Effect of Different Drying Treatments and Sieving on Royal Gala Apple Pomace, a Thickening Agent with Antioxidant Properties

Currently, there is an increasing interest in the search of natural derived materials as valuable substitutes for microplastics. One of the categories investigated, represented by thickening agents deriving from agri-food waste and apple pomace (AP), was considered of interest. In this study AP was submitted to three different treatments and drying conditions (oven drying at 55 degrees C for 12 h; homogenization and oven drying at 55 degrees C for 12 h; homogenization and freeze-drying), and then grinded and sieved obtaining three different dimensional fractions (>400 mu m, 250-400 mu m and <250 mu m). The hydroalcoholic extracts of these fractions, obtained by ultrasound-assisted extraction, were analyzed to compare their total phenol content (TPC), antioxidant properties, and phenol profile. Correlation studies between the above-indicated parameters were also carried out. The highest values of TPC, antioxidant capacity, and phenol content (determined by liquid chromatography) were found for oven dried AP (250-400 mu m) or homogenized and freeze-dried (>400 mu m) samples. Both samples were most suitable to form stable hydrogels and the sample obtained after drying at 55 degrees C showed the best performances in terms of ability to form a stable hydrogel. Among the studied treatments and drying conditions, the oven dried AP was demonstrated to be an interesting stabilizing material with potential applications in many fields (such as food, cosmetics, and nutraceuticals) showing both antioxidant activity and thickening capacity.

Automated summary

There is currently a growing interest in finding natural derived materials as substitutes for microplastics. This study investigated the use of thickening agents derived from agri-food waste and apple pomace. The study found that oven dried apple pomace (250-400 μm) or homogenized and freeze-dried (>400 μm) samples had the highest total phenol content, antioxidant capacity, and phenol content. These samples were also able to form stable hydrogels, with the sample dried at 55 degrees C showing the best performance. The study suggests that oven dried apple pomace could be a promising stabilizing material with potential applications in food, cosmetics, and nutraceuticals.