Non-thermal Processing of Pineapple (Ananas comosus[L.] Merr.) Juice Using Continuous Pressure Change Technology (PCT): Effects on Physical Traits, Microbial Loads, Enzyme Activities, and Phytochemical Composition

A comprehensive study using continuous pressure change technology (PCT) for the non-thermal processing of fresh pineapple juice on pilot scale was conducted (1 L/min, 50 MPa, argon, 3 min, <35 degrees C). The immediate effects of a single and a twofold PCT treatment on the most important quality parameters were examined and compared with those of fresh and thermally pasteurised (90 degrees C) juices. In comparison to the fresh juice, both PCT-treated samples exhibited slightly brighter and less yellowish colour (CIEL*a*b*). A significant reduction in the mean particle size resulted in diminished centrifugable pulp contents and enhanced cloud stability. Moreover, a slightly improved microbial quality (-0.9 to -1.2 log(10)CFU/mL) in terms of total aerobic and yeast and mould counts was attained. Noteworthy, PCT retained a high bromelain activity (-3 to -15% reduction) and efficiently inactivated polyphenol oxidase. Water-soluble vitamins, phenolic compounds, and all further constituents assessed were mostly preserved. However, the high residual peroxidase activity (-10 to -23%) and microbial loads are likely to affect juice quality during storage. In contrast, thermal pasteurisation ensured a complete reduction in both microbial counts (-4.4 to -4.5 log(10)CFU/mL) and effective inactivation of peroxidase. However, bromelain activity was strongly affected (-83%) by heat treatment, and colour was darkened and even less yellowish. Overall, this study highlighted the potential of PCT for the production of fresh-like pineapple juices; however, its current limitations were revealed as well.