Leo A. Goldblatt

Determination of aflatoxins in individual peanuts and peanut sections

Subsamples of a given lot of peanuts may vary greatly in aflatoxin content due to extreme variability in the degree of contamination of individual kernels. A micro method, adapted from the aqueous acetone procedure recently proposed by Pons and Goldblatt for the determination of aflatoxins in cottonseed products, was developed to permit accurate determination of aflatoxins in individual kernels and kernel sections.Use of this procedure permitted the topographic distribution of aflatoxins within single kernels to be mapped and indicated that the toxins are not uniformly distributed within contaminated kernels, even when the kernel contains a high level of aflatoxins. Although wrinkling or discoloration sometimes indicated that a kernel was contaminated, this type of physical damage was not found to be a reliable indication of aflatoxin content. Also it was noted that a few apparently sound and mature kernels contained high levels of aflatoxins.

Direct gas chromatographic examination of volatiles in salad oils and shortenings

A simple, rapid and direct gas chromatographic technique was developed for the examination of volatiles in salad oils and shortenings at the 10 ppb level without prior enrichment. The liner of the inlet of the gas chromatograph is carefully packed with volatile-free glass wool to allow slow diffusion of the sample on the glass wool, but to prevent seepage onto the gas chromatographic column. The liner with sample is inserted in the heated inlet, and the volatiles are eluted rapidly from the samples as the carrier gas flows through the linear and sweeps the volatiles onto the column, which is temperature-programed between 55 and 190C to resolve the volatiles. Numerous samples of salad oils and shortenings were examined, and the better quality oils had only small amounts of volatiles.

Objective fluorometric measurement of alfatoxins on TLC plates

Measurement of the solid state fluorescence of aflatoxins on silica gel-coated TLC plates on a densitometer equipped for fluorescence measurements showed a linear relationship between peak areas and concentration over a range of at least 2 to 105×10−4 μg of aflatoxins per spot. Response of individual aflatoxins was in order of B2>G2>B1>G1. Aflatoxins can be measured with a precision of ±2–4%.

Improved objective fluorodensitometric determination of aflatoxins in cottonseed products

Modifications in the extraction solvent, lead acetate, and silica gel extract purification steps, and the TLC development conditions of the aqueous acetone procedure of Pons et al. [JAOAC49, 554–562 (1966)] for the estimation of aflatoxins in cottonseed products, provides an improved method with essentially quantitative recovery of aflatoxins added to typical cottonseed materials. Both the accuracy and precision of aflatoxin estimates are significantly improved by the incorporation of an objective fluorodensitometric measurement of aflatoxins on TLC plates.

Control and removal of aflatoxin

The best approach to contain the problem of aflatoxin is prevention and enough is now known about prevention to reduce contamination drastically. Guidelines for preventing mycotoxins in farm commodities have been suggested by the U.S. Department of Agriculture. Moisture is the single most important parameter and prompt drying to safe levels is essential for control of toxigenic molds. Foreign matter and damaged seed should be removed. Provision of clean, dry, adequately cooled and ventilated storage is important and good sanitation is essential to minimize mold contamination during storage and processing: Genetic approaches which may result in resistance to elaboration of aflatoxins are under investigation. When aflatoxin is found in a sample of oilseeds the contamination generally resides in only a small proportion of the kernels, commonly less than 1%. Sorting or separation can concentrate the vast majority of aflatoxin-contaminated kernels into relatively small fractions and only a small loss is incurred as a result of their removal. Aflatoxin is frequently found deeply imbedded within individual kernels so removal by simple washing does not seem feasible. However, extraction with polar solvents such as alcohols and ketones to achieve essentially complete removal of aflatoxins appears technically feasible. Heat is relatively ineffective for destruction of aflatoxin although normal roasting, as of peanuts for the preparation of peanut butter, results in considerable reduction in aflatoxin content. Treatment withFlavobacterium aurantiacum removes aflatoxin and may be useful for beverages. Oxidizing agents readily destroy aflatoxin, and treatment with hydrogen peroxide may be useful. Treatment of defatted oilseed meals with ammonia can reduce aflatoxin content to very low or undetectable levels with only moderate damage to protein quality.

Assay of aflatoxin in peanuts and peanut products using acetone-hexane-water for extraction

A quantitative method is described for the assay of aflatoxin in peanut products. The procedure involves extraction of aflatoxin from the sample with a homogeneous acetone-hexane-water solvent mixture followed by purification of the extract by phasic extraction of the aflatoxin with aqueous sodium chloride and then with chloroform. The purified chloroform extract is analyzed by thin-layer chromatography by comparison of the intensity of fluorescence of any aflatoxin with the intensity of a known standard. The aflatoxin analyses of peanuts were found to be very variable due to sampling, and this variability has been greatly reduced by finely grinding and thoroughly mixing 2 kg of the sample before removal of an aliquot for assay. The method is sensitive to approximately 2 parts per billion.

Ricinelaidic acid and methyl ricinelaidate. Their preparation and determination by infrared spectroscopy

SummaryImproved methods for the preparation of ricinelaidic acid and methyl ricinelaidate are described. The methods depend upon the elaidinization of methyl ricinoleate with a relatively small quantity of a nitrite-nitric acid solution, fractional crystallization of the methyl ricinelaidate, and its subsequent hydrolysis to ricinelaidic acid. The infrared spectra of these two compounds are presented, and bands arising from a deformation of the C−H about thetrans C=C group are discussed. Absorptivity values for this band in chlorform and in carbon disulfide solutions are given as additional criteria of purity of ricinelaidic acid and its methyl ester. The infrared absorption procedure for the quantitative determination of isolatedtrans ethylenic bond was applied to the determination of both ricinelaidic acid and methyl ricinelaidate. Details of specific procedures for the determination of each compound are given with the equations necessary for their calculation. Use of these methods is illustrated with the analysis of elaidinization mixtures. The repeatability and accuracy obtaineble are given. A value is reported for the methyl ricinoleate—methyl ricinelaidate equilibrium and the mechanism of the reaction is discussed briefly.

Elution and analysis of volatiles in vegetable oils by gas chromatography

A simple and very sensitive technique was devised to analyze volatiles in vegetable oils by direct gas chromatography. A large sample of oil is diffused on glass wool in an injection port liner. After the liner is inserted in the injection port, the volatiles are rapidly swept into the column of the gas chromatograph for analysis.

Lecithin in oil-in-water emulsions

SummaryA study was made to investigate the use of purified phosphatide in I.V. emulsions. Lecithin isolated from egg yolk and purified by alumina and silica chromatography was analyzed by chromatographic strip techniques as a one-component material. Highly purified lecithin was found to be an inefficient emulsifier. Moreover emulsions containing highly purified lecithin were heat-sensitive. An emulsion physical stability test was developed to evaluate emulsifier formulations containing purified phosphatides for use with small amounts of emulsions (approximately 50 g.). Using this procedure, a considerable number of substances were tested as additives to enhance the purified lecithins emulsifying power. None were found to be as effective as natural soybean phosphatide, which was used as a control. From these observations it is indicated that pure phosphatides are inefficient emulsifiers and that those phosphatide preparations possessing good emulsifying characteristics are presumably mixtures or complexes of the phosphatides with other substances.

Kinetic study of acid-catalyzed conversion of aflatoxins B1 and G1 to B2a and G2a

Adjusting dilute aqueous solutions of aflatoxins B1 and G1 to pH 1, 2 and 3, and heating over a range of 40–100 C resulted in the conversion of B1 to B2a and G1 to G2a as major products. Both B2a and G2a were identified by co-thin layer chromatography with authentic B2a and G2a and M1 on silica gel plates developed in two different solvents. The rate of disappearance of B1 or G1 at given temperature and at constant pH was found to be first order with respect to each aflatoxin. At given temperature the conversion is strongly pH dependent, a 10-fold increase in H+ ion (1 pH unit) producing about a 9-fold increase in the reaction rate, indicating first order dependent of the rate on H+ ion concentration.