Development of a Smart Prototype Solar Cooler to Replace Charcoal Coolers in Maintaining Quality and Shelf Stability of French Beans Along the Supply Chain in Kenya

Abstract

French bean is one of the major horticultural crops exported from Kenya into International markets. French bean production faces several challenges whose magnitude depend on whether the crop is produced in-house or with an out grower. Unlike with the large commercial growers who have well organized infrastructure to ensure quality food safety of the beans, small scale farmers have always struggled to keep up with the quality expectations of the markets. This study was aimed at evaluating the performance of solar coolers in enhancing quality and shelf life stability of French beans with an overall of objective of developing a smart solar cooler to replace the use of charcoal coolers. A survey was done to understand the current knowledge and performance of charcoal coolers. Data were collected primarily from a household survey using a semi-structured questionnaire that was administered to 45 farmers that were selected at fixed interval purposively selected. To evaluate the effects of harvesting time and duration before cooling on the post-harvest quality and shelf-life stability of French beans, five harvesting times were evaluated; 7am, 9am, 11am, 1pm and 3pm. The harvested beans were then subjected to five different delay times before cooling; 0hr, 2 hours, 4 hours, 6 hours and 8 hours. The proximate compositions of the fresh French beans samples were determined using standard methods. The microbial quality of French harvested at different times of the day, 7am, 9am, 11am, 1pm and 3pm was also done using standard plate technique. The samples were later graded and packed in modified atmosphere packaging (MAP) bags. The study revealed that majority (80%) of the farmers adopted evaporative cooling technology using charcoal coolers and stored their produce for one to six hours (68%). Majority of the interviewed famers (67%) harvested between 0 to 5 tons of French beans from their farms while only a few (2.2%) obtained yield above the 20 tons mark. Many of the farmers were not members xxii of farmer groups and as such were not privy to information shared amongst farmers. There was positive correlation (P≤0.05 r-0.332) between harvesting time and age and also between storage time and gender (P≤0.05, r 0.367). However, study level (p≤ 0.01r -0.383) and harvesting (p≤0.01 r- 0.444) was negatively correlated significantly with (p≤0.01) charcoal cooler effectivity. The results showed that samples had the following ranges of proximate parameters: 2.1 -2.4g/100g protein, 0.8–1.0g/100g fiber, 0.8–1.6g/100g ash, 88 –92% moisture, 0.14– 0.15 fat, and 6.1–7.6g/100g carbohydrate and with 3% change in weight for samples harvested late in the afternoon. The study revealed a significant loss of moisture and weight for every delay in start of cooling resulted in increase of protein by 18%, fat by 24%. Total viable counts (TVC) in these samples showed mean values ranging from 0.7 to 3.3×105 CFUs g-1 for total Enterobacteriaceae, Listeria monocytogenes, moulds and Staphylococcus aureus. Of the microorganisms isolated, Enterobacteriaceae (71.6%) was the highest, followed by Staphylococcus aureus (20.9%), Moulds (7.2%) and Listeria monocytogenes at 0.3%. The harvesting time and duration before cooling significantly (P≤0.05) affected the population of microorganisms with those harvested early in the morning recording the highest population.