Preliminary investigation of the potential for small scale production of quality solar dried produce, KwaZulu-Natal.

Abstract

This study undertook to carry out a survey of dried fruits and vegetables that could be dried using a solar drier system and determine the efficiency of solar drying in terms of a) the effect of temperature and humidity on the solar drier; b) effect of this drying system on three fruits and three vegetables in terms of quality which was measured by ascertaining the colour, texture, and flavour and moisture levels; and c) the effectiveness of pre-treatment systems on the above parameters. A small markets survey was conducted to investigate what dried fruit and vegetable products were available in four selected supermarkets in Pietermaritzburg. The findings of this survey were compared with small scale production in the region and the prevailing climate. Experimental dried products were produced and the efficiency of the solar drier to produce quality products on a small-scale farmers level was evaluated through three tests. First, the quality of the dried fruits and vegetables were rated by sensory evaluation of terms of colour, flavour, texture, and moisture content by members of a rural community solar project. The fruits (apple and banana) were treated by three methods, namely soaking in 35% sugar syrup and lemon juice (preserved with sulphur dioxide), 25% lemon juice (preserved with sulphur dioxide), 25% lemon juice (preserved with sodium metabisulphite). Half the vegetables (carrot, tomatoes, and pumpkin) acted as controls while the second half of the samples were pre-treated with steam blanching. Forty-seven panellists used a five-point hedonic scale to evaluate the dried products. Second, the moisture content of dried products was measured using the Association of Official Analytical Chemists, Official Method 934.06 and compared to available standards for dried fruit and vegetable products. Third, a data logger was used to measure the difference between temperature and humidity levels inside and outside the solar drier. The results of the supermarket survey showed that, drying methods used, treatments, packaging, raw material, and processing practical are all appropriate and affordable to small-scale farmers. In addition, the climatic conditions of the study area indicated that the drying process especially solar drying could be applied almost all year round. The results of the sensory evaluation showed that the quality characteristics such as colour, flavour, and texture of the sample dried fruits are better when treated with sugar syrup and lemon juice preserved with sulphur dioxide than those pre-treated only with lemon juice preserved with sulphur dioxide and lemon juice preserved with sodium metabisulphite. Dried vegetables had better texture, colour and flavour when treated with steam blanching. The ability of the solar drier to maintain the desired level of temperature and humidity inside the drier also indicated its efficiency. Therefore, small scale farmers by using solar drier and appropriate pre-treatments and packaging could produce good quality of dried products.