High-pressure and temperature effects on the inactivation of Bacillus amyloliquefaciens, alkaline phosphatase and storage stability of conjugated linoleic acid in milk

• The combination of nisin and HPS reduced endospore counts below the detection limit within 5 min.
• The impact of HPS on the oxidation of milk fat was monitored for up to 60 d at ambient temperature.
• HPS delivered higher CLA retention and lower degree of oxidation compared to the equivalent UHT.

Milk rich in conjugated linoleic acid (CLA, 42 ± 3 mg g− 1 fat) was used to evaluate the impact of high-pressure sterilization (HPS). The pressure, temperature and time needed to reduce 7-log of Bacillus amyloliquefaciens endospores were determined in the presence of nisin (4–64 mg L− 1). In addition, the inactivation of alkaline phosphatase was evaluated. After HPS treatment, the remaining CLA and formation of hydroperoxides were monitored during storage up to 60 d at 25 °C. The addition of nisin (≥ 16 mg L− 1) to milk significantly enhanced the inactivation of B. amyloliquefaciens (7-log reduction) after treatment at 600 MPa, 120 °C and 5 min of holding time. These conditions were selected to evaluate the impact of HPS on the CLA retention and hydroperoxides formation. Milk with the addition of nisin and treated with HPS delivered higher retention of CLA and a lower concentration of hydroperoxides compared with the UHT equivalent process (125 °C/15 s and 135 °C/10 s).Industrial relevanceHigh-pressure sterilization is a valuable alternative to produce superior quality milk products in cases where traditional thermal treatments have failed. This study evaluated the impact of processing conditions on the conjugated linoleic acid content at conditions where commercial sterilization has been achieved (7-log reduction of B. amyloliquefaciens). The outcomes of this study are considered as a step further for the development of high-pressure sterilized milk.