Effects of pH and Catalase Activity on Enzymatic Browning in Apples: Implications for Food Preservation and Waste Reduction

Enzymatic browning in fruits such as apples is a major quality concern that shortens shelf life, decreases nutritional value, and reduces consumer acceptance. This study evaluated the effects of four treatments (lemon juice, bovine catalase, Aspergillus catalase, and a water control) on the browning of cubic apple slices. Slices were submerged in each solution, and browning intensity was quantified by measuring absorbance at 420 nm using a spectrophotometer at 15, 30, 45, and 60 minutes. Solution pH was also recorded to assess its relationship with browning progression. Results showed clear differences between treatments. Lemon juice, with strongly acidic pH values, consistently produced the lowest absorbance increases, confirming the inhibitory effect of acidity on polyphenol oxidase activity. In contrast, bovine catalase produced the greatest browning, with the largest net absorbance increase by 60 minutes, suggesting that near-neutral conditions favored rapid pigment formation. Aspergillus catalase and the control group showed intermediate browning levels, with steady increases over time but lower final values than bovine catalase. These findings demonstrate that catalase did not inhibit enzymatic browning; instead, pH was the dominant factor influencing outcomes. Overall, the results support the hypothesis that acidification with lemon juice slows enzymatic browning, while catalase treatments permit or enhance browning relative to control conditions. This study highlights the importance of pH in controlling oxidative browning and suggests that simple acidulant treatments may be effective in reducing postharvest losses. Such strategies have practical implications for improving food preservation, extending shelf life, and reducing waste in the fresh-produce industry.