Food Chemistry Advances (Oct 2023)
Effect of ultraviolet and pulsed light treatments on ascorbic acid content in fruit juices-A review of the degradation mechanism
Abstract
Ascorbic acid (AA) is a highly sensitive nutrient, which degrades at high temperatures (>60 °C), in the presence of metal ions and oxygen. There is a dearth of studies on the effect of pasteurization on AA in juices. This review attempts to propose a mechanism for the degradation of AA during ultraviolet (UV) and pulsed light (PL) treatments. While photodegradation and aerobic degradation contribute to AA degradation during UV and PL treatments, the anaerobic degradation is the most significant mechanism post UV and PL treatments during storage. The photodegradation of AA results in the formation of ascorbyl radicals, which get converted to dehydroascorbic acid (DHAA). These radicals generated during the UV and PL treatment can induce a cascade of reactions, which can prolong the degradation of AA during storage. The factors influencing AA degradation during UV and PL treatment include extrinsic factors, which majorly include process variables such as fluence, voltage, and temperature of UV and PL processing. The intrinsic factors of the juice such as pH, dissolved oxygen, enzymes, peroxides, sugars, polyphenols, and metal ions significantly affect the AA content in juices. Since the major objective of UV and PL pasteurization is ensuring microbial safety and enzymatic stability, a careful optimization of the process conditions is necessary to achieve maximal retention of bioactives, such as AA. It can be concluded that photodegradation, aerobic oxidation and anaerobic degradation are the major mechanisms governing the degradation of AA in juices.
