Functional Quality and Microbiological Stability of Grape Juice During Processing by UV-C Light Compared to Mild Heat Treatment and Evolution of the Parameters During Cold Storage

The effect of UV-C was assessed on microbiological stability, functional compounds, and quality factors of white grape juice compared to mild thermal treatment (MTT). The inactivation kinetics of <i>Escherichia coli</i> (target microorganism) and <i>Saccharomyces cerevisiae</i> in grape juice by UV-C and MTT (75 °C) were evaluated to define the processing time. The comparative effect on the functional compounds was evaluated. Additionally, microbiological stability and quality factors were assessed during storage at 4 °C. The grape juice was characterized (pH 3.7, 25 °Brix, absorption coefficient 44.2 cm^-1, total phenols (TP) 214 mg GAE/L). UV-C (569 mJ/cm²) reduced <i>E. coli</i> to 5.03 log CFU/mL in 12.5 min, preserved TP (235 mg GAE/L), and antioxidant capacity (AC 4.5 mM TE/L). Thermal treatment reduced <i>E. coli</i> to 5.14 log CFU/mL in 180 s, increased TP (237-312 mg GAE/L), and maintained the AC of the juice. During storage, UV-C and MTT controlled microbiota growth, extending the time of microbiological stability by 42%. All the treatments showed a similar gradual loss of TP during storage. However, MTT has better-preserved color parameters. In conclusion, UV-C was effective from a microbiological perspective without compromising the functional quality of juice. However, further research is needed to improve color.