No abstract

In this study, sheep plasma was submitted to Alcalase-hydrolysis and peptides with better antioxidant properties measured through both the ferric-reducing antioxidant power (FRAP) and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability assays were isolated and identified. After hydrolysate ultrafiltration and semi-preparative reverse-phase high-performance liquid chromatography, nine fractions (F1–F9) were obtained, with the two first (F1 and F2) showing the greatest antioxidant potential. These two fractions were further separated by the AKTA purifier system to generate four (F1-1–F1-4) and five (F2-1–F2-5) fractions, respectively, with two of them (F1-2 and F2-1) exhibiting appreciable FRAP activity and DPPH radical scavenging ability. Using liquid chromatography-tandem mass spectrometry, three antioxidant peptides were identified. From their amino acid sequences (QTALVELLK, SLHTLFGDELCK, and MPCTEDYLSLILNR), which include amino acids that have been previously reported as key contributors to the peptide antioxidant properties, it can be maintained that they come mainly from serum albumin. These results suggested that the sheep plasma protein can be considered as a good source of antioxidant peptides and bring forth new possibilities for the utilization of animal blood by-products.

Porcine blood plasma is a rich source of proteins with high nutritional and functional properties, which can be used as a food ingredient. The plasma is usually processed into powders in applications. In the present study, the effects of drying methods and ash contents on heat-induced gelation of plasma protein powder were investigated. The drying methods had a significant impact on the gel properties of the plasma powder heat-induced gels. The hardness and elasticity of the gels by freeze-dried and spray-dried plasma powders were lower than that of the liquid plasma (p < 0.05). The microstructures of dehydrated plasma were denser and the holes were smaller. The secondary structure of the gels from the spray-dried plasma protein powders exhibited more α-helixes and less β-turns than that from the freeze-dried powder and liquid plasma. The thermostability of dehydrated plasma powder was found to have decreased compared to the liquid plasma. Compared with the gels obtained from the high ash content plasma protein powders, the gel from the 6% ash content plasma powder had the highest water-holding capacity and had the lowest hardness and elasticity. However, the secondary structure and microstructures of the heat-induced gels were not affected by the ash contents in the plasma powders. These findings show that the gel properties of plasma protein powder can be finely affected by drying methods and ash contents.

Heterocyclic aromatic amines (HAAs) are mutagenic and carcinogenic compounds, which are commonly detectable in cooked meat products. The objective of this study was to evaluate the effect of sheep breeds on the formation of HAAs in smoking cooked lamb. The results showed that HAAs in smoked lamb meat products were generally low (2.74-5.42 ng g À1 ), with most being Harman and Norharman. IQ, MeIQx, 4,8-DiMeIQx, Trp-p-2, PhIP and MeAaC were not detected in smoked lamb meat products in the present study. The total content of HAAs differed between meat products of different sheep breeds, but no difference in the order of magnitude was determined. Smoking altered the content of protein, fat, moisture and free amino acids in lamb meat products, which was probably mostly contributed by the reduction in meat moisture. Free tryptophan decreased in all breeds after smoking, which was probably used to synthesise HAAs. In summary, HAAs were low in smoked lamb meat products of all sheep breeds; thus, consumption of smoked lamb meat products should contribute very limited intake of HAAs.

In the present study, sheep plasma (SP) was hydrolyzed with 5000 U alcalase/g protein at 45 ℃, pH 11 for 6 hours to prepare sheep plasma hydrolysate (SPH). The effects of SPH on meat color stability and oxidation of lipid and proteins were evaluated in mutton patties. Data obtained showed that addition of 2 % SPH significantly improved the redness (a* value) of mutton patties in storage (P < 0.05), which was comparable to 0.05 % vitamin C. At the same time, 2 % SPH effectively inhibited metmyoglobin formation and oxidation of lipid and proteins in mutton patties. The inhibition of oxidation in meat by SPH was concentration dependent. In summary, this study showed that SPH was antioxidant and 2 % SPH could be used in production to prevent quality deterioration of meat products in storage, providing a new way for high-value utilization of sheep blood.