浒苔真空冷冻干燥工艺优化

Optimized experiment on technological parameters for vacuum freeze drying of ulva prolifera

为研究并确定浒苔真空冷冻干燥的最佳工艺,以宁波象山港浒苔为原料,采用电阻法测定浒苔真空冷冻干燥的共晶点和共融点。应用二次正交旋转组合设计方法,研究物料厚度、真空度和加热板初始温度对浒苔叶绿素损失率和干燥时间的影响,分别建立了各因素与两者之间的回归模型。运用模糊综合评判法对真空冷冻干燥浒苔的叶绿素损失率和干燥时间进行优化,采用SAS9.2软件建立综合回归方程。结果表明:浒苔真空冷冻干燥的共晶点和共熔点温度分别为-18℃和-14℃。回归方程、响应分析及数学模型与试验数据均显示出良好的拟合(R2=99.43)。3个因素对浒苔真空冷冻干燥的影响均高度显著(P<0.01)。影响浒苔干燥综合指标的主次顺序为真空度、料层厚度、加热板初始温度。优化组合的最佳工艺参数为:料层厚度为13mm,真空度为52 Pa,加热板初始温度为60℃。在此条件下浒苔的真空冷冻干燥叶绿素损失率达到17.88%,干燥时间8.18 h。研究结果可为浒苔的高附加值干燥提供科学可行的理论参考。

In the present study, to optimize technology of vacuum freeze drying of U. prolifera, U. prolifera in Ningbo Xiangshangang was chosen as raw material. The eutectic point and the consolute point of U. prolifera in the vacuum freeze-drying were determined by electrical resistance method. Response Surface Methodology（RSM） based on central composite rotatable design（CCRD） was employed to optimize the conditions of three independent variables（material thickness（7, 10, 15, 20, 23 mm）, vacuum pressure（33, 40, 50, 60, 67 Pa） and starting heating board temperature（43, 50, 60, 70, 77 ℃）） on chlorophy loss ratios and drying time. The regression model between each factor and response were estabilished. The chlorophyll loss rate and drying time of vacuum freeze-drying was optimized through fuzzy comprehensive evaluation method, A predictive polynomial quadratic equations model was developed in SAS 9.2 software, and the influence order of three independent variables was optimized. Experimental results showed that the eutectic point and the consolute point of Ulva prolifera were-18 ℃ and-14 ℃ in the vacuum freeze-drying, respectively. The three variables all had very significant influence on drying（P〈0.01）. Vacuum pressure had the greatest influence than material thickness and starting heating board temperature. The optimal combination parameters for the freeze-drying technology of Ulva prolifera was obtained. They were as follows： the thickness was 13 mm, the vacuum pressure was 55 Pa, starting heating board temperature was 60 ℃, the loss ratios of chlorophy is 17.88%, and drying time is 8.18 h. Results could provide a theoretical reference for drying of high added value Ulva prolifera.