Impact of superchilling storage temperatures on beef quality: Micro-CT analysis of ice recrystallization kinetics in partially frozen samples.

This study aims to investigate the microstructure changes of partially frozen beef under different superchilling storage conditions and relate these changes to quality degradation. Beef samples were partially frozen in an air blast freezer with a heat transfer coefficient of 112 W/m2 K and an air temperature of ‒32 ◦C for 2 min following storage at ‒1.8 ◦C, ‒2.8 ◦C, ‒4 ◦C and ‒5 ◦C for 21 days. "X-ray micro-computed tomography (µCT), a nondestructive 3D imaging technique was used to visualize and quantify ice crystal characteristic, including ice volume fractions, ice crystal size, number and distribution". Recrystallization kinetics were modelled using the asymptotic Ostwald ripening equation and correlated with quality degradation rate through Pearson correlation analysis. Immediately after partial freezing, the average initial ice volume fraction, mean equivalent diameter, and crystal number were 31 ± 1 %, 36.0 ± 0.3 µm, and 421,182 ± 16,524, respectively. Over storage time, ice volume fraction and crystal size increased significantly (p < 0.05), while crystal number decreased, leading to increased drip loss, and reduced firmness of beef upon thawing. In addition, recrystallization rates increased significantly (p < 0.05) with decreasing storage temperature specifically within a range of ‒1.8 ◦C to ‒5 ◦C as lower temperatures resulted in higher ice fractions and more heterogeneous crystal size distributions, thereby promoting recrystallization. A high regression coefficient (R2 > 0.9) indicated a strong fit of the recrystallization rate’s temperature dependence to the Arrhenius model. Recrystallization rate was strongly correlated with all quality degradation rates (R2 > 0.9). Overall, this study demonstrates the critical role of recrystallization in driving deterioration of partially frozen beef and highlights the value of X‒ray µCT for non-invasive monitoring microstructure changes during superchilled storage.