Extraction, polyphenol profiling, and protective effect of Rubus crataegifolius Bunge root polyphenols against myofibrillar protein oxidation in chilled pork

Natural antioxidants have attracted considerable interest for controlling oxidative damage in meat systems. This study investigated the protective effect of polyphenols extracted from the root of Rubus crataegifolius Bunge (RCB) against myofibrillar protein oxidation in chilled pork. Ultrasound-assisted extraction method coupled with response surface methodology was employed to optimize the extraction process, yielding 4.49 ± 0.02% of total polyphenols. Nine polyphenol compounds were identified by LC-MS/MS, with proanthocyanidins being the most abundant. The extracts exhibited good scavenging activities against DPPH·, ABTS+·, ·OH, along with notable ferric reducing/antioxidant power. During storage at 4 °C, RCB polyphenols significantly inhibited myofibrillar protein oxidation in a concentration-dependent manner, as evidenced by reduced carbonyl content and maintained sulfhydryl levels. Density functional theory calculations identified resveratrol as the most intrinsically active compound, but its low abundance likely limited its contribution, while proanthocyanidins may contribute more due to their high content. In vitro digestion further revealed that the bioaccessibility index of total polyphenols remained 91.70%, with quercetin 3-O-β-D-glucuronide showing the highest value (91.07%), and their antioxidant activities largely preserved after digestion. These findings indicate that RCB root polyphenols can serve as potential natural antioxidants for inhibiting protein oxidation in chilled pork.