香菇分段变温红外喷动床干燥工艺参数优化

为获得节能低耗和品质较优的干香菇，利用红外喷动床干燥设备，对香菇分段变温干燥工艺进行试验研究。在单因素试验基础上运用Box-Behnken Design优化试验，研究前期风温、转换点含水率和后期风温对单位能耗、粗多糖含量、亮度L*值和收缩率的影响，通过加权综合评分法推导多项式回归模型，优化红外喷动床干燥工艺参数。经响应面优化的干燥参数为：前期风温56.00 ℃、转换点含水率53.00%、后期风温72.00 ℃，该工艺下单位能耗为143.52 kJ/g、粗多糖含量9.98 mg/g、亮度L*值68.11、收缩率83.15%，综合评分值为35.37，与预测值拟合度高达99.27%，表明应用红外喷动床干燥取得的香菇制品能满足当前香菇干燥的发展趋势及需求，为香菇干制品的综合应用及生产加工提供参考。

Optimization of the drying process parameters for lentinus edodes in segment variable temperature infrared assisted spouted bed

Lentinus edodes are favored by consumers, due mainly to the antitumor, immunoregulation, anti-aging, antioxidation, and anti-radiation. However, the drying process can be used to extend the shelf life, because the fresh lentinus edodes are not easy to store. In this experiment, a new infrared-assisted spouted bed drying equipment was used to investigate the drying process of lentinus edodes under the segment variable temperature. An infrared-assisted spouted bed was utilized to improve the high energy consumption and heat loss of infrared drying with uniform distribution. A single factor Box-Behnken Design was used to optimize the response surface experiment. The parameters included the early wind temperature, water content at conversion point, and late wind temperature on specific power consumption, crude polysaccharide content, brightness value L* and shrinkage ratio. The polynomial regression was derived by a weighted comprehensive score to optimize the drying process parameters of an infrared-assisted spouted bed. The results showed that the crude polysaccharide content of lentinus edodes dried by infrared spouted assisted bed gradually increased, with the increase of early wind temperature (A), where the retention rate increased to a maximum of 9.33 mg/g at 60°C. The materials were also heated evenly during drying. The specific power consumption decreased to reach the minimum of 160.95 kJ/g, while the drying time was shortened, with the increase of temperature, when the early wind temperature was 60°C. Brightness value L* and shrinkage ratio showed a trend of first increased and then decreased, with the increase of early wind temperature at the maximum of 55°C. Appropriate early wind temperature could effectively reduce the specific power consumption, thereby maintaining high nutrients for better economic benefits. The content of crude polysaccharide increased significantly, where the maximum was 10.44 mg/g at 70°C, particularly when the late wind temperature (C) was 60°C-70°C. Furthermore, there was an obvious downward trend, when the temperature continued to rise. Excessive temperature could damage the retention of nutrients during drying, due mainly to polysaccharide degradation produced oligosaccharides and partial caramel. The drying rate accelerated, but the specific power consumption decreased, with the increase of temperature. In addition, there was the most obvious shrinkage ratio at 75°C, with the maximum yellow/blue value b* of 19.93, while the brightness value L* value continued to decrease, with the increase of late wind temperature. Correspondingly, there was a significant difference (P<0.05), particularly slightly browning, and yellow color of Lentinula edodes. The specific power consumption decreased gradually, with the increase of water content at conversion point (B). There was also a trend of first increasing and then decreasing in the crude polysaccharide content. The shrinkage ratio and brightness value L* increased first and then decreased, with the increase of water content at the conversion point. The single factor interaction was ranked in the order of AC>AB>BC. The optimal drying parameters were achieved using the response surface method, where the early wind temperature was 56.00°C, the water content at the conversion point was 53.00%, and the late wind temperature was 72.00°C. In this case, the specific power consumption was 143.52 kJ/g, the crude polysaccharide content was 9.98 mg/g, the brightness value L* value was 68.11, the shrinkage ratio was 83.15%, the comprehensive score value was 35.37, and the fitting degree with the predicted value was 99.27%. Consequently, the infrared-assisted spouted bed drying can widely be expected to fully meet the development trend and demand of lentinus edodes products. The finding can also provide a theoretical foundation for the production and processing of dried lentinus edodes products.