Potential of tea polyphenols to ameliorate the quality of beef meatballs during frozen storage and its action mechanism

Frozen storage is commonly used for preservation of meat products, but it may cause some quality deterioration, due to the repeatedly forming of ice crystals in meat. Effects and action mechanism of tea polyphenols (TP, from 0 to 0.30 g/kg) on the quality of beef meatballs during freeze-thaw cycles were investigated in present study. TP significantly reduced thaw loss of beef meatballs by 36.62% and improved texture (hardness increased by 21.13%, chewiness increased by 18.88%). Low-field nuclear magnetic resonance analysis revealed that TP restricted the conversion of immobilized to free water, decreasing free water by 7.42% and increasing immobilized water by 7.43%. Freezing temperature curve and microstructure image results demonstrated that TP facilitated the rapid formation of uniformly distributed, smaller ice crystals in beef meatballs. After freeze-thaw cycles, TP significantly decreased the content of free sulfhydryl and carbonyl groups of myofibrillar protein, enhanced its surface hydrophobicity and decreased its solubility. Furthermore, multispectral (including fluorescence and infrared spectroscopy) analysis combined with molecular docking indicated that TP could significantly caused a more unfolded secondary structure of myofibrillar protein and expose its hydrophobic centers due to their molecular interaction through hydrogen bonds and hydrophobic interactions. All results suggest that TP show the potential to ameliorate the quality of frozen meat products.