Comparison of calcium hydroxide treated and untreated pumpkin flesh at different dehydration temperature

Abstract

Pumpkin is widely planted worldwide, including Malaysia. Some regions have the limitation of oversupply or limited supply for fresh pumpkin. This has raised the urge to produce pumpkin derived products to avoid spoilage and wastage of fresh pumpkin and to cater the high demand from consumers due to its known health benefits. Dehydration is one of food preservation method. Starting from food dehydrating directly under sunlight to developing time saving and cost effective technologies with the aim to improve the quality of dehydrated products. Food dehydrator is a practical technology that can be used to dehydrate pumpkins. It could be used to dehydrate foods at different temperatures with a good air aeration to accelerate the dehydrating process. Four temperatures (50℃, 60℃, 70℃ and 80℃) had been tested to dehydrate pumpkin flesh in the present study. The pumpkin flesh was treated with calcium hydroxide (Ca(OH)2) for better dehydration and food preservation. The dried pumpkins were then ground into powder for storage. The quality of pumpkin products was proven by extracting bioactive components from dried pumpkin using ethanol extraction. The good quality of dried pumpkins was also determined for its biochemical compounds such as ß-carotene, riboflavin, caffeic acid, and quercetin by HPLC. The antimicrobial activities of the extracts towards four microorganisms (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia) were also analysed using disc diffusion method. Dehydration of pumpkin flesh was found to exhibit falling rate pattern, which is common in the dehydration of agricultural products. The treated pumpkin flesh that dehydrated at 70°C was able to produce the highest extraction yield (73.54%). However, the degradation of bioactive compounds could be happened during the process of pre-treatment, dehydration, extraction and storage. The explanation was given to the observation in the present study because the assigned compounds could not be detected and no significant inhibition was observed for the selected pathogenic microorganisms. Although dehydration was successfully carried out, the quality of dried pumpkin was not satisfied. Therefore, it is recommended to improve the pre-treatment and extraction techniques to ensure high quality of dehydrated pumpkin flesh for human consumption.