Lipids, Oil and Fat Quality Testing
Lipid, Oil and Fat Quality Testing
Oils, fats and lipids are relatively interchangeable names for a variety of chemical compounds that share common solubilities in organic solvents such as ether and chloroform or methanol. Eurofins' laboratories can expertly conduct a number of analyses relevant to determining the quality and/or physical properties of fats and oils. Services include:
- Iodine Value (IV) is the grams of iodine absorbed by 100 grams of fat. This value is used to measure the relative degree of unsaturation in fats.
- MIU is the total of the Moisture, Insoluble Impurities and Unsaponifiable Matter present in the oil. This value provides information about non-fat/oil components of food and feed grade fats and oils. MIU is used primarily to screen incoming materials for industrial applications.
- Titer is a measure of the hardness of fat. It is determined by melting the fat and then measuring the congealing temperature in degrees centigrade. The higher the titer value, the harder the fat is at room temperature.
Rancidity in food and feedstuff may result from oxidation of the lipid component of the sample, microbiological deterioration of the sample or both. Due to the lack of a universally accepted definition of rancidity, no single rancidity test will meet every client's needs. Oils are said to become rancid when they undergo a degradation process known as oxidation. A variety of chemical compounds such as peroxides, aldehydes and free fatty acids are created as oil oxidizes. The tests that follow are those most frequently requested to monitor or predict oxidative degradation.
- TBA Rancidity monitors certain types of aldehydes that form when a fat or oil oxidizes. These aldehydes react with 2-Thiobarbituric Acid (TBA) to form a complex that is easily measured.
- Free Fatty Acids (FFA) is the amount of free (unbound) fatty acids. When fats and oils become rancid, individual fatty acids are liberated and make the material slightly acidic. The FFA test measures this acidity and then expresses it on a fatty acid basis.
- Peroxide Value (PV) is a measure of the present state of rancidity of an oil. Also called Initial Peroxide Value (IPV) because it is determined on a sample as submitted. The result is expressed as milliequivalents of peroxide per kilogram of fat.
- Anisidine Value is frequently partnered with Peroxide Value because it measures aldehydes which are secondary products of oxidation that are more stable than peroxides. The aldehydes react with p-Anisidine creating a colored complex which is measured on a spectrophotometer. The Anisidine Value can be combined with the Peroxide Value to give a Total Oxidation Value (Totox).
Oil Stability testing indicates the ability of the fat to resist becoming rancid. The fat is heated while having air (oxygen) bubbling through it causing accelerated degradation. The reaction of the oil to this process is evaluated by two different tests.
- Oil Stability Index (OSI): As oils degrade they eventually reach a critical point at which the oxidation exponentially increases and the fat quickly becomes rancid. This assay monitors the formic acid produced by the fat as it degrades and reports the number of hours for spike in rancidity to occur.
- Active Oxygen Method (AOM) For this method the peroxide value (PV) is measured after a set time period (usually 20 hours) after being exposed to stressed conditions (heat and oxygen). Alternatively, the peroxide value can be checked periodically until the oil reaches a clearly rancid value (100 meq/kg) with the number of hours reported.
OTHER LIPID TESTS
Eurofins Scientific, Inc. offers all of the tests listed above as well as the following lipid tests of interest to the animal and pet food industries:
- Color Tests (AOCS, Lovibond, Gardner, & FAC scales)
- Flash Point
- Melting Point, Capillary
- Mono, Di, & Triglycerides
- Neutral Oil Los (NOL)
- Refining Loss
- Saponification Value
- Smoke Point
- Soap by Titration
- Solid Fat Index
- Total Fatty Acids
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