Effect of maturity and postharvest handling of prunus persica ‘landrace’ produced in KwaZulu-Natal: case study of physicochemical properties, tunnel solar drying and quality of processed products.

Abstract

Farmers in KwaZulu-Natal produce peach fruit. However, they are faced with overwhelming losses of the fruit due to lack of proper handling techniques, skills and facility during postharvest. In addition, these farmers have limited formal markets where they could sell fresh fruit immediately after harvesting. Thus, they are forced to consume the least they can and leave the rest of the fruit hanging on the tree. As a result, they lose close to 45% of their fruit. The literature review congruently pointed out such challenges of food losses in less developed countries and South Africa is not an exception. With a limited understanding of peach properties, it becomes increasingly difficult for farmers to handle the fruit. The cost of storage and processing facilities (such as sophisticated refrigeration) is very high and a decision table was used to determine which affordable method can be employed to process the peach fruit. The study is significantly important for the reduction of massive losses of fresh produce in the small-scale household farming sector as whole in South Africa. This study had three main aims to address. Firstly, it aimed to understand the physiological maturity and ripening of the peach fruit by determining physicochemical properties such as days to maturity, mass, volume, shape, moisture, pH, total soluble solids, colour (CIELab) and firmness. Secondly, the study aimed to install and test a tunnel solar dryer according to a decision table criteria that used to decide on a fruit processing method. Thirdly, the study aimed to process the fruit into dried peach slice with pre-treatments of lemon juice (LJ), ascorbic acid (AA) and a control, using a tunnel solar dryer. In addition, the study also aimed to process the peach into dried peach leather also using a tunnel solar dryer. This study included both objective and subjective methods to test the quality of the peach slice and leather products processed. Fruits reached maturity 129 days after full bloom (DAFB) and this coincided with fruit mass, volume and moisture content at respective averages of 80.00 g, 66.10 cm3, and 83%. Fruit firmness decreased significantly from 79.00 N to 24.70 N with increasing ripeness. Total soluble solids increased significantly from 13.50 to 19.00 °Brix during ripening. The pH value significantly increased from 3.40 to 4.00 indicating that acidity decreased with ripening. The TSS: TA ratio increased from 21.11 to 35.84. Moreover, it has been statistically verified that due the colour, yellow peach fruit produced the best products (as seen by the receipt of the highest sensory evaluation overall acceptability scores and based on the texture profile analysis results provided by Texture Analyser instrument). The utilisation of treatment such as AA or LJ did not have a significant effect in the overall drying between the yellow and white landraces. Ascorbic acid had a tendency to perform better than LJ which was also better than the untreated slices (control) in terms of the taste and overall acceptabilty. The experiment revealed that white leather moisture was approximately 7% and received the lowest overall acceptability scores from panellists. Less quality results were also received according to the texture profile analysis, in contrast to the yellow peach leather, which had 13% of moisture content. Yellow leather received the highest overall acceptability scores by both texture profile analysis and sensory evaluation tests. Thus, this study suggests that drying is possible in the KwaZulu-Natal Midlands. Overall, the results developed from the current study demonstrate that the fruit produced in small-scale farming sector is of good quality regardless of low yields because fertilizers and pesticides are not used. More importantly, this study reveals the significant potential of solar drying to be used by small-scale farmers to develop on-farm interventions aiming to add value to their produce and thus be able to preserve, use and sell later. It was concluded that DAFB, firmness, mass, TSS, volume, TTS: TA ratio are potential parameters to be used for maturity indexing of white peach ‘landrace’. Regardless of the misty conditions that prevail during the period of harvesting fruits, it was concluded by a statistical significant difference that the tunnel solar drying is a possibility in the KwaZulu-Natal Midlands. Days after full bloom, firmness, TSS, pH and mass have a critical role to play since they significantly differ between different ripeness degrees. These can be used to monitor peach growth stages and estimate yield for the small-scale peach grower in the area. The DAFB are a good tool that farmers can stick to without the use of advance technologies other than monitoring the number of days. Firmness is also a very important parameter for farmers in the area as the fruit hardly changes colour but can be soft showing signs of ripeness. The study has also devised a step-by-step process, which can be followed by small-scale processors in order to reduce losses using solar dryer to process fruit into leather and slice.