Effect Of Ultra High-Pressure Homogenization on hydro- and liposoluble milk vitamins

• UHPH treatments applied increase milk vitamin retention compared to the heat-treated milk.
• Milk treated by UHPH at 300 MPa and Ti = 45 °C presented a vitamin content close to that of raw milk.
• Hydrosoluble vitamin content in milk UHPH-treated at 300 MPa with Ti = 85 °C was higher than heat-treated milks.
• UHPH treatments applied did not affect the retinol and α-tocopherol content in milk.

The Ultra High-Pressure Homogenization (UHPH) process has proved to be an adequate technology to produce milk with similar microbial, sensory and physicochemical characteristics to the heat-treated milk. However, no information has been published regarding the effect of this technology on the vitamin content of milk. For this reason, the aim of this work was to evaluate the effect of the UHPH process on milk vitamins, comparing the results with those obtained by applying heat treatments. The UHPH conditions evaluated were those in which the microbial and physicochemical characteristics obtained in milk were similar to the characteristics of pasteurized (PA) and UHT milks, consisting these treatments in the application of 300 MPa at different inlet temperatures (Ti) of 45, 55, 65, 75 and 85 °C; the heat treatments applied were 90 °C for 15 s and 138 °C for 4 s in PA and UHT milks, respectively. The hydrosoluble vitamins analyzed were nicotinamide, thiamine, pyridoxal, pyridoxamine, folic acid, cyanocobalamin, riboflavin and vitamin C (total vitamin C), and retinol and α-tocopherol in the liposoluble vitamin group. The results showed an important reduction in the destruction of nicotinamide, thiamine, riboflavin and vitamin C in the UHPH-treated milks compared to those heat-treated. Further, the UHPH treatments tested were able to retain most of the vitamin content presented in raw milk. In this sense, the sample treated at 300 MPa with Ti = 45 °C presented the closest vitamin content to that of raw fresh milk. In addition, the increase of the Ti in the UHPH treatments applied produced a significant increment (P < 0.05) on the vitamin destruction, especially in nicotinamide, thiamine, riboflavin and vitamin C in milk, with a maximum of destruction of 19.97, 33.46, 13.46 and 22.56%, respectively at 300 MPa with Ti = 85 °C. On the contrary, an important destruction of nicotinamide, thiamine, riboflavin and vitamin C (27.31, 33.46, 17.30 and 61.28%, respectively) was observed in the UHT milk. Additionally, the content of liposoluble vitamins in milk was almost not affected by both heat and UHPH treatments applied. These results show the possibility of employing the UHPH technology in milk to reduce the vitamin destruction, obtaining a milk with higher nutritional properties than a heat-treated milk.