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热风干燥联合真空降温缓苏提升黄秋葵干制品品质
引用本文:段续,刘文超,任广跃.热风干燥联合真空降温缓苏提升黄秋葵干制品品质[J].农业工程学报,2016,32(18):263-270.
作者姓名:段续  刘文超  任广跃
作者单位:河南科技大学食品与生物工程学院,洛阳,471023
基金项目:国家自然科学基金(31271972);河南省高校科技创新团队支持计划(16IRTSTHN009);河南省高校科技创新人才支持计划(14HASTIT023);河南科技大学研究生创新基金项目(CXJJ-2015-ZR15)
摘    要:为提升黄秋葵热风干燥产品品质,试验将真空降温缓苏技术应用于黄秋葵热风干燥过程中。研究了不同缓苏时长下黄秋葵干燥特性和品质指标的变化规律;利用Weibull分布函数分析缓苏处理对黄秋葵热风干燥过程中水分扩散机制的影响;采用一元非线性回归分析构建适用于黄秋葵真空降温缓苏-热风联合干燥过程中干燥特性和品质指标随缓苏时长变化的学数模型;以总干燥耗时、总干燥能耗、复水比、色相角以及总营养物质保存率为指标,对不同缓苏时长下的黄秋葵热风干燥进行加权综合评价。结果表明:缓苏处理能够提升黄秋葵热风干燥速率,且随着缓苏时长的延长其促进作用会增强;Weibull分布函数能够准确描述(R2>0.99且离差平方和χ2处于10-4数量级)黄秋葵真空降温缓苏-热风联合干燥过程中水分比随干燥时间的变化规律;常用函数一元非线性回归分析能够构建出黄秋葵真空降温缓苏-热风联合干燥过程中各干燥特性和品质指标随缓苏时长的变化规律的动力学模型;联合干燥过程中,缓苏60 min处理的综合评分值最高为0.55,在干燥温度和风速分别为60℃、1.5 m/s条件下,该缓苏时长较适合应用于黄秋葵热风干燥。研究表明,真空降温缓苏处理能够提升黄秋葵热风干燥的干燥速率和干燥品质,该文可为真空降温缓苏技术在高品质黄秋葵干制品工业生产上的应用提供理论依据。

关 键 词:干燥  动力学  模型  机理  真空降温缓苏  黄秋葵
收稿时间:2016/5/18 0:00:00
修稿时间:2016/7/11 0:00:00

Hot air drying combined vacuum ventilation tempering improving quality of dried okra products
Duan Xu,Liu Wenchao and Ren Guangyue.Hot air drying combined vacuum ventilation tempering improving quality of dried okra products[J].Transactions of the Chinese Society of Agricultural Engineering,2016,32(18):263-270.
Authors:Duan Xu  Liu Wenchao and Ren Guangyue
Institution:College of Food & Bioengineering, Henan University of Science and Technology, Luoyang 471023, China,College of Food & Bioengineering, Henan University of Science and Technology, Luoyang 471023, China and College of Food & Bioengineering, Henan University of Science and Technology, Luoyang 471023, China
Abstract:Abstract: Okras (Abelmoschus esculentus (L.) Moench) belong to the Malvaceae family. It is proved that okra can act as a tonic for both man and woman and enable them to increase their vitality and vigour. Due to high content of vitamin A and C, calcium, dietary fiber and low content of saturated fat, okra products, which are consumed in dried, frozen, fresh forms and also available in canned and pickled forms, are popular around the world. Like others vegetables, okra is susceptible to rapid deterioration because of its high moisture content. Various physiological and morphological changes occur after harvest, which make these okras unacceptable for consumption, and thus it is necessary to remove the moisture of okras. Hot air drying is the most widely used and inexpensive drying technique for okra. Nevertheless, long-time drying at relatively high temperature during the falling rate period often leads to the overheating of dried products, and undesirable thermal degradation of the finished products may occur. Hence, it is necessary to apply innovative techniques on hot air drying to solve these drawbacks, which can increase drying rate and reduce quality loss. One of the methods that may be recommended is drying with tempering cycles. Tempering allows moisture diffusion from the interior to the external surface of the sample kernels to decrease the moisture gradients. Hence, the material structure can be well protected during drying process, and with the uniform distribution of moisture, the drying rate of next stage will be higher. While in a vacuum environment, the oxygen (O2) content is in a low level, which can reduce many undesirable oxidation reaction and slow down the physiological activity of materials. Moreover, many researchers have reported the vacuum tempering method can obviously reduce the tempering time compared to traditional natural tempering. Ventilation tempering is carried out under the condition of decreasing temperature, the moisture can be uniformly distributed not only by moisture gradient but also by temperature gradient. Consequently, combining the vacuum tempering method with ventilation tempering can reduce tempering time more significantly along with obtaining good product quality. As above introduction, applying the combined tempering method on hot air drying may overcome some limitations of traditional hot air drying process, which can be called as vacuum ventilation tempering combined with hot air drying (MVVT-HAD). To achieve high quality products, vacuum ventilation tempering was applied on okras hot air drying, and the change trends of drying and quality characteristics of okras were investigated in this study; the effect of tempering process on the drying mechanism of okras was analyzed by using the Weibull distribution function. The drying and quality kinetics model, which was applicable in okras MVVT-HAD process, was constructed by using a nonlinear regression analysis; and the weighted comprehensive evaluation of okras MVVT-HAD process was also carried out based on total drying time, total energy consumption, rehydration ratio, hue angle, and total nutrient retention ratio. Results showed that, tempering treatment could improve the drying rate of okras hot air drying, and with longer tempering time the effect would be more obvious; Weibull distribution function could accurately describe the change tendency of water ratio with drying time of okras during MVVT-HAD process; the scale parameter of okras was reduced with the prolongation of the tempering time length; different tempering time length had the same effect on drying moisture diffusion mechanism in okras hot air drying; taking total drying time, total energy consumption, rehydration ratio, hue angle and total nutrient retention ratio into account, 60 min tempering time length was proposed as the favorable condition for okras hot air drying. The study shows that MVVT treatment can enhance the drying rate and drying quality of okras during HAD stage, and our paper provides a theoretical basis for the application of MVVT-HAD on industrial production of high quality dried products of okras.
Keywords:drying  kinetics  model  mechanism  vacuum ventilation tempering  okra
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