Combined Drying Technologies for Preserving the Quality of Backyard Averroha Carambola L. in Veracruz, Mexico

Star fruit (Averrhoa carambola L.) is cultivated in Asian and Latin American countries and has high nutritional value due to its content of bioactive compounds, polyphenols, vitamins A and C, minerals, and antioxidant activity. However, its high water content makes it highly perishable, limiting its preservation and commercialization; therefore, it is necessary to develop technological alternatives that extend its shelf life without affecting its organoleptic and nutritional quality. The objective of this study was to evaluate combined power ultrasound-assisted drying technologies for obtaining star fruit flakes as a preservation alternative, analyzing their effect on physicochemical, functional, and sensory attributes. Fruit from the Postgraduate College, Veracruz Campus, was used, and osmotic dehydration (OD) curves were performed at 50 and 60 °Brix, using ultrasound (US) as a pretreatment to convective drying (CS). Drying kinetics were performed at 50 and 60 °C, and total phenolic compounds, antioxidant activity (DPPH and ABTS), oxalic acid, color (ΔE), moisture, total solids, water activity (aw), and texture in the center and periphery were evaluated, in addition to sensory analysis. The DO treatments assisted with ultrasound reached equilibrium in less time. The 60°Brix-CUS-60 °C treatment showed lower final moisture content, while the 60°Brix-CUS-50 °C treatment reached an aw of approximately 0.47, favoring microbiological stability. The 60 °Brix DO treatment with ultrasound and 60 °C surface drying showed lower moisture content and higher total solids content. The 60 °Brix DO treatment without ultrasound and 50 °C surface drying preserved phenols better, reducing oxalic acid by >50% and showing improvements in antioxidant activity. High sensory acceptability was obtained. It is concluded that the DO-US-SC combination is effective in preserving carambola with adequate quality and acceptance.