Ice crystal formation is the primary cause of mechanical damage production in meat tissue, and it can be minimized or exacerbated by how large and sharp the ice crystal becomes. Ice crystals form as a result of primary and secondary nucleation, where primary nucleation creates a crystal without the use of another water molecule, and secondary are formed as result of a preexisting crystal structure. As meat freezes at higher temperatures, the period water molecules remain in the “maximum ice crystal zone” extends, thus allowing more secondary nucleation. This causes the production of larger and more irregular shaped formations. To combat this, processing aids such as electrostatic (EF) assisted freezing have been researched. Studies have shown reductions in ice crystal size as well as an increase in their distribution, leading to positive effects on previously frozen beef quality. However, many of these studies focus on small portions of meat products or steaks rather than subprimals. The objective of this study was to determine the effects of EF assisted freezing on beef subprimals.
Striploins were collected from both sides of 12 USDA Choice carcasses from a commercial beef processing facility. The striploins were then halved, weighed, and each half was randomly assigned to one of four EF freezing treatments: 0kV, 2kV, 4kV, or 8kV in a walk-in freezer maintained at -20°C. Following freezing, LLs were stored for 7 days at -20°C then thawed for 72 hours at 4°C. Steaks were fabricated from thawed striploins and subjected to 10 days of simulated retail display. Freezing rate, purge loss, cook loss, aerobic plate count (APC), Warner-Bratzler Shear Force (WBSF), instrumental and descriptive color, muscle fiber spacing, ice crystal diameter, lipid oxidation, antioxidant capacity, and troponin-T and desmin degradation were conducted on each of the samples.
Freezing rate was extended for all EF treatments over the control with the 4 kV treatment resulting in the longest time to reach -18°C (P<0.01). Ice crystal diameter was smallest in the 8 kV treatment (P<0.01), but no differences in muscle fiber spacing were reported (P>0.05). Purge loss was the lowest in the 8 kV treatment (P<0.01), but no differences were reported among the treatments for cook loss (P>0.05). The 8 kV treatment resulted in the lowest percentage of degraded troponin-T while the 4 and 8 kV treatments had lower amounts of degraded desmin (P<0.01). This decrease in degradation had no effect on WBSF (P>0.05). An interaction between treatment and display day was observed for discoloration with the 4 kV treatment reporting the lowest percentage of discoloration for days 9 and 10 (P<0.05). L* values were lower in the 4 and 8 kV treatments, but a* and b* were highest in the 4 kV group (P<0.01). Total antioxidant capacity was higher in the 4 kV samples than those of 0 and 2 kV (P<0.01), but no differences in lipid oxidation were reported (P>0.05).
Electrostatic assisted freezing has shown reductions in ice crystal size, revealing promising results for reductions in purge loss and decreases in protein degradation without negative effects to instrumental tenderness. Secondarily, the shelf life of beef could be extended through the use of EF treatments as color and antioxidant capacity were increased in samples treated at higher intensities. Steaks treated with 4 kV of EF were noticeably reduced in discoloration in a trained panel, potentially increasing consumer acceptability through more days of display. Because of the success of EF in a laboratory setting, finding ways to expand treatment to commercial level is an important next step.
ARMS#010226-08