Effect of Vacuum Drying System on Drying Time and Quality of Banana Slices

Abstract

Drying is a common method for preserving agric-food products. Banana is one of the popular value-added products. Due to its high nutrition, strong aroma, and the convenience for package, storage, and transportation, dried banana is in a growing demand in local and international market. Conventional drying (hot air) offers dried products that can have a long life over the year. Unfortunately, the dried product quality is significantly reduced in comparison with the original food staff. A relatively novel technique, namely microwave-vacuum drying has received great attention in the last few decades for drying of various fruits and vegetables. Banana slices were dried using microwave-vacuum drying, and the drying characteristics under vacuum drying were examined. During the experimental work four different absolute pressures (1, 4, 7, and 10 kPa), two different thicknesses of banana slices (3, and 4 mm), and constant surface temperatures of banana slices of 70oC were employed. The quality of the banana slices in terms of Texture profile analysis (TPA) and hardness were also investigated with an aim to produce a fat-free snack-like product. The obtained results show that, drying time decreased at low drying pressure and ranged between 5.25 to 23.25 h. Deff values increased with the vacuum drying processes. The minimum Deff ranged from -0.507 to -0.1104 m2/s with high coefficients of determination (R2 = 0.9335 to 0.9457). The drying conditions affected the properties of the TPA of the dried banana in comparison with those of the raw fruits prior to drying. The drying conditions resulting in increased hardness, gumminess, and chewiness, while they reduced the cohesiveness and resilience and no adhesiveness after vacuum drying. The most affected properties were the hardness, and chewiness. The hardness and chewiness of the final product were ranged from 71.19 to 645.24 N, and from 38.67 to 290.99 N, respectively.