超声渗透提升双孢蘑菇冷冻干燥热质传递效率机理研究

Currently, freeze drying is one of the best drying methods for maintaining food quality. However, freeze drying in the food industry is restricted due to its high energy consumption, long production periods and high costs. Ultrasound-assisted osmotic pretreatment of food materials before processing is an effective method for improving freezing and drying efficiency which has been widely applied in different food processing fields. However, the mechanism is not clearly demonstrated. Concerning this issue and based on our previous studies, the numerical analysis of heat and mass transfer and hyperspectral imaging characteristics during different stages of freeze drying will be the targeted piontcuts, and the effect of ultrasound-assisted osmotic treatment on the characteristics of osmotic, freezing and heat and mass transfer of button mushroom during freeze drying will be studied in detail. Water states and distribution during Ultrasound-assisted osmotic and freeze drying processes will also be analyzed to provide the mechanism of improving heat and mass transfer efficiency. Besides, hyperspectral imaging system will be performed to collect the characteristics of spectrum and the hyperspectral model of moisture content will be established by using multivariate statistics analysis, combined with parametric analysis to reveal the hyperspectral imaging mechanism of improving the efficiency of freeze drying treated by ultrasound-assisted osmotic. This studies will provide a theoretical basis upon which a state of real-time monitoring and nondestructive intelligence controlling system of button mushroom during freeze drying can be achieved.

冷冻干燥是目前保持食品品质最好的干燥方式之一，但其能耗高、生产周期长、生产成本高的特点限制了食品冷冻干燥的规模化发展。超声渗透技术是提升食品物料冻结和干燥效率的有效手段，但其作用机理尚不明确。针对这一问题，申请人在前期研究基础上，以双孢蘑菇冷冻干燥过程热质传递耦合数值计算和高光谱特征成像分析为切入点，重点研究超声渗透处理对双孢蘑菇渗透传质特性、冻结特性和冷冻干燥过程热质传递动力学特性的影响，通过构建热质耦合传递模型，结合超声渗透与冷冻干燥过程的水分形态分布与迁移规律，明确超声渗透提升双孢蘑菇冷冻干燥热质传递的动力学机理。同时，应用高光谱成像技术对冷冻干燥不同阶段的特征光谱信息进行采集，通过多元统计分析方法构建基于物料含水率的高光谱特征模型，结合模型参数分析揭示超声渗透影响双孢蘑菇冷冻干燥效率的高光谱成像机理。该研究为实现双孢蘑菇冷冻干燥快速实时在线监测和无损智能化控制提供理论依据。

双孢蘑菇是世界上种植面积最大，产量最丰富的食用菌，但是其货架期容易因机械损伤和微生物的侵袭而严重缩短。冷冻干燥可以最大限度保持食品原有的品质和营养价值，但能耗高、干燥周期长、生产成本高制约了其发展。针对这一问题，本项目研究了超声渗透对双孢蘑菇渗透特性、冻结特性、水分相变与迁移、冷冻干燥效率与品质等影响规律，建立了双孢蘑菇超声渗透和冷冻干燥过程可溶性固形物、含水率、硬度等品质指标与高光谱吸收特性相关性的模型 ，从高光谱成像角度揭示了超声渗透对双孢蘑菇冷冻干燥效率影响机理，完成了项目规定的各项任务和指标，达到了预期研究目标。主要成果如下：.（1）研究了不同渗透溶液对超声辅助渗透双孢蘑菇传质动力学特性和品质特性的影响，证明了蔗糖渗透溶液有着良好的有效水分扩散率与有效固形物扩散率，同时最大限度的维持了双孢蘑菇渗透后的微观结构。同时，证明了超声辅助渗透能更好维持双孢菇的质构、营养和呈味物质，明确了双孢蘑菇在不同渗透过程中的水分形态与分布。.（2）研究了恒温渗透和超声辅助渗透处理对冷冻干燥双孢蘑菇冻干效率和品质的影响，证明了与恒温渗透相比，超声辅助渗透处理对双孢蘑菇冷冻干燥效率起到了显著提升效果。同时，与恒温渗透相比，超声辅助渗透对双孢蘑菇冷冻干燥后的色泽、质构、营养品质具有显著的维持作用。.（3）研究了基于高光谱成像对双孢蘑菇超声渗透过程可溶性固形物传质规律，证明了CARS-OSC-SVM模型能够准确拟合双孢蘑菇超声渗透可溶性固形物变化规律，建模集和预测集拟合优度分别为87%和71%。基于预测模型和Matlab R2016a生成双孢蘑菇不同渗透阶段伪彩色图像，从高光谱成像角度揭示了双孢蘑菇在渗透过程中分布规律。.（4）研究了基于高光谱对双孢蘑菇片渗透前后冷冻干燥过程中水分和硬度值的变化规律，证明了SCARS-SVM模型能够准确拟合双孢蘑菇渗透前后冷冻干燥过程变化规律，揭示了超声渗透对双孢蘑菇冷冻干燥效率影响的高光谱成像机理。