Effect of a continuous flow-through pulsed light system combined with ultrasound on microbial survivability, color and sensory shelf life of apple juice

Abstract

The aim of this work was to investigate the effect of a continuous flow-through pulsed light system (PLc, 0.73 J/cm2, 155 mL/min, EEO: 1.8 × 103–4.1 × 103 kW·h/m3/order) single or combined with ultrasound (US, 30 min, EEO: 4.4 × 105 − 1.1 × 106 kW·h/m3/order) at ambient temperature on Escherichia coli ATCC 35218, Salmonella Enteritidis MA44 and Saccharomyces cerevisiae KE 162 and indigenous flora in commercial (CAJ) and freshly pressed (NAJ) apple juices. In addition, for the combined treatment, color evolution, sensory shelf life and consumer sensory field studies were also conducted during NAJ cold storage (4 °C). The Weibull model adequately characterized inactivation curves (R2adj: 95.0–99.1%). No differences in single or combined PL effectiveness were observed between CAJ and NAJ, resulting in 1.8–4.2 log reductions for single PLc while US + PLc led up to 3.7–6.3 log reductions of inoculated microorganisms. Moreover, the combined treatment delayed yeast and mold recovery and prevented from browning development during storage. Processed NAJ was well accepted by a group of consumers who highlighted its fresh natural apple taste. Sensory shelf life was determined by 6 days (25% rejection) with 95% confidence. There is a growing consumer demand for fresh-like products as traditional thermal processing may have undesirable effects over the sensory and nutritional properties of fruit juices. From an industrial perspective, the content of this publication has the potential to be used for the development of novel products, with enhanced quality, processed by a continuous flow-through pulsed light system combined with ultrasound, both emerging technologies with good prospects for the decontamination of foods. In particular, this study showed that apple juice processed by US and PL ensured microbiological safety and was widely accepted by a group of consumers interested in sour products and its fresh natural apple taste.