RHEOLOGY MODIFIERS
41
Figure 1: Chemical structure of xanthan gum (left) and guar gum (right) flow of matter.3
Rheology modifiers are essential
ingredients used in the formulation of BPC products. They serve the critical purpose of changing the rheological behaviour of a finished product to deliver technical and application benefits, including sensory and texture properties.4 The correlation between rheology
modification and aesthetics has been the object of many studies,5,6
with the multidisciplinary
science of rheology playing a fundamental role in determining and understanding key parameters governing product behaviour. Polymers are an essential class of
ingredients used as rheology modifiers.7 They modify rheology by virtue of their high molecular weights, chain entanglements, and polymer-solvent interactions. Additional property control can be achieved using phase changes and associations.8
Guar gum and xanthan gum as natural rheology modifiers Xanthan gum and guar gum are well-known examples of biopolymers used as rheology modifiers in the cosmetics industry. Xanthan gum is a polysaccharide commercially produced by precipitation of the broth isolated from the exocellular coating on bacterial cell walls after fermentation. It has a complex structure comprising a backbone of β-D-(1,4)-glucose with branching trisaccharide side chains of β-D-(1,2)-mannose and β-D-(1,4)-glucuronic acid. The comb-like trisaccharide side chains found on the primary chain confer its water solubility. The anionic charge of xanthan gum is due
to carboxylic acid residues on D-glucuronic acid and pyruvic acid moiety on the terminal D-mannose. The thickening and gelation mechanisms require the formation of junction zones, hypothesised to occur through hydrophobic interactions on the helix.9 Guar gum is a polygalactomannan
found in the endosperm of the seeds of Cyamopsis tetragonolobus. It is a hydrophilic heteropolysaccharide of mannose and galactose monomer units where the mannose
www.personalcaremagazine.com Ingredients Water
GENENCARE OSMS BA Sodium Benzoate Potassium Lactate Glycerin
Propanediol Xanthan Gum Aurist GHI
Lactic Acid, 80%
TABLE 1: FORMULATION PLAN TO EXPLORE RHEOLOGY AND SENSORY PROPERTIES OF AURIST GHI A
B INCI
Aqua/Water/Eau Betaine
Sodium Benzoate Potassium Lactate Glycerin
Propanediol Xanthan Gum
Cyamopsis Tetragonoloba (Guar) Gum Lactic Acid
(w/w%) (w/w%)
QS to 100 QS to 100 1.00 0.20 0.30 15.00 15.00 1.00
0.00
1.00 0.20 0.30 15.00 15.00 0.10 0.40
QS to pH 4.0
TABLE 2: VISCOSITY OF FORMULA A AND B SHOWING THE SYNERGY BETWEEN GUAR AND XANTHAN GUM Viscosity (Brookfield RT, TD /10 rpm, 20˚C) mPa*s
A B
constitutes the main linear chain of the polymer, and the galactose forms the pendant branches. β -1,4 glycosidic bonds link the mannose units, and the galactose units are linked to mannose through β-1,6 glycosidic bonds. The mannose-to-galactose ratio of guar gum is approximately 2:1.10 Two water-based cosmetic products were
535 530 525 520 515 510
Formula A Formula B
Figure 2: Results of the pull-off test performed on Formula A and B
5300 8000
formulated to understand the benefits of employing the synergistic interactions of guar gum and xanthan gum in practical applications. The formulations designed can suit different formats, from facial serums/gels to personal lubricants. In Table 1, it can be seen that Formula A
employs 1% of xanthan gum alone, which, in Formula B, was reduced by a factor 10 and aided by 0.4% of Aurist™ GHI (INCI: Cyamopsis Tetragonoloba (Guar) Gum). Table 2 shows the viscosity of the aqueous
systems reflects the synergistic interaction between the gums. Formulations A and B underwent instrumental pull-off tests performed on a texture analyser (TA.XT, Stable Micro Systems) fitted with a custom-built compression tack probe fixture. After conditioning at 40°C, the sample was
applied onto a stainless-steel substrate using a bar applicator (120 μm wet film thickness). After a 60-second rest time, the sample reached a T of approximately 37°C (to mimic the body temperature), and a pull-off test was performed. A 100g compression force was applied for five seconds, and the probe was then pulled
July 2023 PERSONAL CARE
Peak Force (g)
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92
