Study of combined microwave vacuum drying of apple raw material

Ferenczi, Sándor and Czukor, Bálint: Study of combined microwave vacuum drying of apple raw material. Review of faculty of engineering : analecta technica Szegedinensia 1-2. pp. 59-65. (2011)

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Abstract

A widespread and simple method for preserving fruits and vegetables is drying. Hot-air-, freeze-, vacuum- and dielectric drying are the most common methods. In this work, the microwave-vacuum drying combined with hot-air pre-drying was investigated for apple. This combined drying method produces a snack-like product with crisp and puffed structure, preferred by consumers. It can be an alternative to products like deep-fried potato, or fruit chips. The ovary of the raw apple was removed, and then the apple was cut into slices. After the preparation, the sample was hot-air dried, and then microwave vacuum-dried for 60, 70 or 80% and 97-98% dry basis, respectively. During microwave vacuum drying, the rapid evaporation of residual moisture of raw material causes the fruit tissue to expand, creating a porous crunchy texture with low mass density. In the course of the drying process, pulsed microwave energy is used, with radiation, and relaxation times. The microwave energy is provided by two magnetrons, with severally 850Watts nominal, 450Watts effective output. Our aim is to investigate the technology-related properties of microwave vacuum drying combined with hot-air pre-drying. The experimental pilot plan consists of 3 independent variables (factors) and 2 dependent variables. The mass load of the pre-dried fruit was 200g and the applied vacuum was 50 mbar. The independent factors were investigated in 3 levels: pre-dried dry mass content, (60. 70, 80%) the specific energy input (12, 14, 16 minutes of total microwave radiation, which equals 1.62, 1.89, 2.16 kJ/g specific energy) and the ratio of double-magnetron treatment and total radiation. (0.5, 0.75, 1) Two of the product's measurable properties as dependent parameters were analyzed; the burning ratio and the mass density. Our goal was to create product with minimal burning ratio and minimal mass density. After performing the experiments, the following conclusions can be taken. The mass density and the burning ratio of treated apple are directly proportional to the energy input. Within the studied range, at low initial dry matter content of the pre-dried product (60% dry matter content) with intense energy input, desirable product can be achieved. The ultimate optimum occurs at medium initial dry matter content (70%), 0.8 double magnetron-treatment ratio, and 1.755 kJ/g energy radiation.

Item Type: Article
Journal or Publication Title: Review of faculty of engineering : analecta technica Szegedinensia
Date: 2011
Number: 1-2
Page Range: pp. 59-65
ISSN: 1788-6392
Language: angol
Uncontrolled Keywords: Mérnöki tudományok
Additional Information: Bibliogr.: 65. p. ; összefoglalás angol nyelven
Date Deposited: 2016. Oct. 15. 12:24
Last Modified: 2019. Jan. 04. 12:27
URI: http://acta.bibl.u-szeged.hu/id/eprint/11876

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