本研究以新鲜有棱丝瓜为原料，研究其热泵干燥特性。在单因素试验基础上运用Box-Behnken Design (BBD)方法设计优化实验，研究不同切片厚度、干燥风速和干燥温度对干燥耗时、复水比和多酚含量的影响，利用Design-Expert软件得到回归方程的预测模型并进行响应面法优化，确定丝瓜热泵干燥的最佳条件。以热泵干燥后的有棱丝瓜为原料用丙酮溶液提取多酚，通过DPPH自由基的清除能力评价有棱丝瓜多酚的抗氧化性能。试验结果表明丝瓜热泵干燥的最佳条件为：切片厚度5.22 mm，干燥风速为1.62 m/s，干燥温度62.6 ℃。预测该条件下，干燥耗时为2.56 h，复水比为16.1，多酚含量为1.89 mg/g。考虑实际操作可能性，将参数调整为：切片厚度5 mm，风速为1.6 m/s，干燥温度63 ℃。此条件下，测得干燥耗时为2.34 h，复水比16.05，多酚含量为1.88 mg/g，与预测值比较吻合。一定范围内抗氧化性能与多酚含量成正相关，在质量浓度上升到0.15 mg/mL时，DPPH自由基清除率达到78.13%。采用热泵干燥的有棱丝瓜具有较好的复水性及良好的感官品质，并且有棱丝瓜多酚表现出一定的清除DPPH自由基的能力。

In this study, the heat pump drying characteristics of the raw material, fresh Luffa acutangula (Linn.) Roxb., was studied. On the basis of the results of single-factor experiments, Box-Behnken Design (BBD) was used to design and optimize the experimental conditions for the studies on the effects of different slice thickness, drying air speed and drying temperature on drying time, rehydration ratio and polyphenol content. Moreover, the predictive model of the regression equation was obtained using the Design-Expert software, and the heat pump drying process variables were optimized by response surface methodology. Polyphenols were extracted with acetone from the heat pump dried Luffa acutangula (Linn.) Roxb., and the antioxidant activity of polyphenols from Luffa acutangula (Linn.) Roxb. was evaluated as DPPH free radical scavenging activity. The results showed that the optimal heat pump drying conditions were: slice thickness 5.22 mm, drying air speed 1.62 m/s, drying temperature 62.6 ℃. It was predicted that the drying time, rehydration ratio and polyphenol content were 2.56 h, 16.1, 1.89 mg/g, respectively, under the optimal drying conditions. Considering the actual operational feasibility, the drying process variables were adjusted to: slice thickness 5 mm, drying air speed 1.6 m/s, drying temperature 63 ℃. Under such conditions, the drying time, rehydration ratio and polyphenol content were 2.24 h, 16.05, 1.88 mg/g, which were in good agreement with the predicted values. The antioxidant activity was positively correlated with the polyphenol content within a certain range. When the mass concentration increased to 0.15 mg/mL, the DPPH free radical scavenging rate reached 78.13%. The Luffa acutangula (Linn.) Roxb. dried by the heat pump showed good rehydration behavior and good sensory quality with its polyphenols exhibiting a certain ability to scavenge DPPH free radicals.

国家重点研发计划项目（2017YFD0400902-2）；广东省功能食品活性物重点实验室（2018B030322010）