Stabilisation of modern alcohol-containing emulsions with proteins

Abstract

The purpose of this project was to study the impact of three different protein systems on the physicochemical stability of alcohol-containing emulsions. Egg yolk plasma, sodium caseinate and whey protein isolate (WPI) were used for that purpose. For this reason, the solubility of the three protein systems in the presence of different levels of ethanol was first determined. Oil–in–water emulsions (Φ= 0.15), containing 0, 7 or 15% (v/v) ethanol,
stabilised by the above-mentioned emulsifiers (3% w/v), were prepared by using corn oil as lipid phase. Emulsions were prepared by using mainly the Ultra-Turrax homogenizer, while some trials were conducted by using the high pressure APV homogenizer. The stability of the emulsions was monitored over a storage period of 30 days at two temperatures (4 and 45oC) by measuring the oil droplet size as well as the viscosity of the systems. Additionally, the
interfacial tension between oil and continuous phase was also examined. The emulsions appeared to have similar droplet size distributions at the day of their preparation. Upon storage most of them appeared to be fairly stable with sodium caseinate exhibiting the highest stability

Popular Abstract

New liqueurs new pleasure
Cream liqueur market is anticipated to rise at a considerable rate in the foreseen future. It is the texture of cream, the flavor and the presence of alcohol that makes them very appealing to the consumers.
Many alcoholic drinks are available in the market; wines, beers, whisky, vodka and these drinks have pretty much a standard recipe which can only be altered in very specific limits. If those limits are to be overstepped, then the product will no longer be the initial product. For example, there is a very specific definition of what we call wine. Not much can be done as far as the raw material and the primary procedures that are followed so that wine can be produced.
As opposed to wines, cream liqueurs have a variety of recipes. Some of them are “secret” recipes from the manufacturers, some of them are very well studied by the food scientists. In general milk fat, sugar, protein, ethanol and water are the main ingredients of a cream liqueur. Some solids like non-fat solids are also added but those are beyond the scope of the project.
The main focus of the project is the kind of proteins that are used in cream liqueurs. Probably every person in the world must have heard the term protein in their lives at some point. The reason for this is that proteins are everywhere in our lives. They are present in our body, in our food in the environment. Proteins are versatile molecules with extremely complicated structures. This complexity is exactly what make proteins to be very useful in the food industry as well.
Without too many details on the protein structure one should at least bear in mind that proteins own a part that is friendly to the water and one part that is unfriendly to the water. The friendly part is usually located on the outside of the structure and is called hydrophilic while the unfriendly is located on the inside and is called hydrophobic. This distinction is an important feature of the proteins that are tested in the project.
We must add in this part that the project is about how three different proteins can “stabilize” an “emulsion formation”; otherwise a cream liqueur which is essentially an emulsion. First we should explain a little the terms emulsion and stabilization of an emulsion. An emulsion is a heterogeneous mixture of two or more liquids that cannot be mixed together. When we pure oil in water for example those liquids will not mix unless we start stirring the mixture vigorously. Then and only then will the two liquids appear to be somehow mixed together. What happen in reality is that by stirring the system we managed to break down oil in small droplets that are now diffused in water. If the system is left as it is the oil droplets will eventually come together and merge into bigger droplets and finally completely separate and form two layers (oil and water) as it was before the stirring. If we add a protein in the above oil and water system and stir it, we will observe that the droplets will remain dispersed in water for a longer period of time and this is called stabilization of the emulsion. The reason why this happens is that proteins orient themselves in a way where the hydrophilic part will be close to water and the hydrophobic part closer to the formed droplet surface. This orientation help the droplet maintain its spherical shape through some physical changes that occurs in the surface which is now (inside an emulsion) called interface.
Different proteins orient towards the droplets surface in different ways thus conferring a different result as far as stabilization is concerned. Proteins can be spherical, linear, rigid or more flexible.
In the production of cream liqueurs, a protein called sodium caseinate is usually used for the emulsion formation and stabilization. Sodium caseinate have been extensively studied for its properties in food industry. In the project another two proteins; whey protein isolates and egg yolk plasma proteins are evaluated for their emulsifying capacity. In order to do so, solubility, droplet size formation (homogenization), viscosity and interfacial tension of emulsions prepared with the respective protein are being tested.
Solubility is important because the more soluble a protein is in water the more effective will be in the emulsion formation. Droplet size is also important, smaller the droplet the better the formation and stability of the emulsions. Viscosity has to do with the space that droplets have available to move around the system. A more viscous emulsion could mean that droplets have been merged with each other making the product have visible pieces of proteins which is not appealing to the consumer. Finally, interfacial tension is about how “elastic” the formed droplet and how easy it is to maintain the shape and size acquired after homogenization.
Feedback about whether these proteins are eligible for use or not is given after performing analysis of the above physicochemical procedures in the lab.
The ultimate goal is the production of new alcoholic beverage from grapes. Egg yolk plasma proteins and whey protein isolates are being tested in comparison to sodium caseinate proteins as alternatives in such a production.
The results showed that sodium caseinate has given fairly stable emulsions as we could expect since it is already used in cream liqueur production. Egg yolk plasma proteins have given fairly stable emulsions when a mild homogenization was used as opposed to a more vigorous homogenization which led to more unstable emulsions. Although the droplets were smaller in the latter case, it has been assumed that there was not sufficient quantity of egg yolk plasma to protect those smaller droplets. Finally, although whey proteins gave emulsions with very small droplet size, which is a prerequisite in emulsion’s stability, the emulsion was not that stable leading to an increase in the droplet size over time. Such an increase means that the emulsion will finally “break” and the product will not meet its requirements anymore.
Further experimenting with the quantity of the proteins and the other ingredients present in such a hypothetical product, as well as with the conditions under which the formation happens, will give more firm results about which emulsion system is more stable and eligible for use.

• author: Levanti, Vasiliki
• supervisor: ADAMANTINI PARASKEVOPOULOU; Karolina Östbring
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLG820 20231
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Food technology, protein systems, sodium caseinate
• language: English
• id: 9112698
• date added to LUP: 2023-03-29 10:14:50
• date last changed: 2023-03-29 10:14:50