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Previous research suggests that freezing and thawing of beef steaks impacts consumer palatability, but the extent of change is not clearly understood. Seasonal changes in beef prices could potentially be mitigated by use of rapid freezing cold storage technology to hold beef until the market trends towards a higher selling price. However, this freezing method could potentially have negative effects on meat color if sold in an overwrapped package at retail. Once the product is on the shelf of the grocery store, the consumer can choose to take it home and eat it or to freeze the overwrapped steak in a typical household freezer, therefore producing a product that might have been frozen twice. Although consumers may believe “fresh” is superior to frozen, freezing and thawing has been reported to improve meat tenderness through ice crystal formation and disruption in the muscle. Although tenderness has been shown to improve, some other attributes may perform negatively after freezing steaks. The degree of impairment on meat quality is influenced by both the size and location of ice crystal formation. Rapid freezing rates produced by blast freezers result in smaller, more uniform ice crystals when compared to slower freezing rates produced by consumer home freezers. The objective of this study was to evaluate the effect of double-freezing using commercial blast freezing in vacuum packages, then consumer freezing and thawing of retail, overwrapped Longissimus lumborum beef steaks on objective and subjective measures of beef palatability.
Paired, USDA Low Choice beef strip loins (IMPS #180; n = 16) were collected and fabricated into 2.54 cm-thick steaks. Initial freezing of steaks occurred in a vacuum package, whereas the second freeze was accomplished in an overwrap retail package (polyvinylchloride overwrap and foam tray) after retail display. Retail color evaluation (L*, a*, b*) was evaluated during a 96 h display post-initial freezing and thawing. Percentage total purge loss, loss after each subsequent freeze, and cook loss was observed throughout the study. Trained panelists evaluated each sample for beef flavor identity, browned/roasted, bloody/serumy, fat-like, liver-like, fishy, oxidized, cardboard, rancid, refrigerator-stale, umami, bitter, sour, overall tenderness, and overall juiciness attributes on a 100-point line scale. Objective evaluation of tenderness was assessed via slice shear force and juiciness via expressible moisture. Data were analyzed by a randomized complete block design with a 3 × 3 factorial treatment structure consisting of unfrozen (NOT), blast frozen at -34.4°C (BF), and consumer-frozen at -17.8°C (CF) to accomplish nine treatment combinations.
Steaks not previously frozen (NOT) sustained higher L* (P = 0.027) and a* (P < 0.001) values, whereas both freezing treatments (BF and CF) remained similar during the 96 h retail display. Total purge loss and cook loss percentages were affected by the initial and second freeze interaction (P ≤ 0.046); where the least losses occurred in unfrozen steaks and greatest losses occurred in double-frozen steaks. Objective attribute evaluations (expressible moisture and Slice Shear Force [SSF]) were minimally impacted by freezing; SSF of steaks frozen in overwrap packages after retail display in a blast freezer setting were lower (more tender; P = 0.039) than steaks not frozen or consumer frozen. No interaction between the initial-vacuum freeze and second-overwrapped freeze treatment was observed for trained panel descriptive attributes (P ≥ 0.114), except overall juiciness (P = 0.006). Though similar to steaks initially CF in the vacuum package and followed by a second freeze (CF/BF or CF/CF) in the overwrap package, steaks that encountered a consumer freeze at least once (CF/NOT and NOT/CF) resulted in the overall driest ratings by panelists (P = 0.006). No differences (P ≥ 0.083) in descriptive panel attributes were observed during the initial freeze, except within the bloody/serumy attribute (P = 0.002). Steaks that initially were not frozen (NOT) in the vacuum package rated higher for bloody/serumy (P = 0.002) than those that were frozen (BF or CF). During the second freeze in the overwrapped package, no differences in descriptive panel attributes were observed (P ≥ 0.155), except for within oxidized and refrigerator-stale. Steaks blast frozen in the overwrap package after retail display rated higher for oxidized (P = 0.051) than steaks consumer frozen in the overwrap package and higher than both consumer frozen and unfrozen steaks for refrigerator-stale (P = 0.006) attributes.
The results of this study showed consumers should not be deterred by frozen beef steaks, as tenderness and flavor were unaffected, and juiciness was minimally affected. The industry can use these findings to educate consumers on the important benefits of using freezing practices to increase shelf-life of beef steaks, therefore increasing sustainability of beef without jeopardizing quality.