Key Findings

• Product size has an impact on the product quality of cuts that are frozen and thawed.
• Products frozen in larger sections had increased tenderness and color stability over portioned counterparts.
• Consumers found minimal difference in palatability, however, there is a trend that steak freezing decreases flavor score and acceptability.

background

Freezing is the most common method to prolong the shelf-life of meat products. However, freezing leads to quality deterioration, such as excessive moisture loss, rapid discoloration, and off-flavor development due to ice-crystal damage. The extent of the freezing damage is often influenced by the product freezing rate, which could be influenced by different product sizes. Furthermore, multiple freeze-thaw cycles are prevalent during distribution, retail storage, and even within consumer households, further inducing freezing damages. While the effect of a repeated freeze-thaw cycle on meat quality has often been reported in the industry, the impact of subsequent freezing using consumer freezing methods is still limited.   The objective of this study is to determine the impact of different sizes of muscle (subprimal freezing vs. portion cut freezing) and subsequent freezing using different freezer types (blast freezer, chest freezer, and fridge freezer) on final frozen meat quality and palatability of three different beef muscles.

methodology

Paired M. longissimus lumborum (LL), M. gluteus medius (GM), and M. semitendinosus (ST) muscles were obtained at 3 d postmortem from beef carcasses (n = 15; USDA Low Choice) and aged until 28 d postmortem. At the end of the aging period, paired muscles were assigned to either section freezing (SEC) or steak freezing (STK). All samples were then cut into 3 equal sections and randomly assigned into 3 different freezing methods (blast freezer [BLS], chest freezer [CST], and refrigerator freezer [FRI]). Samples assigned to STK were cut into steaks, and all samples were individually weighed and vacuum packaged. All samples were then placed in a closed box, frozen, and stored at -20C for 35 days. Samples were then thawed until an internal temperature of 2C and were then refrozen and stored at the assigned freezer type for 35 days. At the end of the freezing treatments, samples were thawed like previous methods. After thawing, SEC samples were further cut into steaks. Samples were then collected for water holding capacity, simulated retail color stability, instrumental tenderness, consumer sensory evaluation, and biochemical analyses. Data were analyzed in a balanced, complete block design with a split-plot arrangement using the SAS PROC GLIMMIX procedure.

results and discussion

Overall, the results suggested that product size during freezing had a greater influence in determining the final frozen meat product quality regardless of the muscle type and consumer freezer type. Greater product size led to a slower freezing rate, which potentially caused the formation of larger ice crystals in the product, explaining the greater moisture loss and lipid oxidation as the product incurred more freezing damage. Interestingly, however, the larger SEC sample had greater color and oxidative stability compared to STK samples, exhibiting better lean color and lower discoloration during the simulated retail display. This is potentially due to the fact that the SEC product could obtain a new unexposed surface following processing and cutting into steaks. In terms of palatability, SEC freezing was found to decrease the instrumental tenderness in LL and GM. ST was not impacted potentially due to the high connective tissue content in the product. Consumer evaluation indicated that palatability attributes and acceptability were minimally impacted, although there was a trend that STK samples received lower flavor scores and acceptability compared to SEC samples, potentially from lower positive volatiles released in STK samples.

industry Implications

Different product sizes during frozen storage will influence the final product's color and palatability more than subsequent freezer types. Regardless of muscle type, freezing individual steaks was generally observed to cause a detrimental color impact and alteration in tenderness and flavor in the final product. Although individual vacuum-packed steaks are commonly used in commercial settings, the growing demand for single-serve vacuum-packed products by consumers makes it crucial to ensure the quality of the final product. Further study should investigate the impact of aging/freezing sequence, thawing rate, and storage durations to minimize the detrimental freezing impact.