Programmed emulsions for reduced levels of salt or sugar in liquid and semi-liquid foods

Lead Research Organisation: University of Nottingham
Department Name: Sch of Biosciences

Abstract

This project will deliver rapidly a formulation engineering route to salt or sugar reduction in sauces, dressings, soups and milk shakes. It will also provide non-chemically modified starches as food emulsifiers. The novelty lies in programming one of the formulation ingredients, starch, for dual purpose: product stabilisation and taste experience using ingredients acceptable to consumers.
There are a range of novel strategies to reduce salt and sugar content in dry/solid foods, but these are not practical in liquid foods due to the high solubility of salt and sugar in water. Therefore this project specifically targets the salt or sugar levels of liquid and semi-liquid foods where salt or sugar is primarily added for taste rather than preservation, a particular challenge for the food industry. We hypothesise that the formulation levels of these undesirable nutrients can be reduced without taste compromise by encapsulation in a fashion that, while the delivery vehicles remain stable during shelf life, they break down in the mouth, close to the taste receptors to deliver the tastant right where it will be perceived. Currently salt or sugar is delivered to the taste receptors through the bulk of the food and taste intensity correlates to concentration. Delivery of pockets of sufficiently high concentrations of salt or sugar near the taste receptors will enable lowering their overall concentration in the bulk of the food that is swallowed without contributing to taste. The proposed approach is to use water-in-oil-in-water emulsions (wow/s) to encapsulate the salt or sugar, which will be protected by a starch based shell. This starch will be designed to break down when brought into contact with saliva, thus releasing high concentrations of salt or sugar close to taste receptors in the mouth.
wow emulsions are oil-in-water (o/w) emulsions where the oil droplets are filled with water droplets. Although wow/s have been talked about for some time, they can be very difficult to stabilise to give a long shelf life and therefore are not found in commercial foods or drinks. What happens is termed emptying out: the internalised water diffuses through the oil into the external water phase slowly converting the wow into a simple o/w. There have been different approaches to reduce emptying out, but perhaps the only practically relevant method for this project is through particle stabilisation of the external o/w interface. This has recently been demonstrated to be possible with OSA starch (a chemically modified starch) that is well known to be a good emulsifier. Native starches with small granules have also been reported to show emulsifying ability although our own attempts have shown limited stability. It can be predicted that native starches will not be widely functional across the broad spectrum of emulsion based foods and drinks. Chemical modification of food ingredients is not desired by consumers, so we will explore physical modification via extrusion processing and milling to program starches as emulsifier & for break down delivery of salt or sugar near the taste receptors during consumption. As salivary amylase will be the tastant release trigger, individuals' or consumer groups' amylase levels will be considered in developing this pathway for salt or sugar reduction.
We have proof-of-concept sensory data indicative of the potential success of the proposed technology based on formulating with a commercial OSA starch. Emulsion stability was excellent although encapsulation efficiency was not optimised for product storage. The internal water phase was stabilised with polyglycerol polyricinoleate (PGPR) as in most researches despite the limitations for use of PGPR in processed foods. In this research alternative approaches to stabilise the internal water phase, e.g., by a fat crystal network (which is known to be successful), extremely hydrophobic starches or other food particles not requiring chemical modification will be applied.

Technical Summary

This project is concerned with salt or sugar reduction in emulsion based liquid and semi-liquid foods. The research hypothesis is that programming emulsions for oral release of a concentrated salt or sugar enriched encapsulated aqueous phase will enable reduction of the overall salt or sugar level in the food while maintaining consumer acceptability. The strategy is to encapsulate salt or sugar in starch stabilised water-in-oil-in-water emulsions (wow/s) and quantify their microstructure stability (relevant to product shelf life) and their tastant release properties (relevant to consumer satisfaction) adopting in-vitro and in-vivo methodology. Emulsion breakdown and thus tastant release during oral processing is mediated by the actions of salivary amylase and mechanical forces from teeth and tongue. Starch will be selected from native and ingredient starches which have not previously undergone modification to impart interfacial activity, and processed to impart or enhance ability to stabilise oil-water emulsion interfaces, including co-processing with emulsifying food ingredients, as well as from commercially available chemically modified starches with emulsifying properties. The internal water-oil interface will be stabilised with polyglycerol polyricinoleate (PGPR), fat crystals or food particles. Microstructure changes and saliva-starch interactions during the oral processing of the emulsions both with encapsulated salt and sugar will be and the findings will be correlated to sensory taste perception data. This will guide optimisation of the interfacial design of the emulsions and ultimately lead to a model for the emulsions' taste enhancing properties which will be validated on the basis of relevant foods and sensory analysis.

Planned Impact

The research contributes to Research Challenge 1 & 2 "Understanding the relationship between food processing and nutrition" & "Designing foods to maintain and improve health".
Beneficiaries of this research will be the food industry, food ingredient industry, the government and the general public. The research will enable the food industry to develop a broader range of liquid and semi liquid foods such as sauces, salad dressing, soups and milk shakes with reduced salt and/ or sugar levels quite quickly. It will help the food industry develop more innovative products based on this approach, with novel taste profiles to perhaps enhance the perception of fat and other components to improve the sensory qualities of healthier foods which have been associated with poor sensory quality.
The proposed technology to achieve this goal will not compromise the taste of these foods as it is known to the consumer. Thus, these foods will help contribute towards reduced salt or sugar consumption based on processed foods. A decrease in the occurrence of associated health problems benefits the wider public and has wider consequences on the spending of the government. Current estimates state that up to 9,000 lives could be saved from CVD and high blood pressure and savings to the NHS will be around £1.5b if salt levels reduced to recommended levels. Consumers will also benefit from a greater choice of foods with reduced salt and sugar, and will no longer have to compromise taste in order to rapidly decrease salt or sugar intake.
The research is centred on a widely used food ingredient as technology enabler and this will benefit the food ingredient industry in terms of wider market potential and development opportunities for increased ingredient functionality.

There could also be broader benefits to the pharmaceutical, medical, cosmetic and agrochemical sectors, seeking new and effective ways of targeted delivery of bioactive ingredients.
This project will provide interdisciplinarytraining to two postdoctoral research associates who will gain experience in working with a widely used food system including processing and characterisation (emulsions) applying technology of increasing interest in industry (particle stabilisation) while gaining knowledge on the widely utilised food ingredient starch and exploring physical processes to improve their performance as emulsifiers. The research will also involve use of an extensive range of analytical techniques as well as working with human subjects (oral residence time analysis and sensory panel). This training will equip the researchers with a broad skill base who may then seek future employment in the food industry. The research will also have an impact in the scientific community as we will disseminate our findings through the traditional channels of peer reviewed papers and conference attendance.
 
Description We are developing aqueous based multiple emulsions where salt or sugar solution is encapsulated in the oil droplets. The emulsions are stabilised by starch so they break down after ingestion by the combined action of saliva and chewing. The salt or sugar solution is released and the consumer notices a change in saltiness or sweetness leading to an overall higher perception of this taste. We have in-vitro and consumer perception data to support our conclusions. The emulsions are robust and can be processed in standard manufacturing equipment, adjusted in pH to typical food emulsion product pH and the microstructure will not break down during pasteurisation. We have demonstrated that a few non-chemically modified starches may be utilised, which is of significance for practical purposes wrt consumer demand (no E-number, no chemical modification).
Exploitation Route Publication, direct engagement with food ingredient suppliers and manufacturers.
Sectors Agriculture, Food and Drink,Pharmaceuticals and Medical Biotechnology

 
Description Visitors to University Campus 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Study participants or study members
Results and Impact 116 consumers tasted tomato soups samples to provide data for validation of developed research to salt reduction in close-to-market formulations.
Year(s) Of Engagement Activity 2018