Applying vacuum pulse during ethanol pretreatment to enhance the drying rate and quality of fresh and osmo-dehydrated banana slices using coconut sugar.

Improving convective drying is important for reducing processing time and enhancing dried product quality. This study evaluated the effects of osmotic dehydration (OD), ethanol pretreatment (ET), and ethanol pretreatment with vacuum pulse (ETVP) on the drying kinetics and the physicochemical properties of banana slices. OD was performed by immersing the slices in a 60 % coconut sugar solution for 300 min. ET was performed by immersing the slices in ethanol for 3 min at atmospheric pressure. ETVP was carried out by alternating vacuum pressure (80 kPa) for 1 min and atmospheric pressure for 30 s, totaling 3 min of immersion. Then, the samples were dried at 60 °C until reaching a moisture content of 15.61 %(w.b.). OD, ET, and ETVP increased the drying rates and reduced drying times by up to 19.4 %, 14.5 %, and 20.0 %, respectively. OD increased sample shrinkage, caused higher color alteration, and decreased hardness. ET and ETVP enhanced the hardness of the samples. ETVP minimized the shrinkage of the bananas. The application of the pretreatments maintained or increased the levels of flavonoids and phenolic compounds, as well as the antioxidant activity of the dried samples. The optimal treatment was ETVP, which achieved satisfactory sensory acceptance.