Inactivation of polyphenol oxidase and peroxidase in pineapple juice during continuous ohmic heating and modeling of inactivation kinetics during isothermal holding

Abstract

AbstractContinuous ohmic heating (COH) is a novel thermal technology for fruit juice processing and preservation. The present work demonstrated the effect of COH parameters like electric field strength (EFS: 30–40 V/cm), isothermal holding (0–60 s), and temperature (70–90°C) on the inactivation of polyphenol oxidase (PPO) and peroxidase (POD) in standardized pineapple juice. Statistical parameters and Akaike information criteria were used to compare kinetic models like the first order, distinct isozymes, Weibull distribution, sigmoidal logistic, and fractional conversion for PPO and POD inactivation. The findings revealed that the COH parameters significantly affected the activities of both enzymes. A maximum inactivation of 68.2% of PPO and 82.2% of POD was observed at 90°C, 60 s, and 40 V/cm. The Weibull distribution model, compared to other models, was found to describe the inactivation kinetics better for both PPO (R2 > 0.99; RMSE < 0.0101) and POD (R2 > 0.98; RMSE < 0.042). The accuracy factor (Af) and bias factor (Bf) for both PPO (Af = 1.003–1.010; Bf = 1.000–1.004) and POD (Af = 1.007–1.072; Bf = 0.992–1.009) were closer to simulation line suggesting the accuracy of the Weibull model in predicting the enzyme inactivation. Also, Akaike increment (∆i < 2) substantially supported the Weibull model. The shape factor (n < 1) explained the tailing phenomenon of the enzymes. The PPO's scale factor (δ values) was higher than POD, suggesting higher thermal stability of PPO than POD. Thus, the Weibull model is a good tool for predicting the enzyme inactivation in COH‐treated standardized pineapple juice.Practical ApplicationsContinuous ohmic heating (COH) is a novel electro‐thermal technology that heats the fruit juice quickly, uniformly, and volumetrically. Generally, for inactivating spoilage enzymes like polyphenol oxidase and peroxidase during pineapple juice processing in an industrial set‐up, a conventional method of conduction and convection mode of heat transfer is used. This results in a high‐temperature gradient within the juice matrix, causing a problem of over‐ and under‐processing of juice. Ohmic heating is a potential and efficient way of inactivating these spoilage enzymes to a desired level in a shorter processing time. It can be used to preserve juice by extending its shelf life. COH can reduce the total heat damage to the juice by maintaining its flavor and nutrient compounds. Overall, ohmic heating is a versatile and effective technology for the continuous processing of fruit juice for improved product quality and production efficiency.