Determination of the effect of different drying methods on the phenolic extraction from butternut squash pomace

The aim of this study was to optimize the extraction of phenolic compound from the butternut squash (Cucurbita moschata) pomace using solvent method by the aid of Response Surface Methodology (RSM). In addition, the effect of different drying methods (lyophilization, oven (30 and 60 °C), vacuum (30 and 60 °C) and microwave (120 and 600 W) drying) on the color values (L*, a*, b*, ∆E, C ve H°), total phenolic compounds, total flavonoid content and antioxidant activity of butternut squash pomace was investigated. In the optimization experiments, the total phenolic compound of butternut squash pomace was modeled by RSM using independent parameters of solid/solvent ratio (0.04-0.08 g/ml), temperature (45-65°C) and ethanol concentration (30-80%). Furthermore, the extraction of total phenolic compound from butternut squash pomace dried with different methods were performed at optimum conditions (0.08 g/ml, 56.9% ethanol and 65 °C). Total phenolic content, total flavonoid content and antioxidant activity values of dried pumpkin pomaces changed between 1.88±0.01-4.86±0.27 mg gallic acid equivalent/g dry matter, 1.32±0.05-3.09±0.29 mg catechin equivalent/g dry matter and 1.45±0.15-4.27±0.27 mg ascorbic acid equivalent/g dry matter, respectively. The effect of drying method, temperature or microwave power on the total phenolic content was determined statistically significant (p<0.05). This study showed that the butternut squash pomace, the waste, has a potential in the food sector in terms of enriching the bioactive content when added to the various food.