Recent advances and challenges in the interaction between myofibrillar proteins and flavor substances

Myofibrillar proteins are an important component of proteins. Flavor characteristics are the key attributes of food quality. The ability of proteins to bind flavor is one of their most fundamental functional properties. The dynamic balance of release and retention of volatile flavor compounds in protein-containing systems largely affects the sensory quality and consumer acceptability of foods. At present, research on flavor mainly focuses on the formation mechanism of flavor components, while there are few reports on the release and perception of flavor components. This review introduces the composition and structure of myofibrillar proteins, the classification of flavor substances, the physical binding and chemical adsorption of myofibrillar proteins and volatile flavor substances, as well as clarifies the regulation law of flavor substances from the viewpoint of endogenous flavor characteristics and exogenous environment factors, to provide a theoretical reference for the flavor regulation of meat products.

HS-SPME-GC-MS Combined with Orthogonal Partial Least Squares Identification to Analyze the Effect of LPL on Yak Milk's Flavor under Different Storage Temperatures and Times

Flavor is a crucial parameter for assessing the sensory quality of yak milk. However, there is limited information regarding the factors influencing its taste. In this study, the effects of endogenous lipoprotein lipase (LPL) on the volatile flavor components of yak milk under storage conditions of 4 °C, 18 °C and 65 °C were analyzed via headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with orthogonal partial least-squares (OPSL) discrimination, and the reasons for the changes in yak milk flavors were investigated. Combined with the difference in the changes in volatile flavor substance before and after the action of LPL, LPL was found to have a significant effect on the flavor of fresh yak milk. Fresh milk was best kept at 4 °C for 24 h and pasteurized for more than 24 h. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were employed to characterize the volatile components in yak milk under various treatment conditions. Twelve substances with significant influence on yak milk flavor were identified by measuring their VIP values. Notably, 2-nonanone, heptanal, and ethyl caprylate exhibited OAV values greater than 1, indicating their significant contribution to the flavor of yak milk. Conversely, 4-octanone and 2-heptanone displayed OAV values between 0.1 and 1, showing their important role in modifying the flavor of yak milk. These findings can serve as monitoring indicators for assessing the freshness of yak milk.

Dynamics of Microbial Communities, Flavor, and Physicochemical Properties during Ziziphus jujube Vinegar Fermentation: Correlation between Microorganisms and Metabolites

Jujube pulp separated from Ziziphus jujube is often discarded after processing, resulting in a serious waste of resources and environmental pollution. Herein, Ziziphus jujube pulp was used as a raw material for vinegar fermentation. To investigate the dynamic distribution of microorganisms and flavor substances in ZJV, correlations between environmental variables (e.g., total acid, reducing sugar, temperature) and flavor substances (organic acids, amino acids, volatile substances) and microorganisms were analyzed. Physicochemical indicators (temperature, total acid, alcohol) were the main factors affecting ZJV fermentation. The middle and later stages of ZJV fermentation were the periods showing the largest accumulation of flavor substances. Organic acids (acetic acid, malic acid, citric acid, lactic acid), amino acids (Asp, Glu, Arg) and volatile substances (ethyl phenylacetate, phenethyl alcohol) were important odor-presenting substances in ZJV. In the bacterial community, the Operational Taxonomic Units (OTUs) with an average relative abundance of more than 10% in at least one fermentation stage were mainly Acetobacter, Lactobacillus and Saccharopolyspora, while it was Thermomyces in the fungal community. Pearson correlation coefficients showed that Penicillium, Lactobacillus and Acetobacter were the core microorganisms, implying that these microorganisms contributed to the flavor formation greatly in ZJV fermentation. This study reveals the correlation between physicochemical indexes and flavor substances and microorganisms in ZJV fermentation. The results of the study can provide a theoretical basis for the development of the ZJV industry.

High freezing rate improves flavor fidelity effect of hand grab mutton after short-term frozen storage

Taking the eutectic point as the final freezing temperature, the differences of flavor substances of in hand grab mutton (HGM) frozen at three rates of 0. 26 cm/h (−18°C), 0.56 cm/h (−40°C) and 2.00 cm/h (−80°C) were determined and analyzed. The results showed that the flavor of HGM decreased significantly after freezing. With the increase of freezing rate, the contents of aldehydes, alcohols, ketones, acids, esters, others, free amino acids and 5′-nucleotides were higher, and the content of specific substances was also generally increased. All samples from unfrozen and frozen HGM could be divided into four groups using an electronic nose based on different flavor characteristics. Seven common key aroma components were determined by relative odor activity value (ROAV), including hexanal, heptanal, octanal, nonanal, (E)-oct-2-enal, (2E,4E)-deca-2,4-dienal and oct-1-en-3-ol. The higher the freezing rate, the greater the ROAVs. Taste activity values calculated by all taste substances were far <1, and the direct contribution of the substances to the taste of HGM was not significant. The equivalent umami concentration of HGM frozen at −80°C was the highest. These findings indicated that higher freezing rate was more conducive to the retention of flavor substances in HGM, and the flavor fidelity effect of freezing at −80°C was particularly remarkable.

Lenthionine, a Key Flavor Substance in Lentinula edodes, Is Regulated by Cysteine under Drought Stress

Due to its unique flavor profile, Lentinula edodes has become one of the most popular edible mushrooms in the world, but the regulatory mechanism of its flavor substances has not been revealed. To study the mechanism that regulates the anabolic metabolism of the important flavor substance lenthionine (LT), the effect of cysteine (Cys) synthesized by the cystathionine-γ-lyase (CSE-1) gene participating in the regulation of LT metabolism under drought stress was analyzed. Our results showed that drought stress promoted the accumulation of LT, and the key genes GTT and LECSL were activated. Furthermore, drought stress promoted the accumulation of intracellular Cys and activated the key gene for Cys synthesis, CSE-1. Both inhibition of the CSE enzyme activity by inhibitors and silencing of the CSE-1 gene under drought stress significantly reduced the intracellular contents of Cys and LT, but the inhibition of LT synthesis disappeared after the exogenous addition of Cys. These results indicate that LT synthesis in L. edodes under drought stress is dependent on Cys. In summary, the mechanism of the regulation of flavor substances in edible mushrooms by the environment was revealed for the first time.