乙醇对红枣片CO2低温压差膨化干燥品质的影响

为了提高红枣的干燥品质，探究乙醇喷雾浸润预处理对膨化干燥效果的影响，该研究利用渗入红枣的高压CO2及乙醇作为动力源对红枣片进行低温高压渗透膨化干燥。以单因素试验为基础，对比研究预处理方式为无处理、热风干燥、乙醇喷雾浸润的 CO2低温压差膨化干燥、水分闪蒸干燥的膨化干燥品质及理化特性。优化枣片在乙醇喷润预处理方式下CO2低温压差膨化干燥工艺，研究乙醇喷雾浸润后含湿率、膨化压差、膨化温度、抽真空时长等因素对枣的膨化度、脆度、硬度、复水比的影响。结果表明，优化工艺为：乙醇浸润后含湿率19.3%、膨化压差1.08 MPa、膨化温度81.26 ℃、抽真空干燥时长151.13 min，膨化度为3.48，硬度为1 717.06 g，脆度为3 675.89 g，复水比为2.21。扫描电镜显示，乙醇具有溶解细胞壁成分的能力，可以改变结构来增加其渗透性，使CO2充分进入枣片中增大膨化动力，形成更有规律更大的孔隙。水和乙醇混合物的汽化热低于水的汽化热，与预处理方式为无处理、热风干燥的CO2低温压差膨化干燥及水分闪蒸干燥方法比较，乙醇浸润预处理可以表现出更好的膨化度、色泽、维生素 C 含量和显著缩短的干燥时间（P<0.05）。因此，乙醇喷雾浸润预处理后进行CO2低温压差膨化干燥是一种高效的干燥技术，所得的枣脆片品质较好。研究结果为红枣片的干燥品质及工艺优化分析提供了一定的理论基础。

Effects of ethanol and CO2 on the low temperature pressure explosion puffing drying quality of jujube slices

This study aims to improve the drying quality of fresh jujube, and further explore the effect of ethanol spray infiltration pretreatment on the puffing and drying. The high-pressure CO2 and ethanol infiltrated into the fresh jujube were used as a power source to carry out low-temperature and high-pressure infiltration puffing and drying of red jujube tablets. A single factor experiment was performed to explore the puffing and drying characteristics, as well as the physicochemical properties after the pretreatment under no treatment, hot air drying, CO2 low-temperature pressure difference puffing drying with ethanol spray infiltration, and moisture flash drying. The Response Surface Method (RSM) was selected to optimize the CO2 low-temperature differential pressure puffing and drying process of jujube under the pretreatment of ethanol spraying. A systematic investigation was made to determine the effects of moisture content, puffing pressure difference, puffing temperature, and vacuuming time on the puffing degree, brittleness, hardness, and rehydration ratio of jujube after ethanol spray infiltration. The optimized synthesis process was as follows, where the moisture content after ethanol infiltration was 19.3%, the puffing pressure difference was 1.08 MPa, the puffing temperature was 81.26 ℃, and the vacuum drying time was 151.13 min. After that, the jujube slices were obtained to behave a high puffing degree, excellent color, and crisp taste. The optimal properties were achieved, where the puffing degree of 3.48, hardness of 1 717.06 g, brittleness of 3 675.89 g, and the rehydration ratio of 2.21. Scanning Electron Microscope (SEM) morphologies show that the ethanol greatly contributed to dissolving the cell wall components, further changing the structure for the high permeability. As such, CO2 can be widely expected to fully enter the jujube tablets for the expansion power, as well as the formation of more regular and larger pores. The results show that ethanol can also dissolve some compounds of the cell wall to change the structure for the high permeability, where the solubility of CO2 in ethanol was higher than that in water, indicating a stronger expansion power during the expansion process. The heat vaporization for the mixture of water and ethanol was lower than that of water alone. As such, the drying time can be effectively shortened to increase the retention rate of biologically active compounds in the dried sample for the high oxidation resistance of different components. The CO2 low-temperature differential pressure puffing and drying can be an efficient drying technology after the pretreatment with ethanol spray infiltration. The obtained jujube chips presented an excellent brittleness, hardness, color, retention rate of vitamin C, and rehydration performance.