Exploring the effects of incorporating egg powder from hens immunized with anti-phospholipase α2 to ground striploin on its shelf-life

Abstract

Lipid oxidation is the primary non-microbial degradation mechanism in beef. Phospholipase α2 (PLA2) may enhance this reaction during postmortem storage and retail display by degrading phospholipids into free unsaturated fatty acids and lysophospholipids. Antiphospholipase α2 (aPLA2) could potentially inhibit PLA2 by binding to it before PLA2 degrades phospholipids. Past research has shown that aPLA2 can be mass-produced in eggs from hens immunized against PLA2, and the resulting egg can be spray -or freeze-dried as egg powder to preserve the antibody activity. The present study aimed to determine the effects of incorporating three different levels of egg powder containing antiphospholipase α2 (aPLA2) and assess its potential to extend ground striploin shelf-life by inhibiting phospholipase α2 (PLA2). Enzymatic activity of aPLA2 used in this study was confirmed through an enzyme-linked immunosorbent assay (ELISA). Ten vacuum-packaged USDA choice striploins were obtained from different carcasses 2 d postmortem. On the following day, each loin was ground, divided into 4 batches, hand mixed with 0, 0.4, 0.8, or 1.6% of dried egg powder containing aPLA2, vacuum packaged, and held for 14 d at 2°C ± 2°C. Afterwards, treatments were divided into 114 g batches, formed into patties, randomly assigned into three display times (0, 4, and 7 display days), and displayed under fluorescent lighting at 2°C ± 2°C in a coffin-style retail case in aerobic packaging. Percent visual discoloration and instrumental color measurements were taken on d 7 patties for all treatments. At the end of each designated display period, patties were vacuum packaged and stored at -80°C until pulverized with nitrogen. Proximate analysis (moisture, protein, and fat), phospholipid composition through thin-layer chromatography (TLC), and fatty acid (FA) profile were measured on d 0 samples from all treatments. Lipid oxidation, antioxidant capacity (through oxygen radical absorbance capacity, ORAC), and pH were measured on d 0, 4, 7 samples from all treatments. The aPLA2 egg powder additions had no effect on discoloration or instrumental color measurements (P<0.05), although throughout the 7 d of retail display, a* and b* values decreased, and visual discoloration increased (P<0.05). The L* values were unaffected by display day or treatment (P>0.05). The addition of aPLA2 egg powder decreased the moisture content for the 1.6% treatment when compared to other treatments (P<0.05), but protein and fat percentages did not differ across treatments (P>0.05). Lipid oxidation increased (P<0.05) for all treatments throughout the 7 d display periods. Additionally, striploin patties containing 1.6% egg powder had higher (P<0.05) lipid oxidation than the rest of the treatments. The results for TLC phospholipid classification showed no difference for sphingomyelin (SM) across treatments (P>0.05). Phosphatidylethanolamine relative percentage was higher for the control when compared to the 1.6% treatment (P<0.05) and phosphatidylcholine relative percentage was higher for the 1.6% treatment compared to the control and 0.4% treatment (P<0.05). Display day pH had a main effect (P<0.05), increasing on d 7. Additionally, pH increased as more aPLA2 egg powder was incorporated into ground striploin (P<0.05). The addition of 1.6% egg powder to ground striploin increased the relative percentage of C11-18:1 trans, C18:2, C18:3, C20:1, and C22:6, but decreased the relative percentage of C17:0, and C17:1 when compared to other treatments (P<0.05). Interestingly, the 0.8% treatment showed a higher hydrophilic antioxidant capacity than the control and the 1.6% treatment. Adding aPLA2 egg powder had an effect on striploin a* values over time, moisture content, fatty acid profile, phospholipid composition, lipid oxidation, and hydrophilic antioxidant capacity. However, these reactions could be attributed to components introduced by the egg powder, not necessarily due to the aPLA2 content. The binding of aPLA2 to PLA2 was demonstrated through ELISA, but in this study, the efficacy of aPLA2 activity did not decrease ground striploin lipid oxidation.