Source and Chemical Structure:Amino acid-based surfactants are produced through a condensation reaction between naturally sourced fatty acids (such as coconut oil, palm oil) and amino acids (such as glutamic acid, glycine, sarcosine). Their basic structure can be represented as:R-CO-NH-CH(R')-COOHamong whichROne end is a long-chain alkyl group (lipophilic tail), and the other end is the carboxyl group of an amino acid (hydrophilic head). This structure mimics the composition of the skin's own keratin, giving it an inherent affinity.
Mildness:This is the most prominent advantage of amino acid surfactants, mainly reflected in the following aspects, and compared with the other two categories:
- pH Value and Skin Barrier: Amino acid surfactant solutions typically exhibit weak acidity (pH 5.5-6.5), compared to healthy skin, the pH value range is a perfect match. Meanwhile, soap base is produced through the saponification of oils and fats with strong alkali (pH around 9-10), which is strongly alkaline. Using soap-based products can disrupt the skin's natural acidic protective film, leading to impaired barrier function and causing tightness and dryness. Sulfate surfactants (such as SLS) are mostly neutral or slightly alkaline.
- Irritation: The hydrophilic head of amino acid surfactants is relatively large and contains amide bonds, which leads to the formation of larger micelles with higher aggregation numbers in solution. This makes it less likely to penetrate the healthy stratum corneum of the skin, resulting in significantly lower irritation rates to the eyes and skin compared to sulfate-based surfactants. SLS/SLES, due to their strong degreasing ability and relatively small molecular structure, are considered to have a higher potential for irritation to the skin and eyes.
- Skin feel: Amino acid surfactants leave the skin feeling refreshed and non-tight after washing, while soap-based and SLS products often have a noticeable "scrubbing the plate" dryness.
Biodegradability:Since their primary structure is derived from natural plants and animals, amino acid-based surfactants can be rapidly and thoroughly decomposed by microorganisms in the environment into carbon dioxide, water, and inorganic salts. The final products are harmless to the environment, aligning with the principles of green chemistry. Soap bases themselves are also readily biodegradable, whereas sulfate-based surfactants degrade at a relatively slower rate.
In summary, amino acid surfactants, with their natural origin, mild acidity, low irritation, comfortable post-wash feel, and excellent biodegradability, comprehensively outperform soap-based and sulfate surfactants in terms of gentleness. They are particularly suitable for sensitive skin, infant skincare products, and high-end facial cleansers.