Native Beef Collagenase MMP-9 May Contribute to Tenderness Improvement by Degrading Connective Tissues in Extended Aged Beef

Objective: Collagen is one of the main components in the connective tissue (CT) and contributes to background toughness in beef. It is known that in living animals, collagen can be degraded and remodeled by collagenase matrix metalloproteinases (MMP); however, it is unclear if collagenase MMP can impact CT texture during postmortem aging of beef. Therefore, this study aimed to understand how collagenase MMP activity may impact postmortem connective tissue degradation in beef in three different cuts and four different aging periods. Study Description: Beef boneless striploin, top sirloin butt, and heel were acquired from 10 U.S. Department of Agriculture high choice beef carcasses and assigned to be aged for 3, 21, 42, or 63 days (n = 120). Following each aging time, Warner-Bratzler shear force (WBSF), connective tissue shear force (CTSF), trained panel responses, collagen content, denaturation temperature of connective tissue, collagen crosslinks density, connective tissue degradation product, and native collagenase activity were measured, and collagenase identity was identified as MMP-9 through Western blot. Results: Striploin was considered the most tender muscle (P \u3c 0.01), and tenderness was improved (P \u3c 0.01) after 21 days of aging. In addition, CTSF data and trained panelists demonstrated softening (P \u3c 0.05) of CT after 21 days of aging. Heel and top sirloin butt did not differ (P \u3e 0.10) in collagen content and had greater (P \u3c 0.01) collagen content than striploin. However, no aging effect was found for collagen content (P \u3e 0.10). Denaturation temperature of CT decreased and collagen crosslinks density increased after 42 days of aging for all cuts evaluated in this study (P \u3c 0.01). The MMP-9 activity decreased (P \u3c 0.01) from 3 to 21 to 42 days, and it had the greatest (P \u3c 0.01) activity in heel compared to the other two cuts. Heel and striploin had greater (P \u3c 0.01) connective tissue degradation product than top sirloin butt. It was interesting to note that while striploin and heel showed a decrease (P \u3c 0.05) in the degradation product from 3 to 21 to 42 days, top sirloin butt did not show any changes (P \u3e 0.10) in degradation product during the entire 63 days of aging period. The Bottom Line: These results provide an explanation on CT softening during postmortem aging. Understanding the mechanism of tenderness improvement from the softening of CT may help the industry improve the eating quality of lower quality beef cuts

Evaluating the Effect of Accelerated Aging at Different Temperature and Time Points on Beef Quality and Enzyme Activity of Lower Quality Beef Cuts

Objective: This study aimed to explore the effects of four accelerated aging (AA) methods at different temperature and time points on meat quality and enzymatic activity of two lower quality beef cuts. Study Description: Shoulder clod and top round were collected from 10 U.S. Department of Agriculture choice beef carcasses, fabricated into steaks, and assigned to one of six treatments: 3 days postmortem (control), cooler aged for 21 days, AA 120°F for 2 h, AA 120°F for 3 h, AA 130°F for 2 h, and AA 130°F for 3 h. Yield was calculated based on loss during AA and cooking loss, and purge was collected for collagen analysis. Warner-Bratzler shear force (WBSF) was determined, and purge for microbial analysis was collected from primal bags as well as the package after AA treatment. Steak surfaces were swabbed on the anterior side prior to AA treatment, then swabbed on the posterior side after treatment. Aerobic plate counts (APC) were performed on purge and swab samples. Cathepsin activity was determined through zymography. Soluble collagen content and total collagen in the purge were determined through hydroxyproline content. Results: All AA treatments decreased APC on the steak surfaces (P \u3c 0.01) and in the purge (P \u3c 0.05). The 130°F samples had a lower yield after AA than the 120°F groups (P \u3c 0.05). The cooler aged samples had a lower cook yield than all of the AA samples (P \u3c 0.01), and shoulder clod samples displayed higher cooking yield than the top round (P \u3c 0.01). The WBSF results showed that AA 120°F for 3 h samples and both AA 130°F samples displayed similar tenderness to the samples that were cooler aged for 21 days (P \u3c 0.01). All the AA treatments had higher collagen in the purge than the control or cooler aged samples (P \u3c 0.01). There was heightened cathepsin enzymatic activity during all treatments when compared to the control samples, and the AA at 120°F for 3 h treatment displayed the highest activity compared to other AA treatments (P \u3c 0.01). The Bottom Line: Accelerated aging has shown to be a promising technique to increase value in lower priced beef cuts through increasing enzymatic activity and tenderness without accelerating microorganism growth

Effects of Adding Egg Powder from Hens Immunized Against Phospholipase α2 on Ground Striploin Shelf Life

Objective: The present study investigated the effect of incorporating three different levels of dried egg powder (EP) containing antiphospholipase α2 (aPLA2) on lipid oxidation and discoloration for its potential to extend ground striploin shelf life. Study Description: U.S. Department of Agriculture choice striploins from ten beef carcasses were used. Impacts on beef discoloration, L* (lightness), a* (redness), and b* (yellowness) parameters, and lipid oxidation over a 7-day display period were studied. The fatty acid and phospholipid profiles of the beef patties were also examined. Results: The EP was confirmed to contain active aPLA2. As expected, a* and b* values decreased (P \u3c 0.05), and visual discoloration increased (P \u3c 0.05) throughout the 7 days of retail display. However, the inclusion of EP had no effect on beef patty visual discoloration, a*, or b* (P \u3e 0.05). Lipid oxidation increased (P \u3c 0.05) for all treatments throughout the 7-day display period. Beef patties containing 1.6% EP had higher (P \u3c 0.05) lipid oxidation than the rest of the treatments. The addition of 1.6% EP to ground striploin increased the relative percentage of C11-18:1 trans, C18:2, C18:3, C20:1, and C22:6 fatty acids, but decreased the relative percentage of C17:0, and C17:1 when compared to the other treatments (P \u3c 0.05). Adding more than 0.8% EP containing aPLA2 in ground striploin altered the fatty acid profile by increasing the content of some polyunsaturated fatty acids, particularly 18:2, which likely led to the enhanced lipid oxidation in ground striploin patties. Finally, the phosphatidylcholine relative percentage was higher for the 1.6% EP treatment compared to the control, possibly due to the inhibition of PLA2 by aPLA2 activity. The Bottom Line: These results showed that egg powder containing aPLA2 did not have any effect in extending beef shelf life when incorporated into ground striploin. Further research could introduce aPLA2 through a different vehicle to reduce interference of fatty acid composition