为了研究组织内部孔隙中气体含量对超声辅助浸渍冷冻冻结效果的影响，加深对空气对超声衰减所造成的影响的了解。本研究以萝卜组织为食品材料模型，采用真空脱气方式对萝卜组织中气体含量进行调节，得到气体含量分别为9.91%、6.46%、4.01%及0的4种萝卜组织，分别在28 kHz、0.33 W/cm2的超声条件下进行超声辅助浸渍冷冻处理，并与常规浸渍冷冻比较。结果表明：与常规浸渍冷冻相比，4种不同气体含量的萝卜组织经过超声辅助浸渍冷冻处理后冻结速率分别提高了20.00%、27.00%、29.00%和33.00%，相变时间分别缩短了16.00%、24.00%、27.00%和31.00%。随着组织中气体含量的降低，超声辅助浸渍冷冻冻结速率得到显著提高（p<0.05），样品冷冻解冻后的硬度、微观结构及钙离子含量均得到显著的改善（p<0.05）。研究发现组织内部孔隙中气体含量是降低超声辅助浸渍冷冻冻结效果的一大影响因素，脱气处理可以有效改善含气物料超声辅助浸渍冷冻效果。

To gain a deeper understanding about the effect of air on ultrasonic attenuation, the freezing efficiency of the ultrasound-assisted immersion freezing method was determined on tissue samples with pores comprising different air contents. Radish tissue was used as a food model. The air content in the vegetable tissues was adjusted by vacuum degassing treatments to obtain tissue pores with 9.91%, 6.46%, 4.01%, or 0% of air. These samples were then treated by ultrasound-assisted immersion freezing at a frequency of 28 kHz and power of 0.33 W/cm2, and the results were compared with those from samples subjected to normal immersion freezing at the same temperature. Consequently, relative to the samples that were frozen normally, the freezing rates of the samples with 9.91%, 6.46%, 4.01%, and 0% of air were improved by 20.00%, 27.00%, 29.00%, and 33.00%, respectively, after ultrasound-assisted immersion freezing, and the phase transition times of these samples were reduced by 16.00%, 24.00%, 27.00%, and 31.00%, respectively. With decreasing air content in the radishes, the freezing rate of the ultrasound-assisted immersion freezing method was increased significantly (p<0.05), and the hardness, microstructure, and calcium content of the thawed samples were significantly enhanced (p<0.05) as well. The results suggested that the higher air content in the radish tissue pores was a major factor causing the decrease in the efficiency of ultrasound-assisted immersion freezing, and degassing treatment could effectively improve the efficiency of this freezing technique on air-containing substances.

东普通高校国际暨港澳台合作创新平台（2015KGJHZ001）；农产品保鲜物流共性技术创新团队（2016LM2154）；广州市科技计划（201508020097）