Effects of Freeze-thaw Cycles on the Quality of Cantonese-style Egg Custard Bun

Abstract:

The objective of this study was to investigate the changes in the moisture content, color, specific volume, textural properties of each layer, and the pore structure of the skin and crumb of Cantonese-style egg custard bun after consecutive freeze-thaw cycles. The results demonstrated that the rates of temperature drop during the freezing and the rates of temperature rise during the thawing of each layer decreased in the following order: skin > crumb > filling. Compared with the egg custard buns that were not subjected to freeze-thaw cycles (control group), after the first freeze-thaw cycle, the chewiness of the samples increased significantly (p < 0.05), while the springiness and resilience decreased. The skin moisture content, lightness (L*), and specific volume of egg custard bun decreased significantly after two freeze-thaw cycles, while redness–greenness (a*) and yellowness-blueness (b*) increased significantly. Hardness and adhesiveness did not change significantly after four freeze-thaw cycles. The pore density (CD) value of the egg custard buns showed a downward trend after four consecutive freeze-thaw cycles, but the value of the percentage area fraction (AF) of the pores increased. In addition, the freeze-crack rate of the buns increased to 36% after four freeze-thaw cycles, and the crack became more severe. Therefore, reducing temperature fluctuations in the storage process and avoiding freeze-thaw cycles are helpful strategies for maintaining the quality of Cantonese-style egg custard bun.