Drying characteristics of mushrooms

Abstract

Mushrooms are delicious food with nutritional value, but extremely perishable and due to several physiological and morphological changes, which occur after harvest, become unacceptable for consumption. The most popular way to process mushrooms is drying. This research aims to investigate the drying characteristics of several typical types of common mushrooms. The objectives of the present study are: 1) to investigate the drying rate and diffusion coefficient variation; 2) to compare the drying characteristics of two methods of drying: forced convection drying and natural convection; 3) to compare the drying characteristics of forest mushrooms and mushrooms cultivated by artificial intensive methods. During this research two types of mushrooms growing in the wild and also mushrooms grown commercially and commonly available in shops have been investigated: Oyster mushroom (Pleurotus ostreatus), Portobello mushroom (Agaricus bisporus) and Red cracking bolete (Xerocomellus chrysenteron). These three types of mushrooms have been selected because they differ markedly by their structure, the conditions of the substrate on which they grow, and the verified results of the drying process. The drying process was determined gravimetrically at normal summer temperature about 28.7 ºC and relative humidity of 43%. The total drying time 25 hours was adapted to the need for determination of the lowest moisture content, which can be achieved by convective drying. The research results show that forced convection has a strong positive influence on the drying process comparing with drying by natural convection and reduces the time. The forced convection has significant impact on moisture removal only during the first 7 hours of the experiment. It is recommended to interrupt the air flow for the rest of drying, which allows optimizing the power consumption. Noticeable changes in thickness which decreases should be taken into account in diffusion coefficient determination.