Headspace and Viscosity: Key Factors in the Thermal Processing of Tomato Paste (A CFD Study)

Abstract

This study investigates the effects of headspace conditions (absence of headspace, full air, and full steam) and product viscosity (Brix values of 18 and 28) on the thermal processing of canned tomato paste. The results show that the presence of an air layer within the can's headspace significantly influences the temperature profile and the location of the slowest heating zone (SHZ), without markedly affecting the overall temperature magnitude. The Brix values, which indicate the paste's viscosity, are found to be crucial factors in heat transfer, with lower Brix values promoting convection and higher values favoring conduction. The average velocity for Brix 18 was approximately 10 times higher than that for Brix 28. Among the three main color parameters, the a* index experienced the most significant changes (maximum drop of 67%), while the b* index showed the least variation (maximum drop of 22%) during processing. The time required to reduce the number of bacteria to 10⁻⁶ CFU/g at the cold point of tomato paste cans was 28% higher in the product with Brix 18 compared with Brix 28. These findings underscore the importance of considering headspace conditions and product viscosity to optimize thermal processing methods, thereby enhancing the safety and quality of canned tomato products.