Personal wash additives: here's how to formulate with visual and functional additives.

Many of today's popular personal wash products include visually appealing and functional additives. But development of these products presents challenges that are unique to each specialty ingredient utilized and their targeted functional attributes. The conceptualization of formulation strategy and selection of most appropriate specialty ingredients for optimal delivery of targeted visual and performance attributes of a new consumer product require a disciplined approach. A harmonious blend of the formulator's skills, artful science, regulatory compliance, a competitive edge, cultural aspects and consumer politics are all required for the development of successful products. These activities also need to be superimposed with time and cost constraints.

Plant, Animal or Synthetic?

The popularity of nature-based ingredients, and the unsettling incidence of BSE (bovine spongiform encephalopathy, aka, Mad Cow Disease) has stirred up a consumer-driven movement that requires formulation (or reformulation) of products exclusively utilizing plant-derived ingredients. Some of the most common plant-derived ingredients have attracted negative attention by the press. For example, cocamide DEA has been scrutinized by the Food and Drug Administration (FDA) for possible contamination with N-nitrosodiethanolamine. This has resulted in the avoidance of all fatty am ides in the topical products marketed by some health food chains, although any specific concerns relative to the safety of those ingredients have not been resolved.

Religion and nationality may also play a role in the selection of raw material feed stocks in the world markets. Hindus prefer not to use ingredients derived from bovine sources (beef tallow, for example); Muslims generally ban the use of porcine-derived ingredients (lard, white grease, for example). Kosher ingredients are recommended for the Jewish markets. Political, cultural and consumer perception issues such as these can create significant constraints for formulators, marketers and suppliers and can limit the availability of ingredients that are suitable to deliver targeted product performance at a viable cost. Formulation constrains provide opportunity. Opportunities lead to innovation!

The commercial sources of a few ubiquitous cosmetic ingredients are listed in Table 1. Also included are some of the additives that are derived from the chemical transformation of those ingredients, including stearyl alcohol (source: stearic acid, methyl stearate) and glyceryl monostearate (source: palm oil, tallow, stearic acid and glycerin, methyl stearate and glycerin).

Slight differences may exist in the application of most of these multisource ingredients. For example, USP-grade glycerin may be obtained from natural or synthetic sources. However, synthetic glycerin may have a slightly better color stability in applications that require its prolonged heating at high temperatures. Adding tallow-derived stearic acid in a lotion or cream may create a higher viscosity and better emulsification than the corresponding palm oil-sourced ingredient (especially if it is used at above 2% level in that formulation). Commercial stearic acid is a natural blend principally o stearic and palmitic acids. The ratio o these two acids is different in stearic acid obtained from palm oil or" tallow The physico-chemical attributes o these multi-feedstock-based ingredients should be carefully evaluated prior to reformulation. (1,2)

Personal Wash Products

The personal washes and cleansers of a specific group usually share a common surfactant base. This base should be rich-foaming, clean-rinsing and non-irritating, with good cleansing properties. Additional ingredients are added to a suitable base to achieve specific product claims or performance criteria for marketing purposes. The marketplace is awash with shower gel, shampoo and other rinse-off products that contain only trace quantities of vitamins, specialty additives or botanical ingredients claimed to provide skin care and other consumer benefits.

It is worthy to note that the addition of some of those ingredients in trace quantities usually does not pose formulation problems; their incorporation in significant amounts in high performance products can cause serious formulation issues. Additionally, the quantitative assessment of product claims or benefits that are based on trace quantities of specialty additives often creates scientific and marketing challenges.

It is becoming increasingly difficult to select functional ingredients for these products as consumer sentiment forces manufacturers to shy away from products that contain ingredients associated with health or safety concerns even though such concerns are frequently unsubstantiated or based on misleading information. One recent consumer-driven trend requires the development of plant-based, non-animal origin and non-animal tested personal wash products that are based on safe, natural and high performance a specialty ingredients. Many high-end marketers are forsaking the use of common surfactants, such as ammonium lauryl sulfate (ALS), sodium lauryl sulfate (SLS), ammonium lauryl ether sulfate (ALES), sodium lauryl ether sulfate (SLES), and ubiquitous foam-boosting cocamids due to negative consumer publicity associated with those ingredients. Table 2 lists popular personal wash products and specialty surfactants that are devoid of negative connotations and provide good performance at a reasonable cost.

Choosing the Surfactant

Sodium cocoyl isethionate (CI), sodium methyl cocoyl taurate (MCT), sodium lauroyl sulfoacetate (LSA), acyl glutamates and other fatty amides of amino acids are all high foaming, extra-mild surfactants derived from coconut oil with excellent cleansing properties However, CI, MCT and acyl amino acids have relatively poor cloud points that may result in the formation of turbidity when products containing these ingredients are stored at lower temperatures. The use of a solubilizing hydrotrope is necessary in those cases Sodium methyl 2-sulfolaurate (MSL) is an excellent choice for a naturally derived hydrotrope that can be used in place of (petroleum-derived) sodium xylene sulfonate. MSL helps improve the cloud point and contributes to good foaming and rinsing properties of the products that contain CI, MCT and other poor cloud point surfactants. Cocamidopropyl betaine and sodium lauroyl sarcosinate are additional choices for this application.

As a guideline, a combination of at least two surfactants provides better overall performance than a single surfactant in a personal wash product. For the formulation of high performance shower gel, facial wash and shampoo products, a combination of at least three specialty surfactants in Table 2 is recommended. The relative quantities of these surfactants are adjusted to meet targeted lathering, cleansing, rinsing and cost criteria of the final product. For manufacturing efficiency, a common base can be used for multiple products. A shower gel base can thus be used for a facial wash product, and the base for a liquid soap is adaptable for a milk bath, shampoo or shower gel product with the inclusion of a few functional ingredients, as illustrated in Figure 1.

[FIGURE 1 OMITTED]

Bar Soap Products

The inclusion of specialty additives in bar soap formulations requires special considerations due to the generally alkaline nature of bar soap products, especially in the presence of water. The incorporation of easily oxidized additives, such as ascorbic acid, hydroquinone and polyphenolic antioxidants, results in the rapid degradation of those ingredients with the formation of colored degradation products in most such cases. The deposition of oil-soluble vitamins such as A, E, D and K on skin is inadequate from traditional alkaline soap based products due to their rapid emulsification by soap.

[alpha]-Lipoic acid, a popular antioxidant and antiaging ingredient, is poorly deposited from traditional alkaline soaps because of its conversion into water-soluble sodium salt form that is easily rinsed off during the shower or bath. A popular anti-none additive, salicylic acid, is deactivated due to its conversion into the corresponding sodium salt in alkaline soap base (salicylic acid is active only in its free carboxylic acid form).

The use of a highly superfatted soap base circumvents some of these problems. The formulations based on syndet surfactants (Table 2), especially those that contain free fatty acids, are far better suited for the topical delivery of specialty ingredients that are alkali sensitive, oxidation prone or fat-soluble. This is due to the deposition of free fatty acids on skin that also helps improve deposition of any fat-soluble additives in those formulations. A selection of popular specialty ingredients and soap bases recommended for their formulation are included in Table 3. It is important to understand the chemical structure, chemical reactivity, and solubility properties of specialty additives for their successful incorporation in a bar soap formulation.

All tallow/coco-based soaps are inherently alkaline in nature in the presence of water. As already noted, the addition of an acidic ingredient, such as ascorbic acid, results in the rapid formation of sodium or potassium ascorbate (followed by its oxidative degradation in the presence of air). Even the superfatted soaps have the capability to transfer sodium or potassium cation from the soap molecule to a newly introduced additive that is more acidic in nature than the free fatty acids present in that soap. (3) Syndet-based bars have their sodium or potassium cations bound more tightly to their sulfate, sulfonate, taurate, sulfoacetate, or similar strongly negative anions; these do not undergo such migration of their cations. Also, syndet bars formulated with fatty acid derivatives are usually acidic in nature, as they generally contain free fatty acids. These syndet bar formulations can be made from specialty ingredients listed in Table 2. However, sarcosinates and acyl glutamates have their cations attached to (weakly acidic) carboxylate anions; these can undergo cationic migrations similar to tallow/coco soaps.

Visual Effect Ingredients

The formulation of ingredients to achieve special visual effects (shimmers, colored "pearls," two-phase and three-phase colored liquid products, natural seeds and plant fragments, colored beads, colored confetti, etc.) in consumer products requires formulation technologies that encompass their chemical and physical compatibility, visual aesthetics, long-term stability and cost criteria. The formulation of a shower gel product, for example, with two visually different (water-soluble) colors will result in the diffusion of these colors into each other producing a predominantly single mixed color product. For example, a bottle of shower gel that is filled with yellow color product on the top and blue color product on the bottom will eventually lead to an overall green product after a short period of storage, irrespective of product viscosity.

Visual effect additives are usually formulated as suspension products. Some examples of these include microcapsules, colored mica, colored wax (beeswax, shellac wax, rice bran wax and paraffin) and jojoba ester-based beads, colored wax and paraffin-based confetti, polyethylene-based glitter and shimmer agents, natural and synthetic abrasives (sand, polyethylene, crushed nut shells), fragments of botanical parts (flowers, leaves, herbs, seaweeds), and a host of similar ingredients that are insoluble in the formulation matrix. Microcapsules have been most popular, as they can be made in a variety of colors and loaded with fragrances, emollients and formula-sensitive ingredients. Microcapsules are available in a variety of materials that include urea/formaldehyde, alginic acid/agar, epoxy resin, polyacrylonitrile, polymethacrylate and gelatin. Formulating with these additives requires net-forming agents that provide adequate suspension of the additives without affecting the clarity of the product.

Most of these suspension agents increase viscosity. This viscosity may increase further during storage, so stability tests should be carefully evaluated. The selection of a suspension ingredient is also important. Xanthan gum is a common ingredient used for this function. However, not all xanthan gums are equal, relative to their contribution to clarity and visco-elastic properties of the final product. The compatibility of xanthan gums with surfactants also varies. Certain xanthan gums are especially suited for surfactant-based formulations. It is frequently advantageous to use a combination of suspension agents rather than a single suspension agent alone. A selection of visual effect additives and common suspension agents is included in Table 4.

The evaluation of the compatibility of color in a bead, shimmer or confetti additive with the other constituents of the formulation is of paramount importance. The water-soluble colors, if present in the beads or confetti, may leach out into surfactant-rich formulations. The oil-soluble colors present in these additives may bleed into lotion or cream formulations based on (oil-rich) water-in-oil emulsions. The botanical fragments (leaf, flower, herb and seaweed/ are most problematic in nearly all formulation categories. These additives can cause serious discoloration, microbial contamination, malodor formation, degradation and other product stability-related problems, especially in water-based formulations. The compatibility of packaging with any suspension-type additive should be carefully evaluated. For example, a pump nozzle may get plugged it' the size of the suspended additive is too large for the orifice of the pump's delivery system in a spray product. The smaller sized suspended particles may agglomerate during product storage, also causing nozzle plugging problems.

Product Evaluation

Evaluating the stability, performance and consumer acceptance attributes of new formulations requires a combination of art, science and political skills. Extensive laboratory tests often fail to measure the degree of consumer enthusiasm. A technologically-advanced formula may falter in the marketplace as a result of poor packaging, unpopular fragrance, questionable product claims, unfavorable consumer perception of its ingredients, enhanced competition or unacceptable cost.

Brand loyalty is on a decline. Products often must be brought to market quickly to beat the competition. Marketers must make rapid decisions based on incomplete information. The longevity of many newly launched products is short. This problem can be resolved to some extent by designing laboratory test methods that are more predictive of consumer-perceived benefits targeted for those products. A shampoo that lathers profusely in laboratory tests can still fail in the marketplace because of consumer perception of its poor rinsability, for example. The formula optimization by laboratory tests can usually be accomplished economically and in

less time than the methods requiring consumer testing. The development of predictive laboratory evaluation methods that relate to both consumer testing (in-home use tests) and consumer perception (focus groups) are of paramount importance in the development of successful personal wash and other consumer products.

Table 1: Commercial Sources of Common Cosmetic Ingredients

Ingredient              Plant Source   Animal Source    Synthetic

Source
Stearic acid            Palm oil       Tallow
Oleic acid              Palm oil       Tallow
                        Olive oil
                        Tall oil
Glycerin                Palm oil       Tallow           Propylene
                        Coconut oil
Sodium stearate         Palm oil       Tallow
Stearyl alcohol         Palm oil       Tallow
Cetyl alcohol           Palm oil
Glyceryl monostearate   Palm oil       Tallow

Table 2: Specialty Surfactants in Personal Wash Products

Personal Wash Products                      Specialty Surfactants

Shower Gel                              Sodium cocoyl isethionate
Facial Wash                          Sodium methyl cocoyl taurate
Body Wash                              Sodium lauryl sulfoacetate
Shampoo                             Sodium methyl 2-sulfo laurate
Liquid                                Soap Cocamidopropyl betaine
Milk Bath                              Sodium lauroyl sarcosinate
                                  Acyl glutamates, acyl arginates

Table 3. Specialty Additives in Bar Soap Formulations

Additive        Soap              Superfatted Soap    Syndet

Vitamin C       Rapid oxidation   Slow oxidation      Relatively stable
Hydroquinone    Rapid oxidation   Slow oxidation      Relatively stable
Vitamin E       Poor deposition   Better deposition   Best deposition
[alpha]-        Poor deposition   Better deposition   Better deposition
  Lipoic acid
Benzophenone-   Color formation   Poor deposition     Poor deposition
  3
Salicylic       Inactivation,     Poor activity       Best activity
  acid            color

Table 4. Visual Effect Additives and Suspension Agents

Visual Effect Additives                            Suspension Agents

Microcapsules                                            Xanthan gum
Shimmer (mica, mica derivatives)               Hydroxyethylcellulose
Beads (wax, jojoba, polyethylene)                         Gellan gum
Confetti (wax, paraffin)            Acrylates/[C.sub.10-30] Acrylate
                                                       cross polymer
Polyethylene Glitter                                        Carbomer
Sand, Nut Shells                                 Acrylates copolymer
Botanical Fragments (leaf,
  flower, herb, seaweed)

Acknowledgement: Jesus San Miguel, Gary Grayson, and Lori Murphy provided expert laboratory assistance and ingredient evaluations.

References

(1.) S. Gupta, Formulation of Personal Care, Cosmetic, and Topical Nutraceutical Products with Specialty Additives, SODEOPEC Meeting, Orlando, FL, February 4-6, 2002 (AOCS, Champaign, IL, USA); S. Gupta, Soap Technology for the 1990's, L. Spitz, ed., American Oil Chemists' Society, Champaign, IL, USA, p. 48, (1990); S. Gupta and D. Wiese, Riegel's Handbook of Industrial Chemistry, 9th Edition, J. Kent, ed., Van Nostrand Reinhold, NY, USA, p.1012 (1992); S.K. Gupta, Production of Fatty Acid Methyl Esters and Soaps Therefrom, U.S. Patent 5,468,887 (1995).

(2.) Surfactants in Consumer Products, J. Falbe, ed., Springer-Verlag, NY (1987); Surfactants in Cosmetics, 2nd Edition, M.M.Rieger and L.D.Rhein, eds., Marcel Dekker, NY (1997).

(3.) S.K. Gupta and J.R. Story, Superfatted Soaps, U.S. Patent 4,704,223 (1987).

About the Author:

Shyam Gupta is director of R&D at Arizona Natural Resources, a contract manufacturing company specializing in high performance, visually distinct cosmetics and personal care products. He is also president of Bioderm Research, a technical consulting organization specializing in cosmetic products based on nutraceutical, phytopharmaceutical, and innovative high performance ingredients. (www.bioderminc.com). Tel: [phone], email: shyam@ aznat.com or [e-mail]