The preparation of bone peptides (livestock and poultry bone peptides, LBPs) for the development of bone-derived functional foods is one of the important ways for the high-value utilization of livestock and poultry bone by-products. In this experiment, the leg bone from four main livestock and poultry species were used as raw materials to prepare LBPs based on the same process, and their physicochemical properties and bioactivities were compared and analyzed, so as to provide the reference for the high-value utilization of livestock and poultry bone resources and the development of bone-derived functional foods.

Yak bone peptides (YBPs), bovine bone peptides (BBPs), porcine bone peptides (PBPs) and chicken bone peptides (CBPs) were prepared from yak, bovine, porcine and chicken leg bones, respectively. Physicochemical properties were characterized, including basic nutritional components, amino acid compositions, molecular weight and particle size distribution. Moreover, the bioactivities of the four LBPs, including osteoblast promoting proliferation, immune regulation, angiotensin converting enzyme inhibitors (ACEI) and antioxidation, were compared and analyzed.

The relative contents of crude protein in YBPs, BBPs and PBPs were (89.70±0.77)%, (90.43±0.88)% and (89.36±1.32)%, respectively, which were significant higher than that of CBPs (79.18±1.49)%). The essential amino acids and sulfur-amino acids of CBPs were significant higher than those of YBPs, BBPs and PBPs. The four LBPs were mainly composed of small molecular peptides with MW<2 kD, accounting for about 90%. There was no significant difference in particle size distribution of LBPs powder, which was mainly concentrated in the range of 10-20 µm and 40-60 µm. The bioactivities of different LBPs were analyzed. It was found that YBPs had the most significant osteoblasts promoting proliferation effect, and the proliferation rate was 37.27% at 0.5 mg∙mL^-1; BBPs had the strongest effect on macrophage proliferation, and the proliferation rate was 39.26% at 5 mg∙mL^-1; PBPs had the strongest ACEI activity, and the inhibition rate of ACE activity was 82.37% at 15 mg∙mL^-1; YBPs had the strongest comprehensive antioxidant capacity, compared with BBPs, PBPs and CBPs.

The physicochemical properties of LBPs from four distinct species were different, but they all met the demand of raw material for the development of bone-derived functional foods. The bioactivities of LBPs from different species were different, which were suitable for the development of different bone-derived functional foods: YBPs had the strongest osteoblasts promoting proliferation effect and comprehensive antioxidant capacity, which was more suitable for the development of bone health improving or antioxidant bone-derived functional foods; BBPs had the strongest effect on promoting macrophage proliferation, which was more suitable for the development of immunomodulatory bone-derived functional foods; PBPs had the strongest ACEI activity and was more suitable for the development of bone-derived functional foods with blood pressure control effect; CBPs had the better powder properties and higher mineral content, which could be used as dietary nutritional supplements.

This study clarified the escape behavior of key volatile compounds in stewed beef with soy sauce during air-cooling process and refrigeration, aiming to provide the theoretical basis for the flavor preservation and conformity of stewed beef with soy sauce.

The volatile flavors in stewed beef with soy sauce were identified by the electronic nose (E-nose) and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) combined with odor activity value (OAV) and principal component analysis (PCA), which defined the dynamic change of flavors during cold air-cooling process (the central temperature was reduced from 50 ℃ to 10 ℃, the wind speed was 2 m∙s^-1, and the cooling time was 90 minutes) and refrigeration (0, 6, 18, 30, 42 and 54 h at 4 ℃). Then the escape behavior of key flavor active compounds in stewed beef with soy sauce were revealed.

According to the E-nose analysis, the flavor profiles of stewed beef with soy sauce exhibited significant differences among the three stages (“out of the pot”, before air-cooling and after air-cooling). Nitrogen oxides, alcohols, aldehydes, ketones, aromatics and organic sulfides were considered the main compounds for the discrepancy. On the other side, the stewed beef with soy sauce after 0, 42 and 54 h refrigeration showed differential flavor profiles, which mainly caused by the variety in nitrogen compounds, alcohols, aldehydes and ketones. However, there was no significant difference in the flavor profiles among 6, 18 and 30 h refrigeration. The HS-SPME-GC-MS results showed that 39, 31 and 33 volatile compounds were identified in three cold air-cooling stages, and the contents were 13 636.18, 9 799.21 and 8 213.86 μg∙kg^-1, respectively, with total amounts reducing by 39.8%. Morever, 36, 36, 34, 34, 31 and 29 volatile compounds were identified on different refrigeration periods, the contents were 7 712.65, 6 196.00, 5 319.42, 4 732.69, 5 295.05 and 4 281.82 μg∙kg^-1, respectively, and the total contents decreased by 44.5%. Therefore, the flavor escape of stewed beef with soy sauce mainly occurred in the refrigeration stage. Besides, OAV analysis showed stewed beef with soy sauce in the cold air-cooling stage had 18 key active compounds, while eucalyptol, lauryl alcohol, valeraldehyde, and L-carvone were all lost before cold air-cooling, and acetoin, phenethyl alcohol, geranyl acetone, as well as linalool escaped severely, with their OAV values reducing by 81.3%, 64.0%, 63.7% and 55.1%, respectively. 15 key active volatile compounds were identified during refrigeration. Among them, isobutyl acetate and ethyl heptanoate were lost after 6 h. Anethole, eugenol, 4-allylanisole, and linalool were severely escaped, and the OAV values decreased by 63.9%, 63.8%, 58.1% and 53.9%, respectively. Refrigeration was the main stage for the loss and dissipation of flavor compounds in stewed beef with soy sauce; alcohols, ketones, esters and phenolic ethers were more susceptible to lose and escape during air-cooling and refrigeration; the loss and dissipation of flavor compounds were mainly derived from spices.

This study revealed the escape behavior of flavor active compounds in stewed beef with soy sauce during air-cooling process and refrigeration, and provide the theoretical basis for stewed beef's flavor retention and regulation with soy sauce.

The aim of this study was to clarify the quality characteristics of Wenchang chicken cooked with coconut water, so as to provide an effective basis for the research on the interaction mechanism of Wenchang chicken and coconut water components and the standardized production.

With Wenchang chicken and Hainan green coconut as the main raw materials, the odor substances of Wenchang chicken, Wenchang chicken breast meat, and chicken leg meat cooked with coconut water were analyzed and compared using an electronic nose and gas chromatography-mass spectrometry (GC-MS), combined with odor activity value (OAV) and principal component analysis (PCA). The taste substances of chicken breast meat and chicken leg meat were analyzed using electronic tongue, free amino acid, and nucleotide detection techniques. The physical and chemical indexes of chicken and coconut water, as well as the cooking loss and texture indexes of coconut-boiled chicken and water-boiled chicken, were determined to clarify the changes in the quality characteristics of Wenchang chicken after cooking with coconut water.

The protein content in chicken leg meat was 21.0 g/100 g, and the fat content was 3.08 g/100 g. The protein content in chicken breast meat was 23.6 g/100 g, and the fat content was 1.29 g/100 g. The content of reducing sugar in coconut water was 4.75 g/100 g. The cooking loss of chicken cooked with coconut water was the highest compared with that boiled with water, and there was no significant correlation between the two texture indicators (P>0.05). After cooking with coconut water, five new aldehydes were produced in the chicken, namely 2-heptanal, (E)-2-octenal, (E)-2-nonenal, 2, 5-dimethyl benzaldehyde, and 2-undecenal. The electronic nose was able to distinguish the volatile substances in boiled chicken legs from those in coconut water. After cooking with coconut water, the content of sweet amino acids in chicken legs and chicken soup increased, but the content of savory amino acids in boiled chicken legs, chicken breasts, and broth was higher than that in chicken cooked with coconut water. The contents of 5'-AMP, 5'-IMP, and 5'-GMP in chicken cooked with coconut water were higher than those in boiled chicken.

The fat content in the chicken leg and protein content in the chicken breast differed in various parts of the Wenchang chicken. Boiling Wenchang chicken with coconut water increased the nucleotide content in the muscles and the free amino acid content in the chicken leg meat, significantly enhancing the taste. Boiling Wenchang chicken with coconut water increased the types of aldehydes in the thigh meat, and resulted in better flavor formation than the breast meat.