Process optimization and physicochemical characterization of two pineapple (ananas comosus) cultivars grown in selected areas of Uganda: a case of solar drying

Abstract

Pineapple (Ananas comosus) is one of the most important tropical fruits of economic importance and in our diets and its subsequent dried pineapple products are increasingly becoming popular for the consumption. Though solar drying has been used for the preservation of pineapples in Uganda since the 1980’s, it is a slow process and is constrained by a high proportion of rejects brought about by high variation in quality. Little still remains unknown about the internal quality of the Ugandan pineapple cultivars grown in different parts of the country. Therefore, the physicochemical, mineral and proximate properties of pineapple cultivars grown in Uganda were investigated for their suitability of use as a raw material for solar drying processes. Also investigated in this study were parameters for the solar drying process to find optimal conditions for the processing of solar dried pineapple. The results showed that fresh pineapple cultivars were significantly different in terms of their morphological and physicochemical characteristics at p≤0.05. Findings showed no significant differences (p≤0.05) between cultivars and between production areas with respect to proximate composition across all parameters tested with the exception of dietary fiber. Mineral content varied significantly between different cultivars grown in selected areas of Uganda (p≤0.05). Potassium was the most abundant mineral found in both pineapple cultivars ranging from about 1878 mg/100 g to 239.72 mg/100 g while both cultivars were found to be low in iron ranging from about 2.54 to 6.28 mg/100g. The processing conditions for solar drying pineapple snacks were evaluated and optimized. Optimal conditions for drying of the pineapples were determined. The best optimal conditions obtained for the processing criteria were 5 mm (Slice thickness) and 0.2% (pre-treatment concentration) based on maximum desirability (0.64) were determined using design expert software version 11. For the optimized combination of drying parameters, the vitamin C content, the rehydration ratio and the browning were 9.14, 2.43 and 0.47 respectively. The physicochemical characteristics evaluated in this study can be important postharvest quality criteria for the fruit processing industry, screening and breeding among many other uses.