Optimization of Rhodomyrtus tomentosa (Rose Myrtle) Yogurt Production and Its Antioxidant Activity

Abstract

Rose myrtle (Rhodomyrtus tomentosa) fruit is nutrient-rich and has been shown to exert various beneficial effects on health. This study aimed to use dried rose myrtle fruit as the raw material, and the total antioxidant capacity (T-AOC) as an indicator to determine the optimal extraction process of rose myrtle and prepare a novel rose myrtle yogurt with antioxidant function. We found that the optimal extraction conditions for rose myrtle were as follows: material-to-liquid ratio of 1:15 g/mL, ethanol concentration of 60%, extraction temperature of 50 °C, and extraction time of 40 min. The T-AOC of the extract obtained was 192.43 U/mL. The optimal fermentation process of rose myrtle yogurt was carried out as follows: 50% rose myrtle extract, 16% milk powder, 6 % sucrose, and 0.5% stabilizer were homogenized and autoclaved at 95 °C for 10 min. After cooling, 0.1% fermentation agent was added; the mixture was fermented for 7 h at 43 °C and ripened for 12 h after refrigerating at 4 °C. The T-AOC of the rose myrtle yogurt was 31.48 U/mL, and it had a unique rose myrtle flavor and good sensory quality. This study not only developed a new yogurt product that meets the sensory and production requirements but also provided a scientific basis for developing novel functional food products enriched with rose myrtle.