Problems with silver carp protein (SCP) include a strong fishy odor, low gel strength of SCP surimi, and susceptibility to gel degradation. The objective of this study was to improve the gel quality of SCP. The effects of the addition of native soy protein isolate (SPI) and SPI subjected to papain-restricted hydrolysis on the gel characteristics and structural features of SCP were studied. The β-sheet structures in SPI increased after papain treatment. SPI treated with papain was crosslinked with SCP using glutamine transaminase (TG) to form a composite gel. Compared with the control, the addition of modified SPI increased the hardness, springiness, chewiness, cohesiveness, and water-holding capacity (WHC) of the protein gel (p < 0.05). In particular, the effects were most significant when the degree of SPI hydrolysis (DH) was 0.5% (i.e., gel sample M-2). The molecular force results demonstrated that hydrogen bonding, disulfide bonding, and hydrophobic association are important molecular forces in gel formation. The addition of the modified SPI increases the number of hydrogen bonds and the disulfide bonds. Scanning electron microscopy (SEM) analysis showed that the papain modifications allowed the formation of a composite gel with a complex, continuous, and uniform gel structure. However, the control of the DH is important as additional enzymatic hydrolysis of SPI decreased TG crosslinking. Overall, modified SPI has the potential to improve SCP gel texture and WHC.

The impact of adding mango peel extract (MPE) on lipid oxidation, color deterioration, microbial stability and sensory properties of beef burgers stored at 4 ± 1 °C for 12 days was investigated. The MPE was incorporated into beef burger mix at 0.1, 0.2 and 0.3%, and compared with 0.01% butylated hydroxyanisole (BHA)/butylated hydroxytoluene (BHT) (1:1; positive control) and control (without any antioxidants; negative control). The results showed that mango peel powder contained high total phenolic content (TPC) (45.17 mg/g) and antioxidant activity (92.05%). Also, the results showed that pH and color ( L*, a* and b*) values of MPE-containing burgers were lower than those of both controls. By the end of storage time, the (0.3%) MPE-containing burgers showed the lowest pH (6.03) and color (L*, a* and b*) values (49.95, 11.51 and 10.38, respectively). Also, the (0.3%) MPE-containing burgers had higher TPC (121.85) and lower TBARS values (0.18) compared to the controls (29.57-60.65 mg GAE/100g and 0.19-0.20 mg malondialdehyde/kg, respectively). Consequently, adding the MPE enhanced the antioxidant activity and resulted in a significant inhibition of total aerobic count in comparison to both controls. The results obtained from sensory analyses revealed that adding the MPE to beef burgers was effective with regard to retarding color and taste deterioration, and rancid odor formation. The (0.1%) MPE-containing burgers had the highest overall sensory scores. The results obtained from this study showed that MPE can be an effective additive with regard to retarding deterioration of quality characteristics during the cold storage of beef burgers.