OPTIMIZING FUNCTIONAL AND QUALITY ATTRIBUTES OF SLOE BERRY POMACE POWDER: A STUDY ON THE THERMAL TREATMENT AND GRANULOMETRY

Abstract

Physical and functional properties of sloe berry pomace (SBP) – a recoverable by-product – depend on the physical treatments applied. This paper aimed to highlight the impact of thermal treatment temperature (45, 55, 65 °C) used to reduce SBP moisture, along with particle size (L < 200 μm, 200 μm < M < 300 μm, L > 300 μm), on its color, functional properties, fiber content and protein secondary structure assessed by FT-IR. Response Surface Methodology was used for the experimental design, and the desirability function was employed to establish the optimal processing conditions. The results revealed that the increase in temperature determined an increase in L*, fiber content, water absorption and retention, and β-sheet conformation of protein for all the fractions studied. Both factors (temperature and particle size) exhibited significant impact (p < 0.05) on SBP color, functional properties, fiber content, and protein secondary structure, except for solubility index and β-turn conformations, which were not affected by temperature. The optimal thermal treatment conditions for each particle size were: 64.82 °C for L, 49.48 °C for M, and 45.19 °C for S. Optimal S fraction presented the best color, functional properties, and the most stable protein conformations. The optimal processing parameters identified provide a practical foundation for upcycling SBP into a valuable, functional food ingredient with tailored properties, such as enhanced fiber content and water-holding capacity, for use in the food and nutraceutical industries.