Changes in quality attributes of coconut water treated with UV-radiation and nisin during cold storage: Kinetics modelling and shelf-life prediction

Abstract

Exploring the innovative combination of UV radiation and nisin treatment for enhancing the shelf life and quality of coconut water (CW) offers promising avenues for sustainable beverage processing. This study investigated the effects of UV radiation, nisin, and their combined treatments on the physical and microbiological attributes of coconut water during 20 days of refrigerated storage. The study also aimed to develop mathematical models for tracking changes in coconut water's quality parameters during refrigerated storage and determining its shelf life by integrating quality and microbial metrics. The results revealed that the cold storage period has significant impacts on the physical and microbiological characteristics of coconut water. The combination of UV radiation and nisin resulted in microbiologically stable coconut water, with populations remaining below 106 CFU/mL, for up to 20 days of cold storage. Moreover, a decline in pH over time, particularly in UV and nisin-treated samples, indicated increased acidity by only 15%. Colour analysis showed shifts towards darker and redder hues, accompanied by increases in a*-values. Conversely, b*-values increased in most samples, except for pasteurized coconut water. Additionally, a consistent decrease in antioxidant activity, total phenolic compound, and total flavonoid content was observed in the samples treated with the combination of UV radiation and nisin during storage period, with averages of 50%, 18%, and 20%, respectively. The zero-order model accurately represented most coconut water's properties, exhibiting R2 value of ≥0.85, and the derived reaction rate constants used to predict shelf life. Integration of UV and nisin treatment significantly extended the projected shelf life of coconut water compared to control (untreated CW sample) and individual treatments except thermal treatment, with shelf-life extensions of up to 19.5 days, highlighting the potential of this combination to enhance coconut water's shelf life while maintaining its safety.