REFRACTANCE WINDOW DRYING AND ITS INFLUENCE ON THE BIOACTIVE COMPOUND CONTENT OF PITAYA (Hylocereus costaricensis)

Pitaya, or "dragon fruit", is a Cactaceae family plant typically found in tropical and subtropical regions.Rich in antioxidant compounds like polyphenols, pitaya offers potential health benefits.Refractance Window (RW) drying has emerged as a promising alternative, providing advantages in preserving food products' quality and nutrient content. This study investigated the extraction of bioactive compounds from pitaya using RW drying and compared its efficiency with freeze-drying. Pitaya pulp was dried using RW at 70°C for 50 minutes, with the addition of 3% (w/w) pectin. For comparison, freeze-drying was performed with the same pectin addition, at -63°C and -65 µHg pressure for 72 hours.The preservation of bioactive compounds was evaluated through analyses of total phenolics and total flavonoids, using Folin-Ciocalteu reagent and 2% aluminum chloride solution, respectively.Additional physicochemical characterization included moisture content, water activity (aw),and color analysis. The results indicated that RW-dried product had approximately 33.06% lower moisture content compared to freeze-dried product (12.86% vs. 19.21%),along with 25.53% lower aw (0.35 vs. 0.47), contributing to greater microbiological stability.Notable color differences were observed, with the RW-dried product being 2.10% lighter (L*= 25.82 vs. 25.29),exhibiting 28.68% lower red/green intensity (a*= 25.22 vs 35.36), and a 237.56% increase in blue/yellow hue (b*= 3.04 vs. -2,21). The chromaticity (C*= 25.97 vs. 35.43) of the RW-dried product was 26.70% lower, indicating reduced color saturation.Pitaya retained over 90% of phenolics (151.25 mg/100 g dw) compared to freeze-drying (163.79 mg/100 g dw) and over 65% of flavonoids (34.99 mg/100 g dw vs. 53.01 mg/100 g dw).RW drying achieved a 98.84% reduction in processing time compared to freeze-drying, offering significant time and energy savings.It also enabled the formation of an edible film, enhancing its use in food products, whereas freeze-drying produced "spongy" flakes.These results highlight RW drying as an effective and economical method for preserving pitaya's bioactivity.