Protein oxidation in muscle-based products: Effects on physicochemical properties, quality concerns, and challenges to food industry.

Protein oxidation in meat has received immense attention since it significantly affects the quality of meat-based products. This review sheds light on the effects of protein oxidation on the physicochemical properties of meat and meat-based products during processing, and highlights major quality concerns and challenges to the food industry. Protein oxidation is often initiated by oxidative attack by reactive oxygen species and modifications of side chain amino acids, which may result in protein aggregation, carbonylation, alteration of surface hydrophobicity, and perturbation in primary, secondary and tertiary structures. Thus, protein oxidation during processing (especially thermal treatments) has raised serious concerns about the quality of the final products. These adverse consequences usually intensify with increase in processing temperature and time. Protein oxidation may also cause severe deterioration of nutritional value owing to the loss of essential amino acids and resistance of the oxidized protein molecules to the hydrolytic action of digestive enzymes. In addition, it may promote drip loss and decrease water holding capacity that would eventually negatively impact texture. Furthermore, protein oxidation is closely associated with other processing-induced adverse events, in particular lipid oxidation and formation of toxic Maillard reaction products, such as heterocyclic amines and advanced glycation end-products, but the underlying mechanisms have remained unclear. Several strategies including careful choice of processing methods and use of natural agents, such as polyphenols, hydrocolloids and vitamins alone or in combination have been proposed for the attenuation of protein oxidation and its related undesirable reactions through binding with precursors and/or reactive intermediary compounds.

Evaluation of ultrasound-assisted L-histidine marination on beef M. semitendinosus: Insight into meat quality and actomyosin properties.

This paper aimed to evaluate the effects of ultrasound-assisted L-histidine marination (UMH) on meat quality and actomyosin properties of beef M. semitendinosus. Our results found that UMH treatment effectively avoided excessive liquid withdrawal, and disrupted myofibril integrity by modifying the water distribution and weakening connection of actin-myosin with increased muscle pH. The ultrasound-treated sample provided more opportunity for the filtration of L-histidine to intervene the isoelectric point and conformation of muscle protein. The activated caspase-3 and changes of ATPase activity in UMH-treated meat accelerated the postmortem ageing, and L-histidine might competitively inhibit the actin-myosin binding by the imidazole group. UMH decreased the surface hydrophobicity by shielding hydrophobic area and unfolding the actomyosin structure. In addition, the increased actomyosin solubility with smaller particle size enhanced the SH content for better cross-linking of myosin tail, and formation of heat-set gelling protein structure. Therefore, UMH treatment manifested the potential to improve beef quality.

High fat diet incorporated with meat proteins changes biomarkers of lipid metabolism, antioxidant activities, and the serum metabolomic profile in Glrx1-/- mice.

Red and processed meat consumption has been associated with oxidative stress, diabetes and non-alcoholic fatty liver disease (NAFLD). This study was aimed at exploring the effects of high-fat meat protein diets on potential metabolite biomarkers in Glrx1-/- mice, a well-documented mouse model to study NAFLD. Male Glrx1-/- mice were fed a control diet with 12% energy (kcal) from fat, a high-fat diet supplemented with casein (HFC) with 60% energy (kcal) from fat, and a high-fat diet supplemented with fish (HFF) or mutton proteins (HFM) for 12 weeks. The results of biochemical and histological analyses indicated that the intake of HFM increased hepatic total cholesterol, triglycerides, serum alanine transaminase and aspartate transaminase, and macro- and micro-vesicular lipid droplet accumulation, which were accompanied by altered gene expression associated with the lipid and cholesterol metabolism. HFF diet fed Glrx1-/- mice significantly ameliorated diet-induced NAFLD biomarkers compared to HFC and HFM diets. In addition, serum metabolome profiling identified metabolites specifically associated with lipid metabolism bile acid metabolism, sphingolipid and amino acid metabolism pathways. A HFM diet increased the abundance of LysoPC(15:0), LysoPC(16:0), LysoPC(20:1), LysoPE(18:2), LysoPE(22:0), LysoPE(20:6), O-arachidonoylglycidol, 12-ketodeoxycholic acid and sphinganine that are associated with NAFLD. The KEGG metabolic pathway of identified metabolites of high fat diets showed that the differential metabolites were associated with lipid metabolism, linoleic acid metabolism, amino acid metabolism, bile acid metabolism, sphingolipid metabolism, and glutathione metabolism pathways whereas HFF diet ameliorated NAFLD by modifying these pathways. These results provide potential metabolite biomarkers for NAFLD induced by HFM diet.

Content, causes and analysis of heterocyclic amines in Chinese traditional braised chicken.

Braised chicken is a popular traditional chicken product in China with a special and complicated culinary method. However, there has been little research focused on the food safety problems caused by hazardous compounds in braised chicken. In this study, the contents of heterocyclic amines (HCAs) in representative braised chicken samples were determined. Total HCAs in braised chicken were relatively high (6.20-27.7 ng g-1), and aminoimidazoazaarenes (AIAs) took a large proportion (54.0-86.4%). 2-Amino-3-methylimidazo[4,5-f]quinoline (IQ) was found in all samples with a high level (2.72-13.5 ng g-1), whilst 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was low (0.14-0.41 ng g-1). 9H-pyrido[3,4-b]indole (Norharman) and 1-methyl-9H-pyrido[3,4-b]indole (Harman) were main components in aminocarbolines (ACs). So the potential safety risk in braised chicken caused by high HCAs content should be paid attention. Principal component analysis (PCA) was used to analyse and visualise the differences of HCAs levels among braised chicken samples. The result indicated that the differences among these samples were significant, but there were no obvious similarities between samples produced in the same regions. Moreover, there were rare significant positive correlations between chemical components (including moisture, fat, protein, creatine and free amino acids) and hazardous compounds. Considering PCA and correlation analysis results, these parameters may play a major role in the HCAs levels in Chinese traditional braised chicken.