For example, carrageenans are used to create gels of varying textures: firm and brittle to soft and elastic. “They can hold water very well under the right conditions or they can be designed to give up water,” says Doug Rector, group leader of functional ingredients at a hydrocolloid supplier.
Hydrocolloids act through hydrogen bonding to attract and maintain a layer of water surrounding the hydrocolloid molecule. “Wherever the molecule goes, it 'takes' this layer of water with it,” explains Leslie Lynch, business development manager at a hydrocolloid supplier.
The water-binding function of hydrocolloids allows them to provide viscosity and/or a thicker, richer mouthfeel and to prevent syneresis. Hydrocolloids can minimize syneresis in applications such as fruit preparations for yogurt, dairy desserts, cream cheese and sour cream, says Lynch. Carrageenans help to prevent syneresis in poultry and ham applications by binding water.
Salty Situations
The gelling characteristics of carrageenans are controlled with the addition of several types of salts, including potassium, sodium and calcium chloride. A wide variety of textures can be created by manipulating a carrageenan with the right combination of salts. Certain salts create very firm and brittle gels with high melting points that may tend to release water. Other salts produce weaker gels with much lower melting points, while salts with even lower melting points could potentially form elastic gels.The advantage of having a low melting point depends on processing conditions and how the carrageenan will be used in the products. “We've had a number of customers that wanted the gel to melt,” says Rector. For instance, when used as a fat substitute in a low-fat hamburger, the hydrocolloid mimics the melting characteristics of fat. Carrageenan usage in reduced-fat hamburger is one example where it is used to provide both mouthfeel and water binding. “It won't turn out exactly the same [as a full-fat hamburger], but it does give that impression.”
Along with low-fat processed meats, gums can help to replace the mouthfeel associated with fat in foods such as low-calorie dressings and low-fat yogurt. A carrageenan with a higher melting point is necessary for gelatin replacement in ready-to-eat snacks like gelatin products and for shelf-stable products that do not have to be refrigerated.
Most hydrocolloids are not classified as emulsifiers, but they hold emulsions together. The thickening or gelling properties will slow down creaming or coalescence of fat particles. In coffee creamers, cheese and Alfredo sauces, carrageenans provide a full-body mouthfeel.
The Milky Network
Carrageenans have high protein reactivity. Casein, a milk protein, works especially well with carrageenans. By way of electrostatic interactions with proteins, carrageenans reduce the settling of cocoa particles in chocolate milk-type products. When designed properly, the interaction with the milk proteins forms a very weak gel network, which suspends the cocoa particles in chocolate milk. “You obviously don't want it to appear as a gel. The network is so weak that when you pour it, it basically falls apart. It is not really perceptible, but it's there,” explains Rector.“It's a balancing act between having too much interaction, in which case the proteins will drop out and a small amount of serum will form on top of the milk; and no interaction, causing the cocoa to fall,” says Rector. Both scenarios are visually unappealing. “You really have to be cautious about both the processing conditions and the appropriate choice of carrageenans for that.”
There are few limits by which formulators should use hydrocolloids (21 CFR 172.620 and 21 CFR 172.626). “They are not limited from a health stand point. The limits are dictated more by how much needs to be added to achieve functionality in the product,” says Rector. “You wouldn't want to gel your chocolate milk.” In addition to the practical concerns, a formulator should check the standard of identity for specific end products to ensure these types of materials can be used.
Outside of its gel suspension capabilities in chocolate milk, carrageenan, in general, is used at extremely low concentrations (0.1-0.3%) as a thickening agent. Another use of carrageenan is holding together the food pieces in gel-type pet foods.
Flavor release on carrageenan gels is quite good. “They don't generally absorb, hold or mask flavors,” observes Rector. In most applications, the inherent flavor of carrageenan will not come through.
Carrageenans in Class
The three classes of carrageenan, kappa, iota and lambda, provide a range of characteristics. Kappa gels have to be heated to specific temperatures, depending on what other materials one is using. They can form hard and brittle gels.A kappa-carrageenan contains the fewest number of sulfated units. This allows the k-carrageenan to make a gel network that captures casein micelles, forming a stronger gel that allows for very low carrageenan usage rates in dairy applications, notes Lynch. However, this alignment makes the gel more prone to syneresis (kappa is 35% 3,6-AG and 25% ester sulfate). At 1.5%, kappa has a low viscosity of 50 centerpoise (cP, a measurement taken with a Brookfield viscometer to measure the thickness of a solution), forms a gel at 45-65°C and re-melts at 10-20°C above gel temperature.
When used for suspension characteristics, as in the chocolate milk scenario, the only carrageenan that really works is kappa (because of its reactivity with milk proteins).
In meat applications, k-carrageenans most often are used in both injection processes and tumbling. Usually added to the brine to be injected, they create a gel network that binds water and prevents syneresis, improving the yield and sliceability of the poultry or ham.
Iota-carrageenans tend to have weak gel strength and a very elastic characteristic. They mostly are used as thickeners. The iota form has more sulfated units, hindering the ability of the individual carrageenan strands to align. This creates a gel with less firmness, more springiness and, subsequently, less syneresis since water can be trapped within the gel where the sulfated units are creating space. (Iota is 30% 3,6-AG and 32% ester sulfate).
Lambda-carrageenan has the highest amount of hindrance, which does not allow the carrageenan to gel but to act only as a thickener (lambda is 35% ester sulfate with no 3,6-AG). In a 2% solution, it can produce a viscosity of 600+cP. Carrageenans supply additional structuring in low-carb bread products when starch is removed. They also work well as freeze/thaw stabilizers in frozen dough and ice cream.
Blends of carrageenans with proteins or starch can provide more function than utilizing carrageenans alone. Mintel's (Chicago) Global New Products Database notes that Kraft Foods (Glenview, Ill.) utilizes carrageenan and casein along with xanthan and locust bean gums in DiGiorno's Reduced Fat Alfredo Sauce launched in February 2004. Carrageenan also has a synergy with starch in puddings. There are interactions with a variety of proteins and starches, but hydrocolloids also interact with one another.
Synergistic Relationships
“Often, one gum alone won't do everything that you want it to. Some of the negative stigma that can be attached to gums is partly because people try to solve everything with one particular gum,” says Greg Andon, business development manager at a hydrocolloid supplier. “But, if you start combining two to three gums together in the right combinations, you can hit all the targets that you are looking for--not only for stability, but also for texture.”For example, xanthan gum is an amazing ingredient which repeatedly has proven to have excellent suspension capabilities with spices and particulates in salad dressings. It has a very high yield point, helping to hold emulsions together--an additional reason why it is used in salad dressings.
At the same time, higher usage levels of xanthan gum will result in a texture that is very “gloppy” or “snotty,” says Andon. If formulators blend xanthan, which measures between 1200-1600cP at 1% in water, with locust bean gum (approx. 2500cP at 1% in water), put them into solution and heat it to activate the LBG, it results in a gel. “By themselves, neither of them are gelling agents. They are just thickeners. Add them together and you actually get a true gel,” reveals Andon. The soft gel from that synergy is something that is used often in the cream cheese market. Don Pinos' Cream Cheese with Mango by Webeco Foods (Miami) has xanthan, locust bean and guar gum in its formulation, which is imported from Costa Rica.
Another synergy involves the viscosity of guar and xanthan gums which--when blended together--is greater than the expected viscosity of adding xanthan and guar together. The presence of xanthan helps to protect guar gum, which does not have good pH stability, but performs a little better in the presence of xanthan.
Not all gums form synergies. For instance, carrageenan would not have a strong interaction with guar gum, but it might tend to have a synergistic increase in its gelling capacity and thicken a little bit more if used with locust bean gum. The locust bean and carrageenan and/or agar combination will result in more elastic gels associated with less syneresis.
“We've found that gums work very well in conjunction with sugar alcohols like glycerin or maltitol,” reports Andon. “You'll get very good viscosity, tack and adhesion while obtaining a very low water activity.”
Hydration
Pure hydrocolloids will clump when hydrated. The outside of particles will start to hydrate and it will be very difficult to get complete hydration of the hydrocolloid in that system.“Dispersion and hydration of hydrocolloids is the biggest challenge to using hydrocolloids,” says Lynch. Dispersion can be done by dry blending the colloid with other dry ingredients in the formula; by first adding it to a non-soluble component to disperse it, such as oil or propylene glycol; or by using a vacuum or aspirator to pull the hydrocolloid into solution.
When other dried ingredients are mixed together before hydration, the hydrocolloids will not clump, sweat or form fish-eye type appearances, adds Rector. This concept can be witnessed in the preparation of instant flan, which often is dispersed in sugar. “[The mixture] is not full strength carrageenan and wouldn't have those problems,” he says.
Rapid agitation also is necessary to get full dispersion. Once dispersed, the hydrocolloid must be hydrated or put into solution. In the case of a cold-soluble colloid, only agitation is necessary, but some hydrocolloids are soluble only at elevated temperatures and need heat to become fully hydrated. Locust bean gum is an example of a hydrocolloid that has both a cold-soluble and a hot-soluble portion of the molecule, and needs to be heated to 60 degrees C to fully hydrate.
Between Fiber and Viscosity
Like carrageenan, most gums are non-digestible. “The interesting thing about gums is they truly are functional fibers,” says Andon. “Adding gums and hydrocolloids to a food formula is one of the most efficient ways manufacturers can add soluble fiber to the product.” Compared to oat bran, which has approximately 12% soluble dietary fiber (SDF), most gums have a minimum of 75% SDF, while gum acacia has 85% and guar gum has 80%-85%.Beverages are becoming another big area for adding a SDF. Manufacturers are learning how to add fiber as well as how to prevent phase or layer separation from protein instability.
The prevailing hindrance in adding gums like traditional xanthan or guar gum as dietary fibers is that once levels go above 1.5%, the product will get too thick. However, there are a lot of other gums from which to choose. For example, up to 55% of gum arabic can be added in solution with no problem. “There are an unlimited number of combinations of gums out there,” remarks Andon. “The trick is to use them together in the right combination. If you can do that, you can almost accomplish any goal.”
Gum arabic is very efficient in delivering SDF. In addition, it is used to keep flavor oils emulsified. For this reason, it is very popular in beverages. For the most part, low levels (0.3% to 0.4%) of low-viscosity guar gum or pectin are used only to give more body to acidic fruit beverages, and not to increase the fiber content.
Hydrocolloids provide the texture and stability of finished foods in many other ways, such as by impeding ice crystal development, delaying staling or preventing cracking in tortillas. “The list is endless,” he concludes. “You can go to the grocery store, pick up just about any product, and there is a gum that is used to give that product its shelflife and its texture.”
