TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The methane sulfonic acid is added as a ready-to-use composition comprising 1-99 wt.% of methane sulfonic acid, diluent and optionally one or more additives. Preferred Components: The fatty substance is plant or animal oil or fat, used frying oil, mixtures of above fats or oils, or free fatty acid or its mixture optionally mixed with oils or fats of plant or animal origin. The fatty substance comprises: oil of sunflower, walnut, corn, soybean, peanut, rapeseed, flax, hemp, safflower, milk-thistle, purslane, raspberry, black currant, hazelnut, almond, wheat germ, borage, evening primrose (primrose), carnations, cores, seeds and grains, argan, palm, copra, sesame, olive, castor, coconut, brazil nuts, Jatropha, babassu, karanja, neem, mahua, saijar, jojoba, tung, tall or tall oil, and algae; used frying oils; oils and fat of fish; and/or oil and fat of cattle, pig, goat, horses, poultry and others. The fatty substance comprises 0.1-100 wt.%, preferably 5-95 wt.% of free fatty acid. The free fatty acids are undecanoic acid (11), lauric acid (12), myristic acid (14), myristoleic acid (14:1), palmitic acid (16), palmitoleic acid (16:1), margaric acid (17), stearic acid (18), oleic acid (18:1), ricinoleic acid (18:1), elaidic acid (18:1), petroselenic (18:1), vaccenic (18:1), linoleic acid (18:2), linolenic acid (18:3) and thier isomers, licanic acid (18:3), arachidic acid (20), gadoleic acid (C20:1), arachidonic acid (20:4), behenic acid (22), and/or erucic acid (22C:1). The alcohol is linear 1-6C, preferably 1-4C alcohols, diols, and/or triols, such as methanol (preferred), ethanol, glycerol. The quantity of added methane sulfonic acid is 0.01-5 wt.%, preferably 0.01-1 wt.%. The composition useful in the process, comprises: 1-99 (preferably 30-95) wt.% of methane sulfonic acid; 99-1 (preferably 70-5) wt.% of diluent comprising alcohols, plant or animal oils or fats, and water; and 0-15 wt.% of additives. The diluent comprises water, methanol and/or ethanol. The additives are stabilizer, rheological modifier, viscosity modifier, flame retardants, surfactant, dye, preservative, corrosion inhibitor and/or odorizing agent. EXAMPLE - No suitable example given.