Due to population growth and market competitiveness, traditional bread production has become somewhat obsolete, moving towards automation and semi-automation. In the meantime, the use of various additives in the production of bread has become a necessity. Therefore, emulsifiers are used for modifying agents.
Definition and Classification of Emulsifiers
According to Becher’s definition (1965), an emulsion is a heterogeneous system comprising at least one immiscible liquid that is dispersed in another liquid as fine droplets with a diameter of up to 0.1 μm. Such systems have low stability, and their stability is enhanced by the addition of surface active ingredients, fine solids, etc. A relatively simple classification for emulsifiers is provided, which is an optional subdivision and consists of three main groups.
- Finely divided solids
- Naturally occurring materials
- Surface-active materials
In the industrial production of flatbread, other emulsifiers – especially synthetic ones, which are available individually or in combination with natural ingredients – have great applications.
Naturally occurring materials and surface-active materials are widely used in the food industry. Naturally occurring materials (some gums or hydrocolloids) are, in a sense, among the surface-active materials. The difference is that surface-active materials are synthetic and can be manufactured for special use, while naturally occurring materials are naturally present in products and are often expensive, pH sensitive, and vulnerable to hydrolysis.
Surface-active materials
Based on the hydrophilic molecular group, surface-active materials are divided into the following five groups:
- Anionic active emulsifiers (positive charge)
- Cationic active emulsifiers (negative charge)
- Nonionic active emulsifiers (bipolar, no charge)
- Ampholytic (positive and negative charges)
- Water-insoluble emulsifiers
Nonionic active emulsifiers are widely used in the food industry. Emulsifiers have many economic and qualitative advantages and are not affected by water hardness and pH.
It is noteworthy that the oldest anionic emulsifier, which is soap, is still used in baking a type of flatbread (Sangak) in Iran.
Another method of classifying synthetic emulsifiers is based on their Hydrophilic-Lipophilic Balance (HLB), which depends on their efficiency for use in a particular food system. Emulsifiers with a HLB of 5 to 6 are highly lipophilic (soluble in fat) and are suitable for water-in-oil emulsions, while those with HLB of 8 to 18 are hydrophilic and are suitable for oil-in-water emulsions.
Emulsifiers are used in combination with bread improvers for a number of reasons, including:
- To help controlling the size of gas bubbles
- To improve gas retaining
- To improve dough strength
- To improve and enhance the softness of bread crumb
Proper use of any of the authorized emulsifiers, depending on the type, may have more or less part or all of these effects. The most common emulsifiers used to improve the dough properties and increase the quality of bread are as follows:
Mono- and di-glycerides
These compounds include mixtures containing mono- and di-esters of edible oils and fats or edible fatty acids which constitute edible fat. Commercially available products in terms of consistency are liquid, plastic and hard and have different colors from yellow to cream. They have a mild odor and are insoluble in water. They are used as dough enhancers, emulsifiers, flavors, lubricants, softeners, stabilizers, surface-active materials, texturizers and thickeners in bakery products (fermented with yeast). It should be noted that they are all classified as GRAS materials.
Acetylated Monoglycerides
These compounds consist of esters of glycerin with a mixture of acetic acid and edible fat-forming fatty acids. They have a mild odor and are insoluble in water and they are used as emulsifiers, lubricants and texture modifiers (texture enhancer) and their amount for use in food is no more than the amount needed to achieve the desired effect.
Diacetyl Tartaric Acid Ester of Mono- and Di-glycerides (DATAEM)
These compounds are intermediate products of glycerides of edible oils and fats or their fatty acids with “diacetyl tartaric anhydride”. These esters are either in the form of a viscous liquid, a fat-like or consistent compound, or a waxy solid. They have a slightly acidic odor and are soluble in water and oil. They are used in bakery products as emulsifiers and flavors and are among the GRAS compounds.
Diacetyl tartaric acid (DATA) esters and mono- and di-glycerides produce a smaller cellular structure by reducing the size of the air (gas) cells in the dough. These emulsifiers help preserve gas, improve bread volume, and improve texture and bread crumb softness. These emulsifiers are used in various types of bread and fermented products up to about 0.3% of the flour weight.
Glycerol Monostearate (GMS)
Glycerol Monostearate is used either in liquid or powder form and it doesn’t have a considerable impact on the gas retention and volume of bread and it mostly softens the bread crumb. For this reason, it is known as an anti-staling agent. 263
Ethoxylated Mono- and Di-glycerides (EMD)
These compounds are mixtures of intermediate esters of stearate, palmitate and lesser amounts of myristate glycerin condensed with about 20 moles of ethylene oxide per mole of .alpha.-monoglyceride. They are slightly yellowish, oily or gel-like opaque liquids and have a relatively bitter taste, and are relatively soluble in vegetable oil. They are used as conditioners and emulsifiers in dough and in fermented bakery products up to 0.5% of the flour amount.
Lactylic esters of fatty acids
These compounds are either in the form of hard wax solids or liquids, dispersible in hot water, and soluble in vegetable oil, and act as emulsifiers and create plastic properties in food and bakery products.
Polyglycerol esters of fatty acids
The color range of these compounds is yellow to amber and they are oily, concentrated liquid which is dispersible in water. They are used as emulsifiers in the mixtures of cakes and pastry products.
Propylene glycol mono- and di-esters
These compounds are translucent or white fluids to yellow sequins. They have a mild taste and odor and are insoluble in water. They are used as emulsifiers and stabilizers in cake dough.
Sodium Stearoyl Lactylates and Calcium Stearoyl Lactylates (SSL and CaSL)
These compounds are mixtures of sodium and calcium salts of stearoyl lactic acid and very low proportions of other salts of this acid. They are slightly hygroscopic (moisture-absorbing) and are available in the form of cream colored powders. They have a mild caramel-like odor and are slightly soluble in hot water. They are used as dough conditioners and whipping materials stabilizers. Their use in fermented bakery products is 0.5% of the flour weight.
Sodium stearoyl
Sodium stearoyl improves gas retention, bread volume and bread crumb softness, but is less effective when used in similar amounts to DATA esters and is usually used for products in which sugar is used, such as donut.
Sodium stearyl fumarate
Sodium stearyl fumarate is a soft, water-soluble powder. In bulk and non-bulk bakery products, it is used as a dough conditioner (up to about 0.5% to 1% of the flour weight).
Sorbitan ester (Sorbitan Mono Stearate)
They are mixtures of sorbitol esters of palmitic acid, stearic acid, and their mono- and di-anhydrides. Their color range is light cream color to light brown, and they are in the form of hard waxy solid with a mild taste and odor. They are insoluble in cold water but they spread in warm water. They are used as an anti-foaming, emulsifier and stabilizer compound in cake mixtures in amounts of 0.6%.
Succinylated Monoglycerides
Succinylated monoglycerides are mixtures of esters of mono- and di-glycerides of succinic acid which are obtained by succinylation of the product through glycerolysis of edible fats and oils or direct esterification of glycerol with fatty acids of edible fats. They are in the form of waxy solids, grayish white in color and have a mild taste and are used as a conditioner and emulsifier in bread dough.
Sucrose ester
Sucrose ester is used as an emulsifier, protective coating, and texturizer in baked products at a level not in excess of the amount reasonably required to accomplish the intended effect.
Naturally occurring materials
These emulsifiers are extracted from natural sources such as Spermatophytes, seed gums and seaweed, or are microbial fermentation products such as xanthan gum and dextran. Naturally occurring emulsifiers are often auxiliary emulsifiers because most of them are not sufficient when applied alone, but have a good emulsifying effect in combination. Naturally occurring emulsifiers are divided into two main groups:
- Phospholipids and Sterols
- Water-soluble gums
Phospholipids (lecithin) and sterols (lanolin) are slightly available in fats and oils.