Число омыления и неомыляемые вещества в жирах и маслах

Milligrams of a base required to saponify 1g of fat

Saponification value or saponification number (SV or SN) represents the number of milligrams of potassium hydroxide (KOH) or sodium hydroxide (NaOH) required to saponify one gram of fat under the conditions specified. It is a measure of the average molecular weight (or chain length) of all the fatty acids present in the sample in form of triglycerides. The higher the saponification value, the lower the fatty acids average length, the lighter the mean molecular weight of triglycerides and vice versa. Practically, fats or oils with high saponification value (such as coconut and palm oil) are more suitable for soap making.

To determine saponification value, the sample is treated with an excess of alkali (usually an ethanolic solution of potassium hydroxide) for half an hour under reflux. The KOH is consumed by reaction with triglycerides, which consume three equivalents of base. Diglycerides consume two equivalents of KOH. Monoglycerides and free fatty acids, as well as by other esters such as lactones consume one equivalent of base

Handmade soap makers who aim for bar soap use sodium hydroxide (NaOH), commonly known as lye, rather than KOH (caustic potash) which produces soft paste, gel or liquid soaps. In order to calculate the lye amount needed to make bar soap, KOH values of SV can be converted to NaOH values by dividing KOH values by the ratio of the molecular weights of KOH and NaOH (1.403).

Unsaponifiables are components of a fatty substance (oil, fat, wax) that fail to form soaps when treated with alkali and remain insoluble in water but soluble in organic solvents. For instance, typical soybean oil contains, by weight, 1.5 – 2.5% of unsaponifiable matter. Unsaponifiables include nonvolatile components : alkanes, sterols, triterpenes, fatty alcohols, tocopherols and carotenoids as well as those that mainly result from the saponification of fatty esters (sterols esters, wax esters, tocopherols esters, ). This fraction may also contain environmental contaminants and residues of plasticizers, pesticides, mineral oil hydrocarbons and aromatics. Unsaponifiable constituents are an important consideration when selecting oil mixtures for the manufacture of soaps. Unsaponifiables can be beneficial to a soap formula because they may have properties such as moisturization, conditioning, antioxidant, texturing etc. On the other hand, when proportion of unsaponifiables is too high (> 3%), or the specific unsaponifiables present do not provide significant benefits, a defective or inferior soap product can result. For example, shark oil is not suitable for soap making as it may contain more than 10% of unsaponifiable matter. For edible oils, the tolerated limit of unsaponifiable matter is 1.5% (olive, refined soybean), while inferior quality crude or pomace oil could reach 3%. Determination of unsaponifiables involves a saponification step of the sample followed by extraction of the unsaponifiable using an organic solvent (i. e. diethyl ether). Official methods for animal and vegetable fats and oils are described by ASTM D1065 18, ISO 3596: 2000 or 18609: 2000, AOCS method Ca 6a 40.

Fat / oil Saponification value (mg KOH / g sample) Unsaponifiable matter (%)Beeswax60 – 102> 52Canola oil182 – 193< 0.2Cocoa butter192 – 200 0.2 – 1Coconut oil248 – 2650.1 – 1.4Corn oil187 – 1951 – 3Cottonseed oil189 – 207< 2Fish oil179 – 2000.6 – 3Lanolin80 – 12740 – 50Lard192 – 203< 10Linseed oil188 – 1960.1 – 2Mineral oil0100Olive oil184 – 1960.4 – 1.1Palm kernel oil230 – 254< 1Palm oil190 – 209< 1.4Peanut oil187 – 1960.2 – 4.4Rapeseed oil168 – 1810.7 – 1.1Safflower oil188 – 194< 1.6Shea butter170 – 1906 – 17Soybean oil187 – 1951.5 – 2.5Sunflower oil189 – 1950.3 – 1.2Whale oil185 – 202< 2