Gums+&+Stabilizers

by Tan Lee Hoon
 * Gums & Stabilizers Q&A**

**1. What determines the structural, textural and shelf-life properties of food and beverages?** The structural, textural and shelf-life properties of food and beverages are affected by a broad range of hydrocolloid gelling agents, whose textures and sensory characteristics are determined by their chemical structures and molecular weight.

**2. Describe the structural properties of hydrocolloids. How do these properties affect their characteristics?** Hydrocolloids are mainly long-chain, straight or branched polysaccharides containing hydroxyl groups that can bond to water molecules. These chains can consist of 2,000 to over 10,000 monosaccharide units and can contain linked side units, or substituent groups, such as sulfates, methyl ethers, esters and acetals. Hydrocolloids can be neutral or anionic (negatively charged). The type and number of monosaccharides and their configuration, and the type, number and location of the linked groups are the factors that give each gum its particular characteristics.

**3. Give some examples of gelling hydrocolloids and their sources. Describe their respective characteristic texture.** Seaweeds || · Firm and brittle · Generally develop turbidity due to the microfibrillar structure of the gel network · Can undergo shrinkage and exude water on storage (syneresis) || · Kappa-carrageenan can undergo shrinkage and exude water on storage (syneresis) || · Gels can be soft or firm, depending on alginate type and calcium content, and tend to be very elastic · Calcium alginate can undergo shrinkage and exude water on storage (syneresis) || (by fermentation) || · Forms soft elastic gels in the presence of locust bean gum || · Can undergo shrinkage and exude water on storage (syneresis) ||
 * **Example of gelling hydrocolloid** || **Source** || **Characteristic texture** ||
 * Agar ||
 * Carrageenan ||^  ||  · Vary from firm to soft with varying degrees of elasticity, depending on type
 * Alginate ||^  ||  · Forms gels in the presence of calcium ions
 * Pectin || Citrus peel and/or apple pulp || · Forms soft, short-textured gels in high-sugar jams and confectionery jellies ||
 * Xanthan gum || Microorganisms
 * Gellan gum ||^  ||  · Firm and brittle
 * Locust bean gum || Ground endosperm of carob beans || · Forms soft elastic gels in the presence of xanthan gum ||
 * Gelatine || Collagen || · Completely stable soft gels of chewy texture and with melt-in-mouth properties that give favourable flavour-release qualities ||

**4. What are factors affecting a gum’s viscosity and hydration rate?** The viscosity and hydration rate of a gum is influenced by its chain length, or degree of polymerization (DP).
 * |||| **Hydration rate** ||
 * ^  || **Slow** || **Fast** ||
 * **Viscosity** || **High** || Long molecular chain ||  ||
 * ^  || **Low** ||   || Short molecular chain ||

**5. What is degree of substitution (DS)? Explain how the DS affects the hydration rate of a gum.** The degree of substitution or DS is defined as the number of side units per unit length of the monosaccharide chain. Higher degree of substitution causes more chains to be held apart from each other and prevents them from forming hydrogen bonds. Therefore the hydration rate is faster. The uniformity of this substitution also affects a gum's behaviour. Gums that are more evenly substituted are more soluble in cold water compared to gums that are substituted unevenly.

**6. What is the difference between plastic, pseudoplastic and thixotropic systems?** · Only moves after yield stress is applied · Exhibits a linear increase in rate of shear || · Does not require yield stress to move · Does not exhibit linear relationship between shear stress and shear rate · Exhibits shear thinning: Viscosity decreases with increasing shear, thus flow increases || · Only moves after yield stress is applied · Exhibits shear thinning: Viscosity decreases with increasing shear after a certain yield stress has been applied ||
 * **System** || **Application of yield stress** || **Flow behaviour of the system** ||
 * Plastic || Yes || · Does not flow immediately upon applying force or shear
 * Pseudoplastic || No || · Flows immediately upon applying force or shear
 * Thixotropic || Yes || · Does not flow immediately upon applying force or shear

**7. What are stabilizers? Why are they called "natural stabilizers"?** Stabilizers are polymeric carbohydrates such as gums, fibres and starches, as well as select proteins, that can stabilize a food system. Stabilizing ingredients help minimize water migration, prevent oil from separating, improve mouthfeel, provide suspension, increase viscosity, prevent ice-crystal development and more.

**8. Why there is a growing demand for natural stabilizers?** Consumers are more interested in natural than ever before, so there is definitely a growing demand for natural stabilizers.

**9. What is the typical usage level (amount) of gums in foods?** In general, the usage levels are very low, in the range of 0.5% to 1.0%.

**10. Proteins can also be used as food stabilizers. Give some examples.** Gelatine binds water; it provides a smooth, creamy texture and increases the viscosity of the product while contributing an attractive surface sheen. It forms a thermoreversible gel, which provides a melt-in-your-mouth sensation. These properties allow gelatine to function as a fat replacer in some applications, in particular cultured dairy products such as sour cream and yogurt.

Both milk and whey proteins function as natural stabilizers, as they have the ability to bind water in a food application and hold it throughout heating and other processing steps. For example, many yogurts rely on stabilizers such as gelatine and modified starches to add structure and mouthfeel and reduce syneresis over time. It is possible to achieve the same benefits with added dairy proteins in the form of non-fat dry milk or whey protein concentrates.

The proteins in eggs also function as stabilizers in various food systems as a result of their ability to coagulate. When heated or exposed to acid, egg proteins change from a liquid to a semi-solid or solid state. This transformation assists with the binding of ingredients, including water, in complex food systems, preventing products from crumbling, losing shape or simply falling apart.

Eggs are an ideal all-natural stabilizer for ice cream. The phospholipids, lipoproteins and proteins found in egg yolks are surface-active agents that stabilize the ice cream system by dispersing the milk-fat throughout the ice cream mix, preventing it from clumping. Egg yolks in ice cream also help control density, hardness and texture by encouraging the formation of small ice crystals.

**11. What are the steps that can be taken to prevent coalescing?** Making droplet surfaces less attractive and increasing the viscosity of the continuous phase to limit droplet movement.

**12. What is HLB?** HLB refers to an emulsifier’s hydrophilic-lipophilic balance (HLB), which measures its solubility in water versus oil. The emulsifiers' solubility in water and oil is a function of temperature, as described by the phase-inversion temperature (PIT). When creating an oil-in-water emulsion, it is best to choose an emulsifier on the high end of the HLB scale (8 to18) as opposed to a water-in-oil emulsion requiring an emulsifier with a lower HLB (3 to 6).

**13. Describe polyols and their functions in food systems** Polyols, also called sugar alcohols, are used as reduced-calorie sweeteners and bulking agents in reduced-sugar or low-carbohydrate applications. They cover a wide range of solubility and sweetness, and are also differentiated by properties such as calorie content and cooling effect. Several polyols make excellent humectants, a characteristic that can control texture.

**14. How do gums help extent a product’s shelf life?** Gums help extent a product’s shelf life by first improving moisture retention in the food system. This is because gums can limit the amount of ice-crystal re-growth in frozen foods, thus preventing further damage to fragile cell walls, or incorporated air such as found in ice cream. Gums also provide emulsification necessary for product stability in products such as beverage emulsions and salad dressings. Proper stabilization will allow for extended shelf life, create more visually appealing products and creamier mouthfeel.

**15. Explain how hydrocolloids affect a product’s texture.** Hydrocolloids impact product texture through their relationship with water. Hydrocolloids are water-soluble macromolecules with high molecular weight consisting of hydrophilic long chains. They change the rheological properties of the aqueous systems to which they are added by increasing the viscosity or form a network of molecules to provide a gel texture. In water-limited systems, hydrocolloids reduce moisture loss or migration by lowering water's mobility. Because gums are efficient water binders, they are able to control the movement of water that occurs during freeze/thaw cycling of frozen foods. This prevents water from accumulating and forming large ice crystals in the product. This can also be compared to staling in bread, where dehydration contributes to starch retrogradation. The ability of gums to delay this loss in moisture helps to increase shelf life.

**16. How does cooking affect the structures of amylose and amylopectin in starch?** The linear amylose will tend to gel or form crystalline regions while the highly branched amylopectin creates viscosity when it is cooked.

**17. What are the primary causes of staling in bakery products? What steps can be employed to slow the rate of staling?** The two primary causes of staling in bakery products are crystallization and moisture loss.

Starch crystallization can be controlled by: a. Providing ingredients that will interfere with starch crystallization, or retrogradation. E.g. using crumb softeners like distilled monoglycerides, sodium stearoyl lactylate (SSL) and calcium stearoyl lactylate (CSL). Those are crystallization-retarding or -interfering types of agents; or b. Using enzymes that break up the starch molecule, reducing the size of the starch molecules and their impact on hardening. Enzymes have a more long-term effect, whereas the effect of emulsifiers can be seen upon cooling.

Moisture loss in baked products can be reduced with the help of hydrocolloids and humectants, which slows staling and maintains texture. Some polyols, such as sorbitol, are commonly used in baked applications because they provide excellent humectancy. This helps to extend shelf life by controlling staling and maintaining a moist texture during the wide range of conditions a baked product can experience before it reaches the consumer.

**18. What is syneresis?** Syneresis is the expulsion of water from a gel as it loses its water-holding capacity.

**19 What are the three mechanisms for suspending particulates in food systems using ingredients as stabilizers?** a. Specific electrochemical interactions. E.g. the stabilization of casein micelles by pectin in an acid milk drink such as a smoothie. The net negatively charged pectin chains will be attracted to the net positively charged casein micelles. The attraction will cause the casein to remain suspended in solution, instead of clumping and precipitating to the bottom of the container. b. Increasing the viscosity of the food system. E.g. the suspension of blueberries in a muffin batter. A xanthan gum and guar gum blend develops a synergistic relationship that creates a weak gel in the batter, enabling the blueberries to remain suspended and more evenly distributed throughout the batter, giving a more consistent and more attractive finished product. c. Forming a strong gel network. E.g. the suspension of strawberry pieces in strawberry preserves. A strong gel is formed through cross-chain interactions between pectin molecules. Through the use of proper formulation and processing conditions, the strawberry pieces will be evenly distributed throughout the jar of preserves.

**20. Is the level of hydrocolloids used in food systems important? Explain.** Proper hydrocolloid use level is important. An example is the use of carrageenan in chocolate milk products. Too much carrageenan will over-stabilize the milk and cause gelation, whereas too little can cause settling. During processing, if the filling of chocolate milk into a bottle is done above its gelling temperature, not all the cocoa particles would have been fully trapped in the gel matrix during the slow process. This can cause dusting or settling of the cocoa. Conversely, if a gel matrix is set in the balance tank and then filled into a milk bottle or the finished container at too low a temperature with too much shear, this can also break that matrix down.

**21. Explain the undesirable effect(s) that may arise if the increase of viscosity for suspension purposes is not employed at the right usage level.** Adding too much viscosity can often impart a negative mouthfeel to the product. E.g. in soups, thickening carrageenans, guar gum and locust bean gum can help suspend particulates by adding viscosity. Xanthan gum offers a lot of suspension power due to its helical structure, but too much of it will give a slimy mouthfeel. It is helpful to blend the xanthan gum with a thickening carrageenan, guar gum or locust bean gum, because these ingredients will add viscosity, which supports particulate suspension.

**22. What is the main concern that needs to be considered when formulating sauces?** All sauces have high moisture content. Control of this water is important to design a successful product and requires careful selection of a stabilizer system.

**23. What are the aspects in the production of sauces that may affect the performance of stabilizers?** The two aspects in the production of sauces that have the greatest effect on their performance are temperature and shear. a. Temperature: Heat is especially destructive to starch, particularly those types without crosslinking. As the temperature and time of exposure increase, the starch granule swells until it fragments, loses viscosity and creates a long, stringy texture. Most gums are heat-thinning but will regain viscosity to a certain extent once cooled. Almost all sauces require a cooking step for microbial control, stabilizer functionality and flavour development. Different processes will contribute varying levels of stress. b. Shear: High shear can be encountered in the heat exchanger, especially with methods such as pasteurization or steam injection. Sauces also experience shear in pumping and filling operations. The shear varies with the type of pump used: a positive displacement pump will create less abuse than a centrifugal pump. While high shear can destroy the starch granules and permanently change the viscosity of the finished product, it may only have a temporary effect on the gums used. Many hydrocolloid gums are shear-thinning, losing viscosity only under the influence of shear. Once the shear ceases, these gums return to their normal viscosity. This can provide advantages in heating and filling operations.

**24. What is instant gelatine? How does it differ from normal gelatine? Briefly describe the characteristics of instant gelatine.** Instant gelatine is a powder that dissolves in cold water without any up-front preparation. Instant gelatine consists of pure gelatine without any additives. It has only one glass transition (characteristic of amorphous structures), which gives instant gelatine its characteristics.

Instant gelatine hydrates rapidly and intensively because of its amorphous structure. The molecules' three-dimensional structural network is only loosely cross-linked, and the molecular arrangements are coincidental and chaotic, with weak inter- and intra-molecular binding forces. The gelatine particles attract water and continue to hydrate until all available water is absorbed into the structure. This forms a gel-like texture which is not in fact as hard as its physical and chemical data would suggest. The gels are also slightly turbid, resulting from phase boundaries producing weak points in the overall gel structure.

Gelatine solutions possess viscoelastic properties. If the viscosity properties predominate, a sol is formed; if the elastic properties predominate, a gel is formed. Instant gelatine falls into two main categories, namely acid-based (type A) and alkali-based (type B). Protein content in both types falls into the 94% to 96% range. Each has different physical-chemical properties.

-Relatively stable within the pH 3.0 to 6.0 range -Hardness is reduced only at higher values || -IEP between pH 4.8 to 5.5 -Lose gelling power as pH falls || -Higher hardness -Lower cohesiveness -Higher degree of gumminess || -Higher densities -Lower hardness -Higher cohesiveness -Lower degree of gumminess || IEP: Isoelectric point
 * **Characteristics** || **Type A** || **Type B** ||
 * Bloom value || -Higher-bloom (270 to 310) instant gelatine begins to harden almost immediately || -Lower-bloom (220 to 260) product hardens after three to four minutes ||
 * Particle size distribution |||| A similar product of different particle size shows the same traits; however, hardening decelerates as the mean particle size distribution increases, and final hardness is reduced despite the same binding time ||
 * Mean particle size ||||^  ||
 * pH || -IEP between pH 8.5 and 9.0
 * Foam formation || -Forms lower-density (lighter) foams || -Forms higher-density (heavier) foams ||
 * Overall || -Lower density

**25. Briefly describe the structure of pectin and the main types of pectin.** Pectin is a polymer containing galacturonic acid units (at least 65%). The acid groups may either be free, combined as a methyl ester, or as sodium, potassium, calcium or ammonium salts, and in some pectins amide groups may also be present. a. High-methoxy pectin: Pectin with more than 50% methyl ester groups or degree of esterification (DE). b. Low-methoxy pectin: Pectin with less than 50% methyl ester groups or degree of esterification (DE). c. Amidated pectin: Pectin which is treated with ammonia during manufacture.

**26. What are the legal requirements for products such as jams, jellies, and marmalade with respect to soluble solid content?** Total soluble solids content in these products is approximately 78%.

**27. What is gum arabic?** Gum arabic is the dried, gummy exudation obtained from various species of Acacia trees of the Leguminosae family.

**28. In what respect gum arabic is different (unique) compared to other gums?** Gum arabic is unique among the natural hydrocolloids because of its extremely high solubility in water. Most common gums cannot be dissolved in water at concentrations higher than about 5% because of their very high viscosities. However, gum arabic can yield solutions of up to 50% concentration. At these high levels, it can actually form a highly viscous, gel-like mass similar in character to a strong starch gel. In addition to forming high-solids gels of this type, gum arabic can be used at much lower concentrations in combination with other gums as thickeners and binders.

Gum arabic is insoluble in oils and in most organic solvents. It is soluble an aqueous ethanol up to a limit of about 60% ethanol. Limited solubility can also be obtained with glycerol and ethylene glycol. Whereas most gums form highly viscous solutions at low concentrations of about 1-5%, gum arabic is unique in that it is extremely soluble and is not very viscous at low concentrations. High viscosities are not obtained with gum arabic until concentrations of about 40-50% are obtained.

The viscosity of gum arabic solutions will depend upon the type and variety of arabic used. At concentrations up to 40%, gum arabic solutions exhibit typical Newtonian behaviour. Above 40%, solutions take up pseudoplastic characteristics as denoted by a decrease in viscosity with increasing shearing stress.

**29. Why gum arabic is very important for the food industry?** Gum arabic has the ability to form highly concentrated solutions which are responsible for the excellent stabilizing and emulsifying properties of this gum when incorporated with large amounts of insoluble matters. Since g um arabic is available in various forms such as tears, crystals, granules, powder (by mechanical process), spray- and roller-dried powder, it is useful in many food industry applications.

For example, gum arabic is used widely in the confectionery industry to retard or prevent sugar crystallization and to emulsify the fat and keep it evenly distributed throughout the product. a. Prevention of sugar crystallization: Gum arabic finds its greatest application in confections in which sugar content is high and moisture is low, e.g., in jujubes and pastilles. With these products, the technique of incorporating the flavours is extremely important. Usually, the gum arabic is dissolved in water and the solution is filtered, mixed with sugar, and boiled. The flavour is added with a minimum of stirring to prevent formation of bubbles or opaque spots. b. As a fat emulsifier: is essential to keeping fat distributed uniformly throughout an easily oxidizable, greasy film. This property makes gum arabic extremely useful as an emulsifying agent in caramels and toffees.

The emulsification properties of gum arabic are also utilized in various liquid flavour emulsions. Many citrus oils and other beverage flavour emulsions utilize the emulsification properties of the gum. When used as a flavour fixative, the superior film-forming ability of gum arabic makes it ideal for protecting the flavour from oxidation, evaporation and absorption of moisture from the air.