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58 Special Properties of Fats, Oils, and Shortenings Methods

58-10.01 Cloud Point

To determine the crystallization temperature (cloud point) for animal and vegetable fats and oils. The first stage of crystallization is indicated by a visible cloud in the sample. This method is equivalent to Official Method Cc 6-25 of the American Oil Chemists' Society (AOCS).

58-11.01 Cold Test

To determine the extent of winterization (stearin removal process) of an oil sample. This method is applicable to all normal, refined, and dry animal and vegetable oils. This method is equivalent to Official Method Cc 11-53 of the American Oil Chemists' Society (AOCS).

58-12.01 Determination of Oil Color

To determine oil color by comparison with glasses of known color characteristics. Color glasses are calibrated in accordance with the AOCS Tintometer Color Scale. The method is applicable to all normal fats and oils, providing no turbidity is present in sample. This method is equivalent to Official Method Cc 13b-45 of the American Oil Chemists' Society (AOCS).

58-13.01 Determination of Congeal Point

To measure the solidification temperature (congeal point) of fats under defined conditions. Congeal point differs from titer point in that the former is applied directly to triglycerides, whereas the latter is applied to fatty acids. The method is applicable to fats, oils, and fat mixtures that congeal or solidify within the temperature range of 25-45°. See Note 1. This method is equivalent to Official Method Cc 14-59 of the American Oil Chemists' Society (AOCS).

58-14.01 Consistency—Penetration Method

To determine an arbitrary measure of firmness of plasticized fats by measuring the distance a given weight of defined shape will penetrate fat in a certain period of time. Firmness of the fat is related to the composition and character of the fat, to temperature of the sample at the time of measurement, and to the previous history of the sample. The method is applicable to plastic fats and solid fat emulsions such as shortenings, margarine, butter, and similar products. This method is equivalent to Official Method Cc 16-60 of the American Oil Chemists' Society (AOCS).

58-15.01 Determination of Free Fatty Acids

To determine the free fatty acid (FFA) content in all crude and refined vegetable oils, marine oils, and animal fats. This method is equivalent to Official Method Cc 5a-40 of the American Oil Chemists’ Society (AOCS).

58-16.01 Determination of Peroxide Value—Acetic Acid-Chloroform Method

To determine the peroxide value of fats and oils, in terms of meq peroxide per 1000 g of sample. The method is applicable to all normal fats and oils including margarine. It is highly empirical, and any variation in procedure may result in variation in results. This method is equivalent to Official Method Cd 8-53 of the American Oil Chemists' Society (AOCS).

58-17.01 Preparation of Methyl Esters of Long-Chain Fatty Acids

This method provides means for preparing methyl esters of long-chain fatty acids for further analysis by methods such as gas-liquid chromatography (Method 58-18.01). It is applicable to common fats, oils, and fatty acids. See Note 1. Unsaponifiables are not removed and, if present in large amounts, may interfere with subsequent analyses. Procedure results in partial or complete destruction of epoxy, hydroperoxy, cyclopropenyl, cyclopropyl, and possibly hydroxyl groups, and is not suitable for preparation of methyl esters of fatty acids containing these groups. This method is equivalent to Official Methods Ce 1-62 and Ce 2-66 of the American Oil Chemists' Society (AOCS).

58-18.01 Fatty Acid Composition by Gas Chromatography

This method permits quantitative separation of mixtures containing saturated and unsaturated methyl esters. It is applicable to methyl esters of fatty acids having 8-24 carbon atoms and to animal fats, vegetable oils, and fatty acids after their conversion to methyl esters. Conditions specified are not suitable for determining epoxy or oxidized fatty acids nor for fatty acids that have been polymerized. This method is unsuitable for quantitation of fatty acids for labeling purposes. It is equivalent to Official Method Ce 1-62 of the American Oil Chemists' Society (AOCS).

58-19.01 Total, Saturated, Unsaturated, and Monounsaturated Fats in Cereal Products by Acid Hydrolysis and Capillary Gas Chromatography

Lipid is extracted from the sample by digesting with hot HCl. Extracted lipid is partitioned into ethyl ether and petroleum ether, and the ethers are removed by evaporation. The extract is saponified with NaOH, and the free fatty acids are methylated with a mixture of boron trifluoride (BF3) and methanol. Fatty acid methyl esters (FAMEs) are separated into saturated, monounsaturated, and polyunsaturated fatty acids and quantitated by capillary gas chromatography (GC). A table is available for converting FAME content to triglyceride equivalents for labeling purposes. See Note 1.

58-20.02 Refractive Index

The refractive index of a substance is the ratio of speed of light in a vacuum to speed of light in the substance. For practical measurements, including this method, scales of standard instruments indicate refractive indexes with respect to air rather than vacuum. Index of refraction of oils is characteristic within certain limits for each kind of oil. It is related to degree of saturation but is affected by other factors such as free fatty acid content, oxidation, and heat treatment. The method determines the origin and quality of normal oils and liquid fats. This method is equivalent to Official Method Cc7-25 of the American Oil Chemists' Society (AOCS).

58-25.01 Solid Fat Index—Dilatometric Method

To determine solid fat index (SFI) as an empirical measure of solid fat content. It is calculated from the specific volume at various temperatures, using a dilatometric scale graduated in units of ml × 1000. Results are therefore expressed as melting dilation in ml/kg of fat. Because the method is empirical, departures from the procedure may cause variations in results. The method is applicable to margarine oils, shortenings, and other fats with a solid index of 50 or less at 10°. This method is equivalent to Official Method Cd 10-57 of the American Oil Chemists' Society (AOCS).

58-30.02 Iodine Value of Fats and Oils—Cyclohexane-Acetic Acid Method

This method measures the unsaturation of fats and oils and is expressed in terms of the number of cg of iodine absorbed per g of sample (% iodine absorbed).It is applicable to all normal fats and oils with iodine values in the range of 18-165 that do not contain conjugated double bonds. This method is equivalent to Official Method Cd 1d-92 of the American Oil Chemists' Society (AOCS). See Note 1.

58-35.01 Acetone-Insoluble Lecithin

This method determines the acetone-insoluble fraction of soybean and corn oils, free from sand meal. Benzene-insoluble material and phosphatides are included in the acetone-insoluble fraction. This method is equivalent to Official Method Cc 4-46 of the American Oil Chemists' Society (AOCS).

58-39.01 Dropping Point—Automatic Determination of Melting Point in Fats

Dropping point is the temperature at which a fat or oil becomes sufficiently fluid to flow. This method determines dropping point in hydrogenated and nonhydrogenated fats and oils that solidify sufficiently when held in a freezer for the allotted time. This method is equivalent to Official Method Cc 18-80 of the American Oil Chemists' Society (AOCS).

58-40.01 Melting Point—Capillary Method

Natural fats and oils are mixtures of glycerides and other substances and consist of several components that do not exhibit either a definite or a sharp melting point. Therefore, the term melting point does not imply the same characteristics that it does with pure substances of a definite crystalline nature. Fats pass through a stage of gradual softening before they become completely liquid. The melting point, then, must be defined by the specific conditions of the method by which it is determined, and in this case it is the temperature at which the sample becomes perfectly clear and liquid. This method determines the melting point of normal animal and vegetable fats. It is equivalent to Official Method Cc 1-25 of the American Oil Chemists' Society (AOCS).

58-45.01 Monoglycerides and Free Glycerol

This method determines alpha-monoglycerides from periodic acid (HIO4) consumed in oxidation of adjacent hydroxyl groups. beta-Monoglycerides are not oxidized by periodic acid because hydroxyl groups are not adjacent. This method is applicable to fats, oils, monoglycerides, and blends. It is not applicable when sample contains, in addition to monoglycerides, chloroform-soluble polyhydric substances with two or more adjacent hydroxyl groups. This method is equivalent to Official Methods Ca 11-57 and Cd 14-56 of the American Oil Chemists' Society (AOCS).

58-50.01 Saponification Value

Saponification value is amount of alkali necessary to saponify a definite quantity of sample. It is expressed as number of mg of KOH required to saponify 1 g of sample. The method is applicable to all normal fats and oils. This method is equivalent to Official Method Cd 3-25 of the American Oil Chemists' Society (AOCS).

58-53.01 Slip Melting Point

The slip point (open tube melting point) is an index of temperature at which fat softens or becomes sufficiently fluid to slip or run. This method determines the slip point of a sample and is applicable to such fats as coconut oil, stearin, hydrogenated fats, and hard tallows. It is less satisfactory for lard, soft tallow, and animal greases and is unsatisfactory for lard compounds and mixtures of hard and soft fats or emulsions. This method is equivalent to Official Method Cc 3-25 of the American Oil Chemists' Society (AOCS).

58-54.02 Oil Stability Index

Resistance of oil to oxidation depends on the degree of saturation, natural or added antioxidants, prooxidants, or prior abuse. Oxidation is very slow until this resistance is overcome, at which point oxidation accelerates and becomes very rapid. The length of time before the rapid acceleration of oxidation is the measure of resistance to oxidation, and is commonly referred to as the "induction period." This method determines the induction period. It is equivalent to Official Method Cd 12b-92 of the American Oil Chemists' Society (AOCS).

In this method, a stream of purified air is passed through a sample of oil or fat that is held in a thermostated bath. The effluent air from the oil or fat sample is bubbled through a vessel containing deionized water. The effluent air contains volatile organic acids, swept from the oxidizing oil, that increase the conductivity of water as oxidation proceeds. Water conductivity is monitored continuously until the point of maximum change in rate (or the second derivative) of conductivity with respect to time is obtained. The oil stability index (OSI) is the point of maximum change of the rate of oxidation. The OSI may be run at temperatures of 110-140°C and, because of this flexibility, results should specify the OSI time with the temperature (for example, "OSI 11.7 hr at 110°C"). This method is applicable to all fats and oils. See Note 1.

58-82.01 Smoke, Flash, and Fire Points

To determine temperature at which a sample will smoke, flash, or burn. The method is applicable to animal, vegetable, and marine fats and oils. Flash point is not applicable to samples that flash below 149° (300°F). This method is equivalent to Official Method Cc 9a-48 of the American Oil Chemists' Society (AOCS).

58-99.01 Glossary—Lipids