Production of shelf-stable Annurca apple juice with pulp by high pressure homogenization

Annurca apple juice was processed by high pressure homogenization (HPH) to inactivate the endogenous microbial flora, with the aim of maintaining the organoleptic properties and the polyphenolic content of the fresh juice. In particular, it was shown that the shelf life of clear juice can be prolonged for many weeks of storage both at 4_C and 37_C upon HPH treatment at 250 MPa. Instead, the juice with pulp required higher pressure levels (300 MPa) for microbial stabilization both at 4_C and 37_C. The sample stored at 37_C exhibited a physical instability, with deviation in color and pH, which reduced the shelf life, but the samples stored at 4_C exhibited an excellent microbial stability and no observable variation of pH and color, suggesting that HPH can represent a good option for non thermal pasteurization of Annurca apple juice. Interestingly, the HPH treatment delivered also significant changes to the distribution of sospende particles, whose comminution had a measurable effect on viscosity.