Department of Animal Science, University of Nebraska, Lincoln 68583-0908, USA.
Department of Statistics, University of Nebraska, Lincoln 68583-0908, USA.
Meat Sci. 2020 Dec;170:108232. doi: 10.1016/j.meatsci.2020.108232. Epub 2020 Jul 11.
Consumers consider beef color to be an indicator of freshness and therefore it is a major factor when purchasing beef. The ideal conditions for maintaining color throughout retail display following frozen storage have yet to be well established. Therefore, the objective of this study was to determine the effects of myoglobin oxygenation levels (especially high oxygenation) during freezing on color stability of thawed steaks during retail display (RD) and to determine the impact that frozen storage duration, aging, and packaging films have on meat color after thawing under RD conditions. USDA Choice strip loins (n = 36) were aged for 4 or 20 d. Steaks were randomly assigned to a myoglobin oxygenation level [deoxymyoglobin (DeOxy; packaged within 3 min), oxygenation (Oxy; oxygenated in air for 30 min), or high oxygenation (HiOxy; packaged for 24 h in 80% O)]. Steaks were then vacuum packaged in oxygen permeable or impermeable film and immediately frozen (-10 °C). Following either 0, 2, 4, or 6 months of frozen storage at -5 °C, steaks were removed from the packaging and immediately placed under simulated RD conditions for 7 d. During RD, instrumental color and subjective color were measured every day after the initial 24 h thaw period. Steaks were analyzed for instrumental color (L*, a*, b*), a*:b* ratio, percentage oxymyoglobin, metmyoglobin, and deoxymyoglobin, delta E, redness ratio, subjective discoloration, and lipid oxidation. For all days of RD, steaks that were frozen for 0 months had higher a* values (greater redness) than steaks frozen for 6 months which typically had the lowest a* values (P < .0001). HiOxy steaks frozen for 6 months had the lowest amounts of percentage oxymyoglobin than all other frozen storage periods and myoglobin oxygenation levels on days 4-7 of RD (P < .05). The HiOxy steaks frozen for 4 and 6 months had higher percentage metmyoglobin than DeOxy and Oxy, regardless of packaging (P < .05). Delta E, discoloration, and lipid oxidation were greatest for HiOxy steaks compared to Oxy and DeOxy (P < .05). Extended storage brought about detrimental color effects for all differing levels of myoglobin oxygenation. The HiOxy steaks through the first few days of RD and frozen for under 6 months provided had bright cherry red color, similar to that of DeOxy and Oxy. However, with extended frozen storage and RD, HiOxy steaks had worse color characteristics (more discoloration) than the other myoglobin oxygenation levels.
消费者认为牛肉的颜色是新鲜度的指标，因此在购买牛肉时，这是一个主要因素。然而，在冷冻储存后零售展示期间保持颜色稳定的理想条件尚未得到很好的确定。因此，本研究的目的是确定冷冻过程中肌红蛋白氧合水平（尤其是高氧合水平）对解冻牛排在零售展示（RD）期间颜色稳定性的影响，并确定冷冻储存时间、老化和包装薄膜对解冻后在 RD 条件下肉色的影响。美国农业部选择的带骨里脊肉（n=36）经过 4 或 20 天的老化。将牛排随机分配到肌红蛋白氧合水平[脱氧肌红蛋白（DeOxy；在 3 分钟内包装）、氧合（Oxy；在空气中氧合 30 分钟）或高氧合（HiOxy；在 80%O 下包装 24 小时）]。然后将牛排用氧气渗透或不渗透的薄膜真空包装，并立即在-10°C 下冷冻。在-5°C 下冷冻 0、2、4 或 6 个月后，从包装中取出牛排，并立即在模拟 RD 条件下放置 7 天。在 RD 期间，在最初的 24 小时解冻期后，每天测量仪器颜色和主观颜色。对牛排进行仪器颜色（L*、a*、b*）、a*:b* 比、氧合肌红蛋白百分比、高铁肌红蛋白百分比、脱氧肌红蛋白百分比、ΔE、红色比、主观变色和脂质氧化分析。在 RD 的所有日子里，冷冻 0 个月的牛排的 a值（更红）高于冷冻 6 个月的牛排，后者的 a值通常最低（P<.0001）。在 RD 的第 4-7 天，冷冻 6 个月的 HiOxy 牛排的氧合肌红蛋白百分比低于所有其他冷冻储存期和肌红蛋白氧合水平（P<.05）。无论包装如何，冷冻 4 和 6 个月的 HiOxy 牛排的高铁肌红蛋白百分比均高于 DeOxy 和 Oxy（P<.05）。与 Oxy 和 DeOxy 相比，HiOxy 牛排的ΔE、变色和脂质氧化最大（P<.05）。所有不同肌红蛋白氧合水平的延长储存都会对颜色产生不利影响。HiOxy 牛排通过最初几天的 RD 和冷冻储存不到 6 个月，呈现出鲜艳的樱桃红色，类似于 DeOxy 和 Oxy。然而，随着冷冻储存和 RD 的延长，HiOxy 牛排的颜色特征（更多的变色）比其他肌红蛋白氧合水平更差。
