EVALUATING THERMAL AND STORAGE STABILITY OF SELECTED FOOD PRODUCTS PROCESSED USING MICROWAVE AND HIGH PRESSURE ASSISTED THERMAL PROCESSES

Abstract

Microwave-assisted thermal sterilization (MATS) and pressure-assisted thermal sterilization (PATS) are advanced in-package thermal processing technologies that feature with much shortened processing time compared to conventional canning processes. The short processing time can potentially improve the quality of the processed food. However, the polymeric packages that interact with the processing conditions of MATS and PATS may partially lose gas barrier properties, which can compromise the food quality after processing and during storage. Therefore, compatible polymeric packages with MATS and PATS are crucial for successful MATS and PATS processes. It is essential to systematically study the effect of the processing conditions of MATS and PATS on food quality attributes including color in processing and during storage. This study aims to evaluate the thermal and storage stability of the quality attributes, primarily color and pigments in selected food products after MATS and PATS. The first study explored the feasibility of the development of shelf stable PATS-treated avocado puree. Two polymeric packaging was used, which were EVOH based film (PP/PA//EVOH//PA/PP) and PET based film (AlOx-coated PET //AlOx-coated PET //AlOx-coated PET //ONy//CPP). The PATS treatment was conducted at a processing pressure of 600 MPa at an initial temperature of 90oC for a processing duration of 5 min. The results of this study indicated that PATS can be used to successfully develop shelf stable avocado with limited shelf life. The second study looked at the effect of MATS on the quality attributes of red beetroot, red cabbage, and carrot purees. Additionally, the storage stability of the MATS- processed purees at 37.8oC was evaluated. A high barrier package of AlOx-coated PET //AlOx-coated PET //AlOx-coated PET //ONy //CPP was used in this study. The results showed different levels of quality attribute degradation in the puree after MATS and during storage, depending on the composition of the puree. The third study evaluated the efficacy of PATS on the inactivation of polyphenol oxides (PPO). Additionally, the effect of PATS on the quality attributes of red cabbage, red beetroot, and carrot purees was also evaluated after PATS and during storage at 37.8oC. A significant reduction in PPO took place after PATS. However, changes in the puree quality attributes were observed after PATS. During storage, different trends in the PPO activity were observed. Additionally, the quality attributes of the PATS-treated purees showed different levels of degradation. Overall, MATS and PATS affected the quality attributes in the processed purees such as color and pigments. However, this effect was relatively less compared to the effect of conventional in-package thermal processing. Additionally, the developed kinetic data of quality attributes during storage (from the second and the third study) can be a helpful tool to optimize both MATS and PATS processing conditions for higher quality products with bright color pigments.