Osmotic dehydration optimization of butternut squash (Cucurbita moschata Duch) using response surface methodology

Abstract

Butternut squash (Cucurbita moschata Duch) has a reasonably high carotene content. The flour-making process of it is related to the carotene content and antioxidant activity. It is essential to determine the optimum conditions of osmotic dehydration process by treating the concentration of the salt solution (5-15%), immersion time (60-180 mins), and stirring speed (10-40 rpm) on colour, beta-carotene content, and antioxidant activity using Response Surface Methodology (RSM) with Box-Behnken Design (BBD). All responses had a quadratic model fit (p<0.05). The R2 values are 86.7 for water loss, 84.9 for a solid gain, 96.3 for colour (ΔE), 94.3 for colour (chroma), 65.5 for beta-carotene, and 70 for antioxidant activity, respectively. The decrease in water content was strongly influenced by the salt solution concentration, stirring speed, and soaking time. However, among three factors, the salt solution concentration was the most influential. The stirring speed significantly influences the addition of solids to the material (solid gain) during the osmotic dehydration process. In contrast, ΔE and chroma were influenced by the stirring speed and immersion time for colour changes. Stirring speed influences beta-carotene levels. The amount of antioxidant activity was influenced by the stirring speed and immersion time. The optimization results obtained a salt solution concentration of 15%, a stirring speed of 25 rpm, and an immersion value of 155.8 mins. The magnitude of the three factors above provides a predictive value for water content to decrease to a maximum of 8.57%, solid gain to increase by 8.34%, beta-carotene content to decrease by 11.07% on a wet basis, antioxidant activity to decrease by 2.74, ΔE 20.22, and chroma of 71.07. The composite desirability value was 77.30%. Treating the salt concentration, soaking time, and stirring frequency affect the colour change, water loss, addition of solids, beta-carotene levels and antioxidant activity. The research finds that reducing the water content in the DO process has a significant effect, so the drying process can be carried out more quickly. In addition, the significance of the optimal conditions for the honey gourd DO process can be applied to further processing, for example, for the manufacture of industrial-scale flour