反复冻融对广式奶黄包品质的影响

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

摘要:

本文研究了奶黄包经过反复冻融（0、1、2、3、4次）后，各层水分含量、色泽、比容、质构特性和皮瓤孔隙结构等品质指标的变化。结果表明：奶黄包在冻结过程中各层（皮、瓤、馅）温度下降速率和解冻过程中各层的温度上升速率均为皮＞瓤＞馅。以未经冻融（0次）的奶黄包为对照组，冻融1次后，奶黄包的咀嚼性显著增大（p<0.05），弹性和回复性显著减少；奶黄包皮的水分含量、L*值和比容均在冻融2次后显著减少，而a*和b*值显著增大；硬度和粘性在4次冻融后变化不显著（p>0.05）；冻融4次的奶黄包气孔稠密度CD值减小，气孔表面占有率AF值增大；奶黄包的冻裂率随冻融次数增加而上升，冻融4次后达至36%，且冻裂程度明显加深。因此，减少贮藏过程中的温度波动，避免反复冻融有利于保持广式奶黄包的品质。

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.