Molecular Encapsulation For Stable Emulsions
Wednesday, September 13th, 2017
Salad dressings, whipped desserts, ice cream or even mayonnaise are a big part of our lives today. However they contain an oil-in-water phase and need to be stabilised with the aid of emulsifiers. What can be used and how is it beneficial for these food applications? By Rachela Mohr, business development manager, nutrition, Wacker Biosolutions
Vegan Feast Catering
Many foods today contain an oil-in- water phase and so need to be stabilised with the aid of emulsifiers. Unfortunately, traditional emulsifiers such as lecithin and other protein-based substances are problematic for a number of reasons, including heat and acid sensitivity, their animal origin, allergenicity and the fact that they are additional sources of cholesterol.
However, a small, ring-shaped glucose molecule offers a completely vegan solution: alphadextrin is an oligosaccharide obtained from non-animal renewable raw materials and is 100 percent vegetarian, non-allergenic and cholesterol-free. All of these properties make it a highly attractive emulsifying agent for the food and beverages industry.
Current trends in our fast-moving world, coupled with busy lifestyles, are fuelling demand for ready-made, processed food products that have a long shelf life, a nice look and feel, and a good taste. That is why many of the modern food products all around us contain oil-in-water emulsions—ice cream, whipped toppings and fluffy desserts, as well as salad dressings, dips and mayonnaise.
As the water and the oil phases will only form a stable emulsion if emulsifiers are added, emulsifiers are widely used throughout the food industry for this purpose.
Conventional Emulsifiers And Their Drawbacks
Conventional emulsifiers include mono- and diglycerides (derivatives of fatty acids), lecithins which are also present in egg yolk, as well as proteins and some low-molecular weight emulsifiers.
Unfortunately, animal-derived emulsifiers have certain properties and characteristics that pose challenges for food manufacturers. They tend to be quite sensitive to heat and acidic conditions and some do not have a long shelf life. They may also be allergenic or act as a source of undesirable cholesterol.
Liquid egg-based products also have the drawback of being difficult to handle and of losing viscosity during storage. Further, given the animal origin of egg- and protein-based emulsifiers, there may be concerns about possible contamination and food safety risks.
More importantly, products derived from animal sources are taboo for many people in Asia and Southeast Asia who only consume vegetarian or halal-certified food. Added to which, the current growing trend of adopting an animal-free, vegan diet by consumers is irrespective of ethnic background or religious reasons, and instead is fuelled by growing health awareness.
There is thus a great interest and need in finding a feasible alternative to animal-based emulsifiers for stabilising oil-in-water emulsions. Current expectations are that the market for vegan emulsifying solutions will experience further growth.
Alphadextrin As An Emulsifying Fibre
A plant-derived, cholesterol-free approach to stabilising oil-in-water emulsions is to use the soluble fibre alphadextrin. This non-reducing, chiral cyclic oligosaccharide consisting of six glucose units is stable in alkaline solutions and in acidic solutions down to approximately pH 2.5-3.0.
Alphadextrin is a natural starchconversion product and, for industrial use, is manufactured biotechnically by enzymatic degradation of vegetable raw materials, such as corn and potato starch.
In general, alphadextrin is a well-defined, chemically pure substance with consistent technical properties. Native alphadextrin is a colourless, nonhygroscopic crystalline solid which can withstand temperatures of up to about 220 deg C.
By virtue of its special structure, alphadextrin is capable of stabilising oil-in-water emulsions and thus replacing conventional animal-derived emulsifiers, such as egg yolk. The hydrophobic interior of alphadextrin enables it to attract and encapsulate selected molecules, such as triglycerides.
Once the triglycerides are ‘trapped’ inside the cavity, the hydrophilic exterior of alphadextrin acts as one part of a surfactant-like structure.
It is worth noting that only one of the fatty-acid tails of the triglyceride is encapsulated in the hydrophobic cavity of the alphadextrin, whereas the other two are not.
The two non-encapsulated fatty-acid tails then form the lipophilic portion of the surfactant, while, as already mentioned, the exterior of the alphadextrin represents the hydrophilic part. In an oil-in-water emulsion, the newly formed triglyceride/alphadextrin complex ‘sits’ on the surface of the oil droplet, thereby producing stabilised oil-in-water micelles.
Alphadextrin not only successfully stabilises oil-in-water emulsions. Varying the oil-to-water ratio and the amount of alphadextrin enables viscosity and therefore the organoleptic properties of the emulsion to be changed too.
As a result, many different viscosities ranging from those of ketchup to peanut butter become feasible. Furthermore, it can even yield stable emulsions at elevated temperatures, giving a crucial advantage for high-temperature processing operations.
Alphadextrin proves to be a suitable emulsifier for a variety of applications in the food industry. Not only does it stabilise oil-in-water emulsions, but it also regulates the viscosity and is even capable of keeping the emulsion stable at elevated temperatures. Among the many applications here are sauces, dressings, mayonnaise and whipped desserts, to name but a few.
Suiting A Variety Of Applications
Thanks to their special structure, alphadextrins can stabilise oil-in-water emulsions and thus replace a growing number of conventional animal-derived emulsifiers such as egg yolk in mayonnaise and salad dressings, egg white in whipped mousses, and caseinate (milk protein) in instant coconut milk powder.
For example, a mayonnaise substitute without animal-derived components can be easily made with alphadextrin. First, the alphadextrin is dissolved in water, and the desired amount of oil is added (together with ingredients for taste such as sugar, white vinegar, mustard etc.). Next, the preparation is homogenised at moderate temperature (lower than 25 deg C). The resulting product has a viscosity wholly comparable to that of conventional commercial mayonnaise.
Another interesting application example is the use of alphadextrin to replace sodium caseinate in coconut milk powders. The emulsifying properties of sodium caseinate are exploited by adding it to coconut milk powder, which will subsequently yield a stable, creamy-milky product when mixed with water.
Yet, this same effect can be achieved with alphadextrin with added benefits: it additionally improves the stability of the coconut milk made from powder and water and imparts caseinate-like creaminess to the milk.
The process for manufacturing coconut milk powder containing alphadextrin is almost the same as for the conventional process using sodium caseinate. Coconut milk reconstituted from powders with alphadextrin is further characterised by excellent mouthfeel and creaminess, and exhibits good stability over time.
What is more, the dietary fibre will not impart any taste to the product and is very competitive in terms of cost in use. In this way, alphadextrin constitutes a vegan, non-allergenic solution for replacing sodium caseinate in coconut milk powders.
Finally, alphadextrin also enables stable whipped toppings, creamy desserts and fruit mousses to be made without the addition of animal-derived whipping aids. The use of alphadextrin improves overrun during whipping, making it possible to whip fruit juices, fruit purees or honey into light, stable creams without the use of additional proteins or fat.
Alphadextrin therefore represents a vegan alternative for a large variety of desserts, while offering the additional advantage of lowering the fat content, and hence the calorie level, of the foods.
Alphadextrin As An Emulsifying Agent
In general, using alphadextrin as an emulsifying agent offers multiple advantages. It is a soluble fibre that is haze-free, odourless, stable even at high temperatures and at low pH, has a neutral taste and low viscosity.
Alphadextrin can come in the form of a colourless, soluble powder, which makes it easy to handle, store and process in food and beverage applications. The ingredient is moreover fully in line with the current trends toward avoidance of animal-based raw materials, as it is completely based on natural, renewable raw materials such as corn starch, and is therefore purely vegan. It is also cholesterol-free and non-allergenic.
Currently, alphadextrin is eligible to carry a ‘Clean Label’ claim as it does not have an E number, and has been approved in the US as GRAS (Generally Recognised As Safe), in the EU as Novel Food, and in Japan as a food additive. Finally, the compatibility of alphadextrin with a variety of stabilisers, such as hydrocolloids, starches and gelatin, creates synergies in terms of volume and stability increase.
It is therefore the ideal emulsifying agent for use in numerous high-quality food applications, such as creamy desserts, whipped toppings, salad dressings, margarines, sauces, dips or mayonnaise, to name but a few.
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