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.

New Insights into the Loss of Antioxidant Effectiveness of Phenolic Compounds in Vegetable Oils in the Presence of Phosphatidylcholine.

It has been proposed that lipid oxidation reactions in edible oils primarily occur in reverse micelles (RM) of amphiphilic components. While the prooxidative effect of RM has been demonstrated, the mechanism involved is not fully understood. Both reductions and enhancements in the antioxidant efficacy (AE) of α-tocopherol and Trolox have been observed in different studies when phosphatidylcholine (PC) was added and PC RM were formed. However, most of these investigations employed lipid systems consisting of stripped vegetable oil diluted in saturated medium-chain triacylglycerols (MCT) and utilized antioxidant concentrations well below those found in edible oils. These two specific factors were investigated in the present study. The effect of RM of purified egg yolk PC on the AE of 1.16 mmol kg-1 α-tocopherol or Trolox in stripped sunflower oil (SSO) was studied by the Rancimat (100 °C) and oven (50 °C) tests. Increasing PC concentrations (50-1000 ppm) had no significant impact on α-tocopherol, but substantial reductions in AE were observed for Trolox. This phenomenon may be attributed to the partitioning of Trolox into the pre-existing PC micelles, suggesting that primary oxidation reactions occurred in the continuous lipid phase. In addition, the effectiveness of both antioxidants decreased significantly in the presence of PC when a low antioxidant concentration (0.06 mmol kg-1) was assayed in SSO:MCT (1:3, w/w).

Comparison of tropomyosin released peptide and epitope mapping after in vitro digestion from fish (Larimichthys crocea), shrimp (Litopenaeus vannamei) and clam (Ruditapes philippinarum) through SWATH-MS based proteomics.

Tropomyosin (TM) is a major shellfish allergen and a minor fish allergen. Different digestion profiles affect potential allergen anaphylaxis of protein. In this study, released peptides of fish-TM, shrimp-TM, and clam-TM by in vitro digestion of simulated gastric fluid (SGF), simulated intestinal fluid (SIF), and gastrointestinal (GI) were analyzed using sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH-MS) based proteomics. Results showed that digestion products of shrimp-TM yielded a lot of peptides matched T/B cell epitopes while core regions matched epitopes were distributed along the entire chain. Pepsin or trypsin-based digestion products of shrimp-TM presented many more peptides matched T/B cell epitopes compared with those of fish-TM and clam-TM. Besides, a differentiating peptide of VEKDKALSNAEGEVAAL (72-88) overlapped T/B cell epitopes could be used as a candidate peptide marker to identify tropomyosin allergen. These findings would supply new insight into the different allergenicity of tropomyosin.

A chemometric study on the identification of 5-methylfurfural and 2-acetylfuran as particular volatile compounds of oxidized fish oil based on SHS-GC-IMS.

Fish oil develops particular off-odors, mainly fishy odor, from the oxidation of its characteristic fatty acids, docosahexaenoic (DHA) and eicosapentaenoic (EPA). Anchovy oil (AO) was taken as representative of fish oils. This was compared to three vegetable oils with different fatty acid compositions, i.e. camellia, sunflower and linseed oil, and differential volatile compounds were identified by static-headspace gas-chromatography ion-mobility-spectrometry (SHS-GC-IMS) and orthogonal partial-least-squares discriminant analysis (OPLS-DA) during oxidation at 60 °C. Three groups of differential volatile compounds detected at higher concentrations in the AO were screened out and two compounds, identified as 5-methylfurfural and 2-acetylfuran, were characteristic to the AO and not found in the vegetable oils. They were formed from both EPA and DHA, only present in the AO, and their formation mechanisms were proposed. The contents of 5-methylfurfural and 2-acetylfuran increased linearly with the oxidation time and consequently they could be used as oxidative markers of fish oils.

Concomitant oxidation of fatty acids other than DHA and EPA plays a role in the characteristic off-odor of fish oil.

The aim of the present research was to explore the development of off-odors in fish oil from the perspective of fatty acid oxidation. It was found that the off-odors elicited by the two major ω-3 PUFAs in fish oil, i.e. DHA and EPA, were different from those by fish oil. Results showed that simultaneous oxidation of fatty acids other than DHA and EPA can be involved. The off-odors of fish oil was successfully simulated by combining oxidized samples of DHA, EPA and sunflower oil. Therefore, oxidation of oleic and linoleic acids also contributed to the off-odors in fish oil. A novel analytical approach that consisted in the combination of gas chromatography-ion mobility spectrometry (GC-IMS) and orthogonal partial least squares discriminant analysis (OPLS-DA) was applied to identify differences in the volatile components between the recombinant oil and the fish oil.

Major shrimp allergen peptidomics signatures and potential biomarkers of heat processing.

It is important to develop tools that can be used to understand the effects of processing on allergenic foods in order to achieve personalized food labeling. To evaluate the effect of heating on the allergy-relevant structural properties of tropomyosin (TM), arginine kinase (AK), myosin light chain (MLC) and sarcoplasmic calcium-binding protein (SCP) shrimp allergens, trypsin digests of raw, fried and baked shrimp extracts were analyzed by peptidomics and epitope correlations. Processing altered the number of peptides released from the distinct allergens, and each treatment generated a specific epitope-matched peptide allergen fingerprint. Among the four allergens, TM led to a number of released peptides and epitope changes being detected, and AK provided the epitope-matched 331MGLTEFQAVK340 sequence as a common differentiating peptide for heat processing. These results provide new views on the structural effects of processing on major shrimp allergens and peptide candidates as processing biomarkers.

Effect of Stored Humidity and Initial Moisture Content on the Qualities and Mycotoxin Levels of Maize Germ and Its Processing Products.

With high fat and protein content, maize germ is easily infected with fungus and mycotoxins during its storage. The qualities and safety of germ and its processing products may be affected by the storage. However, studies on the effect of storage on quality and polluted mycotoxin level of maize germ are limited. In this study, maize germ was stored with different initial moisture contents (5.03, 9.07, 11.82 and 17.97%) or at different relative humidity (75, 85 and 95%) for 30 days. The quality indices of germ (moisture content and crude fat content) and their produced germ oils (color, acid value and peroxide value) as well as the zearalenone (ZEN) and deoxynivalenol (DON) levels of germ, oils and meals were analyzed. Results showed that maize germ with high initial moisture contents (11.82, 17.97%) or kept at high humidity (95%) became badly moldy at the end of storage. Meanwhile, the qualities of these germ and oils showed great changes. However, the ZEN and DON contents of this maize germ, oils and meals stayed at similar levels (p < 0.05). Therefore, the storage could produce influence on the qualities of germ and oils, but showed limited effect on the DON and ZEN levels of germ and their processing products. According to this study, the storage condition of germ with no more than 9% moisture content and no higher than 75% humidity was recommended. This study would be benefit for the control of germ qualities and safety during its storage.

Application of Plackett-Burman Design in Screening of Natural Antioxidants Suitable for Anchovy Oil.

Considering the safety of synthetic antioxidants, more and more natural antioxidants have been developed and utilized in foods. This study aimed to screen out a natural antioxidant combination from many antioxidants, which could significantly affect the oxidation stability of anchovy oil, while Plackett-Burman design (PBD) methodology was employed in this screening. According to the statistical results of this design, sesamol, dihydromyricetin, teapolyphenol, and rosemary acid were four significant parameters on the oxidation stability of anchovy oil. Moreover, dihydromyricetin presented the best antioxidant effect among nine kinds of selected antioxidants when they were used alone in anchovy oil. Meanwhile, a combination including sesamol (0.02%), teapolyphenol (0.02%). and rosemary acid (0.02%) was adopted, and its antioxidant ability was similar to that of tert-butylhydroquinone (TBHQ). Additionally, phytic acid as a synergist was used and combined with sesamol, and the antioxidant ability of this combination was better than that of TBHQ. This study presented a reference for the industrial applications of natural antioxidants and synergists in anchovy oil.

Occurrence of deoxynivalenol in maize germs from North China Plain and the distribution of deoxynivalenol in the processed products of maize germs.

69 maize germ samples from North China Plain, 40 processed products of maize germs obtained in lab, 30 crude corn oils from factories and 40 refined corn oils from supermarkets in China were analyzed of deoxynivalenol (DON) by HPLC combined with ultraviolet detection and immunoaffinity column. 95.7% of maize germs were contaminated by DON. The average content was 449.0 µg/kg. The average of DON in processed products of maize germs including solvent extracted oil, cold-press oil, meal and cake was 163.7, 113.1, 1111.5 and 1175.2 µg/kg, respectively. Only 20% of crude corn oil and 12.5% of refined corn oil were contaminated by DON with the range of 67.5-340.5 µg/kg and 57.1-207.5 µg/kg, respectively. During the production of corn oil, solvent extraction oil had a larger amount of DON than pressing oil. The contamination of DON in corn oil was not serious or widespread, which indicated a low risk of health.

Occurrence of polycyclic aromatic hydrocarbons in various types of raw oilseeds from different regions of China.

Ninety-five samples of 18 types of oilseeds used for edible oil production were collected from different origins of China. The occurrence of polycyclic aromatic hydrocarbons (PAHs) in these oilseeds was presented after the analysis by using a simplified gas chromatography-mass spectrometry method. The results indicated that some of these oilseeds were not found of indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene, and benzo[ghi]perylene. Naphthalene and phenanthrene had higher concentration than other individual PAH in the same sample. The range of BaP, PAH4, and PAH16 concentration in these 95 samples was 0.1-14.1, 1.1-74.6, and 81.8-466.8 µg/kg, respectively. LPAH accounted for 87.1-99.5% of the total concentration of PAHs in all of studied oilseeds. The average concentrations of PAH16 in different types of oilseed were different. Meanwhile, the samples collected from different origins of China presented various levels of PAH16. The differences between herbaceous plant oilseeds and woody plant oilseeds in terms of PAH levels were not observed.