Types of emulsifiers used in ice cream making

 Emulsifiers

     Emulsifiers have been used in ice cream mix manufacture for many years. 

    They are usually integrated with stabilizers in proprietary blends but their function and action differ remarkably from those of stabilizers. They can be classified as :

       Hydrophobic :Examples include sorbitan esters,mono- and diglycerides of fatty acids, polyglycerol polyricinoleate, highly substituted sugars, polyglycerol esters, and propylene glycol esters.

      Hydrophilic : Examples include ethoxylatedsorbitan esters, monoglyceride derivatives such as lactates, tartarates,citrates, low-substituted polyglycerol esters, and monosubstituted sugaresters.

    Role of emulsifiers in ice cream

Emulsifiers are used to:

  Promote nucleation of fat during aging thus reducing aging time

      Improve the whipping ability of the mix due to their function at the air interface resulting in reduced air cell sizes and homogenous distribution of air in the ice cream

     Produce a dry and stiff ice cream as they enhance fat destabilization, facilitating molding, fancy extrusion and sandwich manufacture

     Increase resistance to shrinkage and rapid melt down due to a combination of the above two factors

        Increase resistance to the development of coarse/icy texture, due to the effect of fat agglomerates, more numerous air bubbles, and thinner lamellae between adjacent air bubbles on the size and growth of ice crystals

       Provide smooth texture in the finished product, due to fat structuring and interaction of fat agglomerates within the mouth during consumption.

HLB concept

Griffin (1949) forwarded hydrophilic-lipophilic balance concept. A specific emulsifier HLB is required to produce a particular type of emulsion. The HLB number indicates the percentage weight of the hydrophilic portion of an emulsifier molecule divided by 5. The HLB scale ranges from 0 to20.

Glycerol Mono Stearate (GMS) has got a HLB number of 3 whereas polysorbate 65 has got a HLB number of 13.

Properties of individual emulsifiers

a) Mono-/diglycerides

The most commonly used emulsifiers in ice cream manufacture are mono-/diglycerides (E471). 

       Mono- /diglycerides are mixtures of monoglycerides and diglycerides. Mono- and diglycerides are surface active because the glycerol end of the molecule is hydrophilic and the fatty acid end is hydrophobic. 

      Mono- /diglycerides are made by partially hydrolysing vegetable fats, such as soybean oil and palm oil. They normally contain 40-60% monoglyceride, together with diglyceride, and a small amount of triglyceride. Fully saturated mono-/diglycerides that contain predominantly stearic and palmitic acids, such as glycerol monostearate, are often used for ice cream production and typically make up about 0.3% of the ice cream mix.

          Materials with high monoglyceride content (> 90%) are available. These are difficult to disperse because they can become extremely viscous and form a gel in aqueous systems. 

b) Sorbitanesters

        The sorbitan esters are similar to monoglycerides in that the sorbitan esers have a fatty acid molecule such as stearate or oleate attached to a sorbitol (glucose alcohol) molecule, whereas the mono glycerides have a fatty acid molecule attached to a glycerol molecule.

           To make the sorbitan esers water soluble polyoxyethylene groups are attached to the sorbitol molecule. Polysorbate 80, polyoxyethylene sorbitan monooleate is the most common of these sorbitan esters. Polysorbate 80 is a very active drying agent in the ice cream and is used in many commercial stabilizer/emulsifier blends. 

           Although it is normally a component of stabilizer/ emulsifier blend, it can be added in pure form directly to mix flavour tank post homogenization and will become effective at enhancing dryness within a few minutes. Sorbitan esters of fatty acids, such as polyoxyethylene sorbitan monooleate (also known as polysorbate 80) are structurally similar to monoglycerides. 

            These consist of a fatty acid attached to a sorbitol molecule instead of glycerol. Polyoxyethylene groups are also attached to the sorbitol molecule to make it water soluble. Polysorbate 80 can be used as an ice cream emulsifier, typically at concentrations of 0.1-0.2%.

c) Egg Yolk

         Egg yolk, which contains several components with emulsifying properties, notably lecithin, is often used in  ̳all-natural‘, premium or homemade ice creams. 

         Egg yolk has the approximate composition (by weight) of 50% water, 16% protein, 9% lecithin, 23% other fat, 0.3% carbohydrate and 1.7% minerals. Lecithin consists of phosphatides and phospholipids. 

         Egg yolk is usually used in ice cream manufacture either as pasteurized fresh egg yolk, frozen sugared pasteurized egg yolk (which has about 10% sucrose added to protect it from damage during freezing) or as dehydrated egg yolk. Egg yolk solids are normally used at about 0.5-3%. 

         High concentrations are only used for super- premium products, and cangive the ice cream an eggy flavour.

         Stabilizers and emulsifiers are important ingredients in ice cream and they contribute to a great extent to the desired body and texture characteristics of ice cream and other frozen desserts. 

        Generally a mixture of two or more emulsifiers/stabilizers is preferred to overcome drawbacks of individual compounds. 

        Most of the commercial preparations are blends of emulsifiers and stabilizers which not only provide the convenience of use, but also make it possible to integrate stabilizers in a continuous emulsifier phase thereby facilitating dispersion of the stabilizer. 

        The ice cream industry in India is growing at a commendable rate so the demand of good quality stabilizers and emulsifiers is bound to go up. Intensive research is required to produce stabilizer emulsifier formulations to suit varying needs of the ice cream manufacturer.