Evaluation of the effect of oven and freeze drying on chemical composition and functional properties of carrot pomace

Unfortunately, the food processing waste has recently increased, prompting researchers to develop new economical products based on food waste to reduce the environmental problems caused by waste accumulation.  Among these, carrot pomace as a nutrient-rich waste with appropriate functional properties can be mentioned. In this study, fresh carrot pomace was dried using a hot-air oven (60℃ and 80℃) and a freeze dryer. Then the dried-pomace quality in terms of functional properties (bulk density, particle size, water and oil holding capacity, antioxidant activity, carotenoid content, color, and microstructure) and chemical compounds were examined. The results showed that the drying method and temperature had a significant effect on pomace’s chemical compounds. A significant decrease in moisture and lipid content was perceived due to the oven temperature increment (from 60℃ to 80℃), while no significant changes were observed in crude fiber content. Freeze-dried samples also had the least moisture content in comparison to the oven-dried samples. Also, the functional properties of the dried samples showed that the drying method and temperature had no significant effect on the carotenoid content and particle size of the samples. The oven temperature increment significantly reduced the bulk density and water holding capacity (from 15.97 to 14.57 g/g). The freeze-dried sample also showed the lowest bulk density, the highest water and oil holding capacity, and antioxidant activity compared to the oven-dried counterpart. It also had better color and more porosity. Therefore, freeze-dried carrot pomace can be used to fortify food products.