This study aimed to examine the effects of grape seed extract (GSE) on enhancing the quality of Altay sheep meat during repeated freeze-thaw cycles. The surface of the Longissimus dorsi muscle was sprayed with 0.5 g/100 mL GSE aqueous solution prior to undergoing 1, 3, 5 or 7 freeze-thaw cycles. At each cycle, meat color, myoglobin oxidation status, pH, shear force, thiobarbituric acid reactive substances (TBARS) value, total volatile basic nitrogen (TVB-N) content and volatile compound profile were determined. The results indicated that with increasing freeze-thaw cycles, lightness (L*), redness (a*), relative content of oxymyoglobin (OMb), pH, and shear force decreased; yellowness (b*), TBARS value, and relative contents of deoxymyoglobin (DMb) and metamyoglobin (MMb) showed an increasing trend; TVB-N contents initially increased and then decreased. The incorporation of GSE was found to mitigate the pH decrease and significantly lower the TBARS value (P < 0.05) during freeze-thaw cycles, but had no significant effect on the color, shear force or TVB-N content of mutton. Additionally, the levels of major volatile flavor compounds such as hexanal, 1-octene-3-ol, (E,E)-2,4-decenal, (E,Z)-2,4-decenal, (E)-2-octanal, octanal, heptanal, 3-octanone, carbon disulfide, and 2-pentylfuran initially rose and then fell with increasing freeze-thaw cycles, resulting in flavor deterioration. Compared with the blank group, GSE addition significantly curtailed the formation of aldehydes, ketones, alcohols, and furans resulting from lipid oxidation during repeated freeze-thaw cycles, thereby improving mutton flavor. This research provides a theoretical foundation and technical support for the flavor preservation and regulation of meat products during cold-chain circulation.

Hemoglobin hydrolysate is derived from the enzymatic degradation of hemoglobin. This work aimed to evaluate whether hemoglobin hydrolysate promotes the absorption of non-heme iron and the safety of absorbed iron in mice by analyzing the iron binding content, iron circulation, and liver homeostasis. We found that hemoglobin hydrolysate promoted the absorption of non-heme iron with high efficiency in duodenum by spontaneously binding non-heme iron during digestion, and increased hepatic iron content by up-regulating divalent metal transporter 1, zinc transporter 14, but hepatic iron content only increased at 3 weeks. Duodenal iron entered the blood through ferroportin without restriction at 3 weeks, and excessive iron entered the liver and then affected the hepatocyte membranes permeability and lipid synthesis through oxidative stress. With the prolongation of dietary intervention, the up-regulated hepcidin acted on the ferroportin to restrict excess iron from entering the blood, and then the hepatic homeostasis recovered. In addition, hemoglobin hydrolysate enhanced the hepatic antioxidant capacity. Taken together, hemoglobin hydrolysate has a strong ability to promote the absorption of non-heme iron in vivo, and the absorbed iron is relatively safe due to the regulation of hepcidin.

To determine the effects of plant-based meat analogues on the metabolic health and the possible mechanisms, mice were fed with a real pork diet (AP), a real beef diet (AB), a plant-based pork analogue diet (PP) and plant-based beef analogue diet (PB) for 68 days. Compared with real meat, the plant-based meat analogues increased food and energy intake, body weight, white fat and liver weight and caused adipocyte hypertrophy, hepatic lipid droplet accumulation, and inflammatory responses in mice. Metabolomics revealed that plantbased meat analogues altered the composition of serum metabolites, which regulated lipid metabolism homeostasis. The PB diet upregulated gene expression related to lipid synthesis, lipolysis and adipocyte differentiation while the PP diet upregulated expression of lipolysis-related genes but downregulated expression of adipocyte differentiation-related genes in white adipose tissue. Meanwhile, both PP and PB diets upregulated lipid influx- and synthesis-related genes but downregulated lipid oxidation-related genes in liver. The specific metabolite biomarkers may affect fat accumulation mainly by direct lipid metabolism pathways or indirect amino acid metabolism, protein digestion and absorption, bile secretion, aminoacyl-tRNA biosynthesis, neuroactive ligand-receptor interaction and ABC transporters pathways. These findings provide a new insight into understanding the differences in nutritional functions of meat and plant-based meat analogues.