Investigation of the peptides with calcium chelating capacity in hydrolysate derived from spent hen meat.

Calcium peptide chelates are developed as efficient supplements for preventing calcium deficiency. Spent hen meat (SHM) contains a high percentage of proteins but is generally wasted due to the disadvantages such as hard texture. We chose the underutilized SHM to produce peptides to bind calcium by proteolysis and aimed to investigate chelation between calcium and peptides in hydrolysate for a sustainable purpose. The optimized proteolysis conditions calculated from the result of response surface methodology for two-step hydrolysis were 0.30% (wenzyme/wmeat) for papain with a hydrolysis time of 3.5 h and 0.18% (wenzyme/wmeat) for flavourzyme with a hydrolysis time of 2.8 h. The enzymatic hydrolysate (EH) showed a binding capacity of 63.8 ± 1.8 mg calcium/g protein. Ethanol separation for EH improved the capacity up to a higher value of 68.6 ± 0.6 mg calcium/g protein with a high association constant of 420 M-1 (25°C) indicating high stability. The separated fraction with a higher amount of Glu, Asp, Lys, and Arg had higher calcium-binding capacity, which was related to the number of ─COOH and ─NH2 groups in peptide side chains according to the result from amino acid analysis and Fourier transform infrared spectroscopy. Two-step enzymatic hydrolysis and ethanol separation were an efficient combination to produce peptide mixtures derived from SHM with high calcium-binding capacity. The high percentage of hydrophilic amino acids in the separated fraction was concluded to increase calcium-binding capacity. This work provides foundations for increasing spent hen utilization and developing calcium peptide chelates based on underutilized meat.

Study on film forming characteristic of ε-polylysine grafted chitosan through TEMPO oxidation system and its preservation effects for pork fillet.

The present study synthesized a new type of ε-polylysine (PL) modified chitosan film (TO-CH-PL) through TEMPO (2,2,6,6-Tetramethylpiperidine) oxidation system. Firstly, the physicochemical properties of the TO-CH-PL were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive spectrometer analysis. Results proved that PL was successfully grafted onto chitosan molecules. Based on the water vapor, oxygen permeability, and mechanical analysis, the TO-CH-PL film demonstrated higher physical properties than chitosan and PE films. Secondly, the TO-CH-PL film's preservation effect on pork fillets was evaluated. Due to the significant retardation of growth of the aerobic plate count (APC), total volatile basic nitrogen (TVBN), and thiobarbituric acid reactive substances (TBARS), as well as the changes of pH and color in packaged pork, TO-CH-PL film exhibited better preservation effects for the pork samples. According to the criteria of TVBN values (<15 mg/100 g), compared with CH and PE films, TO-CH-PL film can prolong the shelf life of pork for 2 to 3 days. Therefore, PL-modified chitosan films could be introduced as an alternative method to maintain the quality indices and extend the shelf life of pork during refrigerated storage.

Effects of conjugates of ε-polylysine-dextran created through Maillard reaction on quality and storage stability of the chicken gel.

The present study mainly focused on the effects of the conjugates of PL-dextran produced through the Maillard reaction on the quality and storage stability of chicken gel for 5 days at 4 ℃. According to the results of the texture profile, water retention capacity (WRC), low-field nuclear magnetic resonance (LF NMR), aerobic plate count (APC), and total volatile basic nitrogen (TVBN), ε-polylysine (PL) could improve chicken gel storage stability while decreasing the quality of protein gels (p < 0.05). Additionally, adding dextran with high or low molecular weight could significantly increase the quality of gel during storage (p < 0.05), whereas decreased storage stability could be obtained (p < 0.05). In general, conjugates formed by PL and dextran with high molecular weight were beneficial for quality maintenance. In comparison, the polymers produced from the low molecular weight of dextran could modify the storage stability of gels. Adding conjugates of dextran and PL benefited the structure formation of protein gel, while PL would retain part of antibacterial activity when crosslinked with dextran. Therefore, it could be concluded that the quality improvement effect of PL-dextran addition on gel quality was greater than its antibacterial effect, which would impact the formulation design of novel emulsion-type meat products.

Modification of myofibrillar protein gelation under oxidative stress using combined inulin and glutathione.

The effects of inulin (1.5%), glutathione (GSH, 0.05%), and their combination (1.5% inulin + 0.05% GSH) on the conformational structure and gel performance of pork myofibrillar protein (MP) under oxidation condition were examined. The addition of GSH significantly prevented oxidation-induced carbonylation, reduction of α-helix content, and protein aggregation. As a result, treatment with GSH significantly reduced the particle size of oxidized MP by 35%, increased the solubility by 17.3%, and improved the gelling properties. The presence of inulin also obviously enhanced the gelling behavior of MP under oxidation condition, although it could hardly inhibit the modification of MP structure caused by oxidation. Treatment with inulin + GSH exhibited the highest cooking yield (84.2%) and the best textural characteristics, with a denser and more uniform network structure comprising evenly distributed small pores. The findings of this study provide a useful method for processing meat protein gel products with better oxidative stability and textural properties.