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

Lead Research Organisation: University of Birmingham
Department Name: Chemical Engineering


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

Technical Summary

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.


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Le Révérend B (2010) Colloidal aspects of eating in Current Opinion in Colloid & Interface Science

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Pichot R (2013) Phospholipids at the interface: current trends and challenges. in International journal of molecular sciences

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Tchuenbou-Magaia F (2009) Hydrophobins stabilised air-filled emulsions for the food industry in Food Hydrocolloids

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Tchuenbou-Magaia F (2011) Suspensions of air cells with cysteine-rich protein coats: Air-filled emulsions in Journal of Cellular Plastics

Description Air filled emulsions have the potential to be used in many applications in a range of industrial sectors eg foods, biomedical, and pharmaceutical. However, air filled emulsions are inherently unstable entities due to ripening effects. We have shown that hydrophobins, which are naturally occurring proteins have an ability to stabilize micron-sized, air droplets.

As the use of hydrophobins for air filled emulsions was previously unknown and the control of air droplet size/stability was unpublished, a patent application was filed.
Exploitation Route More recently, small air cells with other cysteine-rich proteins such as bovine serum albumin and egg albumen (egg white protein) have been constructed using a sonochemical method. The majority of the air cells had a diameter between 1 and 10 microns.

The air droplet shells are dense enough to form a cage-like structure and are equally as robust as those from hydrophobins.
Sectors Agriculture, Food and Drink

Description Collaboration with Prof Tristan Baumberger (Paris) 
Organisation Paris Diderot University
Country France 
Sector Academic/University 
PI Contribution A number of new collaborations have resulted from the DRINC club. These now both have a PhD studentship funded by industry. In addition, academic contacts and small scale collaborations have started with a Professor at the Institute of Nanosciences (Paris) There is potentially two new industrial collaboration (1) with Kraft and (2) with Diageo
Start Year 2012
Description The invention discloses a shelf stable food product. The product comprises a continuous aqueous phase, liquid oil droplets dispersed in the continuous aqueous phase, and protein coated gas bubbles. The continuous aqueous phase constitutes from 20% to 80% by volume (or weight) of the food product and the liquid oil droplets and protein coated gas bubbles are from 0.5[mu]m to 10 [mu]m in diameter. The protein comprises cysteine amino acid residues, but is not a hydrophobin. The invention also discloses a method of forming an aqueous dispersion of protein coated gas bubbles suitable for forming the above food product. The method comprises dissolving a protein capable of forming coated gas bubbles in water with stirring, sonicating the protein solution at a temperature below but within 6 DEG C of the protein's denaturation temperature in the presence of oxygen, and controlling the temperature within these limits. Any protein debris from the resultant dispersion of protein coated gas bubbles is separated out. 
IP Reference WO2010067059 
Protection Patent application published
Year Protection Granted 2010
Licensed No
Impact None
Description Public information/education 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact We have publicised the work through the University press office, appearing in a number of national news papers and many trade journals. This has resulted in international coverage in for instance the USA and main land Europe.

Stimulate press interest
Year(s) Of Engagement Activity 2008