Sodium carboxymethyl cellulose (CMC) is a kind of highly polymeric fiber ether obtained by chemical modification of natural cellulose. Its structure is mainly composed of D-glucose unit connected by β (1→4) glucoside bond. It is dissolved in cold water to form a viscous solution. The viscosity of the solution is related to the vitamin raw material DP (high, medium, low), and the concentration and dissolution conditions, for example: dissolving and applying high shear force to the solution, if the CMC is low DS, or the substitution distribution is uneven, then the gel aggregate is produced; Conversely, if the high DS and substitution are evenly distributed, a transparent and uniform solution is formed.

Other factors that can change the solubility and viscosity of CMC solutions are temperature, PH, salt, sugar or other polymers.

Temperature effects:
When the temperature of CMC solution is increased, the viscosity of the solution decreases (as shown in Figure 1). However, in the case of short heating time, when the temperature drops to the original temperature, the solution can recover the original viscosity. If the heating temperature and time are long (such as 125℃, 1 hour), the viscosity of the solution decreases due to the degradation of cellulose. This situation, such as food disinfection occurs
PH effects:
For CMC, the solution, PH acidic, is very sensitive, because CMC-NA will be converted to CMC-H, insoluble. In order to control the good solubility of CMC in acidic media, it is usually used to dissolve with high DS (0.8-0.9) and before adding acid.

Salt effect: CMC is an anionic type, can react with a salt to form a soluble CMC salt, bivalent or trivalent salt, then promote the formation of more or less network, or cause the CMC viscosity reduction, or cause gelation or precipitation, if the CMC is first dissolved in water, and then add salt, the impact is small.

Effects of other substances:
Changes are also caused by the addition of certain solvents, or others such as sugars, starches and gums.

Other properties:
CMC aqueous solution is thixotropic. CMC aqueous solution exhibits pseudoplastic behavior at high shear rate. Therefore, depending on shear rate, high-viscosity CMC solution can become even lower viscosity than medium-viscosity CMC solution.
The application of CMC in food

CMC-Na is mainly used in food as a thickener, stabilizer, etc., and can also help obtain the desired organizational structure, as well as the desired sensory properties. Due to these many functions, CMC is widely used in the food industry, which is now introduced in the following:

First, frozen dessert - ice cream - sugar water sorbet

In frozen products, a stabilizer should be added to keep the organization of the product stable to consumption. Among the many stabilizers, CMC is the most commonly used stabilizer for ice cream and other frozen products. The reason is that, first of all, when CMC is well dispersed, it can quickly dissolve in water, form the required viscosity, and can control the expansion well. Secondly, CMC, like other stabilizers, can control the formation of ice crystals, maintain a uniform and consistent organization, and maintain stability when the product is stored, even if it is repeatedly frozen/thawed. CMC is used in small quantities and gives excellent sensory properties (texture and taste).

In low-fat ice cream and milk sorties, CMC is reportedly mixed with 10-15% carrageenan to prevent separation of the mixture before freezing. With the decrease of fat content, the amount of CMC increases appropriately, and the greasy and slippery structure can be obtained.

CMC can also be used as a stabilizer for refreshing fruit juice drinks. In sugar water sorbet, CMC can release aroma and reduce the effect of masking color and flavor.

In frozen dairy products such as dry mix, about 0.2% CMC stabilizer can be added, and in syrup, the amount of CMC can be as high as 0.75~1%. In general, the amount of CMC added varies with the ingredients of the frozen product. In some countries, plant matter is used instead of milk fat, artificial sweet foods such as sorbitol are used instead of sugar in ice cream, and CMC can also be used.

Two, baked food

Baked goods include many kinds: such as special bread, various cakes, pies, fritters and so on.

In the production of bread, bread and other products, are dough as the base material, because CMC instant, can be quickly combined with different ingredients, quickly obtain sticky dough. In some cases, the use of CMC to adjust the ingredients, most of the water to be added more, per gram of CMC, water between 20 to 40, the amount of CMC varies with the product, generally 0.1 to 0.4% of the solid.

The addition of CMC to baked products can improve the uniformity of dough and the distribution of ingredients, such as raisins or crystal fruits. These ingredients can be evenly distributed in the product when baking.

In many cases, the added water can be maintained during baking to get soft products, even for a few days, so CMC can slow down the aging of products. Because the interior contains more soft particles, it usually shows an increase in product volume.

CMC can improve the tissue structure of fillings, supplements and icing, while avoiding the dehydration shrinkage of fillings and controlling the icing of sugar crystals. In soft products, CMC for structural stability, can be used alone, can also be used with other additives.
3. Soft Drinks

CMC is widely used in soft drinks to levitate juices, improve taste and texture, eliminate the formation of oil rings at bottlenecks, and shelter the undesirable bitter aftertaste of artificial sweeteners.

The effect of CMC in beverages is related to a series of parameters, such as CMC model, viscosity, CMC usage, soft drink type and ingredients.

In general, the addition order and homogenization of ingredients have little effect on stability. In another case, the CMC is added, preferably at the end of the production. This improves stability.

Although viscosity is not often the cause of juice suspension, it is often shown in 25°Brix juice drinks and is easier to stabilize than in immediately drinkable drinks with 7-10% soluble solids.

4. Dairy Products

There are two types of products: neutral products, such as dessert cream; Acidic products, such as yogurt drinks.

Neutral products: CMC can be added to make a variety of different structures of dessert cream, CMC can eliminate the dehydration of starch, carrageenan or CMC carrageenan, so it can be made to store stable whipped whipped cream.

Yogurt: CMC is used to make yogurt, which is very common, due to its anionic nature, which allows casein to react in the PH isoelectric point range (PH4.6) to form soluble heat treatment and storage stable complexes. Therefore, a range of products can be produced and stabilized: such as sour milk, beverages, buttermilk, dairy products, milk juice drinks, etc.

Special attention should be paid to achieving good stability. First, the amount of CMC added must be determined. This is related to the type of CMC (at the same equivalent ratio, the stability of the high viscosity type is better); Related to casein content ratio; Related to the PH value of the beverage; In relation to fermentation or acidification conditions, it can produce more or less casein aggregates. The consistency of the product is related to CMC ratio, fat, solid matter, and also related to mechanical treatment, such as homogenization under pressure, which can reduce the consistency but does not affect the stability.

Sour cream, sour milk, cream cheese jam, etc., can also add CMC stabilization.

CMC and other proteins can also form soluble complexes, such as soy protein, gelatin.

Salad dressing and various jams

CMC is used to make salad dressing, and it is easy to form emulsion, especially when it is stored for a long time under unsuitable temperature conditions, which can improve its stability.

Depending on the desired consistency and oil content, use medium-viscosity or high-viscosity CMC, the amount is between 0.5-1%. The production of salad dressing is made by gradually adding oil to the CMC water phase and stirring it. This operation method can be made directly, mix the ingredients well, disperse in water with a fork or whisk, stir for a few minutes, slowly add the oil to form an emulsion. When CMC is insoluble in the process, it is dispersed in the oil, under the action of high shear force, when the water phase contains other ingredients (such as egg yolk, vinegar, salt...). When emulsification is also formed.

CMC can be used for a variety of jams as deep frozen dish food. Because of the characteristics of CMC, different structures can be formed
(smooth, long or short), in particular, it has the ability to absorb water and prevent dehydration and shrinkage when thawing and reheating in the oven.

In tomato sauce, CMC is added to give the desired consistency and texture. The dosage is 0.5-1%, which decreases as the amount of M tomatoes used increases.

6. Whip whipped cream products

CMC can be used as a stabilizer for tissue loose (pore) products, from the stability of the effect of consideration, HPC foaming effect is excellent, when it and vegetable fat together to make foaming supplements, the effect is very good.

Its most significant stabilizing effect is to prevent the binding of caking and fat particles, to prevent the stratification of the liquid phase during storage, and to prevent shrinkage and dehydration shrinkage.

8. Other applications

CMC Other applications:
The calorific value of the CMC is low. Therefore, CMC is used to make low-calorie products.

In fast food, CMC dissolves quickly, giving a certain consistency and texture, which can suspend a certain component, such as coffee in chocolate drinks.

In meat products, CMC is used as a thickening agent for pouring gravy and to prevent fat separation. It also has bonding and water-holding effects to prevent the shrinkage of the sausage meat.