Effect of osmotic dehydration pretreatments on drying rate and post-drying quality attributes of red bell pepper(capsicum annuum)

Abstract

Bell pepper (capsicum annuum) is a common vegetable plant and the most popular world-wide and mildest member of capsicum family. It is very easy to cultivate but highly perishable because of its characteristic lower sugar and acidic contents. It lacks built-in protection mechanisms which makes it more vulnerable to deterioration and thus leading to rapid metabolic activities within its cells once harvested. As a result of the aforementioned, it usually experience high postharvest losses in its season and becomes scarce and of low standard at off-season. This work was done to study the factors affecting the drying process of pretreated red bell pepper; and also to investigate the effect of osmotic pretreatments(solution concentration, solution temperature and process duration) on the drying rate and quality attributes (vitamin C, vitamin A and ash content) of red bell pepper. A 43 factorial experiment in Randomized Complete Block Design (RCBD) was used. The factors taken into consideration were osmotic process duration (60 min-150 min), osmotic solution concentration 5% (w/w)-20% (w/w), and osmotic solution temperature (30°C-60°C), all at four levels and replicated three times. A drying temperature of 60˚C was used for all the pretreated samples inside a temperature-controlled fabricated dryer. Results revealed that not all the osmotic dehydration pretreatments showed significant effect on the drying rate at p≤0.05. Also, increase in osmotic dehydration pretreatment conditions did not cause the average values of vitamin C, vitamin A and ash content to fall below 120 mg/100g, 1.40 mg/100g and 8.0% respectively. Further studies should be carried out on the storability, shrinkage and rehydration properties of dried samples, and modeling and optimization of the process.