Kinetics and Predictive Modeling of Patulin Degradation by Ozone in Apple Juice and Apple Cider

Open Access
Author:
Ashirifie-Gogofio, Julius.
Graduate Program:
Food Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
January 20, 2010
Committee Members:
  • Luke F LaBorde, Thesis Advisor
  • John D Floros, Thesis Advisor
Keywords:
  • Modeling
  • Degradation
  • Patulin
  • Kinetics
  • RSM
Abstract:
Patulin is a secondary metabolite of fungi activity predominant in apples. It is a polyketide lactone mycotoxin proven to be carcinogenic and mutagenic according to animal studies. The FDA has established a 50µg/kg (50ppb) limit for patulin in apples and apple products. Previous studies have demonstrated that lactones are sensitive to ozone induced oxidation. Moreover, ozone has been shown to reduce microbial populations in juice products. The objectives of this study were to evaluate the kinetics of ozone-induced patulin reduction in an apple juice model system, to establish relationships between factors and the rate constant of the degradation reaction, to develop and validate a predictive model and to test its predictive power in apple juice and apple cider. Changes in the quality of ozone-treated apple juice and apple cider were also studied by comparing instrumental and sensory data. HPLC analysis for patulin showed that ozone induced degradation could be described by first order kinetics, and that initial patulin concentration, ozone concentration and temperature were significant (p<0.05) variables influencing patulin degradation. However, the reaction rate constant was not significantly affected by pH. A Response Surface Methodology (RSM) model was developed that adequately described the reaction. It was significant at p<0.001, and explained 99.30% of the variability in the reaction rate constant. The RSM model confirmed the significance (p<0.05) of the main effects and demonstrated a significant interaction between ozone concentration and temperature. Validation experiments showed no significant (p<0.05) difference between the predicted and observed values for the model system and apple juice, but a difference existed for apple cider. Total color change (&#916;E) for apple juice was twice that for apple cider with greatest changes occurring for yellow (+b) values. Conversely, sensory studies showed greater overall effects on perceived color changes in apple cider compared to apple juice. Nevertheless, the results from this study demonstrate that ozone treatment can achieve more than 90% reduction in patulin levels without significantly (p<0.05) affecting perceived color, flavor, and aroma attributes of apple products.