Physicochemical, Microbiological, and Sensory Characteristics of Functional Yogurt Fortified with Dragon Fruit (Hylocereus polyrhizus) Peel Powder During Refrigerated Storage

Abstract

The growing consumer demand for functional foods has encouraged the development of dairy products enriched with bioactive compounds derived from agricultural by-products. Dragon fruit (Hylocereus polyrhizus) peel represents approximately 30–35% of the total fruit weight and contains substantial amounts of dietary fiber, phenolic compounds, flavonoids, and betalains with recognized antioxidant properties. This study investigated the effects of dragon fruit peel powder (DFPP) incorporation on the physicochemical, microbiological, antioxidant, and sensory characteristics of yogurt during refrigerated storage. Yogurt samples were prepared with four concentrations of DFPP: 0% (control), 1%, 2%, and 3% (w/w), then stored at 4 ± 1°C for 21 days and evaluated periodically for pH, titratable acidity, viscosity, syneresis, total phenolic content, antioxidant activity, lactic acid bacteria count, and sensory acceptability.
The results demonstrated that DFPP significantly enhanced the nutritional and functional properties of yogurt. Total phenolic content increased from 28.45 mg GAE/100 g in the control to 78.62 mg GAE/100 g in the 3% DFPP treatment, while antioxidant activity rose proportionally, reaching 71.4% DPPH radical scavenging activity at the highest fortification level. DFPP supplementation also improved yogurt viscosity (up to 2,480 cP) and reduced syneresis (down to 8.7%) throughout storage, while lactic acid bacteria counts remained above the minimum recommended level of 10⁷ CFU/g. Sensory evaluation revealed that yogurt fortified with 2% DFPP achieved the highest overall consumer acceptability. Incorporation of 2% DFPP is recommended as the optimal concentration for producing functional yogurt with improved antioxidant properties and high consumer acceptance.