Novel air filled emulsions as the basis for fully functional low fat foods

There is a need for a substantial reduction in the amount of dietary fat. The aim here is to help achieve this by developing a reduced fat replacement for a range of traditionally high fat foods by employing naturally occurring but novel surfactants. The new candidate structures will have a significantly reduced lipid content (50% at least is envisaged) and reduce the dietary calorific intake. However, the technology should also allow for an undetectable form of, otherwise unpalatable but beneficial, bioactive peptides or lipids to be carried. Many dressings, and sauces are high lipid foods and used widely in the diet e.g. salad dressing, mayonnaise etc. As such they can contribute heavily to the fat intake. These foods have the effect of increasing the fat intake in quite disparate areas; mayonnaise as a condiment on high fat foods, or as a dressing on other wise low fat salads. Hence, mayonnaise has been chosen as a model to illustrate the application of the proposed method of food design and generic production. It is intended to replace at least 50% of the lipid droplets in the model system with air cells. However, so that consumer perception is not adversely affected by a change of the structure, the rheology of the mayonnaise will be maintained by manipulating the size and functionality of the air cells so the mouth-feel of the full and reduced fat versions are identical. Hydrophobin emulsions Fungal hydrophobins have been identified as having massive potential for the stabilisation of emulsions1. Their amphipathic nature has been shown to stabilise oil emulsions (non food) and very high gas/liquid volume foams; this stabilisation has been shown to be more stable than with other common emulsifiers2. The enhanced stability offers the potential to form shelf stable air or lipid vesicle with very high angles of curvature so that small size distributions (1-5um) may be produced to accurately mimic mayonnaise or dressing emulsions. The self assembly potential of the hydrophobins offers a huge potential beyond just emulsion stabilisation. Hydrophobin stabilised interfaces are reported to provide a size exclusion barrier to the movement of small molecular weight solutes across the interface. Here, small refers to molecules of a size greater than 200 Da and offers an immense potential for bio-molecular partitioning. Indeed, such a potential might be realised as an ability to design bio-functional novel foods; i.e. hydrophobin stabilised air/oil aqueous emulsion may be engineered to carry bio-molecule payloads in each of the distinct phases or prevent the undesirable partitioning of molecules to unwanted phases.Two classes of biomolecules will be examined and their partitioning behaviour studied and exploited. Primarily, the opportunity to include an undetectable form of otherwise extremely unpalatable but strongly bio-active bitter peptides is attractive. These short chain peptides have been shown to have a variety of beneficial health properties including anti-hypertensive activity3. In their naked form they can't be used in foods due to their associated bitterness. Interestingly though, bitterness is a consequence of their extreme hydrophobicity; and so if partitioned into a stabilised lipid (i.e. rheologically stable to survive through the mouth without rupture) and held away from the lipid/aqueous interface these molecules might be administered routinely without detection. As bitter peptides are ~350 Da they should be amenable to hydrophobin partitioning and competitive adsorption at interfaces should lock the bitterness to an unperceivable form. Secondly, the lipid phase of the new candidate structures might be derived from essential fatty acids, Omega 3 & 6. The bioactive molecules are readily oxidised and commonly carry strong unfavourable flavours and locking these compound in an unperceivable form should help consumer acceptance. 1.Curr Op Biotechnol 2005 16 434 2.Biophys J 2005 88 3434 3.Am J Clin 2003 77 326

The main technical consideration for the proposed novel foods are: controlled formation and storage properties of air/lipid/aqueous emulsions, the rheology and surface characteristics of the emulsions, maintenance of partitioned biomolecules, flavour release dynamics and structural integrity of the emulsion during a) formation b) storage c) ingestion and d) digestion. Controlled formation of lipid droplet and air cells will have to be controlled and their proportions quantified and compared to full fat mayonnaise. The surface properties and rheology of the hydrophobin phases will be measured and emulsion models developed. Storage stability, particularly with respect to droplet/bubble coalescence, will be examined and stability of candidate structures measured. Effects of other common surfactants (e.g. lecithin) along with the hydrophobins will be examined to find tailor made solutions for candidate structure design. Confocal based image analysis with lipids and hydrophobins is a particular possibility here as all phases and the hydrophobins can be fluorescently labelled or contrasted. The droplet size/rheology of the model foods will be controlled and the partitioning of the bioactive payload examined. Partitioning dynamics and the order of addition of additives is not obvious and will require consideration to achieve the full functionality expected. Once the examination of the functional food has been achieved then studies of flavour release and finally the effects of production unit operations may be covered. Flavour release may be monitored via MS nose, a mature method at the University of Nottingham. Here, the release of flavour to the buccal or nasal cavity can be correlated to the engineering parameters of the test candidate structure e.g. bubble size. Engineering studies of the formation of the emulsions at scale and the downstream effects on the structure and functionality quantified in pilot scale equipment; subsequent engineering models will then be made.