Equivalent processing for pasteurization of a pineapple juice-coconut milk blend by selected nonthermal technologies.

Abstract

Identifying equivalent processing conditions is critical for the relevant comparison of food quality attributes. This study investigates equivalent processes for at least 5-log reduction of Escherichia coli and Listeria innocua in pineapple juice-coconut milk (PC) blends by high-pressure processing (HPP), pulsed electric fields (PEF), and ultrasound (US) either alone or combined with other preservation factors (pH, nisin, and/or heat). The two blends (pH 4 and 5) and coconut milk (pH 7) as a reference were subjected to HPP at 300-600MPa, 20°C for 0.5-30min; PEF at an electric field strength of 10-21kV/cm, 40°C for 24µs; and US at 120µm amplitude, 25 or 45°C for 6 or 10min. At least a 5-log reduction of E. coli was achieved at pH 4 by HPP at 400MPa, 20°C for 1min; PEF at 21kV/cm, 235Hz, 40°C for 24µs; and US at 120µm, 45°C for 6min. As L. innocua showed greater resistance, a synergistic lethal effect was provided at pH 4 by HPP with 75ppm nisin at 600MPa, 20°C for 5min; PEF with 50ppm nisin at 18kV/cm, 588Hz, 40°C for 24µs; and US at 45°C, 120µm for 10min. The total soluble solids (11.2-12.4°Bx), acidity (0.47%-0.51% citric acid), pH (3.91-4.16), and viscosity (3.55×10-3 -4.0×10-3 Pas) were not significantly affected under the identified equivalent conditions. HPP was superior to PEF and US, achieving higher ascorbic acid retention and lower color difference in PC blend compared to the untreated sample.