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

Lead Research Organisation: Quadram Institute Bioscience
Department Name: Food Innovation and Health

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 interdisciplinary training 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 It was possible to stabilise emulsions with non-hydrophobic starch using a combination of shear and thermal treatment as a result of the homogenisation, to create a stabilising layer around emulsion droplets. This layer appeared to be able to encapsulate tastants within multiple emulsion structures, and then release them during oral processing through the action of salivary amylase. The presence of salivary protein appeared to slow down the breakdown of the stabilising starch layer, and could potentially reduce the rate of release of salt and sugar. Further research is required to determine whether this is a significant effect in vivo.
Exploitation Route The basic findings from this project could be used to help improve the design of responsive emulsions. The design and optimisation of their functional performance has been extremely challenging due to the unusual and novel approaches required to get the starch to form a stabilising layer, nevertheless, the researchers have learned a lot about the behaviour and limitations of these emulsion systems, that will be extremely useful to future research projects in this field.
Sectors Agriculture, Food and Drink

 
Description Public lecture and Discussion Eaton Summer Programme 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Public lecture and discussion session as part of the Eaton Summer Programme in Norwich in August 2018. Talk entitled "Are your eyes bigger than your belly? The science behind controlling digestion and reducing appetite"
Aimed to educate the public on the role of food structure on digestion and health outcomes. To inform of the developments with the new Quadram Institute aims and research objectives. Enter into a discussion with the audience regarding the health benefits of certain foods and the role of processing, preparation and structure on nutrient availability.
Year(s) Of Engagement Activity 2018
 
Description Public lecture to local members of the University of the Third Age 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Public lecture organised for members of the University of the third age held at Quadram Institute, Norwich to disseminate and inform of the research activities and outputs of the Institute in the area of food structure and health.
Year(s) Of Engagement Activity 2017
 
Description Public lecture to the North Norfolk National Trust Society 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact A public lecture to the North Norfolk National Trust society to communicate some of the research activities of the Institute as part of our outreach activities.
Year(s) Of Engagement Activity 2016