Effects of Gnaphalium affine extract (GAE) and sodium pyrophosphate (PP) on •OH induced oxidation and the structure of myofibrillar proteins

Summary This study investigated the effects of the combination of Gaphalium affine extract (GAE) and sodium pyrophosphate (PP) on the structure and oxidative stability of porcine myofibrillar proteins (MPs) under oxidative stress. The results showed that GAE was rich in total flavonoids and total phenols (37.09% and 67.50%, respectively). GAE had strong free radical scavenging ability, especially for • OH, and the semi‐inhibitory concentration (IC 50 ) of • OH reached as high as 3.59 μg/mL, which was slightly lower than that of the standard antioxidant vitamin C (V c ). The addition of GAE and PP significantly inhibited the formation of carbonyl groups compared to the control group ( P < 0.05). The presence of GAE further promoted the loss of total sulphydryl groups by 3.52% compared to the oxidative control group ( P < 0.05). However, PP and PP+G significantly inhibited the loss of total sulphydryl groups ( P < 0.05). The further reduction in the carbonyl content, increase in the hydrogen bond content, inhibition of the conversion of sulphydryl groups to disulphide bonds, and decrease in the cross‐linking aggregation of corresponding proteins all indicate that GAE and PP could cooperatively regulate the oxidation of MPs. An appropriate amount of PP effectively modified the damage caused by GAE on both the secondary and tertiary structure of MPs to maintain their structural stability, however, a relatively higher concentration of PP led to a substantial degree of MP collapse and affected the quality of the proteins. These results suggest that the oxidative stability of MPs can be improved by the addition of an appropriate amount of GAE (0.2 mg/g protein) combined with PP (1 mM).