achieve high quality fermentation with low salt.

RESULTS

In this study, aroma-active and taste compounds in soy sauce were reviewed and listed. Then, soy sauce fermentation inoculated with different combinations of T. halophilus (at different inoculated time) and C. versatilis were completed. Aroma-active and taste compounds in different samples were quantified. Multivariate analysis was used to analyze these data. The aroma-active compounds which were highly related to the inoculation of T. halophilus and C. versatilis were found. Meanwhile, the addition time of T. halophilus could also be highly related to the production of aroma-active compounds. More importantly, T. halophilus was highly correlated with the production of umami-taste compounds in soy sauce, including aspartic acid, glutamic acid, alanine and N -succinyl-glutamic acid.

CONCLUSION

These results will provide a better understanding of the effects of T. halophilus and C. versatilis on the formation of significant aroma-active and umami-taste constituents in soy sauce. Furthermore, it will be helpful to realize fermentative control of soy sauce with high quality at low salt. © 2020 Society of Chemical Industry.

Desired soy sauce characteristics and autolysis of Aspergillus oryzae induced by low temperature conditions during initial moromi fermentation

This is the first report on the effect of low temperature stress applied during initial moromi fermentation on the quality and taste of soy sauce. Koji was prepared to yield initial moromi under three comparative fermentation conditions over 9 days: (1) 4 °C and 0% brine (i.e., water) (LTSF); (2) 4 °C and 16% w/w brine (LTSH); (3) 25 °C and 16% w/w brine (the control, CRTH). Greater extent of autolysis in samples was found under low temperature stress conditions (i.e., at 4 °C, a temperature much lower than the normal temperature range like 25 °C for natural microbial growth and performance). Compared to CRTH, LTSF had a two-fold increase of glutaminase activity in dregs and 65.17% increase in supernatant, and after 60 days of moromi fermentation, a 5.73% and 3.47% increase, respectively, in the contents of glutamic acid (Glu) and aspartic acid (Asp). LTSF had the highest total free amino acid content due to both the low temperature stress and absence of salt. The intensity ranking of umaminess and kokumi sensation (LTSF > LTSH > CRTH) revealed by sensory analysis followed the changing trends of their umami and sweet amino acid contents with a trend reversal in the bitter amino acid content. Low temperature (4 °C) without brine for initial moromi fermentation seemed beneficial, leading to a soy sauce product with desired taste and amino acid contents.

Soy sauce fermentation: Microorganisms, aroma formation, and process modification

Soy sauce is an increasingly popular oriental fermented condiment produced through a two-step fermentation process called koji (solid-state fermentation) and moromi (brine fermentation). Complex microbial interactions play an essential role in its flavor development during the fermentation. Tetragenococcus halophilus and Zygosaccharomyces rouxii are predominant among the microbes involved in the moromi stage. Despite their importance for producing a wide range of volatile compounds, antagonism can occur due to different growth condition requirements. Furthermore, microbial interactions in moromi fermentation are affected by current efforts to reduce salt in soy sauce, in order to tackle slow fermentation due to low metabolic activity of microbes and increased health risk related to high sodium intake. Attempts to enhance and accelerate flavor formation in the presence of high salt concentration include the inoculation with mixed starter cultures, genetic modification, cell, and enzyme immobilization. Although salt reduction can accelerate the microbial growth, the flavor quality of soy sauce is compromised. Several approaches have been applied to compensate such loss in quality, including the use of salt substitutes, combination of indigenous cultures, pretreatment of raw material and starter cultures encapsulation. This review discusses the role of microorganisms in soy sauce production in relation to flavor formation and changes in production practices.