January 2024 • Vol. 30 • Issue 1
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Naturally Derived Rheology Modifiers and Emulsion Stabilizers …Hani Fares
odern-day formulators have relied on polymers to stabilize oil-in-water (O/W) emulsions much more than surfactants. The introduction of polyacrylic acid-derived polymers many years ago enabled formulators to develop stable emulsions with minimal effort. Formulators used polymers as their primary stabilizers, and they selected the surfactants and esters to tailor the texture and sensorial properties of emulsions. In fact, polyacrylic acid-based polymers enabled steric stabilization of emulsions due to their anionic charge and contributed to the entropic stabilization due to their ability to bind water very efficiently. The art of formulation using the concepts of hydrophilic lipophilic balance (HLB) almost became extinct and was replaced by the fast-paced polymeric stabilization. In recent years, consumers have been driving the trend of naturality demanding that manufacturers formulate their products with naturally derived ingredients rather than fossil-based ones. This push towards naturality forces formulators to remove their fossil-derived polymers from their products and replace them with their naturally derived counterparts. At the same time, formulators are also replacing their efficient polyoxyethylene-based (POE) surfactants with polyglyceryl based ones since POE is no longer in vogue with some consumer groups. One can say that formulators, who have been spoiled for many years with ease of formulation and guaranteed stability outcomes, are faced with one of the biggest challenges in recent history. To fill the gap, the search for an identical, naturally derived replacement of polyacrylic acid-based polymers has created a frenzy among finished goods companies and raw material suppliers. The first instinct for many formulators is to step back and rely on the good old substitute, xanthan gum. Produced by fermentation, xanthan gum is considered naturally derived. It is used at relatively low concentrations and has good yield value. Although xanthan gum has many good attributes, it still has several draw backs. First, its impact on viscosity is minimal and does not build efficiently in formulation. Second, it adds negative slip and tack properties to formulations which is quite undesirable. Third, its effect on stability is positive but not nearly as much as polyacrylic-based polymers. Formulators need to make several trials before achieving good stability with xanthan gum. Another substitute ingredient is starch. Starches have been used to thicken and generate yield in emulsions for many years. An example of a commonly used starch ingredient is hydroxypropyl starch phosphate. Starches typically work over a wide pH range (pH 3 – pH 9) and have good salt tolerance. However, starches are not efficient thickeners as they must be used between 1 – 4% (w/w) in the emulsion to impart stability. When a high level of polymer is used in emulsions it not only reduces the (continued on Page 5)
NYSCC HITS THE SLOPES •
JANUARY 19TH
...see page 8 for more information.