How Laundry Detergent Actually Works: Enzymes, Surfactants and pH

Understanding the chemistry inside laundry detergent gives you a much better basis for choosing one than any marketing claim. The three main cleaning mechanisms — surfactants, enzymes and alkalinity — each target different types of soiling, and their balance determines what a detergent is and isn't good at.

Surfactants: the core cleaning mechanism

Surfactants (surface-active agents) are molecules with a dual structure: one end is attracted to water (hydrophilic) and the other end is attracted to oil and grease (hydrophobic). When a garment is washed, surfactant molecules surround grease and oil particles — the oil-loving end attaches to the grease, the water-loving end faces outward — forming spherical structures called micelles. These micelles are water-soluble and are carried away in the rinse. Every laundry detergent contains surfactants; they are the fundamental cleaning mechanism.

Enzymes: targeted stain removal

Biological (enzymatic) detergents contain enzymes that break down specific types of soiling at a molecular level. Proteases break down protein stains: blood, sweat, dairy, egg. Lipases break down fats and oils. Amylases break down starch. Cellulases break down cotton fibre pills and refresh fabric texture. Enzymatic detergents are measurably more effective on biological staining than non-enzymatic ones. The limitation: enzymes work best between 30–50°C and are denatured (destroyed) by very hot water or bleach. This is why enzymatic detergents and 60°C+ washes are not a good combination.

pH and fabric compatibility

Standard laundry detergents are alkaline — typically pH 9–11. Alkalinity improves cleaning performance by helping to loosen mineral deposits and supporting surfactant action. However, sustained alkaline exposure damages protein-based fibres: wool and silk are both made of protein (keratin and fibroin respectively) and will degrade over repeated washes with standard alkaline detergents. This is why specialist wool and silk detergents are pH-neutral or slightly acidic. For these fabrics, pH matters more than cleaning performance claims.