Effects of high hydrostatic pressure on the microbial inactivation and extraction of bioactive compounds from açaí (Euterpe oleracea Martius) pulp.

Abstract

The aim of this study was to investigate the effects of high hydrostatic pressure (HHP) on the inactivation of Lactobacillus fructivorans, on the inactivation of Alicyclobacillus acidoterrestris spores and on the extraction of anthocyanins and total phenolics from açaí pulp. The tested conditions comprised pressures of 400-600MPa, treatment times of 5-15min, and temperatures of 25°C and 65°C. Results were compared to those of conventional thermal treatments (85°C/1min). Regarding A. acidoterrestris spores, applying HHP for 13.5min, resulted in a value of four-decimal reduction. L. fructivorans presented considerable sensitivity to HHP treatment, achieving inactivation rates above 6.7 log cycles at process conditions at 600MPa and 65°C for 5min. All samples of açaí pulp processed showed absence of thermotolerant coliforms during the 28days of refrigerated storage (shelf life study). The açaí pulps processed by HHP (600MPa/5 min/25°C) had anthocyanin extraction increased by 37% on average. In contrast, conventional thermal treatment reduced anthocyanin content by 16.3%. For phenolic compounds, the process at 600MPa/5min/65°C increases extraction by 10.25%. A combination of HHP treatment and moderate heat (65°C) was shown to be an alternative to thermal pasteurization, leading to microbiologically safe products while preserving functional compounds.