Kinetics of lactulose formation in milk treated with pressure-assisted thermal processing

• Kinetics of lactulose formation was evaluated at pressure-assisted thermal processing (PATP) conditions.
• PATP yielded lower lactulose formation compared to UHT data.
• Pressure–temperature diagrams for lactulose formation were developed.

The combined effect of temperature and pressure on the kinetics of lactulose formation was investigated in the range of 100–120 °C and 100–600 MPa up to 15 min. The kinetics data were fitted using the Weibull model and the parameters were evaluated through joint confidence regions. The scale parameter (α) was affected by temperature and pressure, following Arrhenius-type and Eyring-type equations, respectively. The calculated kinetic parameters, Ea = 182 ± 8 kJ mol− 1 and ∆V# = − 7.5 ± 0.1 cm3 mol− 1, revealed that the combination of temperature and pressure accelerated the formation of lactulose, reaching a maximum concentration of 650 mg L− 1 after 15 min of holding time at 120 °C and 600 MPa. Interestingly, lactulose contents obtained were lower after PATP treatments compared with values reported in the literature for equivalent UHT treatments. The formation of lactulose was also represented in pressure–temperature diagrams. This information can be used to determine the impact of pressure-assisted thermal processing in milk-based products.Industrial relevanceThe dairy industry uses the lactulose concentration as a heat damage indicator to distinguish between sterilized and pasteurized milk. Pressure-assisted thermal processing (PATP) is a relative new technology with potential applications in the dairy industry. This study provides new kinetic data on the formation of lactulose at PATP conditions. The information obtained in this study can be used to assess the impact of PATP on other shelf-stable dairy products, including functional beverages that contain milk.