25 May 2012

CoC Seminar – Nutritional quality following application of high pressure processing

Friday 29 June 2012 – Presented by Sobhan Savadkoohi

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Summary

In the last five years, there has been a marked increase in the application of high pressure processing (HPP) in the food industry worldwide by creating a range of novel products such as “fresh” fruit juices with enhanced natural flavour and retention of natural vitamins compared to conventional, thermally treated products. To this end, HPP effects on inter- and intra-molecular interactions and the extent of denaturation or modification of functionality of proteins in dilute and semi-dilute systems (i.e. < 20% w/w solids in formulations) have been thoroughly investigated. However, there has been no fundamental work on pressure effects on physical functionality and nutritional quality of protein systems at higher levels of solids (up to 80%, w/w, in formulations).

The aim of this PhD project is to formulate the scientific basis for optimal utilisation of non-thermal, high pressure processing in the development of a greatly extended range of highly nutritious, microbially safe food protein products and functional protein ingredients at levels of solids between 10 and 80% (w/w) in formulations. A range of experimental techniques are utilised to characterise these products including small-deformation dynamic oscillation in shear, MDSC, ATR-FTIR, wide angle X-ray diffraction, ESEM and standard food microbiological/enzymatic tests.

Work focuses on three globular-protein systems: the 11S molecular fraction of soy protein (glycinin), bovine serum albumin (BSA) and ovalbumin. Preliminary results thus far indicate that BSA with 17 disulfide linkages exhibit pressure stability (600 MPa for 15 min at 25°C) throughout the experimental concentration range by conserving its native conformation. Soy glycinin with 12 disulfide bonds display protein unfolding and irreversible denaturation at low to intermediate solid levels (up to 60%, w/w) but, critically, maintain native conformation at 70 and 80% (w/w) solids.

Pressurised protein networks at 80% solids exhibit comparable strength to that of thermally treated counterparts in the glassy state, apparently due to the reduction in polymeric free volume and the development of an efficient friction coefficient amongst tightly packed particles. This combination of a coherent structure with native conformation in condensed globular proteins treated with high pressure is entirely unexpected but extremely interesting on both scientific and technological grounds. It may have industrial significance in relation to the formulation and stabilisation of “functional food” products as well as in protein ingredient powders and concentrates.

Supervisors

• Professor Stefan Kasapis
• Dr Anna Bannikova

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Seminar coordinator: robert.shanks@rmit.edu.au