Experiment on Banana Vacuum Drying and Moisture Absorption

Abstract

Bananas are rich in vitamin B6 and are a good source of fiber, vitamin C, magnesium and potassium. Banana contains rich glue, fructose, and a variety of enzymes which lead not only to storage difficulties but flesh browning during the products processing. It affects the color, the nutrition and taste of banana and causes the quality deterioration. Kinds of banana products have be very popular such as banana powder, banana slice, canned banana, banana jam and other processed products. Many people are all interested in the banana drying [1-8]. Zhang Bin [9] studied on banana slice drying process by combining hot air and microwave. Results showed that hot air-microwave drying method as faster drying speed and lower energy consumption, and products quality produced by this method approximated single vacuum freeze-drying ones. Zhang Bin [10] studied on quick-freezing of banana Slice under vacuum freeze-drying condition and results showed that taking product quality and shortening sublimation time into account, the quick freezing method of bananas，material thickness of 6~8 mm, temperature of heating plate 43~47.5 ℃ , and 50~60 Pa vacuum for drying chamber were advised to be the optimum processing conditions for vacuum freeze-drying bananas. The thermodynamic properties of foods relate the concentration of water in the food to its partial pressure, which is crucial in analysis of the heat and mass transport phenomena during dehydration. So it is very important to research the drying and adsorption characteristics of banana. 2 MATERIALS AND METHODS 2.1 Banana drying 2.1.1 Materials and methods Banana: Picking fresh, neat and hard fruit, the banana skin was bright yellow and slightly a little green. Pay attention to the maturity and size uniform of banana and eliminate pests, mechanical damage, and overripe banana. The experiment used the vacuum drying to dry banana slice. Banana slice were placed in drying chamber and were heated in the vacuum system. Moisture diffused to the surface of banana slice under the action of pressure difference and concentration difference. Water molecules on the surface of material absorbed enough energy for escaping to the vacuum chamber of low voltage space, and were taken out by vacuum pump. Pretreatment: Strip the banana peel, remove the vein with a small stainless steel knife, and cut the banana into thickness uniform flake according to the experiment request. After pretreatment, put a certain quality sliced bananas in the material boxes, weigh every material box and banana slice before the drying. Weigh and recording were repeated during the process of drying. ABSTRACT: In order to research the drying and adsorption characteristics of banana. Experiment on banana slice drying and absorption were analyzed in the article. The vacuum drying was used in the banana slice drying experiment. In drying experiment, moisture of banana slices decreased at 75°C in 151 minute. G1 weight decreased from 33.95g to 28.99g and G2 weight decreased from 33.51g to 28.8g. In absorption experiment, the weight of banana slice increased from 28.99g to 30.75g.When the humidity reached balance between the banana slice and the atmosphere, banana slice weigh had no changes. Banana slice surface has a huge difference in character before and after drying. The sorption process in some materials was irreversible because the entropy changed during the adsorption and desorption process. 132