Wheat is a crop grown in a large area in China. For a long time, various pasta made from wheat flour have been the staple food preferred by the people in northern my country.
With the development of the food industry, flour has been widely used as a major base material. Various types of flour products are accepted by more and more people for their rich nutrition, unique flavor, and convenience.
However, the quality of noodle products is affected by the place and variety of wheat. There are many problems with the quality of wheat flour in my country. It is often necessary to add some improvers to improve the quality of the products when producing noodle products.
Monoglyceride is currently the most used emulsifier in the world, and it is also a commonly used emulsifier in my country's food industry.
It is used in the production and processing of bread, biscuits, cakes, pasta and other pasta products. It can emulsify and interact with the main ingredients in wheat flour to give the pasta a good appearance and taste.
01 Classification and properties of monoglycerides
The full name of monoglyceride is monoglyceride (or monoglyceride), and the English name is Monoglycerides (MG). According to the name of the main fatty acid, monoglycerides can be further divided into glycerol monostearate (Glycerolmonostearate) , Glycerolmonolaurate (Glycerolmonolaurate), Glycerolmonooleate (Glyc-erolmonooleate), etc., among which glycerol monostearate is the most widely used.
Monoglycerides are generally oily, fat or waxy. The color is light yellow or ivory, oily or tasteless. This is related to the size and saturation of fatty groups. It has excellent sensory characteristics. Monoglycerides are insoluble Water and glycerin, but can form a stable hydrated dispersion in water, and its HLB value is 2 to 3.
The HLB value can be adjusted by changing the length and saturation of the fatty acid carbon chain that makes up the monoglyceride. Similar to oils, monoglycerides exist in multiple crystal forms or metamorphic forms.
02 Functional properties of monoglycerides
In addition to the typical surface activity, monoglycerides also have many other functions in food. The combination of these surface-active effects and the 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, extend food storage period, improve food sensory properties, but also prevent food deterioration, 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. The lipophilic group is composed of fatty acid, and the hydrophilic group is composed of glyceryl group.
This amphiphilic molecular structure is a prerequisite for surface activity, and it enables monoglycerides to be easily enriched on the surface of the solution and adsorbed, and oriented on the surface and interface to produce surface activity and interface activity, reducing the surface or interface tension.
In addition, the monoglycerides are oriented and arranged on the gas-liquid or gas-fat interface to improve the mechanical strength and elasticity of the bubbles, so that the air bubbles can expand without breaking.
The most commonly used glyceryl monostearate has two hydrophilic hydroxyl groups and one lipophilic octadecyl group, so it can be adsorbed on the mutually repelling phases 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 The interaction between monoglycerides and flour ingredients
In the complex process of producing noodle products, carbohydrates, proteins and lipids play a decisive role. The role of various flour components is determined by their composition or the product of interaction. The monoglyceride and flour ingredients may interact in many ways, and can correspondingly affect the quality of the product.
2.2.1 The interaction between monoglycerides and starch
When starch is heated to gelatinize and swell, the monoglyceride and water together form a layered dispersed phase of liquid crystals to penetrate into the starch granules and interact with the amylose outside the starch granules and the amylose outside the starch granules.
Monoglycerides are tightly wrapped in the helical structure of amylose to form a strong complex, that is, amylose is fixed in the starch granules, and the amount of amylose dissolved in the free water around the starch granules is reduced, and the affinity of monoglycerides The oil base enters the helical structure of amylose to form an insoluble complex, which prevents recrystallization between starch grains and aging.
Which molecules can be embedded in starch depends on chemical and geometric factors. The ability to form complexes of homologous monoglycerides largely depends on the chain length of fatty acid groups, and hydrocarbon chains with 16 and 18 carbon atoms are preferred.
The complex 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. From an energetic point of view, the cavity in the helical structure of starch is an unfavorable configuration, but this configuration can be stabilized by inserting a suitable ligand.
Because the inner diameter of the starch spirochete is only about 4.5-6*10-10m, it can only preferentially form a closed-loop compound with an emulsifier whose lipophilic group also has a similar order of diameter. In the case of saturated fatty acid monoglycerides, this condition can be best achieved. R. Cui, C. G. The research of Oates_6 found that the complex is not easily decomposed by amylase, which is also the reason to prove the above point. Amylopectin has a few linear helical structures and is extremely difficult to form complexes.
In addition to forming an insoluble compound with amylose to produce anti-aging effects, monoglycerides also directly affect the distribution of moisture in the dough and indirectly delay aging.
During the dough mixing stage, monoglycerides are adsorbed on the surface of the starch to produce water-insoluble substances, which inhibit the movement of water and the expansion of starch grains, and prevent the interconnection between starch grains. As the water swelling capacity of starch is reduced and the gelatinization temperature is increased, more water is transferred to the gluten, thus increasing the softness of the product and delaying aging.
2.2.2 The interaction between monoglycerides and protein
There are two non-water-soluble proteins in flour, namely glutenin and gliadin. In the process of adding water to flour to form dough, these two proteins absorb water and swell. Glidin forms a single-chain small molecule substance with strong viscosity but no elasticity; glutenin forms a large molecular multi-chain substance with good elasticity but no viscosity.
During dough processing, small molecules of glutenin are dispersed into large molecules of glutenin to form a special network structure that is both elastic and viscous, namely gluten. After adding the monoglyceride, the monoglyceride can interact with the gluten protein to form a complex, that is, the hydrophilic group of the monoglyceride is combined with gliadin, and the lipophilic group is combined with the glutenin, which makes the processing process due to mechanical agitation. Scattered gluten protein molecules are connected to each other, and small molecules become large molecules, which then form a firm and 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 The interaction between monoglycerides and lipids
The α-crystal form of grease is the most unstable and has a low melting point, while the β-crystal form and β'-crystal form are both stable and have a higher melting point. The β'-crystal form of grease also has a good Processing performance.
In order to maintain the β'-crystal state of the grease, it is necessary to add a crystal modifier. When the monoglyceride and the oil are eutectic, the stable β'-crystal state can be obtained. The β'-crystalline grease has a high melting point, good plasticity and spreadability.
Monoglycerides can improve the cohesion between fats and the ability to combine with fats to form a crystal network structure, thereby improving the crystal crystallization of fats and improving the stability of fats, which is very beneficial for the production of heavy oil cakes and biscuits. It can prevent the occurrence of oil-water separation in the dough or products due to excessive storage time, that is, the occurrence of "oil leakage", which improves the storage period and ensures the quality.
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