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Wednesday, April 25, 2012

FOOD PRODUCT DEVELOPMENT: Tricks for Taming Texture

From dispersion to viscosity control, optimizing product mouthfeel requires an understanding of ingredients 

Getting the most out of hydrocolloids requires well dispersed ingredients during processing.

"No man is an island." This psychological tidbit is also apropos for food ingredients, including thickeners and other texturizing agents, that interact together and with other components in a food or beverage matrix. 

As experienced, hands-on product developers know, knowledge of ingredient functionality is critical in an efficient development process. However, with the plethora of ingredients available, even experienced formulators run into situations where a bit of troubleshooting is needed. Here are solutions to some of the more common difficulties impacting product texture.
Dispersion: The Biggest Challenge
"The dispersion or dissolution of gums is generally the biggest problem people have with hydrocolloids," says Varsha Vaishnav (Ph. D), application manager, Degussa Texturant Systems, Langhome, Pa. Depending on the application and equipment available, three common tactics address this challenge. 

First, gums can be pre-mixed with sugar or salt, preferably in a ratio of one to two or three parts gum to sugar. The maximum amount of water (as allowed by the formula or equipment) is added under a good vortex. This method is applicable for dairy products, soups, fruit preps and most products that contain an adequate amount of water.

Another tactic, typically used for products such as dressings, involves adding the gums to oil to disperse and then adding the resulting mix to water. Less agitation is required than pre-blending gums with dry ingredients. However, since most gums have minimal hydration under a pH of 5.0, hydration should occur under as neutral conditions as possible before an acidifier (e.g., vinegar) is added.

A third alternative is to add gums to sugar syrup such as HFCS 42 (or syrup with similar viscosity), and then add this mix to water such that the total soluble solids do not exceed 20%. Hydration is expedited by heating the mix (~65°C). The remaining ingredients are then added. Preferably, setting salts and acidulants are added at the end of processing under good agitation. This approach is applicable for dairy desserts, jams and jellies, for example. "The preferred method, however, is to incorporate hydrocolloids just with agitation," says Vaishnav. "Dairies use Likwifiers, which work beautifully."

Competition for water also impacts the hydration (i.e., gelation) of starches, another hydrocolloid category. Sugars, salt, dextrose and other soluble ingredients that raise the total solids of a solution will negatively effect gelatinzation, that is, longer times or temperatures will be needed, notes Monica Zelaya, technical service supervisor, National Starch & Chemical, Bridgewater, N.J.

One Plus One is Three

The ability to make one and one add up to more than two maximizes valuable viscosity-enhancing ingredients. Xanthan gum, for example, can complex with galactomannans such as guar, locus bean or tara gum. One supplier advises that maximum viscosity is reached when the galactomannan to xanthan gum ratio is about one to one. The maximum synergy is reached anywhere between 60:40 to 40:60, so for all practical purposes you may choose 50:50 ratio, notes Vaishnav. Other ingredient properties determine how much of an advantage can be taken of this synergy, however. Under lower pHs, guar gum tends to depolymerize, resulting in less viscosity over time within some finished products.

"Starches are synergistic with iota, lambda and especially the kappa fraction of carrageenans," says Zelaya. Viscosity or firmness is especially maximized when the starch-carrageenan combination is used in protein systems such as meat emulsions (e.g., lowfat sausage-type products) or dairy products (e.g., chocolate drinks).

Other synergistic combinations include carrageenan with locust bean gum and pectin with alginates, adds Vaishnav. The pectin-protein interaction in products, such as a soy or milk drink, is complex. "High-methoxyl pectins should be used when the pH of the beverage is below the proteins isoelectric point (IP) which occurs at about pH 4.6," says Vaishna. Components stay in suspension due to hydrophobic interaction between protein and pectin and due to electrostatic interactions between pectin and protein. Flocculation occurs when the system is above the protein's IP. The process is somewhat complex. The most important point is that the pectin must be hydrated completely and the product must be homogenized after the protein and pectin are mixed, she advises.

Thick and Thin...When Needed

A loss of or lower than expected viscosity of a product can be due to many factors. Microbial contamination can hydrolyze starch (not necessarily with obvious off-odors) or proteins in refrigerated products such as puddings and sauces.

One formulator noted that high chlorine levels in the water caused modification of starch during a product's cook cycle. The "modified" starch resulted in a thin product over storage time.

Depending on starch type and certain other factors, emulsifiers and other surfactants may reduce the viscosity contributed by starch.

For acidic systems, xanthan, pectin, alginates (depending on the pH) and certain CMCs are appropriate. Whey proteins are generally more acid-resistant than caseinates, which in turn are more heat-resistant than whey proteins. "Gelatin, carrageenan and the galactomannans do better in neutral to only mildly acidic conditions," says Vaishna.

Salt can also interfere with some hydrocolloids such as CMC.

Reduced viscosity can be desirable, such as during heat-treating products (pasteurization or retorting) or while pumping and filling a product. A low viscosity improves heat transfer and handling, but the end-product may require a thicker consistency. The use of starch in conjunction with carrageenan is one solution because viscosity tends to increase during product storage.

Non-texturing Ingredients

Functional ingredients added to products for reasons other than viscosity or texture control can have significant impact on these attributes.

For example, products fortified with certain nutritional ingredients can increase in viscosity. (See sidebar on Thickening Nutrients.) Suppliers offer protein ingredients, whether plant or animal, for their ability to gel and otherwise change texture. A textured vegetable protein, however, not only adds the appearance and some of the nutrition of meat to a product, but also functions as a sponge to soak up excess moisture. When the moisture is "flavored," such as juice drained from canned tuna in the formulation of a tuna salad, the products flavor can be enhanced overall.

Other viscosity enhancers include fruit and vegetable purees or powders, including seasonings, particularly those with high fiber content. Powdered onion absorbs about five times its weight in water. Generally, as particle size of such ingredients increase, water absorption decreases.

One product developer noted that vegetable pulp increased protein coagulation when the dairy system into which it was placed was heated. She theorized that the suspended pulp particles adsorbed protein on their surface, which reduced protein stability and denaturation occurred.

Thus, as with ingredients and people, the best way to make it through situations, both thick and thin, is with a companion. PF

Thickening Nutrients 

Certain nutritional ingredients can impact the texture of a dietary supplement or food product. Chitosan, which is derived from a cellulose-like compound called chitin, and prebiotics, such as oligosaccharides, increase a product's viscosity depending on their concentration and length of molecules. (The short prebiotic raffinose molecule shown here would add little viscosity.)

"Inulin can contribute 'fat mimetic' properties to create a texture from a soft cream to a margarine-like consistency. But the concentration must be fairly high, some 30% in the latter case," says Kathy Niness, vice president, Orafti Active Food Ingredients, Malvern, Pa. Higher DPs (degree of polymerization) translates to higher viscosity.

Bagel Challenge: The Right Bite 



Technical journals generally support the view that sensory measurement is the only way to measure texture, even as the instrument industry claims that objective texture measurements can simulate sensory perception. Both sides can be argued. However, what is certain is that while the methodology to measure texture may be simple, characterizing and defining textural attributes is not. The best approach is a combination of subjective and objective measurements that serve as directional tools. In the end, consumers make the final analysis of any product texture as evidence by its success. 

In the development process, ingredient selection such as types of flour, fat, emulsifier, starch and gum play a significant role in product texture. However, their combination and the specific processing techniques are equally critical.

A sandwich bagel is a typical example. Desired textural attributes may be a crispy exterior (crust) with a slightly tough/chewy bite (crumb) that dissolves quickly upon mastication, that is, without sticking to teeth. Although a plain bagel has a simple, "lean" formula, which is generally composed of flour, water, sugar, salt, dough conditioners, and yeast, the desired textural attributes make the development process complex.

Ingredients: Product formulators often start with different types of wheat flours with varying protein content. A higher protein content produces a chewier bagel, but may result in other issues such as tighter dough that is difficult to process through forming machines. Dough tightness is reduced through use of dough conditioners, humectants and other ingredients. A good formulator speculates what will happen when specific oxidants and reducing agents are used in combination with each other and/or with high-protein flours. For example, ascorbic acid may be used as an oxidant to achieve a chewy bagel, but reducing agents (e.g., sulfites or cysteine) will soften the tight dough for handling through processing steps.

Processing: The project becomes even more complex as the dough passes through multiple processing steps. Generally, bagel dough is formed, proofed, boiled and baked. Specific processing parameters are determined by the developer's past experience and from values derived through experimental design. For example, setting the proof time and height, boiling water temperature and time and percent starch to be removed from a bagel's surface requires a thorough understanding of the effect that each step has on the dough mass. All parameters are important--from the beginning ingredient selection to final processing in that a "chain reaction" occurs where each step impacts the outcome of the next. The desired texture is obtained through controlled sets of experiments in combination with subjective and objective measurements, including experienced palates providing feedback to the product developer.

The happy conclusion comes when the product hits consumer shelves with great success.