Chemical and sensory characteristics of low molecular weight fractions obtained from three types of Japanese soy sauce (shoyu) – Koikuchi, tamari and shiro shoyu

High-intensity ultrasound promoted the maturation of high-salt liquid-state soy sauce: A mean of enhancing quality attributes and sensory properties

High-intensity ultrasound was used as a means to promote maturation of soy sauce. The optimal conditions for ultrasound treatment were 90℃ at an ultrasound intensity of 39.48 W/cm2 for 60 min. The total reducing sugars and soluble salt-free solids content was significantly increased after ultrasound-assisted maturation. The free amino acid content was significantly decreased, mainly due to the Maillard reaction (MR). The promoted MR produced several types of flavor compounds, including esters, pyrazines, and ketones, which imparted an attractive aroma to the maturated soy sauce. The proportion of peptides with a molecular weight of 1-5 kDa provided umami as an important flavor characteristic, and the content in the ultrasound-matured soy sauce (10.19 %) was significantly higher than that in the freshly prepared soy sauce (8.34 %) and the thermally treated sample (8.89 %). Ultrasound-assisted maturation would improve product quality and meanwhile, shorten the duration and reduce the cost for the soy sauce industry.

Recent advancements in the taste transduction mechanism, identification, and characterization of taste components

In the realm of human nutrition, the phenomenon known as taste refers to a distinctive sensation elicited by the consumption of food and various compounds within the oral cavity and on the tongue. Moreover, taste affects the overall comfort in the oral cavity, and is a fundamental attribute for the assessment of food items. Accordingly, clarifying the material basis of taste would be conducive to deepening the cognition of taste, investigating the mechanism of taste presentation, and accurately covering up unpleasant taste. In this paper, the basic biology and physiology of transduction of bitter, umami, sweet, sour, salty, astringent, as well as spicy tastes are reviewed. Furthermore, the detection process of taste components is summarized. Particularly, the applications, advantages, and distinctions of various isolation, identification, and evaluation methods are discussed in depth. In conclusion, the future of taste component detection is discussed.

Evaluation of the differences between low-salt solid-state fermented soy sauce and high-salt diluted-state fermented soy sauce in China: from taste-active compounds and aroma-active compounds to sensory characteristics

BACKGROUND

The present study aimed to determine the components related to sensory properties in soy sauce and to characterize the differences between low-salt solid-state fermented soy sauce (LSFSS) and high-salt diluted-state fermented soy sauce (HDFSS). The taste and aroma active components of 18 commercially available soy sauces (eight types of LSFSS and 10 types of HDFSS) were characterized. The relationship between these compounds, soy sauce samples, and sensory properties was modeled by partial least squares regression.

RESULTS

The analysis showed that the 11 taste-active components, including glutamic acid, glycine, alanine, threonine, malic acid, citric acid, tartaric acid, acetic acid, lactic acid, reducing sugar and salt, contributed greatly to the taste of soy sauce. In addition, umami, saltiness and sweetness are the characteristic tastes of HDFSS, whereas sourness and bitterness were the characteristic tastes of LSFSS. At the same time, seven aroma-active compounds, namely 4-ethyl-2-methoxyphenol, ethanol, 3-methyl-1-butanol, ethyl acetate, 2-phenethyl alcohol, 3-methyl thiopropanol and 2-ethyl-4-hydroxy-5-methylfuran-3-one, played a decisive role in the flavor of soy sauce. In addition, HDFSS presented the aroma attributes of smoky, alcoholic, floral, fruity and caramel-like, whereas LSFSS mainly presented sour and malty aroma attributes.

CONCLUSION

The present study reveals new insight into the relationship between the chemical composition and sensory characteristics of soy sauce, which is of great significance for developing an objective measurement system and providing a theoretical basis to improve the sensory quality of soy sauce. © 2023 Society of Chemical Industry.

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.

Characterization of Peanut Protein Hydrolysate and Structural Identification of Umami-Enhancing Peptides

Umami peptides are naturally found in various foods and have been proven to be essential components contributing to food taste. Defatted peanut powder hydrolysate produced by a multiprotease (Flavorzyme, Alcalase, and Protamex) was found to elicit an umami taste and umami-enhancing effect. The taste profiles, hydrolysis efficiency, amino acids, molecular weight distribution, Fourier transform infrared spectroscopy (FT-IR), and separation fractions obtained by ultrafiltration were evaluated. The results showed that peanut protein was extensively hydrolyzed to give mainly (up to 96.84%) free amino acids and peptides with low molecular weights (<1000 Da). Furthermore, β-sheets were the major secondary structure. Fractions of 1−3000 Da and <1000 Da prominently contributed to the umami taste and umami enhancement. To obtain umami-enhancing peptides, these two fractions were further purified by gel filtration chromatography, followed by sensory evaluation. These peptides were identified as ADSYRLP, DPLKY, EAFRVL, EFHNR, and SDLYVR by ultra-performance liquid chromatography (UPLC), and had estimated thresholds of 0.107, 0.164, 0.134, 0.148, and 0.132 mmol/L, respectively. According to the results of this work, defatted peanut powder hydrolysate had an umami taste and umami-enhancing effect, and is a potential excellent umami peptide precursor material for the food industry.

Isolation, identification and characterization of taste peptides from fermented broad bean paste

Pixian broad-bean paste (PBBP) is a famous fermented condiment in China, which may produce abundant flavor peptides during fermentation process. Herein, the tasteful peptides from fermented broad-bean (FB) were separated...

Transport of Amino Acids in Soy Sauce Desalination Process by Electrodialysis

Soy sauce is a common condiment that has a unique flavor, one that is derived from its rich amino acids and salts. It is known that excessive intake of high-sodium food will affect human health, causing a series of diseases such as hypertension and kidney disease. Therefore, removing sodium from the soy sauce and retaining the amino acids is desirable. In this study, electrodialysis (ED) was employed for the desalination of soy sauce using commercial ion exchange membranes (IEMs). The influence of the current density and initial pH on the desalination degree of the soy sauce was explored. Results showed that the optimal desalination condition for ED was reached at a current density of 5 mA/cm² and pH of 5, with the desalination degree of 64% and the amino acid loss rate of 29.8%. Moreover, it was found that the loss rate of amino acids was related to the initial concentration and molecular structure. In addition, the amino acid adsorption by IEMs was explored. Results implied that the molecular weight and structure affect amino acid adsorption. This study illustrated that the ED process can successfully reduce the salt content of the soy sauce and retain most of the amino acids without compromising the original flavor.

Comparative study on the novel umami-active peptides of the whole soybeans and the defatted soybeans fermented soy sauce

BACKGROUND

Two kinds of soy sauce produced via fermentation of the whole soybeans and the defatted soybeans (soy sauce termed 'SSS' and 'SSD', respectively) were subjected to the treatment using aqueous ethanol solutions with high concentrations. Then tasty peptides were separated from SSS and SSD by sensory guided fractionation, using macroporous resin and reverse-phase high-performance liquid chromatography (RP-HPLC), and identified by ultra-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS).

RESULTS

The result showed that umami-active fractions and ≤ 3 kDa peptides were mainly concentrated in the supernatants resulted from the treatment with 60% ethanol and the precipitates resulted from the treatment with 80% ethanol. The contents of ammonia nitrogen, non-salt solids, bitter amino acids, amino acids in peptides and the proportion of ≤ 3 kDa peptides in SSS were higher than those in SSD. Sixteen and fourteen tasty peptides were separated from SSS and SSD, among them five dipeptides (γ-Glu-Glu, Glu-Glu, γ-Glu-Cys, γ-Glu-Leu, Glu-Leu and Ile-Glu) with a glutamic acid residue were identified both in SSS and SSD, which have been reported as umami/kokumi-active peptides in soy sauce. Several peptides identified from SSS (Thr-Gly-Cys, Gly-Leu-Glu, Val-Glu-Ala-Leu and Gly-Gly-Gly-Glu) and SSD (Asp-Arg, Asp-Ala-Glu, Glu-Val-Cys and Gly-Gly-Gly-Glu) are tasty and/or umami-active peptides but have not been reported as tasty peptides in the past.

CONCLUSION

Most of the peptides separated from SSD and SSS could impart an umami-enhancing effect on soy sauce, and the marginally more kokumi and bitterness hydrophobic peptides were found in SSS than SSD. © 2020 Society of Chemical Industry.

Two-stage selective enzymatic hydrolysis generates protein hydrolysates rich in Asn-Pro and Ala-His for enhancing taste attributes of soy sauce

This study demonstrated the contribution of peptides to umami soy sauce taste. Asn-Pro and Ala-His with remarkable umami taste and umami-enhancing capacity were found in original soy sauce, possessing umami thresholds of 175 and 160 mg/L and umami-enhancing thresholds of 10 and 13 mg/L, respectively. Firstly, an industrially viable two-stage hydrolysis at 55 °C (a 12-h hydrolysis with the neutral protease, then a 12-h hydrolysis with the aminopeptidase) was established to produce protein hydrolysates rich in umami-tasting and umami-enhancing peptides (e.g. Asn-Pro and Ala-His) from non-soy sauce protein preparations (soy protein isolate, rice proteins, wheat proteins, peanut proteins or pea proteins). The soy protein isolate hydrolysate produced via the two-stage hydrolysis had Asn-Pro and Ala-His contents 3.32 and 1.15 times higher than those produced via the one-stage hydrolysis using the neutral protease only. Adding the hydrolysate to original soy sauce at 5% w/v significantly increased umami and reduced bitterness.

Chemical and Sensory Characteristics of Soy Sauce: A Review

Soy sauce is a fermented product, and its flavor is a complex mixture of individual senses which, in combination, create a strong palatable condiment for many Eastern and Western dishes. This Review focuses on our existing knowledge of the chemical compounds present in soy sauce and their potential relevance to the flavor profile. Taste is dominated by umami and salty sensations. Free amino acids, nucleotides, and small peptides are among the most important taste-active compounds. Aroma is characterized by caramel-like, floral, smoky, malty, and cooked potato-like odors. Aroma-active volatiles are chemically diverse including acids, alcohols, aldehydes, esters, furanones, pyrazines, and S-compounds. The origin of all compounds relates to both the raw ingredients and starter cultures used as well as the parameters applied during production. We are only just starting to help develop innovative studies where we can combine different analytical platforms and chemometric analysis to link flavor attributes to chemical composition.

Rapid detection of quality of Japanese fermented soy sauce using near-infrared spectroscopy

This study investigated the feasibility of rapidly evaluating the final quality of Japanese fermented soy sauce (shoyu) using NIR spectroscopy and partial least-squares (PLS) regression. In total, 110 shoyu samples that had been entered in the annual soy sauce competition from 2016 to 2018 were collected and analyzed. The transmittance spectra (400-1800 nm) and the transflectance spectra (680-2500 nm) of these samples were acquired and processed by different pre-treatments. PLS regression was applied to the raw and processed spectra to construct models based on a calibration set (76 shoyu samples from 2016 and 2017) and to evaluate these models using a validation set (34 shoyu samples from 2018), according to their values for bias and root mean square error of prediction (RMSEP). The results showed that the models constructed using the full spectra of transflectance performed better than those using transmittance spectra. Comparing the influence of different regions in the transflectance spectra enabled the accuracy of the models to be improved. The model constructed from transflectance spectra from the 1800 to 2500 nm region using pre-treatment of second derivative was superior to the other models, with a bias value of -2 and the lowest RMSEP value of 13 in the validation set. To further narrow the wavelength range, the models constructed using the spectral region from 2050 to 2400 nm also showed a better performance for predicting the sensory quality of soy sauce products. This study has demonstrated that the NIR spectroscopy technique could be used as an alternative routine quality control procedure, which can rapidly and economically classify the quality of soy sauce products.

Umami fractions obtained from water-soluble extracts of red oncom and black oncom-Indonesian fermented soybean and peanut products

Red oncom, a fermented product from solid waste of soybean curd process, and black oncom, a similar fermented product but made from defatted peanut cake, have been known to have umami taste. Umami fractions of red oncom and black oncom that are responsible for umami taste have not been investigated yet. The objective of this research was to characterize umami fractions obtained by ultrafiltration and chromatography of both oncoms. The first step, water-soluble extracts of oncoms were ultrafiltered using a membrane with cutoff 3,000 Da and followed by gel filtration chromatography (Sephadex G-25) to obtain umami fractions. Ultrafiltration fractions of red oncom (molecular weight [MW] less than 3,000 Da) and black oncom (MW more than 3,000 Da) had an intense umami taste. The further fractionation by gel filtration chromatography linked to taste dilution analysis yielded umami fractions. Chemical characterization revealed that free glutamic acid, free phenylalanine, and peptides containing their residual amino acids were present in the fractions. PRACTICAL APPLICATION: Umami fractions of red and black oncoms can be used as a source of umami compounds for food industries and food services. The information from this paper can be used by other researchers who will explore umami peptides.

Effect of microwave sterilization on maturation time and quality of low-salt sufu

The objective of this study was to reduce the microorganism number and salt content in pehtze by microwave sterilization. The maturation time and quality of low-salt sufu were evaluated. The microorganism inactivation rate, moisture content and water activity of the pehtze, which was used for the growth of the starter culture, showed that 4,250 W for 30 s was suitable for the preparation of low-salt sufu. With regard to the physicochemical properties of sufu, 120-day sufu samples obtained by traditional high-salt (14%) fermentation and 75-day sufu samples obtained by low-salt (4%) fermentation met the standard requirements. With regard to the sensory characteristics of sufu, the taste and after taste scores of 75-day low-salt sufu samples were significantly higher than those of 120-day high-salt sufu samples (p < .05).The overall acceptance score of low-salt sufu samples also was higher than that of high-salt sufu samples. The contents of free amino acids and the profiles of typical flavor compounds partly explained the sensory quality and shorter ripening time of sufu manufactured. The total biogenic amine contents were reduced by 46%.

Enhancing the taste of raw soy sauce using low intensity ultrasound treatment during moromi fermentation

Sonication can significantly enhance amino acids (AAs) release to accelerate maturation during short-term and low-salt soy sauce fermentation. Here, sonication was applied at 68 kHz (60 W/L/10 min/8 circles) to determine its effects on the taste during long-term and high-salt soy sauce fermentation. The possible mechanisms were explored by analyzing differences in enzymes profile, proximate indices, molecular weight distribution of peptides, AAs composition and microstructures of sonicated moromis and their controls. Sonication greatly elevated levels of organic taste compounds ranging from 8.4% to 22.2%, but lowered levels of NaCl (6.0%), peptides ≤ 1 kDa (5.2%), histidine (20.5%) and glutamic acid (3.4%). Compared to its controls, sonicated raw soy sauces also had a more harmonious and palatable taste. Increased enzymes' activities and formation of more surface area and reaction sites in sonicated moromis might be the possible mechanisms for sonication to elevate levels of taste compounds and sensory quality of soy sauce.

Protein hydrolysates of porcine hemoglobin and blood: Peptide characteristics in relation to taste attributes and formation of volatile compounds

The objective of this study was to investigate the impact of endo- and exo-peptidase treatment on certain structural characteristics of peptides and volatile compounds of porcine hemoglobin and whole blood hydrolysates. Porcine hemoglobin and whole blood were hydrolyzed by endo- and exo-peptidases. The presence of exopeptidases reduced the bitterness and altered the volatile profiles of protein hydrolysates. Exopeptidase treatment can release terminal amino acids from peptides, which in turn may contribute to formation of volatile compounds by Maillard reactions. In contrast, endopeptidases conferred a slightly bitter taste and different volatile profiles. For hemoglobin hydrolysates, principal component analysis revealed that proteases were categorized into three groups based on endo- or exo-peptidase activity. Whole blood is a more complex raw material, yet the proteases were still categorized in a similar fashion. This work contributes to understanding structural characteristics responsible for taste and volatile profiles of protein hydrolysates.

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.

Microfiltration of raw soy sauce: membrane fouling mechanisms and characterization of physicochemical, aroma and shelf-life properties

Refinement to remove fermented mash residue is essential for obtaining clarified, stable and high-quality soy sauce. In this study, raw soy sauce microfiltration was investigated. Four widely-used microfiltration membranes were employed: ceramic, polyethersulfone (PES), polyvinylidene fluoride (PVDF) and mixed cellulose ester (MCE). Membrane fouling mechanisms were identified based on the blocking filtration model, indicating that the dominant fouling mechanism during soy sauce microfiltration was cake formation on the membrane surface. Microfiltration delivered highly dispersed soy sauce having superior clarity and a light color, with satisfactory sterilization quality, and preserved well the NaCl, reducing sugar, total acid and amino nitrogen content, leading to a product having a longer shelf life as compared to pasteurization. The loss of volatile compounds after refinement (microfiltration and pasteurization) was not neglected, particularly the ester groups (total loss of 76.3% to 96.4%), which affected the aroma profile of the soy sauce; all the samples from microfiltration seemed to lack the floral aroma. Ceramic membrane filtration and pasteurization exhibited relatively good preservation of the aroma of soy sauce, which then obtained the best scores in sensory analysis.

Membrane fouling mechanisms and characterization of physicochemical, aroma and shelf-life properties of soy sauce subjected to refinement.

Extracellular Proteome Analysis and Flavor Formation During Soy Sauce Fermentation

Aspergillus oryzae is an excellent strain for soy sauce fermentation because of its complicated enzyme system, especially protease. The aim of this study was to investigate the key enzymes and flavors during soy sauce fermentation, and a comparative assessment of extracellular enzymes during various fermentation stages at the proteomic level via iTRAQ analysis is presented. Many important enzymes related to the amino acid and glucose metabolisms participated in the material decomposition under high-salt stress. Dipeptidase, dipeptidyl aminopeptidase, leucine aminopeptidase, aspartic protease pep1, and extracellular metalloproteinase played positive roles during the early stage of soybean mash fermentation, whilst leucine aminopeptidase A and extracellular metalloproteinase NpI were the dominant proteolytic enzymes during the later period of fermentation. At the same time, β-glucosidase and β-xylanase exerted great effects upon glucose metabolism throughout the fermentation process. The results show that protease and amylolytic enzymes are complementary in the formation of flavors such as alcohols, acids, esters, aldehydes, furans, and pyrazines during soy sauce fermentation.

Umami compounds present in low molecular umami fractions of asam sunti - A fermented fruit of Averrhoa bilimbi L

Salted fermented fruit known as asam sunti (Averrhoa bilimbi L.) in Indonesia has been used as a source of umami taste. This study was aimed to characterize the three types of asam sunti and their water soluble extracts, and to trace the compounds responsible for umami taste in umami fractions. Umami fractions were obtained by ultrafiltration followed by Sephadex G-15 chromatographic separation. The three types of samples could be differentiated by physicochemical and sensory analyses. Low molecular weight fraction had the highest umami intensity. Further chromatographic separation revealed three umami fractions, F-II, III and IV. Umami taste of F-III was due to the presence of free l-glutamic acid at 6 times, while FII and FIV were due to succinic acid at more than 30 times their respective umami thresholds. Organic acid as well as amino acid seemed to play an important role in the intense umami taste of asam sunti.

Microbe participation in aroma production during soy sauce fermentation

Soy sauce is a traditional Japanese fermented seasoning that contains various constituents such as amino acids, organic acids, and volatiles that are produced during the long fermentation process. Although studies regarding the correlation between microbes and aroma constituents have been performed, there are no reports about the influences of the microbial products, such as lactic acid, acetic acid, and ethanol, during fermentation. Because it is known that these compounds contribute to microbial growth and to changes in the constituent profile by altering the moromi environment, understanding the influence of these compounds is important. Metabolomics, the comprehensive study of low molecular weight metabolites, is a promising strategy for the deep understanding of constituent contributions to food characteristics. Therefore, the influences of microbes and their products such as lactic acid, acetic acid, and ethanol on aroma profiles were investigated using gas chromatography/mass spectrometry (GC/MS)-based metabolic profiling. The presence of aroma constituents influenced by microbes and chemically influenced by lactic acid, acetic acid, and ethanol were proposed. Most of the aroma constituents were not produced by adding ethanol alone, confirming the participation of yeast in aroma production. It was suggested that lactic acid bacterium relates to a key aromatic compound, 2,5-dimethyl-4-hydroxy-3(2H)-furanone. However, most of the measured aroma constituents changed similarly in both samples with lactic acid bacterium and acids. Thus, it was clear that the effect of lactic acid and acetic acid on the aroma profile was significant.

Identification of a key umami-active fraction in modernized Korean soy sauce and the impact thereof on bitter-masking

Food protein hydrolysates created by natural fermentation have been used for centuries as food flavorings. The aim of this study was to define the key umami-active fraction of modernized Korean soy sauce (mJGN) and the impact thereof on bitter-masking of human sensory and bitter-taste receptor-expressing cells. We found strong correlations between taste profiles of mJGN and a contained fraction (F05). The latter contained compounds of less than 500Da, and elicits a distinct umami taste. Both free amino acids and Glu-enriched oligopeptides are suggested to be crucial in terms of the effects of F05 on taste. F05 not only reduced human-perceived bitterness, but also effectively suppressed the intracellular Ca²⁺ response induced by caffeine in the hTAS2R43 and hTAS2R46 human bitter-taste receptor-expressing cells. This suggests that F05, a key umami-active fraction of mJGN, contains components that at least partially modulate human bitter-taste receptor action, improving food flavor.

(13)C-NMR-Based Metabolomic Profiling of Typical Asian Soy Sauces

It has been a strong consumer interest to choose high quality food products with clear information about their origin and composition. In the present study, a total of 22 Asian soy sauce samples have been analyzed in terms of (13)C-NMR spectroscopy. Spectral data were analyzed by multivariate statistical methods in order to find out the important metabolites causing the discrimination among typical soy sauces from different Asian regions. It was found that significantly higher concentrations of glutamate in Chinese red cooking (CR) soy sauce may be the result of the manual addition of monosodium glutamate (MSG) in the final soy sauce product. Whereas lower concentrations of amino acids, like leucine, isoleucine and valine, observed in CR indicate the different fermentation period used in production of CR soy sauce, on the other hand, the concentration of some fermentation cycle metabolites, such as acetate and sucrose, can be divided into two groups. The concentrations of these fermentation cycle metabolites were lower in CR and Singapore Kikkoman (SK), whereas much higher in Japanese shoyu (JS) and Taiwan (China) light (TL), which depict the influence of climatic conditions. Therefore, the results of our study directly indicate the influences of traditional ways of fermentation, climatic conditions and the selection of raw materials and can be helpful for consumers to choose their desired soy sauce products, as well as for researchers in further authentication studies about soy sauce.

Sequence, taste and umami-enhancing effect of the peptides separated from soy sauce

Five tasty peptides were separated from soy sauce, by sensory-guided fractionation, using macroporous resin, medium-pressure liquid chromatography and reverse phase-high performance liquid chromatography, and identified by ultra-performance liquid chromatography tandem mass-spectrometry as ALPEEV, LPEEV, AQALQAQA, EQQQQ and EAGIQ (which originated from glycinin A1bB2-445, glycinin A1bB2-445, cobyric acid synthase, leucine-tRNA ligase and glycoprotein glucosyltransferase, respectively). LPEEV, AQALQAQA and EQQQQ tasted umami with threshold values of 0.43, 1.25 and 0.76mmol/l, respectively. ALPEEV and EAGIQ had minimal umami taste, but ALPEEV, EAGIQ and LPEEV showed umami-enhancement with a threshold estimated at 1.52, 1.94 and 3.41mmol/l, respectively. In addition, the synthetic peptides showed much better sensory taste than mixtures of their constitutive amino acids. It indicated that peptides might play an important role in the umami taste of soy sauce.

Evaluation of autochthonous micrococcus strains as starter cultures for the production of Kedong sufu

AIMS

The technological properties of 22 micrococcus strains from traditional fermented Kedong sufu were evaluated in order to develop autochthonous starter cultures.

METHODS AND RESULTS

The proteolytic, autolytic and lipolytic activity, salt tolerance, production and degradation of the biogenic amines of six Micrococcus luteus, nine Kocuria kristinae and seven Kocuria rosea were evaluated. The results indicated that these micrococcus strains exhibited a certain technological diversity, and the results also indicated the best properties to be used in mixed starter cultures. Based on the above findings, two sets of autochthonous starters were formulated. Considering the physicochemical properties and sensory characteristics of sufu, the maturation period of sufu was shortened by 30 days. The profiles of free amino acids and peptides partly revealed the mechanism of sensory quality and shorter ripening time of sufu manufactured using autochthonous mixed starters. Compared to back-slopping fermentation, sufu manufactured with selected autochthonous starter cultures exhibited lower levels of total biogenic amines.

CONCLUSIONS

The selected strains could be used as starter to avoid the accumulation of high concentrations of biogenic amines while also maintaining typical sensory characteristics and preserving the autochthonous strains of the traditional Kedong sufu. The maturation times of Kedong sufu were shortened by 30 days with application of the autochthonous starter.

SIGNIFICANCE AND IMPACT OF THE STUDY

Autochthonous mixed starters can reduce the generation of biogenic amines, speed up the sufu maturation process and preserve typical sensory quality. Furthermore, the rotation of two sets of mixed starter cultures can effectively resist phage attack during the production of sufu.