Effect of Alternating Electric Field Assisted Freezing on Energy Metabolism in Beef during Thawing and Aging

In order to explore the effect of alternating electric field (AEF) assisted freezing on energy metabolism in beef during thawing and aging, bovine Longissimus dorsi muscle samples were assigned to three groups: direct aging at 4 ℃ (control), thawing and then aging at 4 ℃ after 30 days of freezing at −18 ℃ (FA), and thawing and then aging at 4 ℃ after 30 days of AEF assisted freezing −18 ℃ (EA). The changes of muscle pH, adenosine triphosphate (ATP) content, glycogen content, lactic acid content, lactate dehydrogenase activity, hexokinase activity and Ca2+-ATPase activity were analyzed during the aging process. The results showed that as aging time increased, the pH of the OA group initially increased, then decreased and finally increased again, reaching the ultimate pH at the third day of aging. The pH of the FA and EA treatment groups remained relatively constant during aging. For all groups, there was a decreasing trend in ATP content. The ATP content of the OA group decreased from 7 245.43 to 752.38 µmol/g after seven days of aging. The ATP content of the EA group was significantly lower than that of the OA group on day 0 of aging (P < 0.05). The muscle glycogen contents in the FA and EA groups were significantly lower than that in the control group during the entire aging process (P < 0.05), and the lactic acid content, and hexokinase and lactate dehydrogenase activities decreased significantly with aging time (P < 0.05). On day 5 of aging, the glycogen and lactate contents, and lactate dehydrogenase activity in the EA group were significantly lower than those in the FA group (P < 0.05), and the activity of Ca2+-ATPase was significantly higher than that in FA group (P < 0.05), indicating that alternating electric field can accelerate the process of energy metabolism. In conclusion, aging after freezing and thawing can prolong the stiffening time of beef, and AEF assisted freezing effectively can promote energy metabolism, thus improving muscle quality. These findings may provide a basis for the development of new storage and preservation technologies for meat products.