Food glue is a very important and unique food additive. It has many important functions such as thickening, gelling, emulsifying, suspending, stabilizing and clarifying, and acting as dietary fiber. It can be applied to frozen food, beverages, dairy products, Condiments, pastries, starch, candy, wine making, food preservation and cold storage, etc.
1. Basic characteristics of food glue
Food glue is also called hydrophilic colloid or hydrosol. It can be dissolved or dispersed in water. Under certain conditions, the hydrophilic groups in the molecule, such as carboxyl, hydroxyl, amino and carboxylate, can interact with water molecules. Hydration forms a viscous, slippery solution or gel, which plays a role in thickening, thickening, adhesion, gel forming force, hardness, brittleness, compactness, stable emulsification, suspension, etc. in food processing. Foods require various shapes and various tastes such as hard, soft, crisp, sticky, and thick, so they are often called food thickeners, thickeners, gelling agents, stabilizers, suspending agents, gums, etc.
2) Composition and structure
The main components of food glue are polysaccharides or protein macromolecular substances. Polysaccharide food glues are basically composed of monosaccharides and their derivatives. The chemical structure is a macromolecular polysaccharide formed by monosaccharides. Because of the different types of monosaccharides, degree of polymerization, linkage and arrangement between sugar units, and the substitution of hydroxyl groups on sugar units, different functional properties are produced, which are mainly reflected In terms of solubility, viscosity, fluid characteristics, stability of the gel solution to acid, alkali and temperature, gel forming ability and gel strength, compatibility of the gel solution to other electrolytes, pseudoplasticity, and synergy and complementarity among various polysaccharides, etc. . Protein food glues are generally composed of amino acids, and their functional properties are directly affected and restricted by their type, quantity and spatial structure arrangement.
2, functional properties of food glue
1) Gel effect
The function of food glue gel is that under the action of hydrogen bond, electric field polarization force or the bond bridge of some high-valent ions in the solution, the long chain molecules of the hydrophilic colloid are formed by cross-linking each other and the liquid is wound and fixed inside. The three-dimensional continuous network obtains a firm and tight structure to overcome external pressure and ultimately prevent the flow of the system.
The winding degree of the three-dimensional network, the number and properties of molecular cross-linking, the mutual attraction and repulsion of the units forming the network, and the difference in interaction with different solvents, etc., form the different gelling properties of various food glues. Certain food gums are not gelatinous when they exist alone, but they exhibit synergistic effects of thickening and gelling when combined with other gums.
2) Thickening effect
Almost all food gums have a thickening effect due to the hydration of their molecules. Different types of food gums have different thickening and rheological properties due to their own structure. The greater the relative molecular mass of the same food gum, the greater the viscosity of the system with the same mass concentration.
The viscosity of food glue increases to varying degrees with the increase of its concentration, showing a certain positive correlation, but it is negatively correlated with the system temperature. Generally, as the temperature increases, the viscosity decreases; as the temperature decreases, the viscosity increases. The food glue solution is affected by the electrolyte, pH, and pressure of the system, showing obviously different changes, which are mainly related to the difference in the structure of the food glue molecule itself.
3) Emulsion stabilization
After the food glue is added to the food, the viscosity of the system increases, and the dispersed phase in the system is not easy to aggregate and agglomerate, which makes the dispersion system stable. It can be used as an emulsion stabilizer for fruit juice drinks, beer foam, pastry decoration, etc., but it is not true The emulsifier or foaming thorn, its mode of action is not in accordance with the hydrophilic-lipophilic balance mechanism of general emulsifiers, but by thickening or increasing the viscosity of the water phase to prevent or weaken the migration and migration of dispersed oil particles. It is done in a way of aggregation tendency.
4) Suspended dispersion
Most food gums are surface active and can be adsorbed on the surface of the dispersed phase, making it hydrophilic and easy to disperse in water systems. The addition of food glue to the food system can increase the viscosity. According to Stokes' law, the greater the viscosity of the liquid phase, the slower the particle settling speed, which can delay the precipitation of solid particles.
5) Dietary fiber function
The vast majority of food gums used in foods can also play the role of dietary fiber in health care. In recent years, there have been many reports on the physiological effects of polysaccharide edible gums as dietary fibers at home and abroad, such as guar gum, pectin, konjac gum, chitosan and xanthan gum, etc., all of which are used as dietary fibers* *Physiological effects.
Food glue as a fat substitute is more accurately used in the production of low-fat food, curative food and health food. At present, most of the fat substitutes are based on food gum as the main raw material or food gum as the key ingredient.
6) Crystallization control effect
Many important properties in food such as shape, brightness, chewiness and melting properties are directly related to the crystal structure.
Food glue has 3 ways to crystallize:
①Compatibility: Combining with the crystal and attaching to the growing crystal surface, changing the normal growth mode of the crystal;
②Competitiveness: compete with crystals to form crystals;
③Associativity: Combine with other substances, and then affect crystal growth.
Therefore, when used in candies, dairy products, and frozen foods, it can increase the expansion rate, reduce the possibility of ice crystal precipitation, make the product taste fine, improve the melting resistance and preservation stability, and improve the system shape and structure.
7) Coating agent and capsule action
Food glue is used as a coating agent to cover the surface of food to form a protective film. Protect food from contact with oxygen and microorganisms. It has the functions of quality preservation, freshness preservation, fragrance preservation or glazing, and can also be made into edible film.
In addition, it can also be used as an outer capsule for packaging food, mainly using western ionized food gels containing different positive and negative charges to form complex compounds, and at the same time form a micro-cell membrane covering the surface of the core material, which is covered with a fixed core material. It can be released in food through physical pressure, pH or temperature changes.
8) Foam formation
Food glue can foam to form a network structure. Its solution can contain a large amount of gas when it is stirred, and it is stable due to the increase in the viscosity of the liquid bubble surface. Using protein denaturation by heating, mixing food glue with hot syrup and then cooling can achieve foam stabilization, or using carrageenan, sodium alginate or locust bean gum to form a stable foam product.
9) Flavor fixation
Fragrance immobilization technology is the use of suitable emulsifiers to embed small fragrance droplets in the oil-water emulsification system. When the moisture is removed, it can prevent the fragrance from evaporating, prevent oxidative deterioration or absorb moisture from the air, and the embedded fragrance liquid The drops can be dissolved or effectively dispersed in the water medium, and the same fragrance can be obtained when the essence is released from the embedded film.
Encapsulate the flavor with gelatin, put it in chewing gum, and release the flavor after chewing. Gum arabic is the most important carrier in all natural food gums or other substances. Sucrose, starch and their derivatives also have the function of fixing flavor, but the effect is inferior to gum arabic.
Many food glues have a fairly obvious multiplication effect. Various monomer food glues have certain defects in the use process, which are difficult to meet people's needs and adapt to the increasingly fierce market competition. Through compounding, various food glues can play a complementary role, resulting in "l+1>2" Synergistic effect to meet the different needs of food production, expand the scope of use of food glue, and improve the use of functions.
11) Water retention and stabilization
Because of the hydrophilic polymer, food glue has a strong hydrophilic effect, which can effectively improve the syneresis in food production or storage, and can also improve the structure and chewing taste.
12) Other functions
Food glue also has some other functional properties, including adhesion, bulking, fat replacement, flavor correction, etc., which play an important role in the processing and improvement of many foods. Studies have shown that under certain conditions, food glue can simultaneously adsorb on multiple dispersion media to make it agglomerate, and can mask some unpleasant odors.
3. The mechanism of action of functional characteristics
1) Physical action
The molecular structure of food glue contains many hydrophilic groups, such as hydroxyl, carboxyl, amino, carboxylate, etc., which are evenly dispersed in the solution after hydration to form a viscous colloidal solution, which slows down the movement of protein molecules and reduces the binding of protein molecules. The probability and the settling speed of it make it evenly and stably suspended in the system. At the same time, it can also stabilize the suspended tissue, limit the activity of metal ions, and avoid agglomeration and precipitation of food ingredients.
2) Chemical action
Food glue macromolecules contain hydroxyl, carboxyl, alkoxy, oxygen atoms in glycosidic bonds, and nitrogen atoms in peptide bonds. The outer layer contains sp3 hybrid orbitals, and the unshared lone electron pairs in the orbitals can be part of the water molecule. The positively charged hydrogen ions combine to form a hydrogen bond. The bonding force of the hydrogen bond is extremely strong. When the cohesion between the food glue molecular chains is greater, the food glue molecular chains stretch, and the food glue molecules combine with water to form long molecular chains, which are dissolved and dispersed in water , Forming a thermodynamically stable system.
The expansion of food glue molecules fully exposes a variety of groups. Each polar group and polar water molecules restrict each other by hydrogen bonding or dipolar force to form an inner water film. The inner layer of water then associates with the outer layer of water. The extremely bulky sol molecules serve as the skeleton, and a large amount of water is bound, and the free movement of the medium is hindered to generate resistance between laminar flows, showing viscosity.
4. The application of edible gum in the food industry
1) Application in meat products
Adding food glue to meat products can not only improve the edible quality of meat products, such as color, flavor, texture, water retention and other functional characteristics, but also reduce production costs. It has huge market application prospects and actual production value.
The application of carrageenan in chopped high-temperature ham sausage can improve the texture and slicing properties of the product, enhance the gelling of meat protein, increase water retention, and reduce oiliness.
2) Application in frozen food
Adding food glue to frozen foods can increase viscosity, improve gel properties, prevent or ** microscopic ice crystals from increasing, delay the appearance of ice slag, improve taste, internal structure and appearance, and improve system stability and resistance to melting.
3) Application in jelly candy
Gel candies have become a new hot spot in the development of candies due to their good chew, chewy, non-sticky, non-tooth decay, low sweetness, and low calorie characteristics. The food with linear rubber particles is cemented into a large-voided network structure, and by adsorbing more fillers, the soft candy is elastic and tough.
4) Application in beverage and food
Agar gum and xanthan gum are good thickening and suspension stabilizers for beverages and foods. They are used in a small amount and can reach the required viscosity and suspension force at low concentrations, and are relatively less affected by temperature and pH. At room temperature It can maintain the relative stability of viscosity and suspension force, and maintain the taste and appearance of beverages and foods. Studies have reported that the application of 0.1% propylene glycol alginate to juice can not only improve the stability of the fruit pulp, make the juice thicker and have a better taste, but also stabilize the oil components in the juice.
The development of China's food glue is still in its infancy. With the current development trend of "natural, nutritious and multifunctional" food additives, and the mature application of modern technology (such as enzyme engineering and genetic engineering), the development of the efficacy of food glue will become possible.
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