Physical and Chemical Characteristics

Physical Characteristics
Characteristic Butter
Refractive Index 1.453-1.457 at 104°F (40°C)
1.4465 at 140°F (60°C)
Analysis: The refractive index is related to the ease with which light passes through an oil or fat. Temperature and degree of saturation affect the value. Butter's refractive index value can be used as an indirect measurement of unsaturation.
Melting Point 82.4-96.8°F (28-36°C)
Analysis: Melting point measures the temperature range at which a solid becomes a liquid. Butter's narrow melting range provides a sharp melting curve, for a quick flavor release and smooth mouthfeel.
Solid Fat Index
Solid Fat Index (SFI) is an empirical measure of solid fat content at standardized temperature check points. Butter's SFI curve illustrates that butter will only partially solidify at room temperature.
Values apply to butterfat

Chemical Characteristics
Characteristic Butter
Iodine Value 26-42
Analysis: The iodine value indicates the number of double bonds, or degree of unsaturation. It can be used as an estimate of the oxidative stability of a lipid. As butter has a low iodine value it is less likely to undergo oxidation.
Saponification Value 210-250
Analysis: Saponification value is a value which identifies the length of fatty acid chains in the fat. The range for butter indicates a larger amount of short-chain fatty acids, which gives butter a sharper melting curve.
Unsaponifiable Matter 0.4%
Analysis: Unsaponifiable matter refers to compounds which are not saponified by alkalies, including sterols, hydrocarbons, pigments and tocopherols. The low value for butter indicates few of these compounds are present in butter, and hence butter does not have a delayed crystallization time.
pH salted 4.31-6.7
unsalted 4.2-5.2
Analysis: Butter has a pH range from slightly acidic to neutral, which is compatible with most any food.
Analysis: The Acid Degree Value (ADV) indicates the amount of free fatty acids present in a fat. The low ADV range for butter indicates few free fatty acids in butter. This in turn indicates that butterfat has not undergone undesirable hydrolysis, which would result in flavor deterioration.