Patulin Degradation in a Model Apple Juice System and in Apple Juice during Ultraviolet Processing

Abstract

Factors affecting ultraviolet (UV) radiation-induced degradation of patulin in a malic acid model system, apple cider and apple juice were studied. First-order rate constants (cm 2 /J) in the model system were not significantly (P > 0.05) affected by pH (3.0‐3.6), initial patulin concentration (0‐1000 mg/L), glucose (0‐10%), sucrose (0‐10%) and ascorbic acid (0‐100 mg/L). Tannic acid (0‐1 g/L) reduced patulin degradation while fructose (0‐10%) accelerated it. Although suspended particles yielding nephelometric turbidity units values between 0 and 100 did not affect patulin degradation, higher turbidity levels in unfiltered apple cider reduced degradation rates. Even in clarified apple juice, the UV dose required for 50% patulin reduction in apple juice (4.62 J/cm 2 ) was higher than that required for a 5-log reduction of Escherichia coli O157:H7. Therefore, achieving efficient UV reduction of patulin in apple juice products, without quality losses, may require particulate filtration, phenolic adsorption treatments, and addition of compounds that accelerate patulin degradation. PRACTICAL APPLICATIONS This study demonstrates that apple juice constituents affect patulin degradation during ultraviolet (UV) processing. High turbidity levels in apple cider suggest that this technology may be impractical for this product. UV irradiation can be used to decrease patulin levels in clarified apple juice, although the required dose levels remain higher than that required for 5-log reduction of human pathogens. Filtration, adsorption treatments that lower levels of UV scattering and absorbing suspended particles and polyphenols can result in substantially greater patulin degradation during UV processing. Because fructose had an accelerating effect on patulin reduction in the model system studied, addition of high-fructose sweeteners to apple beverages prior to UV processing may result in further patulin reductions.