Resistant moulds as pasteurization target for cold distributed high pressure and heat assisted high pressure processed fruit products

High pressure processing (HPP), also known as high hydrostatic pressure (HHP) is a modern method of food pasteurization used commercially in many countries. It relies on the application of very high pressures (up to 600 MPa) to the food/beverage to inactivate microorganisms. Since no heat or mild heat is applied, most of the original food sensory, nutrient and functional properties are retained after processing, and fresh-like fruit products with longer shelf-life are produced. In this study, a review of the resistance to HPP and HPTP (high pressure thermal process) of key bacteria, moulds and yeasts which often contaminate fruit products was undertaken. Spores of moulds Byssochlamys nivea - anamorph name Paecilomyces niveus or Neosartorya fischeri anamorph name Aspergillus fischeri, are very resistant. A HPTP process of 600 MPa-75 degrees C-15 min only caused a reduction of 1.4 log. Moulds are able to grow at temperatures between 10 and 43 degrees C, water activity between 0.892 and 0.992, over a wide range of pH (3-8), under reduced oxygen conditions inside food packs and in carbonated beverages, sometimes producing mycotoxins. Furthermore, HPP treated fruit products are cold stored, and therefore moulds can be an issue as they grow at temperatures as low as 10 degrees C. Therefore, in view of the acidity of fruit products, the high resistance to HPTP in particular older spores, the use of B. nivea or N. fischeri spores as reference microorganisms in the design of new HPP and HPTP processes with fruit products was proposed.