Functional Properties of Food Additive Monoglycerides

Wheat is a crop planted on a large scale in my country. For a long time, various pasta made from wheat flour has been the favorite staple food of the people in northern China.

With the development of the food industry, flour has been widely used as a main base material, and flour products of various colors are accepted by more and more people because of their rich nutrition, unique flavor, convenience and quickness.

However, the quality of flour products is affected by the origin and variety of wheat. There are many problems in the quality of wheat flour in our country. It is often necessary to add some improvers when producing flour products to improve the quality of the products.

Monoglyceride is the most widely used emulsifier in the world, and it is also a commonly used emulsifier in my country's food industry.

When used in the production and processing of bread, biscuits, cakes, pasta and other flour products, it can emulsify and interact with the main components of wheat flour, giving flour products a good appearance and taste.

Classification and properties of monoglycerides

The full name of monoglyceride is monoglyceride (or glycerol monofatty acid ester), and the English name is Monoglycerides (MG). According to the name of the main fatty acid, monoglyceride can be further divided into glycerol monostearate (Glycerolmonostearate) , Glycerol monosilicate (Glycerolmonolaurate), Glycerol monooleate (Glyc-erolmonooleate), etc. Among them, glycerol monostearate is the most widely used in production.

Monoglycerides are generally oily, fatty or waxy, light yellow or ivory in color, oily or odorless, which is related to the size and saturation of the fatty group, and has excellent sensory properties. Monoglycerides are insoluble Water and glycerol, but can form stable hydrated dispersions in water with HLB values of 2 to 3.

By changing the length and saturation of the fatty acid carbon chains that make up the monoglycerides, their HLB values can be adjusted. Similar to oils and fats, monoglycerides exist in a variety of crystalline or variable crystalline forms.

Functional properties of monoglycerides

In addition to the typical surface-active effect of monoglycerides, there are many other functions in food. The combination of these surface-active effects and special effects in food is the basis for the application of monoglycerides in the processing of flour products.

On this basis, monoglycerides can not only improve food quality, prolong food storage period, and improve food sensory properties, but also prevent food spoilage, facilitate food processing and preservation, and contribute to the development of new foods.

2.1 Surface activity of monoglycerides

Monoglycerides are nonionic surfactants with an amphiphilic molecular structure. Its lipophilic group is composed of fatty acid, and its hydrophilic group is composed of glycerol.

This amphiphilic molecular structure is the premise for the generation of surface activity, and enables monoglycerides to be easily enriched on the surface of the solution for adsorption, and oriented and arranged on the surface and interface, resulting in surface activity and interface activity, reducing the surface or interface. tension.

In addition, the monoglycerides are oriented on the gas-liquid or gas-fat interface, which improves the mechanical strength and elasticity of the air bubbles, so that the air bubbles can expand more without breaking.

The most commonly used glycerol monostearate has two hydrophilic hydroxyl groups and one lipophilic octadecyl group, so it can be adsorbed on the mutually repelling surfaces of oil and water to form a thin molecular layer. Reduce the interfacial tension of the two phases, so that the original incompatible substances can be uniformly mixed to form a uniform dispersion system, which changes the physical state of the raw materials, thereby improving the internal structure of the food and improving the quality.

2.2 Interactions between monoglycerides and flour components

Carbohydrates, proteins and lipids play a decisive role in the complex process of producing pasta. The actions of the various flour components are determined by their composition or the products of their interactions. Monoglycerides can interact with flour components in many ways and can correspondingly affect product quality.

2.2.1 Interaction between monoglycerides and starch

When the starch is gelatinized and swelled by heat, the monoglyceride and water together form a lamellar dispersed phase of liquid crystals and penetrate into the starch granules, interacting with the amylose outside the leached starch granules and the amylose outside the starch granules.

The monoglyceride is tightly packed in the amylose helical structure to form a strong complex, that is, the amylose is fixed in the starch granules, the amylose dissolved in the free water around the starch granules is reduced, and the affinity of the monoglyceride is reduced. The oil group enters the amylose helical structure to form an insoluble complex, which prevents the recrystallization between starch granules and causes aging.

Which molecules can intercalate into starch depend on chemical and geometrical factors. The complex-forming ability of homologous monoglycerides depends to a large extent on the chain length of the fatty acid groups, among which hydrocarbon chains with 16 and 18 carbon atoms are preferred.

The compound rate of unsaturated fatty acid monoglyceride is low, mainly because its molecule is not linear, there is steric hindrance, and it cannot smoothly enter the starch structure. The presence of cavities within the starch helical structure is an unfavorable configuration from an energetic point of view, but this configuration can be stabilized by intercalation of suitable ligands.

Because the inner diameter of the starch spirochetes is only about 4.5-6*10^-10m, it can only preferentially form closed-ring compounds with emulsifiers whose lipophilic groups also have a diameter of a similar order of magnitude. This condition is best achieved with saturated fatty acid monoglycerides. R. Cui, C. g. The Oates_6 study found that the complex is not easily decomposed by amylase, which is also the reason to prove the above point. Amylopectin has few linear helical structures and is extremely difficult to form a complex.

In addition to forming an insoluble complex with amylose to produce anti-aging effect, monoglyceride directly affects the moisture distribution in the dough and indirectly delays aging.

During the dough mixing stage, monoglycerides are adsorbed on the starch surface, producing water-insoluble substances, which inhibit the movement of water and the expansion of starch granules, and prevent the interconnection between starch granules. Since the water-swelling ability of starch is reduced, the gelatinization temperature is increased, so that more water is transferred to the gluten, thereby increasing the softness of the product and delaying aging.

2.2.2 Interaction between monoglycerides and proteins

There are two water-insoluble proteins in flour, glutenin and gliadin. In the operation process of adding water to flour to form dough, these two proteins absorb water and swell. Glutenin forms a single-chain small molecular substance with strong viscosity and no elasticity; glutenin forms a macromolecular multi-chain substance with good elasticity and no viscosity.

During dough processing, small molecular glutenin is dispersed into macromolecular glutenin to form a special network structure that is both elastic and viscous, namely gluten. After adding monoglyceride, monoglyceride can interact with gluten protein to form a complex, that is, the hydrophilic group of monoglyceride is combined with gliadin, and the lipophilic group is combined with glutenin. Scattered gluten protein molecules connect to each other, turning small molecules into large molecules, which in turn form a strong, tight gluten network. It is precisely because of this good "bridging effect" that the free protein in the dough is significantly reduced, while the bound protein is significantly increased.

2.2.3 Interaction between monoglycerides and lipids

The α-crystal form of oil is the most unstable and has a very low melting point, while the β-crystal form and the β'-crystal form are both stable and have a higher melting point. processing performance.

To keep the oil in the β'-crystalline state, it is necessary to add a crystal modifier. A stable β'-crystal state can be obtained when monoglycerides are co-crystallized with oils and fats. β'-crystalline oil with high melting point, good plasticity and spreadability.

Monoglycerides can improve the cohesion between oils and fats and the ability to combine with fats to form a crystal network structure, thereby improving the crystal crystallization of oils and improving the stability of oils, which is very beneficial for the production of heavy oil cakes and biscuits. It can prevent the occurrence of oil-water separation of dough or products due to long-term storage, that is, the phenomenon of "going oil", which improves the storage period and ensures the quality.