Food glue is a very important and unique food additive. It has many important functions such as thickening, gelling, emulsifying, suspending, stable clarification, and serving as dietary fiber. It can be widely used in frozen food, beverage, dairy, and seasoning. Products, cakes, starch, candy, wine, food preservation and refrigeration.
1, the basic characteristics of food gel
1) Concept
Food glue, also known as hydrocolloid, hydrosol, is soluble or dispersible in water, and under certain conditions, hydrophilic groups in its molecule, such as carboxyl, hydroxyl, amino and carboxylate, can occur with water molecules. Hydration forms a viscous, slippery solution or gel that acts to thicken, thicken, adhere, gel, hardness, brittleness, tightness, stable emulsification, suspending, etc. in food processing. The food is obtained in various shapes and hard, soft, brittle, sticky, thick and other mouthfeel, so it is also often called food thickener, tackifier, gelling agent, stabilizer, suspending agent, colloid and the like.
2) Composition and structure
The main component of food glue is a macromolecular substance of polysaccharide or protein, and the basic composition of polysaccharide food glue is monosaccharide and its derivative. The chemical structure is a macromolecular polysaccharide formed by monosaccharide. It has different functional properties due to the type of monosaccharide, the degree of polymerization, the linkage and arrangement between sugar units, and the substitution of hydroxyl groups on the sugar unit. In terms of solubility, viscosity, fluid properties, stability of acid solution to acid and alkali and temperature, gelation ability and gel strength, compatibility of glue solution with other electrolytes, pseudoplasticity and synergy between various polysaccharides . Protein-based food gels are generally composed of amino acids, which directly affect and restrict their functional properties due to the arrangement of species, quantity and spatial structure.
2, food gel functional characteristics
1) Gelation
The role of food gelatin gel is that under the action of hydrogen bond, electric field polarization or some high-valent ions in solution, the long-chain molecules cross-link together to form and fix the liquid. The three-dimensional continuous network obtains a strong and rigorous structure to resist external pressure and ultimately prevent the flow of the system.
The degree of entanglement of the three-dimensional network, the number and properties of molecular cross-linking, the mutual attraction and repulsion of the various units forming the network, and the difference in function with different solvents form different gelling properties of various food gels. Some food gels are not gelatinous when present alone, but when combined with other gums, they exhibit thickening and gel synergistic effects.
2) Thickening effect
Almost all food gels have a thickening effect due to the hydration of their molecules. Different types of food gels have different thickening and rheological properties due to their own structure. The same kind of food glue, the greater the relative molecular mass, the greater the viscosity of the system with the same mass concentration.
The viscosity of food increased with the increase of its concentration, showing a certain positive correlation, but negatively correlated with the temperature of the system. Generally, the temperature rises and the viscosity decreases; the temperature drops and the viscosity rises. The food glue solution showed obvious different changes due to the electrolyte, pH and pressure of the system, which was mainly related to the structural difference of the food glue molecule itself.
3) Emulsification stabilization
After the food glue is added to the food, the viscosity of the system increases, the dispersed phase in the system is not easy to aggregate and aggregate, and the dispersion system is stable, and can be used as an emulsion stabilizer for juice drinks, beer foam, cake scent, etc., but it is not true. Emulsifier or blistering, which works in a manner that does not follow the hydrophilic-lipophilic balance mechanism of a typical emulsifier, but by thickening or increasing the viscosity of the aqueous phase to prevent or reduce the migration of dispersed oil globules and The aggregation tendency is completed.
4) Suspension dispersion
Most of the food gums are surface active and can be adsorbed on the surface of the dispersed phase to make them hydrophilic and easy to disperse in the water system. The addition of food glue to the food system increases the viscosity. According to Stokes' law, the greater the liquid viscosity, the slower the sedimentation rate of the particles, and the precipitation of solid particles can be delayed.
5) dietary fiber function
The vast majority of food gels can be used in foods to function as a functional health care for dietary fiber. In recent years, there have been many reports on the physiological effects of polysaccharides as dietary fiber in domestic and foreign countries, such as guar gum, pectin, konjac gum, chitosan and xanthan gum, which have significant effects as dietary fiber. Physiological effects.
Food gums are widely used as fat substitutes in the production of low-fat foods, therapeutic foods and health foods. At present, most of the fat substitutes are based on food glue or food gel as a key component.
6) Crystallization control
Many important properties in foods such as shape, brightness, chewiness and melting are directly related to the crystal structure.
There are three ways for food gel to crystallize:
1 compatibility: combined with the crystal, and attached to the surface of the growing crystal, changing the normal growth mode of the crystal;
2 Competitive: Competing with crystals to form crystals;
3 combination: combined with other substances, which in turn affect crystal growth.
Therefore, in confectionery, dairy products, and frozen foods, the expansion ratio can be increased, the possibility of ice crystal precipitation can be reduced, the product can be finely tasted, the melt resistance and preservation stability can be improved, and the shape and structure of the system can be improved.
7) Film and capsule action
The food glue is used as a filming agent to cover the surface of the food to form a protective film. Protect food from contact with oxygen and microorganisms. It can also be made into an edible film by the functions of quality preservation, preservation, fragrance or glazing.
In addition, it can also be used as an outer capsule for packaged foods, mainly using western ionized food gels containing different positive and negative charges to form complex compounds, and simultaneously forming a core material coated on the surface of the core material and coated with the core material. It can be released in food by physical pressure, pH or temperature changes.
8) Foam formation
The food glue can be foamed to form a network structure, and the solution can contain a large amount of gas when stirred, and is stabilized by the increase in viscosity of the surface of the bubble. The protein is heat-denatured, and the food gel and the hot syrup are mixed and stirred to cool, and the foam can be stabilized, or a gel reaction such as carrageenan, sodium alginate or locust bean gum can be used to form a stable foam product.
9) Fragrance fixation
The essence immobilization technology is to embed small droplets of essence in a water-oil emulsification system by using a suitable emulsifier to prevent evaporation of the essence when moisture is removed, to prevent oxidative deterioration or to absorb moisture from the air, and to embed the essence liquid. The droplets are dissolved or effectively dispersed into the aqueous medium, and the same aroma is obtained when the fragrance is released from the embedding membrane.
Encapsulate the essence with gelatin, put it in the gum, and release the fragrance after chewing. Gum arabic is currently the best carrier of all natural food gels or other substances. Sucrose, starch and its derivatives also have the function of fixed essence, but the effect is inferior to gum arabic.
10) Multiplication
There is a considerable amount of multiplication between many food gels. Various monomeric food gels have certain defects in the process of use, which is difficult to meet the needs of people and adapt to the increasingly fierce market competition. Through compounding, the complementary functions of various food gels can be exerted, resulting in "l+1>2". Synergistic effect, to meet the different needs of food production, expand the use of food glue, improve the use of functions.
11) Water retention stability
The food gel has a hydrophilic polymer and exhibits a strong hydrophilic effect, which can effectively improve the syneresis problem in food production or storage, and can also improve the structure and chewing taste.
12) Other functions
Food gum also has some other functional properties, including adhesion, bulk expansion, fat substitutes, flavoring, etc., which play an important role in the processing and improvement of many foods. Studies have shown that under certain conditions, food glue can be adsorbed on a plurality of dispersion medium bodies to coagulate, and can mask some bad odors.
3. Mechanism of action
1) Physical effects
The molecular structure of food gel contains many hydrophilic groups, such as hydroxyl, carboxyl, amino, carboxylate, etc., after hydration, it is uniformly dispersed in the solution to form a viscous colloidal solution, which slows the movement of protein molecules and reduces the binding of protein molecules. The probability and settling speed make it evenly and stably suspended in the system. At the same time, it can stabilize the suspended tissue, limit the metal ion activity, and avoid the aggregation and precipitation of food components.
2) Chemistry
The food gel macromolecule contains a hydroxyl group, a carboxyl group, an alkoxy group, an oxygen atom in a glycosidic bond, and an outer layer of a nitrogen atom in a peptide bond, all of which contain an sp3 hybrid orbital, and a lone pair of electrons not shared in the orbital may be partially associated with a water molecule. The positively charged hydrogen ions combine to form a hydrogen bond, and the bonding force of the hydrogen bond is extremely strong. When the cohesion between the molecular chains of the food gel is greater, the molecular chain of the food gel stretches, and the food glue molecules combine with water to form a long molecular chain, and are dissolved and dispersed in the water. Form a thermodynamically stable system.
The molecular stretching of the food gel fully exposes a plurality of groups, and each polar group and the polar water molecules are mutually restricted by hydrogen bonding or dipole force to form an inner water film. The inner layer of water is then associated with the outer layer of water. The bulk of the sol molecule acts as a skeleton, a large amount of water is bound, and the free movement of the medium is hindered to produce a resistance between the laminar flows, showing a viscous property.
4. Application of edible glue in food industry
1) Application in meat products
The addition of food glue to meat products not only improves the eating quality of meat products, such as color, flavor, texture, water retention and other functional characteristics, but also reduces production costs, and has great market application prospects and actual production value.
Carrageenan can improve the texture and slicing of the product in the high-temperature ham sausage, enhance the gelatinity of the meat protein, improve the water retention, and reduce the oil release.
2) Application in frozen foods
The addition of food glue to frozen foods can increase the viscosity, improve the gelation, prevent or inhibit the increase of the particle ice crystals, delay the appearance of ice slag, improve the taste, internal structure and appearance, and improve the stability and resistance of the system.
3) Application in gelatin candy
Gel candy has become a new hot spot for the development of candy because of its chewing ability, bite, non-sticking, non-cracking, low sweetness and low calorie. The food selected from the linear rubber particles is cemented into a large void network structure, and the soft sugar is elastic and tough by adsorbing more filler.
4) Application in beverages and foods
Agar and xanthan gum are good thickening and suspension stabilizers for beverage foods. They are used in small amounts to achieve the desired viscosity and levitation 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. Research reports that 0.1% propylene glycol alginate is applied to juice, which not only improves the stability of the pulp, but also makes the juice taste thicker, has a better taste, and also stabilizes the oil components in the juice.
5. Outlook
The development of China's food gel is still in its infancy. With the current development trend of food additives “natural, nutritious and multifunctional”, the mature application of modern biotechnology (such as enzyme engineering, genetic engineering), the full development of the efficacy of food gel will become possible.