Affiliation:
1. Akdeniz University, Institute of Natural and Applied Sciences, Division of Food Engineering
2. Akdeniz University, Faculty of Engineering, Department of Food Engineering
Abstract
The effect of osmotic and convective drying treatments on main physicochemical properties of frozen sliced red peppers was investigated. Sliced red peppers were dried partially using either osmotic dehydration or convective hot air drying before freezing in an air blast freezer at constant air velocity (2 m/s) and temperature (-25°C). The center temperature of osmo- and convective dehydrofrozen peppers reached -25°C in about 105 min, while it took 270 min for control samples. Frozen samples were stored at -18±2°C for 60 days, and the color, texture, ascorbic acid, enzyme activities, antioxidant activity (DPPH and ORAC) and total carotenoid content of samples were monitored during storage. Results showed that skin puncture values of samples decreased by storage time. The ascorbic acid content of sliced red pepper decreased by both treatments and storage time. The antioxidant activity values of control samples were higher than those of convective dehydrofrozen and osmo-dehydrofrozen samples. Both partial drying treatments reduced carotenoid loss significantly. The losses in total carotenoid contents were 58.0, 47.5 and 46.9% at the end of the storage period in control, osmo-dehydrofrozen and convective dehydrofrozen peppers, respectively. Significantly lower energy was used in osmotic dehydration compared to convective drying since no heating required for osmotic dehydration. Moreover, pre-drying of sliced red pepper required one-third of lower energy for freezing compared to direct freezing. This study showed that osmo-dehydrofreezing can be an economical method for sliced red peppers production.