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

Abstract

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.

Keywords: Alicyclobacillus; Heat; Kinetics; Lycopene; Spores; Tomato; UV-C.