Optimization of pulsed electric fields combined with mild heat treatment on microbial inactivation of tender coconut water and evaluation of quality attributes during storage

Abstract

This work aimed to investigate the processing conditions of pulsed electric fields (PEF) combined with mild heat for microbial inactivation in tender coconut water (TCW) using response surface methodology and to evaluate the quality of the products. Combining 40 °C with PEF at a field strength of 22.5 kV/cm and specific energy of 119 kJ/l was optimal to inactivate Escherichia coli K12 and Listeria innocua by a 6.60 and 5.90 log CFU/ml from the initial numbers of 6.65 and 6.04 log CFU/ml, respectively, thereby meeting USFDA requirements. This was seen to damage bacterial cell membrane and reduce total plate and yeast mould count in TCW comparable to thermal pasteurization (85 ± 2 °C for 10 min), resulting in a shelf-life extension of >35 days at 8 ± 2 °C while retaining physicochemical properties and polyphenols similar to the untreated sample. During refrigerated storage, the development of a pink colour in the TCW was also delayed for 7 days compared with the heat treatment. This study proved that the combination of PEF with mild thermal treatment (40 °C) was effective in regard to microbial inactivation for food production while preserving the fresh-like attributes of TCW as confirmed by volatile profile along with sensorial analysis. Industrial relevanceThis research provides the industry with an original investigation into the use of a combination of mild heat treatment and pulsed electric fields (PEF) to inactivate Escherichia coli K12 and Listeria innocua, achieving more than a 5-log reduction. The results highlighted the potential of PEF as an alternative technique for pasteurizing tender coconut water and extending the shelf-life. This approach shows promise in extending the shelf-life of the product, which can be advantageous for both transportation and stock management purposes.