This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

Avocado products were the first international success story for high pressure processing (HPP), and they remained a highlight use of the technology. Hydrostatic pressures of up to 700 MPa (100,000 psi or 7000 bars) were used to inactivate bacteria without affecting the food’s delicate flavour notes and texture, which could be negatively impacted by thermal processing.

However, the technical know-how required for effective, safe manufacture and distribution of avocado products was not readily available in the public domain. This project investigated essential technical aspects including the microbiological, physical and processing properties of HPP avocado products.

The experiments concentrated on:

• Optimal texture of raw material for HPP-treated Hass avocado pulp, halves and slices
• Packaging material selection
• Processing temperature’s effect on the product’s final quality and storage stability
• A microbiological challenge study with Listeria monocytogenes
• Optimised treatments and processing conditions; and understanding the effect of processing condition on the microbiological, sensory, physical and chemical properties of the processed products during storage at 4°C for up to four weeks
• Processing and evaluation of the Shepard variety under the previously optimised processing conditions for the Hass variety.

This study found that high pressure could be used successfully to process avocado products with the right processing and storage conditions to give products of excellent quality and sufficient shelf-life under good refrigeration. HPP inactivated high levels of L. monocytogenes, the major pathogen of concern for refrigerated products, in selected inoculated avocado products challenged with this pathogen. Good temperature control of the product at all times, in conjunction with the proper application of a HACCP plan, and good hygienic practices, were essential to minimise food safety risk and achieve four weeks shelf life. Pre-treatments, selected packaging and HPP could maintain the colour and texture of avocado products at a desirable level for 4 weeks at 4°C. Similar conditions may be used for the Hass and Shepard varieties.