Effect of power ultrasound application on the drying kinetics and the organic acids content of pineapple

Abstract

The effect of the power ultrasound (US) application (23.2 W/L) previous to drying on the drying kinetics and the organic acid contents (citric and malic) of pineapple (A. cosmosus v. Perola) has been studied. US application was carried out at 30 °C during 10-30 min using distilled water (DW) and pineapple juice (PJ). Drying was carried out at 60 °C and 0.5 m/s. The effective diffusion coefficient during drying was higher when US was applied and DW was used as soaking media. Citric and malic acid contents were measured in untreated and treated samples (with and without US application) before and after drying. The US application promoted an average reduction of the citric acid content of 9.2±0.7% (DW) and 28.4±0.8% (PJ); however; an average increment of malic acid of 8.5±3.7% (DW) and 8.0±2.4% (PJ) was observed. In general, when US was applied, treated-dried samples exhibited higher contents of citric and malic acid than the untreated-dried sample.