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Emulsifiers: trend towards natural



Because of their versatility, food emulsifiers can be found in a huge variety of food applications, for example mayonnaises, bakery products, ice creams, fat spreads and salad dressings.

Emulsifiers are primarily used to produce and maintain emulsions. These additives also have other functionalities in food matrices, such as aeration, increasing shelf life, mouthfeel, texturing and fat replacement. The latter especially is interesting from a possible health perspective, the more so when the emulsifiers do not have to carry an E-number.

 

Because of their versatility, food emulsifiers can be found in a huge variety of food applications: mayonnaises, bakery products, ice creams, fat spreads, salad dressings etc. (see page 22 for a comprehensive overview).
The main functionality is producing and maintaining emulsions, in essence mixes of oil and water (see box text 1). There are basically three options: oil-in-water, water-in-oil and oil-water-in-oil. Emulsions are formed by dissolving an emulsifier with the aqueous phase (in the case of oil water emulsions), after which both phases are being mixed via a high-shear mixer or a homogenizer. The emulsifier then must adsorb rapidly onto the droplets at the oil-water interface. Whereas the initial emulsion contains relatively thick droplets (larger than 1 mm in diameter), the emulsifier’s lowering surface tension ability causes the droplets to break down into smaller ones. By coating these droplets, the emulsifier prevents their coagulation. Droplet size in general is an indicator of the stability of an emulsion: the smaller the size, the more stable the emulsion.


Broad functionalities
Because of emulsifiers main functionality, mayonaises or salad dressings - just to name a couple of examples - do not break down in a water and oil phase over its shelf life.
As mentioned before, emulsifying is not the only functionality. For example, stearoyl lactylates and mono- and di-glycerides can retard staling in baked goods by interfering with starch retrogradation. In chocolate, emulsifiers are used to reduce viscosity, which allows for a reduction in the amount of cocoa butter, and subsequently lowers costs as well as a few calories. Emulsifiers in cake batter facilitate the release of cake from pans.
Sucrose esters have been used as fat replacers, including in the frying of snacks, to reduce calories. Unfortunately, in that application, the non-digestible fat replacers are said to have some unpleasant effects on the digestive system. Most notably, Procter & Gamble’s Olestra at the end of the nineties suffered rather negative reporting. Although later studies found the additive safe for consumption, Olestra was never a big success in the food industry.

Growth expected in Asia Pacific region

Olestra’s demise, however, hasn’t affected the fat replacement potential of emulsifiers. According to RnR Market Research, the quest for fat replacers by the food industry has pushed the emulsifiers market forward. The market research agency states the global market will reach 933,400 tonnes in 2018 and that this segment is already the largest in the food industry. RnR states that health concerns, consumer awareness, a flourishing functional food market, bakery and confections are major drivers of industry demand. At the moment Europe is the biggest market for emulsifiers but the market on the continent is mature. Further growth is expected in the Asia Pacific region in which economic growth, increasing per capita incomes and the rise of processed foods will feed industry demand. China and India are front runners as consumers in these markets are interested in lower fat food products.
 
Negative side-effects

A possible downside, ironically, for emulsifiers could be reports about some negative side effects of these additives.
In a study at Georgia State University in the US, published in Cancer Research, mice were administered polysorbate 80 (E433) and carboxymethyl cellulose (E466) via their food. They were given dosages corresponding to high levels of consumption of the processed foods that contain these emulsifiers.
The diet led to a change in the gut flora in the mice, causing mild inflammation that made the mice more susceptible to the development of intestinal tumours.
Criticism of this study, pinpoints the disproportionate amounts of emulsifiers the mice were fed. Similar criticism arose about studies on aspartame. What is also missing is further research. The study needs to be reproduced by other teams and possible side effects should be eventually confirmed by human clinical trials with control groups that hardly consume emulsifiers. Furthermore, the relation between inflammation of the gut flora and intestinal cancer needs to be investigated. For the time being, there is no causal effect demonstrated.

Nanoemulsions
Because of market saturation in some regions, the future of emulsifiers may lie in other functionalities, for example encapsulating, stabilizing and delivering functional compounds. Nanoemulsion technology is particularly suited for the encapsulation and delivery of these compounds, leading to products which have more potential advantages than conventional emulsions. Nanoemulsions are ultrafine dispersions of at least two immiscible liquids (oil and water) possessing globules of submicron size range (10 nm - 100 nm). Nanoemulsions garner increasing interest in a number of sectors, including the food industry. These emulsions could be used for lipophilic constituents like flavours, omega-3 fatty acids, vitamins, preservatives or nutraceuticals. They have a number of potential advantages over conventional emulsions like incorporation into optically transparent products, may enhance the texture, stability, and bioavailability of certain food products. The formation of nanoemulsions requires processes like high energy emulsification with the help of high pressure homogenizers, sonication, and some low energy emulsification.

Natural emulsifiers
Another area which could foster innovation is the nature of emulsifiers. Most emulsifiers are synthesized and have to carry an E-number. The latter is an indication that the additive in question is safe for human consumption. The current trend - clean labelling - in the food industry, however, is to eliminate these E-numbers as much as possible, due partly to recent negative reporting on some E-numbers, mainly a combination of various food colourants.
This has sparked R&D activity into natural resources that are able to offer the same functionalities as synthesized emulsifiers. There are various sources available, such as biosurfactants, phospholipids, biopolymers (proteins, polysaccharides) and colloidal particles (starch).
In terms of functionality, natural emulsifiers need to be improved. For example, proteins are able to create small droplets, but they are sensitive to factors  such as pH, tempeature and ionic strength. Polysaccharide emulsifiers are more stable than protein-based ones but do not produce small droplets during homogenization. Research has shown that a combinatory approach might do the job by which protein-based and polysaccharide-based emulsifiers are combined (see box on this page). From a cost perspective this process prove uneconomic. However, if natural emulsifiers can save on costlier ingredients - for example cocoa butter in chocolate - this option actually wouldn’t look too bad.


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