Freezing of meat and aquatic food : Underlying mechanisms and implications on protein oxidation

Publisher Copyright: © 2021 Institute of Food Technologists®Over the recent decades,protein oxidation in muscle foods has gained increasing research interests as it is known that protein oxidation can affect eating quality and nutritional value of meat and aquatic products. Protein oxidation occurs during freezing/thawing and frozen storage of muscle foods, leading to irreversible physicochemical changes and impaired quality traits. Controlling oxidative damage to muscle foods during such technological processes requires a deeper understanding of the mechanisms of freezing-induced protein oxidation. This review focus on key physicochemical factors in freezing/thawing and frozen storage of muscle foods, such as formation of ice crystals, freeze concentrating and macromolecular crowding effect, instability of proteins at the ice–water interface, freezer burn, lipid oxidation, and so on. Possible relationships between these physicochemical factors and protein oxidation are thoroughly discussed. In addition, the occurrence of protein oxidation, the impact on eating quality and nutrition, and controlling methods are also briefly reviewed. This review will shed light on the complicated mechanism of protein oxidation in frozen muscle foods.Peer reviewe

A new two-step rapid fermentation method for shrimp paste based on strain fortification and analysis of flavor quality

A two-step rapid fermentation shrimp paste process based on strain enhancement was developed by inoculating functional strains into shrimp paste in two steps. This improved the drawbacks of traditional fermented shrimp paste products, such as their lengthy fermentation times, high salt contents, and unstable fermentation quality. Single factorial and response surface analyses was employed to optimize the two-step fermentation process, and the physicochemical indices, sensory and volatile components of the rapid fermentation products were analyzed and compared with the uninoculated fermented shrimp paste. The results showed that the optimal process parameters for the one-step fermentation with Cladosporium Z3 were 12 d, 21 ℃ and 3% (V/V) inoculum, and the optimal parameters for the two-step fermentation with Enterococcus faecalis X1 were 4 d, 25 ℃ and 4% (V/V) inoculum. Compared with the uninoculated fermented shrimp paste, the two-step fermented shrimp paste samples with starters had higher amino acid nitrogen (AAN) content, more complete protein hydrolysis and lower total volatile base nitrogen (TVB-N) content, while the two-step fermentation method with intensified starters was able to promote the formation of good flavor and the good quality of shrimp paste

Application and Mechanism of High-Sensitivity Indicator Film for Monitoring Fish Freshness

The sensitivity of freshness indicator labels/films has become an important research direction of intelligent food packaging. In this study, a high-sensitivity indicator film containing gelatin and Fe2＋ was prepared by electrospinning using blueberry anthocyanins as the indicator and zein as the matrix for monitoring fish freshness. The validity and sensitivity of the indicator film for detecting the freshness of silver carp were tested and the potential mechanism was elucidated. The results of pH sensitivity, ammonia sensitivity and anthocyanin release showed that the addition of gelatin and Fe2+ improved the sensitivity of the indicator film to pH and ammonia, and contributed to better binding of the anthocyanins in the film. There was a strong correlation between the color response (P = (L* + a* + b* + R + G + B)/a*) of the film and the content of total volatile basic nitrogen (TVB-N) content in fish meat as a freshness indicator (R2 > 0.98). In conclusion, the prepared indicator film can effectively monitor fish freshness, and the hydrogen bond interactions between anthocyanins and gelatin/Fe2+ may affect the color response characteristics and sensitivity of the indicator film

Effect of the Time of NaCl Addition on Nutrient Migration and Micro and Nanoparticles of Channa argus Head Soup

Channa argus is a bottom-dwelling freshwater fish with high nutritional and economic value and, in China, is known as the "treasure of fish". C. argus meat is mainly used to produce fish fillets; however, head and bone are occasionally utilized in food production. The head of C. argus is rich in mineral elements, amino acids, and unsaturated fatty acids and is commonly used in China for fish head soup. The preparation of fish head soup is particularly time-consuming and can take several hours. Therefore, a high demand exists for the research and development of instant fish head soup products. With the development of modern food colloid research technology, the formation of micro/nanoparticles (MNPs) in soups and the biological effects of the tissue units as active ingredients have attracted increasing attention. In terms of the cooking process of fish soup, in addition to the heating method and cooking time, the seasoning added during cooking is also an important factor. In particular, salt is a key determinant of soup flavor. Although the content is the same, the addition of salt affects the dissolution and migration of nutrients from the fish head during the cooking process. However, the effect of the addition time of salt on the nutritious flavor during the preparation of fish soup has not been studied clearly. Furthermore, the stability of fish soup has not been adequately evaluated.In this work, the C. argus head was chosen as the base material for the soup and the nutrient migration and particles in the C. argus head soup were studied. Water-soluble protein, total sugar, total minerals, solids, nucleotides, free amino acid content, and colloidal particle stability were chosen as indicators to evaluate the transfer of nutrients and flavor. In addition, the morphological structure and distribution of MNPs in the soup were observed using laser scanning confocal microscopy (LSCM). The results showed that the content of water-soluble proteins first increased and then decreased with the delay in salt addition time. The migration trend of total sugars was similar to that of the proteins. Meanwhile, the ash content in the soup generally increased and then decreased. The change in the content of soluble solids could represent changes in various nutrients. The migration of solids and the content of ash peaked when the salting time was at 90 min. The boiled samples with salt added at different times showed significant differences in the migration of nucleotides. It could be concluded that salting was ideal at 60 min or 90 min, based on the changes in the total amount of nucleotides. Furthermore, the contents of total free amino acids and umami-flavored amino acids were also the highest in the samples with salt added at 60 min or 90 min. When the addition time was 60 min, the stability of the MNP system in the fish head soup could effectively be improved by inhibiting the aggregation of macromolecules, which would promote the retention of various nutrients. The particle size and polydispersity (PDI) were lowest in the samples with salt added at 60 min. In addition, the zeta potential value of the sample with salt added at 60 min was higher than that at 90 min. Therefore, the system was relatively stable at 60 min, which was conducive to nutrient retention. This is consistent with the results of the microstructure analysis.The maximum dissolution of nutrients and flavor substances occurred when salt was added after boiling for 60 min. Meanwhile, MNPs in the soup were stable, uniform, double-layer, spherical particles. The results of LSCM showed that nonpolar triglycerides self-assembled into spherical particles, which were located in the center of the particles, and protein molecules dispersed around or were bound to the surface of the particles. The fish head soup system was the most stable under the conditions of particle size, potential, and polydispersion index. Therefore, adding salt after boiling for 60 min was the optimal procedure for making fish soup with high nutritional value, delicious taste, and stable content. This study provides a baseline procedure for C. argus head soup with high and stable nutritional content.The results provide technical support for preparing a convenient and delicious fish head soup. People can enjoy delicious food shortly after a hard day´s work. In addition, the results showed that the timing of adding salt had a significant impact on the nutrition of fish head soup, which suggests that attention should be paid to the timing of adding salt when preparing fish head soup at home. C. argus head, a by-product of processing, can increase in value and provide a solution for producers to decrease waste and increase profits

Uncovering the differences in flavor volatiles of different colored foxtail millets based on gas chromatography-ion migration spectrometry and chemometrics

The differences of volatile organic compounds in commercially available foxtail millets with different colors (black, green, white and yellow) were assayed through gas chromatography-ion migration spectrometry (GC-IMS) to explore their volatile flavor characteristics. Fifty-five volatile components were found in various colored foxtail millets, including 25 kinds of aldehydes (accounting for 39.19–48.69%), 10 ketones (25.36–32.37%), 15 alcohols (20.19–24.11%), 2 ethers (2.29–2.45%), 2 furans (1.49–2.95%) and 1 ester (0.27–0.39%). Aldehydes, alcohols and ketones were the chief volatiles in different colored foxtail millet, followed by furans, esters and ethers. These identified volatile flavor components in various colored foxtail millets obtained by GC-IMS could be well distinguished by principal components and cluster analysis. Meanwhile, a stable prediction model was fitted viapartial least squares-discriminant analysis (PLS-DA), in which 17 kinds of differentially volatile components were screened out based on variable importance in projection (VIP>1). These findings might provide certain information for understanding the flavor traits of colored foxtail millets in future

Mobility and redistribution of waters within bighead carp (Aristichthys nobilis) heat-induced myosin gels

Water-holding capacity is closely related to gel microstructure, and is a very important quality trait in surimi and surimi product. The changes in the secondary structure, gel microstructure, and the migration of water in bighead carp (Aristichthys nobilis) myosin gel induced by different temperatures (50–90°C) were investigated. The α-helical structure of myosin decreased at temperatures of 40°C or higher. The fractal dimension of the gels increased at 40, 50, and 60°C, but decreased at temperatures over 60°C. The pore size of the gels increased with temperatures up to 50°C, decreased at 60°C, and then increased with temperatures up to 90°C again. The transverse relaxation times also varied; T21 remained constant at temperatures over 40°C; T22 decreased at temperatures lower than 50°C, increased at 60°C, and then decreased with temperatures up to 90°C; and T23 increased at temperatures lower than 50°C and then remained constant until 90°C. Principal component analysis showed that the proportion of T22 water (PT22) was inversely correlated with the unfolding of myosin, whereas directly correlated with the pore size. The proportion of T23 water (PT23) was positively correlated with the fractal dimensions of the gels, whereas negatively correlated with the pore size. The migration of the secondary layer of water was mainly caused by hydrophobic force and the physical space formed by the myosin backbone, and the migration of water within the third layer was mainly caused by capillary pressure. Therefore, the mobility and redistribution of waters depend on the water retention mechanism, which is determined by the physical structure of gels. This study provides further information about the relationship between the NMR data, gel microstructure, water mobility, and distribution

Recombinant human collagen digestates exhibit higher protective effect on UVA-damaged skin fibroblasts than animal-derived collagens

Recombinant collagen offers an attractive alternative to the animal-derived collagens in cosmetics and tissue engineering. But its anti-skin-aging effect as food remains unclear. Compared to fish and bovine collagens, recombinant human collagen (RHC) digestates had a higher Pro content and average molecular weight (7222.96 Da). In UVA-damaged human skin fibroblasts, RHC digestates increased proliferation to 133.41 % and migration by 3.23-fold. They decreased ROS levels by 54.02 % via enhancing the activities of superoxide dismutase and glutathione peroxidase. They also stimulated the expression of mRNA and protein of COL1A1, COL3A1, HAS2, and TIMP-1, and inhibited the expression of MMP-1. Overall, RHC digestates exhibited a higher protective effect on UVA-damaged fibroblasts than animal-derived collagens, which was due to their special molecular structure that provided a more cell-friendly microenvironment and/or directly exerted a higher biological activity. These suggested that RHC might be a promising and more effective anti-skin-aging agent as macronutrient or functional food

Flubendiamide Enhances Adipogenesis and Inhibits AMPKα in 3T3-L1 Adipocytes

Flubendiamide, a ryanoid class insecticide, is widely used in agriculture. Several insecticides have been reported to promote adipogenesis. However, the potential influence of flubendiamide on adipogenesis is largely unknown. The current study was therefore to determine the effects of flubendiamide on adipogenesis utilizing the 3T3-L1 adipocytes model. Flubendiamide treatment not only enhanced triglyceride content in 3T3-L1 adipocytes, but also increased the expression of cytosine-cytosine-adenosine-adenosine-thymidine (CCAAT)/enhancer-binding protein α and peroxisome proliferator-activated receptor gamma-γ, two important regulators of adipocyte differentiation. Moreover, the expression of the most important regulator of lipogenesis, acetyl coenzyme A carboxylase, was also increased after flubendiamide treatment. Further study revealed that 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) or A769662, two Adenosine 5′-monophosphate (AMP)-activated protein kinase α activators, subverted effects of flubendiamide on enhanced adipogenesis. Together, these results suggest that flubendiamide promotes adipogenesis via an AMPKα-mediated pathway

Purification and identification of anti-inflammatory peptides from sturgeon (Acipenser schrenckii) cartilage

Cartilage is a nonedible byproduct with little saleable value. However, previous studies have proposed the possibility of producing peptides from cartilage with immune function modulation potential. The current study aimed to investigate the potential anti-inflammatory activity of peptides derived from sturgeon (Acipenser schrenckii) cartilage in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Five peptide sequences, including four novel peptides, were identified from ethanol-soluble cartilage hydrolysates. Among these five peptides, LTGP, LLLE, LLEL and VGPAGPAGP reduced the production of nitric oxide (NO) and interleukin-6 (IL-6) while increasing interleukin-10 (IL-10) excretion. Transcriptome analysis suggested the inhibition of activated mitogen-activated protein kinase (MAPK) and interleukin-17 (IL-17) signaling pathways after LLEL intervention. MAPK, which is involved in the IL-17 signaling pathway, was further proved to be blocked by downregulating the phosphorylation of p38, extracellular-signal regulated protein kinase (ERK), and c-jun N-terminal kinase (JNK). This novel peptide offers an attractive approach to develop functional foods