Nonthermal preservation of coconut water by forward osmosis concentration and high pressure processing

Abstract

In this study, combined nonthermal technologies, forward osmosis (FO) and high pressure processing (HPP) were utilized to concentrate (from 6.6 to 22°Brix) and pasteurize the coconut water. These were the parameters set for each operation: FO (20 ± 1 °C, potassium lactate draw solution) and HPP (600 MPa, 2 min, 4 °C), with pH adjustment to 4.6. Total soluble solids content, pH, and water activity of the forward osmosis-high pressure processed (FOHPP) concentrate remained stable during the 18-week refrigerated storage. A significant change in color (a∗-value) in the FOHPP coconut water concentrate was observed four weeks after processing due to the presence of peroxidase and polyphenol oxidase. Microbial growth was monitored for 4 weeks at 4 °C showing no changes in aerobic plate counts, total coliforms and yeast and molds counts. A 5-log reduction was achieved for E. coli O157:H7, Salmonella and L. monocytogenes during the HPP validation. FOHPP concentrate was also acceptable in terms of its sensory properties based on the sensory evaluation results. Thus, these results indicated that nonthermally concentrated coconut water could be preserved under refrigeration for at least 1–3 months by applying FO and HPP treatments.