Packaging materials withstand high pressure thermal processing

The commercialisation of foods processed by high pressure thermal sterilisation (HPTS) could soon be possible, with new research by CSIRO showing that some commercially available packaging materials are able to withstand the vigorous conditions of the technology.

Lead researcher and author Dr Michelle Bull at CSIRO’s division of Food and Nutritional Sciences said the technology had the potential to improve the quality of processed foods.

“Thermal processing has been the mainstay of food processing for food safety for around 90 years," Dr Bull said. "Over the past decade in particular, with increasing consumer demands for better tasting and more nutritious foods, much of the developments in food processing for food safety have centred on minimising thermal processing.

“Due to the reduced thermal exposure of the food, HPT processing has the potential to deliver quality benefits to a range of processed foods compared with conventionally thermal processed products.”

Commercially available processed foods such as fruit juices, fruit jams, sliced small goods, avocado based dips and seafood have been delivered by high pressure processing at ambient or near ambient temperatures.

HPTS involves applying high pressures to foods at elevated temperatures. Temperatures up to 130 °C are used in combination with pressures between 400–800 MPa to render foods commercially sterile.

Ms Bull and her team analysed the effects of HPTS on 11 commercially available packaging materials consisting of vapour-deposited silicon and aluminium oxide, orientated nylon/polyamide, aluminium foil, or PVDC-methyl acrylate based films.

Barrier properties such as seal integrity, oxygen and water vapour transmission rates of each film were analysed.

The results showed that all packaging materials experienced cosmetic deformation on the outer surfaces after exposure to HPTS. Only the barrier properties of the packaging materials consisting of aluminium foil or PVDC-methyl acrylate films were not significantly affected.

However, the authors of the research concluded that the development of even small delamination spots on the latter two films could deem them unsuitable packaging options for foods processed by HPTS.

Dr Bull said more research was needed before the commercialisation of foods processed by HPTS would be possible.

“Limitations identified to date are mainly related to the development of non-uniform temperature distributions caused by heat losses at extended pressure hold times; this feature of the technology has major implications for delivering safe foods, and is being addressed by CSIRO Food and Nutritional Sciences using a combined microbiological and engineering approach.”

The CSIRO research was published in the scientific journal, Innovative Food Science and Emerging Technologies.

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