Effects of freezing on physicochemical properties of Wagyu and crossbred beef : a thesis presented to Massey University for the partial fulfilment of the requirements of the degree of Master of Chemical and Bioprocess Engineering, Massey University, Manawatu, New Zealand
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2024
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Massey University
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This study investigates and compares the effects of different freezing rates (slow and fast freezing) on the meat quality parameters of Wagyu and crossbred beef. To study the effects on the meat quality of Wagyu and crossbred beef, different treatments were set up, and 60 beef rump samples were used in total. The samples were randomly assigned to three different regimens named FR (fresh, never frozen), FF (fast frozen), and SF (slow frozen), followed by thawing of the FF and SF samples at 4 °C for 24 hours. A compositional analysis was performed to compare the moisture and fat levels of both breed meat samples. The impact of moisture and fat levels on the freezing rate was then analyzed by mathematically modeling the freezing kinetics of Wagyu and crossbred beef. This analysis aimed to highlight the primary differences in thermal behavior between the two breeds. The effects of different regimens on meat quality were also evaluated using various meat quality measurements such as pH, color, tenderness, and water holding capacity. Both the uncooked and cooked meat samples of Wagyu and crossbred beef were used to compare various meat quality attributes. Other analyses used to indicate quality differences between raw meat samples were light and transmission electron microscopy (TEM). The experiment data shows that Wagyu beef generally outperforms crossbred beef in terms of tenderness (warner- bratzler shear force, WBSF), lower thaw, and cook losses. In addition, Wagyu beef consistently exhibited superior color characteristics, with higher values for lightness, redness, yellowness, chroma, and hue angle compared to crossbred beef. The freezing rate and breed significantly affected the moisture and fat content (p < 0.0001). Wagyu beef exhibited higher fat and low moisture content compared to crossbred beef. The freezing kinetics indicated that crossbred beef cools faster compared to Wagyu beef. During the pre-cooling phase of fast freezing, despite the rate constant (k = 1) being the same in both breeds, the cooling process for crossbred beef was faster, with a larger pre-exponential factor of 10.017 against 9.523. Additionally, during the subcooling phase of slow freezing, crossbred beef cools slightly faster than Wagyu beef, as evident by the larger value of the rate constant (0.69 versus 0.646) and the pre-exponential factor (17.245 versus 16.15). Regarding the meat quality analysis, Wagyu beef had a higher pH compared to crossbred beef for both uncooked and cooked samples. Freezing rate (slow or fast freezing) did not significantly affect pH (p > 0.05), but there was a statistically significant (p < 0.05) interaction between freezing rate and breed for both uncooked and cooked samples. Wagyu beef exhibited lower warner-bratzler shear force (WBSF) values for cooked samples, indicating greater tenderness compared to crossbred beef. Both freezing rate and breed type significantly affected warner-bratzler shear force (WBSF) (p < 0.05), with slow-frozen samples being the most tender. Crossbred beef (both fast and slow frozen samples) had a higher thaw loss (p < 0.05) than its Wagyu counterpart. Slow-frozen samples of both breeds exhibited greater thaw loss than fast-frozen samples (p < 0.05). Fast-frozen samples (both breeds) showed the least cook loss, while slow-frozen crossbred samples had the highest cook loss, indicating the freezing rate significantly affected cook loss (p < 0.05). Breed type did not significantly affect cook loss (p > 0.05), but there was a statistically significant interaction between freezing rate and breed (p < 0.05). Light microscopy (LM) and transmission electron microscopy (TEM) images of uncooked samples revealed that Wagyu samples, both slow and fast frozen, maintained their structure more effectively than crossbred samples under each regimen, as evidenced by their lower WBSF, thaw loss, and cook loss values. The difference between uncooked and cooked meat samples related to moisture retention, tenderness, and structural changes was also observed. Uncooked samples, particularly Wagyu, had higher fat and lower moisture, with thaw loss more pronounced in slow-frozen crossbred beef. Cooking reduced moisture further, with fast-frozen samples showing less cook loss. In terms of tenderness, uncooked Wagyu beef was naturally more tender than crossbred beef, but this difference became more pronounced after cooking, with slow-frozen samples of both breeds being more tender due to the structural breakdown of muscle fibers during freezing and cooking. Color differences, with Wagyu showing superior lightness and redness, persisted after cooking, maintaining better visual quality. Significant advantages were identified for the meat processing industry by the results of the Wagyu and crossbred beef quality experiments. Overall, these findings suggest that Wagyu beef, with its superior fat content and tenderness, offers distinct quality advantages over crossbred beef. The findings also suggest that fast freezing (FF) should be preferred method for both Wagyu and crossbred beef to minimize moisture loss during thawing and cooking. If tenderness is the primary concern, slow freezing (SF) method may be considered, particularly in case of Wagyu beef. However, the increase in thaw and cook loss must be taken into account.
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Figures 1 & 2 are re-used under a Creative Commons Attribution 4.0 International (CC BY 4.0) license.