Abstract:
Abstract: Cherry tomato decays easily. Generally, it can be preserved only for 5-7days under normal pressure and temperature. The dehydration of cherry tomatoes into dried or preserved fruits can prolong their shelf life and enrich the market of the fruit. Currently, cherry tomatoes is dehydrated through natural drying. The advantage of this method is simple, and low cost. But the drying time is long and is affected by the climate and sanitary conditions. The product quality is difficult to control. In order to shorten the drying time and prevent mildew, cherry tomatoes are often soaked or sprayed with the alkaline solution. These chemicals are bad for our health. Multi-stage temperature-and-humidity drying is conducted through the material drying characteristics. This method can speed up the drying rate, improve drying quality, and reduce energy consumption. It has been successfully applied for apricot, lyceum barbarum, grapes and other materials. In this study, internal recycling hot-air drying technology was employed for the drying of cherry tomatoes. The effects of drying temperatures, humidity, drying stages and slicing forms on the drying characteristics and the appearance quality of the cherry tomatoes were investigated. Each experiment was composed of four drying stages. The drying temperatures were fixed, the humidity of the environment was changed in processⅠ, Ⅱ and Ⅲ. The drying temperature was low, the humidity was high at the beginning of process Ⅳ. Gradually, the temperature was raised, the humidity was reduced. At the end of the process, the drying temperature was higher, the humidity was lower compared with their values at the beginning. The experimental results indicated that pre-heated and falling rate periods exist during the drying of cherry tomato. Previous studies only shown falling rate period. The increase in temperature and humidity has bad effects on the nutrition, color and the appearance quality of cherry tomato. Even though cherry tomato can be heated quickly by increasing the enthalpy. This paper presents a multi-stage temperature-and-humidity drying process as process Ⅳ. This process included four drying stages, each lasted 0.5, 2.5, 2 h. The end temperatures were 50, 60, 65 and 70℃, the humidity were 70%, 50%, 30% and 10%, respectively. This method not only effectively reduces losses of the nutrition in cherry tomato and changes its color, but also shorten the drying time. However, further researches on multi-stage temperature-and-humidity drying methods and optimistic process parameters for different drying materials are necessary. In this study, some of the cherry tomatoes were cut along their axes, some were obliquely cut, and others were radically cut. Under the same drying conditions, the drying rates of the above ranked in descending order as follows: the axes-directionally, obliquely and radically cut cherry tomatoes. It is expected that this research will add knowledge for the cherry tomato drying theory of hot-air drying technology and support for the industrial development of cherry tomato.