Volume: 4, 2025
4th International PhD Student’s Conference at the University of Life Sciences in Lublin, Poland:
ENVIRONMENT – PLANT – ANIMAL – PRODUCT
Abstract number: F007
DOI: https://doi.org/10.24326/ICDSUPL4.F007
Published online: 9 April 2025
ICDSUPL, 4, F007 (2025)
Drying conditions and in vitro digestion as determinants of phenolic content and antioxidant activity in apple pomace powders and fortified biscuits
Anna Krajewska1*, Dariusz Dziki1, Łukasz Sęczyk2
1 Department of Thermal Technology, University of Life Sciences in Lublin, Głęboka 31, 20-612 Lublin, Poland
2 Department of Industrial and Medicinal Plants, University of Life Sciences in Lublin, Akademicka 15, 20-950 Lublin, Poland
* Corresponding author: anna.krajewska@up.lublin.pl
Abstract
Apple pomace (AP), a by-product of juice production, represents a significant source of bioactive compounds, particularly polyphenols, which makes it a valuable ingredient for enhancing the nutritional profile of baked goods. However, the retention of these compounds is highly dependent on processing conditions, particularly drying methods and temperatures. The objective of this study was to investigate the impact of various drying techniques and temperatures on the total phenolic content (TPC) and antioxidant activity (AA) of AP powders, as well as their subsequent influence on the functional properties of biscuits enriched with AP, both prior to and following in vitro simulated digestion. AP was obtained by pressing apples using a twin-screw juicer, followed by freeze-drying or contact drying at different temperatures. The dried pomace was milled to achieve the desired particle size, and biscuits were prepared by substituting 20% of wheat flour with AP powders. TPC was determined using the Folin–Ciocalteu assay, while AA was assessed via ABTS, DPPH, and FRAP methods. Both AP powders and biscuits underwent in vitro digestion to evaluate changes in TPC and AA. The drying method and temperature significantly affected phenolic retention, with the highest TPC levels observed in freeze-dried powders at 60°C and 20°C, outperforming those subjected to contact drying. Simulated digestion resulted in a reduction of TPC in the AP powders; however, an increase in TPC was noted in the biscuits post-digestion, indicating enhanced bioaccessibility of the polyphenols. Biscuits enriched with contact-dried pomace at 40°C exhibited the highest bioaccessible TPC after digestion. The pomace samples demonstrated the highest antioxidant activity in the ABTS assay, moderate activity in the DPPH assay, and the lowest activity in the FRAP test. Furthermore, in vitro digestion led to a notable decrease in the AA of the AP powders. Overall, drying method and temperature were found to be critical factors in preserving the antioxidant properties of AP powders and enhancing the functional quality of the fortified biscuits.
This research was funded by National Science Centre, Poland (2023/49/N/NZ9/00218).
Keywords: apple waste, fruit pomace, plant by-products, enriched cookies, digestion simulation
How to cite
A. Krajewska, D. Dziki, Ł. Sęczyk, 2025. Drying conditions and in vitro digestion as determinants of phenolic content and antioxidant activity in apple pomace powders and fortified biscuits. In: 4th International PhD Student’s Conference at the University of Life Sciences in Lublin, Poland: Environment – Plant – Animal – Product. https://doi.org/10.24326/ICDSUPL4.F007