The Perfect Pour for Dressings

As the dressing industry has grown into a billion-dollar business, dressings have evolved into a category of products from which consumers demand excellence in flavor and texture. Its all in the presentation and expectations from consumers, says Michelle Ludtke, senior food technologist, Grande Custom Ingredients Group, Lomira, WI. Texturizing, thickening, suspending and emulsifying effects are important to manufacturers of dressings because they rely on the presentation to the consumer.

Despite the innumerable styles and types of dressings, texturally speaking, dressings are separated into two groups: pourable and spoonable. The former, as the name would imply, is thinner, characterized by varying degrees of flowability, generally applied directly from a bottle or other container. The latter is thicker, typically applied as a dollop or by spreading.

Salad dressings are emulsionscolloidal structures formed by combining two immiscible liquids. In this case, oil (discontinuous phase) dispersed and stabilized in water (continuous phase). Generally speaking, smaller oil droplets are more stable, i.e., less likely to coalesce and separate. In addition to maintaining homogeneity, stable emulsions also provide a major portion of the dressings body.

The order the ingredients are added and the mixing conditions are critical to build a proper emulsion, says Karen Carlson, director of research and developmentdressings, sauces, and dips, Ventura Foods, Brea, CA. A few extra seconds of shear during processing of an emulsified vinaigrette will make it too light in color. Not enough shear, and the product will separate during processing and fill unevenly. Over-processing a spoonable dressing can cause the emulsion to break and, ultimately, separate on the store shelf.

In many cases, formulations include emulsifying agents to assist in maintaining emulsion stability. Emulsifiers are polar on one end, and nonpolar on the other. By aligning the polar (hydrophilic) end with the water, and the non-polar (hydrophobic) end with the oil, emulsifiers surround the oil droplets, hindering their ability to come together.

Monoglycerides are made by breaking the glycerin backbone of a fat triglyceride, leaving a single fatty acid with a lipophilic end and a hydrophilic end. Another common emulsifier, lecithin, is a combination of phospholipids obtained from soybean oil. Other ingredients can exhibit emulsification properties by virtue of their structure. Some proteins can isolate oil droplets by forming a film around them. Molecules of gum arabic have hydrophilic and hydrophobic areas that can provide some emulsifying, as well.

More than a feeling

A dressings character has many facets, each of which affects the way that product behaves, feels and tastes.

Texture can be used to describe the rigidity or gel of the product. It might describe the surface texture or appearance, such as dry or glossy, says Celeste Sullivan, technical managerfood applications, Grain Processing Corporation, Muscatine, IA. It might describe the way the product falls from the spoon, such as long, stringy, gloppy. Texture provides a unique mouthfeel, or mouth coating, such as smooth or gummy or chalky.

Viscosity, or thickness, indicates a products resistance to flow, but tells consumers much more. Thickening is important for body and mouthfeel, as well as enhancing the cling, according to Sullivan. It might prevent separation or contribute to shelf life of the dressing. Suspension is important for particulates, vegetables and spices. Thickening and body relate to suspension.

Starch search

Starches are composed of two polymers: straight-chain amylose and branched-chain amylopectin. Straight chains group together into bundles for a rigid gel that yields a stiff texture often prone to syneresis. Branched chains do not align as closely, resulting in less gelling, creamier texture and greater moisture retention.

Composed almost entirely of amylopectin, waxy starches are excellent low-cost thickeners for salad dressings, according to Rachel Wicklund, associate food scientist, Tate & Lyle, Decatur, IL. Dent corn starches amylose will contribute a slightly gelled texture that is especially desirable for spoonable dressings.

Starches are often modified to optimize viscosity, texture and stability during processing and shelf life. In fact, Wicklund suggests modified starches are used almost exclusively over native starches in the formulation of salad dressings. Chemical crosslinking provides the starch granule stability to heat, acid and shear, all of which are present in a heat-processed salad dressing, she says. Substitution opens and expands the starch granule structure, which adds viscosity, improves the water holding and stabilizes the texture during the shelf life of the dressing.

Starches can also be modified to be functional for dressings that are cold-processed. Pregelatinized instant starches are manufactured by cooking and drying the starch, which results in broken granules, Wicklund explains. Granular instant starches, also referred to as cold-water-swelling (CWS), are processed in such a way as to swell the starch granule and dry it, while keeping the granule intact. The intact granules create a smooth, glossy appearance that is characteristic of many dressings, whereas broken granules may result in a rough, grainy appearance. The intact granule also has greater stability in the high-shear, low-pH system.

Modification can also transform starch into an emulsifier. Lipophilic starches are modified by the addition of lipophilic substituents (octenly succinate anhydride, OS), says Wicklund. OS starches contain lipophilic and hydrophilic regions that give them great emulsifying and stabilizing properties. Since the starch thickens and stabilizes the aqueous phase while also emulsifying the oil phase, the total amount of starch and other thickeners is reduced, which can help save on cost. Lipophilic starches can also replace egg yolk to address economic, allergenic and logistical concerns. Replacement of other emulsifiers, such as polysorbate 60, can simplify and increase appeal of the ingredient statement.

Hydrolysis of starch yields maltodextrins, which are used in both pourable and spoonable dressings to build solids and lubricity when fat levels are reduced, says Sullivan. They provide mouthfeel and body, and have very clean flavor profiles that do not mask other flavors.

Maltodextrins functionality is dictated by the extent to which the original starch is processed. Dextrose equivalence (DE) is a quantitative measure of the degree of starch polymer hydrolysis. As the product is further hydrolyzedhigher DEthe average molecular weight decreases and the carbohydrate profile changes, Sullivan says. A low-DE maltodextrin contributes to a smooth, creamy mouthfeel and exhibits fat-like lubricity in reduced-oil applications.

Jumping the gum

Three food gums have dominated the dressing industry: xanthan, propylene glycol alginate (PGA) and guar.

Xanthan gum provides cold-soluble viscosity and emulsion stability that is virtually unaffected by heat, pH, salt and enzymes. Xanthan also imparts shear-thinning behavior: Its pourable after applying shear (shaking), then returning to peak viscosity when shear is ceased (at rest on salad).

PGA ,a derivative of alginic acid, is a strong emulsifier that imparts a range of viscosities, depending on its degree of esterification. PGA can also be used to create thick, creamy texture and lingering mouth-coating. Gum acacia also has emulsification properties.

Guar gum is often utilized as a low-cost thickener. While guar alone can yield a slimy mouthfeel, synergy with xanthan gum provides an excellent texture at reduced cost (compared to xanthan alone).

Grace Wang, food scientist, TIC Gums, Inc., White Marsh, MD, suggests that blends are often needed to create and stabilize the complex textures of dressings. Xanthan used for thickening may be combined with emulsifiers that help keep oil and water from separating, she says. Blends might also incorporate additional gums to provide specific textural properties. Microcrystalline cellulose, MCC, helps provide a fatty mouthfeel, she notes. Cellulose gel acts as a fat mimetic, giving a full-fat mouthfeel in lower-fat products.

In dairy-based dressing, kappa-carrageenan can be useful because of its interaction with protein. And in vinaigrettes, iota carrageenan might be used to help suspend herbs and other particulates.

Blends can also be used to replace ingredients. Combining xanthan and modified gum acacia, for example, can replace a portion of eggs. According to Wang, modified gum acacia delivers greater emulsifying power than regular acacia, and at lower cost than PGA.

Protein punch

Proteins can also enhance viscosity and mouthfeel in dressing applications. Whey protein concentrates are treated under different processing conditions to obtain the differences in mouthfeel, texture and flavor, says Ludtke. These specialized whey protein concentrates (WPCs) can deliver a range of textural effects, from mild increases in viscosity to creamy gel-like mouthfeel, as well as flavor notes such as mild, milky and creamy; slightly sweet dairy; or a slightly tart dairy, which she says is especially complementary with cheese flavors.

Ludtke suggests a 2% use level will create a notable difference in viscosity. Specific levels will, of course, vary, especially when using WPC to replace another ingredient. If you use nonfat dry milk in your formula, you can use half the amount of WPC as your nonfat and replace the rest with water to get the same viscosity, she says.

Creamy mouthfeel, dairy notes and opacity make WPCs ideal for fat replacement, especially in buttermilk or ranch-type dressings. Ludtke adds that WPCs are often added to gum-containing systems to enhance the creamy texture while providing a longer, smoother pour.

R. J. Foster is a wordsmith with a B.S. in food science from the University of Wisconsin-Madison and over 15 years of experience in the food industry. He can be reached through his website, wordsmithingbyfoster.com.

Dressing Data

According to a recent Kraft Foods Salad Dressing Pure Taste survey, a national consumer poll of 1,000 adults conducted by TSC, a division of Yankelovich, 81% of Americans eat at least one salad a week, with one in five eating a salad almost every day. Most (77%) refuse to eat salad without dressing and many (70%) use salad dressing as a dip or marinade. In addition, many prefer salad dressing with no artificial preservatives (66%) and nearly half (46%) prefer low-fat or fat-free salad dressing. The favorite flavor list is topped by ranch (30%), followed by blue cheese (14%), Italian (10%) and French/Catalina (9%).