Impact of drying techniques on strawberry powder characteristics

Abstract

Convection dryers are cost-effective and widely used, but they present challenges for fruit and vegetable powders. High temperatures or prolonged drying times can cause browning and nutrient degradation, leading to a loss in color vibrancy and nutritional value. These limitations reduce their suitability for functional applications that require high-quality powders with preserved bioactive integrity. This study examines the effects of freeze-drying and air-drying on the physicochemical properties, color attributes, and phenolic composition of strawberries. Both drying methods resulted in similar moisture (~ 6.5%) and ash (~ 3.5%) contents. However, freeze-dried samples retained higher potassium and magnesium levels, while air-dried strawberries exhibited higher iron content. Color analysis showed that freeze-drying better preserved redness (a* value: 29.14 vs. 24.04) and resulted in a lower total color difference (ΔE: 38.93 vs. 44.72), highlighting its superior ability to maintain visual quality. Polyphenolic composition analysis revealed a notable variation. Freeze-dried strawberries contained higher concentrations of catechin (18.720 ng/g vs. 3.463 ng/g) and syringic acid, while air-dried samples were richer in coumaric acid (12.755 ng/g vs. 653 ng/g) and ellagic acid (131.527 ng/g vs. 118.454 ng/g). These findings demonstrate that the choice of drying method significantly affects the nutritional and bioactive profiles of strawberries. Freeze-drying is advantageous for retaining antioxidant-related compounds and visual quality, whereas air-drying enhances specific bioactives like coumaric and ellagic acids. These insights provide a foundation for optimizing drying processes to enhance the functional and nutritional value of strawberries in food applications.