Pulsed UV Light Irradiation Processing of Black Tea Infusions: Effect on Color, Phenolic Content, and Antioxidant Capacity

Tea-based ready-to-drink (RTD) beverages have been commercialized in recent years, which are usually preserved by conventional thermal processes. However, intense thermal processing can significantly affect their sensory and nutritional quality. Pulsed UV light processing has emerged as a potent non-thermal technology for processing of liquid foods, which can be applied as a hurdle approach with milder thermal processing. This makes it important to study the effects of the pulsed UV light on quality of tea. Therefore, this study was carried out to assess the effect of pulsed UV light on black tea infusions (at two different concentrations-1:100 w/v and 1:50 w/v). The pulse frequency (1-10 Hz) and treatment time (5-50 s) were varied to impart pulsed light fluence in the range 1.07-17.2 J/cm(2), and their effect on physico-chemical properties, total phenolic content, and antioxidant activity of tea infusions were studied. The temperature and color of the samples were significantly affected, whereas the total phenolic content and antioxidant activity remained mostly unaffected. The effects of the processing variables were also analyzed using response surface methodology and optimized treatment conditions were determined. Overall, pulsed UV light treatment can be used to assist thermal processing of polyphenol-rich liquid foods.