Quality and safety of reformulated tomato products processed by continuous heat and UV-C pasteurization

UV-C is a nonthermal disinfection method with strong germicidal effect and minimal impact on nutrient quality compared to thermal processing. This work investigated the advantages of combining continuous-flow UV-C with heat (UV-C-H) over single heat treatment (H), for preserving lycopene and ensuring microbial safety in two reformulated tomato products: a juice (RTJ; pH 3.70 ± 0.06, °Brix 5.27 ± 0.21) and a sauce (RTS; pH 4.04 ± 0.02, °Brix 7.96 ± 0.16). Kinetic parameters for lycopene degradation (rate constant and activation energy) and inactivation of Alicyclobacillus acidoterrestris spores (D- and z-values) were estimated using the Paired Equivalent Isothermal Exposures method, based on the Arrhenius and Bigelow models, respectively. Regarding lycopene stability, UV-C-H reduced the temperature sensitivity of lycopene in the RTJ, lowering the activation energy (Ea) by approximately 4.3-fold relative to H, while the degradation rate constant (k_80°C) was comparable between treatments. In the RTS, the Ea under UV-C-H was 1.24-fold lower and the k_80°C was 1.75-fold higher, suggesting faster lycopene loss in the sauce exposed to UV-C-H. For microbial inactivation in the RTJ, the D-value (D_80°C) of A. acidoterrestris spores was ∼3.8-fold lower under UV-C-H relative to H, and the z-value decreased by ∼1.3-fold, indicating faster inactivation with a lower temperature requirement. A similar trend was observed in the RTS, where the D- and z-values reduced by ∼3.8-fold and ∼1.3-fold under UV-C-H, respectively. Overall, UV-C-H pasteurization achieved greater inactivation of A. acidoterrestris spores with comparable or slightly higher lycopene degradation relative to heat, supporting its potential as an enhanced pasteurization strategy for acidic tomato products.