1 Overview ofGuar Gum
1.1 Sources of Guar Gum
Guar gum is mainly derived from the endosperm part of Cyamopissutrtragomolobus, an annual herbaceous crop widely cultivated in semi-arid regions of India and Pakistan. It also grows in Oklahoma and some African countries. Guar beans were used to make food additives after World War II. The current general production process is as follows:
Guar bean slices→add water and mix to soften→beaten into flocs→coarse grinding→fine grinding→high temperature hot air sterilization, drying→sieving→packaging
The classification of guar gum powder products is mainly determined by the particle size and viscosity of the processed gum powder. Generally speaking, the higher the viscosity, the finer the particle size and the higher the price. As the cheapest hydrocolloid, guar gum is very versatile. In addition to being used as a quality improver in food, it is also widely used in petroleum exploration, textile printing and dyeing, mining, papermaking, daily chemicals, medical health products, tobacco, blasting and other fields. Generally speaking, the quality of guar gum produced in India is better, followed by Pakistan, and the quality of guar gum produced in the United States is lower, and it is mostly used in the non-food industry.
1.2 Guar gum is a linear galactomannan, a non-ionic polymer. Structurally, D-mannan units connected to each other by β-1,4 bonds are in the main chain, and a single D-galactose is unevenly connected to the C6 position of some D-mannan units in the main chain. (α-1,6 bond) is a branched chain, and the ratio of galactose to mannose is about 1:1.8. The ideal guar gum structure has galactose branches evenly spaced on the mannose chain.
In fact, the distribution of galactose on the main chain of mannose is not uniform. In addition to the possible distribution in Figure 1, they have various non-uniform distributions similar to 'hair with many burrs', burrs It's the visual galactose.
1.3 Physicochemical properties of guar gum
Guar gum is a neutral polysaccharide with a relative molecular mass of about 200,000 to 300,000. It can be fully hydrated in cold water (generally takes 2 hours), and can be dispersed in hot or cold water to form a viscous liquid. The viscosity is between 4 and 5 Pa·S. The specific viscosity depends on the particle size, preparation conditions and temperature. It is the highest viscosity among natural rubbers. Generally speaking, more than 0.5% guar gum solution has the pseudoplastic fluid properties of non-Newtonian fluid, and has the effect of dilution. The aqueous solution of guar gum is neutral, and the pH change in the range of 3.5 to 10 has little effect on the properties of the gum solution. Generally, the viscosity decreases with the decrease of pH in the range of pH 3.5 to 6.0, and the viscosity is below pH 3.5. The viscosity of the solution can reach the maximum value in the range of pH 6 to 8, and the viscosity decreases rapidly when the pH is above 10.
Guar gum is a swelling polymer for which water is the only universal solvent, but is also soluble in water-miscible solvents such as ethanol with limited solubility. In addition, guar gum has good compatibility with inorganic salts, and the concentration of monovalent metal salts, such as table salt, can be as high as 60%; but the presence of high-valent metal ions can reduce the solubility. Under the condition of controlling the pH of the solution, guar gum can react with cross-linking agents, such as borates, metal ions, etc., to form a slightly elastic viscosity, and guar gum can also form a water-soluble film with a certain strength . Like other polysaccharides, guar gum and its derivatives degrade in acidic solutions at pH 3 or below, hydrolyzing the glycosidic bonds, resulting in a rapid loss of viscosity. At a slightly alkaline pH, the cleavage reaction at the β-position at the end of the chain reduction reduces the chain slowly, which is slower than acid hydrolysis. Guar gum can cause thermal degradation when heated to very high temperatures, and guar gum solution can lose viscosity when heated to 80-95°C for a certain period of time.
Guar gum is a straight-chain macromolecule. The hydroxyl groups on the chain can form hydrogen bonds with certain hydrophilic colloids and starch. Co-cooking of guar gum and wheat starch can achieve higher viscosity. Some linear polysaccharides, such as xanthan gum, agarose and kappa-type carrageenan interact to form complexes. Guar gum and xanthan gum have a certain degree of synergy, but there is no synergistic effect with carrageenan. This interaction is relatively weaker than that of locust bean gum. At low ionic strength, there is a synergistic effect of enhancing viscosity when combined with anionic polymers and anionic surfactants. These anionic compounds are adsorbed on neutral polymers and thus expand the molecules of guar gum. This is the result of mutual repulsion between the adsorbed anion-bearing functional groups. If an electrolyte is added, the introduction of opposing ions neutralizes the anionic charge and thus destroys the synergy.
2 guar gum uses in dairy products
Due to the high viscosity of guar gum, it is mainly used as a thickener, stabilizer, water-holding agent, etc. in the dairy industry, usually alone or in combination with other edible gums.
2.1 Ice CreamA small amount of guar gum does not appreciably affect the viscosity of this blend as it is made, but it imparts a slippery and waxy mouthfeel to the product. An additional benefit is that the product melts slowly and improves the product's resistance to thermal shocks. Ice cream stabilized with guar gum avoids the presence of particles due to the formation of large ice crystals.
2.2 CheeseIn soft cheese processing, guar gum controls the consistency and spreading properties of the product. Due to the water-binding properties of the glue, the product coats the cheese more evenly, potentially with more water. Guar gum has good stability to salts containing monovalent, divalent or trivalent cations. Increasing the sucrose concentration reduces the viscosity of the guar gum solution. Guar gum can have a strong adsorption effect with some linear polysaccharides, such as xanthan gum, agar, K-type carrageenan, etc., which greatly increases the viscosity.2.3 Yogurt
Guar gum is used in yoghurt products to thicken and stabilize, prevent product stratification and precipitation, and make the product rich in smooth and greasy taste.
2.4 Whipped cream
Guar gum has a very significant effect on the apparent viscosity of whipped cream emulsion; if the concentration of guar gum is too high or too low, the particle size of the thawed emulsion will become larger; the higher the mass fraction of guar gum high, the faster the coalescence of the fat globules, the greater the foam hardness; the whipping foaming rate decreased with the increase of the guar gum mass fraction.
3 Application of guar gum in flour products
The application of guar gum in noodle products mainly refers to dried noodles, instant noodles, etc. It mainly plays the role of bonding, water retention, and gluten-increasing force, which can improve the quality of noodle products and prolong the shelf life of the product.
In the production of dried noodles, guar gum can be said to be the most ideal binder. Adding 0.2 to 0.6% guar gum during the noodle making process can make the surface of the noodles smooth, not easy to break, and increase the elasticity of the noodles; during the drying process of the noodles In the middle, preventing sticking, reducing drying time, good taste, and the noodles made are resistant to cooking and continuous.
In the production of instant noodles, adding 0.3% to 0.5% guar gum, on the one hand, can make the dough flexible, and it is not easy to break when cutting into noodles, and it is not easy to form burrs; on the other hand, the colloid can change the surface of the noodles in contact with the oil The tension can quickly close the pores formed when the water evaporates in the noodles, so that it can prevent the infiltration of cooking oil during frying, saving cooking oil.
4 Application of guar gum in meat products
Guar gum is used in meat products such as ham, luncheon meat, various meatballs, etc., which can play a role in bonding, refreshing and increasing volume.
The addition of guar gum to sausages and stuffed meat products can quickly bind free moisture in minced meat, improve casing filling, eliminate separation and movement of fat and free water during cooking, smoking and storage, and improve cooling The firmness of the product; guar gum can reduce the bumping of meat and other accessories during the cooking process, control the viscosity of the liquid phase, and make the contents of the product easy to pour after the product is opened.
5 Application of guar gum in bakery products
Usually fresh bread and pastries will dry and hard after one or two days. Adding guar gum can make bread and pastries retain more pores, increase their volume, and retain moisture, so that they can remain in two to four days. Moisture and soft taste can significantly improve the quality of baked goods and prolong the shelf life.
6 Applications of Guar Gum in Condiments
Since guar gum produces high viscosity at low concentrations, its application in sauces and salad dressings, etc., can improve the organoleptic qualities such as texture and rheology of these products.
7 Applications in Industry
Printing paste: improve water retention, reduce the seepage phenomenon of hydrophobic fiber printing, and improve printing quality.
Petroleum industry: Special thickener, tackifier and suspending agent for fracturing oil wells in oil fields.
Construction putty: can improve anti-aging performance, increase leveling, and save costs.
Others: used in pharmaceuticals, cosmetic skin care, paper making, mining, etc.
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