R. L. Gregory

A comparison of several analytical techniques for prediction of relative stability of fats and oils to oxidation

Three analytical methods proposed by various workers for predicting the relative stability of fats and oils to oxidation have been compared on a series of samples. The Eckey Oxygen Absorption, the modification of the A.S.T.M. Oxygen Bomb (4), and the Active Oxygen Method (AOM) were applied to combinations of animal and vegetable fats and oils, with and without added monoglycerides and antioxidants. The results indicate that the Eckey Oxygen Absorption and modified ASTM Oxygen Bomb methods are more precise than the AOM method, and more in keeping with the experience in the fat and oil field in relation to actual performance stability than the AOM. Experimental relationships of these factors and methods to shelf life storage studies measured organoleptically will be the subject of a later paper.

A study of methods for evaluation of the stability of fats and shortenings

The data from several laboratory tests [Active Oxygen Method (AOM), modified ASTM bomb, modified ASTM bomb with catalyst added to the fat, a manometric method and an accelerated oven test] were compared with data from a storage test at 85F evaluated organoleptically at selected intervals. Tests were carried out on lard, hydrogenated vegetable oil and tallow, with and without added monoglyceride, and with and without selected antioxidants. A comparison of the data from the laboratory tests with that from the storage tests indicated: 1) that the different types of fats behave differently, 2) the laboratory tests cannot be used as an index of shelf stability except for a given type of formulation of fat for which the relationship between the laboratory test and the shelf stability is known, 3) the modified ASTM bomb method is the most reliable for estimating shelf life, and 4) the modified ASTM bomb method with catalyst is not as precise as the bomb method, but may be used for control purposes where some accuracy may be sacrificed in the interest of shorter time.

A comparison of nuclear magnetic resonance and dilatometry for estimating solids content of fats and shortenings

The percent solids values of fats and shortenings using nuclear magnetic resonance (NMR) and solid fat index (SFI) have been compared. The samples used were: blends of hard fat and safflower oil, safflower oil hydrogenated to varying degrees, and different types of shortenings.This investigation demonstrated the empirical nature of the SFI technique and shows the nature of the deviations from the solids content determined by the NMR method. The magnitude of the deviation of SFI from the NMR solids content increased with the level of the solids. The SFI values and the NMR solids content were similar at the lower levels (SFI values of 10) but at the upper limit for the SFI method (SFI values of 50) the solids content by the NMR method can be 80% or more, a difference of 30 units.Although the determination of solids content by NMR is reliable, the relationship between SFI values and NMR values for different types of samples is so variable that the calculation of the SFI value from percent solids by NMR, or percent solids from SFI values from prediction equations is not very reliable.Since NMR measures the solids content more accurately than SFI and is applicable over the entire range of solids, 0 to 100%, it will be very useful in fat and oil research and control.

Application of wide-line NMR to analysis of cereal products and fats and oils.

The principal areas of interest to cereal and oil chemists of wide-line NMR have been reviewed. It provides a rapid method for moisture in cereals where a large number of analyses are required. In the field of plant breeding and genetics of oil seed it provides a non-destructive means of selecting seeds for test and evaluating the seeds grown. In the area of fats, oils and shortenings it provides a rapid and accurate means of measuring the solids content over a wide range of temperatures and can be applied to a finished product as is, under selected conditions.

Standardization of nuclear magnetic resonance measurement of solids in fats and shortenings

An investigation of factors that influence the measurement of solids in fats and shortenings by nuclear magnetic resonance was directed toward standardization of the method. The aim was to select abbreviated tempering conditions that would yield results comparable with those existing at temperature equilibrium. Conditions were found which reduced the time and gave an accuracy that made the method suitable for both research and control purposes.

Relationship of peroxide value and thiobarbituric acid value to development of undesirable flavor characteristics in fats

The peroxide value and thiobarbituric acid value were compared with the flavor score for a series of different types of fats, with and without added monoglyceride and with and without different stabilizers. The data indicated that the flavor score cannot be estimated for any given fat from either the peroxide value or the thiobarbituric acid value. Either can be used to follow the development of off flavors in a given product or formulation but the relative level may vary from product to product.

Measurement of solids in triglycerides using nuclear magnetic resonance spectroscopy

A rapid and accurate method using nuclear magnetic resonance (NMR) spectroscopy is presented for determining the percentage of solids in fats and shortenings conditioned at selected temperatures or as received in the laboratory. This method provides more reliable information on the solids content of fatty materials than the empirical dilatometric solid fat index, and is applicable in the range of 50–100% solids which is beyond the limit of the official solid fat index method.The relationship between instrument response and actual solids present was determined on known mixtures of liquid and solid triglycerides. NMR and solid fat index (SFI) measurements were made on a series of commercial margarine oils of varying composition and consistency. Comparisons are presented giving the precision of the two techniques and the relationship between percentage of solids by the NMR technique and the solids fat index.

A laboratory centrifugal refining method for control application

A control method is presented for selecting the appropriate processing conditions for alkali refining of crude vegetable oils by the centrifugal process to yield lowest losses with satisfactory color. This technique is sufficiently analogous to actual processing conditions to provide reliable information upon which plant performance can be based.The cup method cannot be used in this manner in that it no longer approximates operating procedures as in the days of kettle refining. The chromatographic neutral oil method, on the other hand, provides an index of the amount of oil available for recovery without regard to the possibility of attaining such levels.For these reasons the centrifugal method fills a void of long standing. Other tangible benefits that accrue from this technique are: selection of sources of oil that can be most profitably refined by establishing the relative value of competitive oils, and a means of evaluating plant efficiency.

The estimation of lactic acid in lactylated monoglycerides and shortenings containing lactylated monoglycerides

A titrimetric method has been presented for the determination of lactic acid in lactylated monoglycerides and shortenings containing these products, when the only water soluble acid present is lactic acid. Analyses by this method: of knowns, samples from a material balance test, and commercial products, indicate that it is applicable to these types of product. Comparison of analyses of the material balance samples and commercial products by the titrimetric method and the colorimetric p-phenylphenol method indicated that the latter gave lower and more variable results.