Impact of Foam Mat Drying Methods on Physicochemical Properties, Anthocyanin Stability, and Probiotic Viability in...

The stability and quality retention of probiotic-enriched fruit powders are critical for developing functional non-dairy food products. This study aimed to evaluate the effects of freeze drying (FD), microwave-assisted drying (MW), and hot air drying (AD) on the physicochemical properties, anthocyanin retention, color stability, and probiotic viability of Lactobacillus plantarum in jamun (Syzygium cumini) juice powders during 90-day storage at 25°C and 4°C. Based on pre-experiments and previous studies, 5% egg white protein (EWP) was selected in this study to improve foam properties, thereby enhancing drying efficiency and powder quality. Physical analyses showed that FD powders had low moisture (2.47%), low water activity (aw) (0.21 ± 0.01), high porosity (17.31 ± 1.05%), and solubility (91.67 ± 1.32%), preserving microstructural integrity, whereas AD powders exhibited higher moisture (6.78%), aw (0.57 ± 0.01), and lower solubility (68.78 ± 2.12%). FD samples exhibited minimal anthocyanin degradation and color alteration, retaining 89.55% total anthocyanins (6.67 ± 1.05 mg C3G/g) and 95.31% antioxidant activity, whereas AD powders showed pronounced pigment loss and browning due to extended thermal exposure. Probiotic viability declined under all drying methods, but remained above the functional threshold (≥ 6 log CFU/g) in FD and MW powders; FD sustained >7 log CFU/g after 90 days at 25°C and >8 log CFU/g at 4°C, whereas AD showed the greatest loss (< 6 log CFU/g). Findings of the current study indicate that foam mat FD best preserves quality and bioactivity, while microwave drying (MW) provides acceptable functional retention, representing a viable alternative to conventional techniques. PRACTICAL APPLICATIONS: This research provides a method for producing shelf-stable, probiotic-rich jamun fruit powders with preserved antioxidants and color, making them suitable for incorporation into functional foods and beverages. The findings support potential industrial applications in the development of non-dairy probiotic supplements, instant drink mixes, or nutraceutical formulations. This approach may benefit consumers seeking plant-based, health-promoting alternatives, particularly those with lactose intolerance or dietary restrictions.