Hydrocolloids
Pages 91-103
DOI: https://doi.org/10.1094/1891127381.008
ISBN: 1-891127-38-1
Abstract
Topics Covered
- Salad Dressings
- Tomato- and Mustard-Based Products
- Processed Meat Products
- Baked Goods
- Hydrocolloid-Based Fat Replacers
- Pancake Syrup
- Pet Food
- Water Gel Desserts
- Troubleshooting
Introduction to Chapter
Most pourable salad dressings today are sold ready to use and contain all the flavorings and ingredients in one bottle. A wide range of products is possible, from the simplest vinaigrette (oil, vinegar, and a few spices) to rather complex products, such as thousand island and blue cheese dressings. Most salad dressings today are nonstandard of identity and are 10-45% oil. The viscosity of these products results primarily from the addition of hydrocolloids, such as xanthan, propylene glycol alginate (PGA), and microcrystalline cellulose (MCC), with contributions from other ingredients such as oil and proteins. Some gums also possess emulsion-forming properties: gum tragacanth (not often used any more because of its cost and microbial load), gum acacia (a natural emulsifier and flavor carrier), and PGA (a good emulsifier but not natural). Formulations may need to be adjusted because of the emulsifying properties of these gums.
Dressings are oil-in-water emulsions that may contain dairy products (e.g., buttermilk powder and blue cheese), spices (e.g., ground mustard and turmeric powder), vegetable pieces (e.g., onion, green and red peppers, and pickles), and other ingredients. Hydrocolloids maintain the uniformity of these mixtures by preventing the coalescence of oil droplets and suspending the spices and vegetable pieces. They also thicken the dressing and provide additional body.
Gum tragacanth was used traditionally to stabilize salad dressing because it is acid stable and it is an efficient thickener. However, because it is an exudate gum, it may contain a high microbial load (plate count).
When xanthan gum was approved for food use in 1969, it became the stabilizer of choice in many salad dressings because it is less expensive on a cost-in-use basis and it contains lower microbial loads than gum tragacanth. Xanthan's one slight disadvantage is that it gives the dressing a slightly “pituitous” or “snotty” texture, so other hydrocolloids such as low molecular weight PGA, methylcellulose, MCC, or Tara gum are used in combination with xanthan to modify and improve the overall salad dressing texture. PGA, the propylene glycol ester of alginic acid, displays reasonably good acid stability, low reactivity with calcium, and a high degree of emulsification. It also provides thickness and creaminess, mouth-coating, and a slow dispersion rate in the mouth. In dressings that require phase separation, such as some Italian dressings, the high degree of emulsification from a small amount of PGA temporarily holds the combined phases together after shaking until the dressing is poured and then allows the phases to separate again in the bottle after use.
In most cases, it is desirable that the dressing cling to the salad greens and not drain quickly and collect in the bottom of the salad bowl. This ability to cling to the greens is related to yield point. Hydrocolloids such as xanthan gum, PGA, MCC, and Tara gum are used at concentrations of 0.05–0.75% to give the desired viscosity and yield point.
