Alva F. Cucullu

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.

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.

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.

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.

Relationship of physical appearance of individual mold-damaged cottonseed to aflatoxin content

Abstract and SummaryOver 700 individual aflatoxin-suspect cottonseed were hand-selected from a heterogenous stockpile of ginned seed. The seed were categorized on the basis of (a) bright greenish-yellow, fluorescence termed cateye, on the linter fibers under ultraviolet light; (b) partially bald seed with part of the linter fibers removed by ginning; (c) a combination of cateye and balding; (d) thin and discolored lint; and (e) bluish, not cateye, fluorescence. Aflatoxin assays on each of the 771 selected seed showed that 142 out of 771 (18%) were contaminated by aflatoxin (B1+B2) in the range of 150 ppb—5.75 million ppb. Some 93% of the aflatoxin-contaminated seed was concentrated in categories (a), (b), and (c), with the highest concentration, 61%, in category (b). Eight seed in these three categories contained over 1 million ppb of aflatoxins. The data suggest that removal of cateye and partially bald seed from contaminated lots of cottonseed should be more effective for controlling aflatoxin contamination in cottonseed than removal of cateye seed alone.

Aflatoxin-negative cottonseeds in bright, greenish yellow fluorescent seed locks

Bright, greenish yellow (BGY) fluorescent locks were removed from an aflatoxin-contaminated sample of lint cotton. Hand ginning of these fluorescent locks yielded 51 seeds, 26 with BGY linters, and 25 with nonfluorescent linters. All seeds were analyzed individually for aflatoxins. Two of the seeds with BGY lint accounted for 99.9% (2.75 μg) of the total aflatoxins. Four other seeds each contained 0.02 μg of total toxins, and all others contained no toxins. Our results show that 88% of the seeds necessarily lost in discarded fluorescent locks would contain no aflatoxins.

Separation of aflatoxin-contaminated cottonseed based on physical characteristics of seed cotton and ginned seed

Abstract and SummarySamples of aflatoxin-contaminated stored ginned cottonseed and of freshly harvested seed cotton and companion ginned seed were examined under long wave ultraviolet (UV) and visible light to develop physical criteria for separating aflatoxin-contaminated seed from sound seed. Seed locks characterized by bright greenish-yellow, or cateye, fluorescence when viewed under long wave UV light were separated from samples of 12 varieties of freshly harvested seed. As a result, 80–100% (mean 96%) of the aflatoxin contamination that was concentrated in 2–9% (mean 6%) of the seed weight was effectively removed. The cateye fluorescence separation technique was slightly less effective for removing aflatoxins from companion freshly harvested, ginned samples, but most of the aflatoxins were concentrated in only 0.5–3% (mean 2%) of the seed weight. This approach was relatively ineffective for stored ginned seed, probably due to deterioration of the cateye fluorescence.

Quantitative determination of cyclopropenoid fatty acids in cottonseed meal

A rapid analytical procedure for determining the residual cyclopropenoid fatty acids (CPA) in cottonseed meal has been developed. The procedure involves room-temperature extraction of crude CPA-containing lipids with a hexane-water-acetone azeotrope solvent, followed by a benzenemethanol wash. The crude lipids are then converted to methyl esters by methanolysis with sodium methoxide. Extraction with petroleum ether, followed by washing with aqueous acetone, results in a substance which is free from interfering materials. The purified methyl esters are then analyzed for CPA by a spectrophotometric modification of the Halphen reaction.

Determination of Moisture, Oil, and Free Fatty Acids in Castor Beans

SummaryCastor beans may be satisfactorily prepared for analysis by grinding in a food chopper equipped with a 12-tooth blade.For the determination of moisture and volatile matter a 5-g. sample of ground beans or pomace or a 50-g. sample of whole beans should be dried for 2 and 4 hours, respectively, at 130°C. in a forced-draft oven.For the determination of oil in castor beans a 5-g. sample of ground beans should be extracted as directed by the A.O.C.S. Official Method Aa 4-38, using carbon tetrachloride for 2 hours, reground with 0.5 g. of 60- to 80-mesh sand, and subsequently extracted for 2 additional hours. For castor pomace similar extraction for 4 hours without regrinding is satisfactory.The free fatty acid content of castor beans can be determined by extracting the ground beans at room temperature with methyl alcohol and titrating the extracted oil as directed in A.O.C.S. Official Method Aa 6-38 after removal of solvent by heating under reduced pressure.

Determination of aflatoxins in peanut and cottonseed soapstocks.

An accurate and sensitive procedure is proposed for estimating aflatoxins in both alkaline and acidulated soapstocks. Sample suspensions in aqueous acetone are adjusted to pH 3 with hydrochloric acid, extracted in a high speed blender, treated with lead acetate and partitioned into chloroform. After silica gel cleanup, aflatoxins in purifie extracts are estimated by thin layer chromatography. The use of acetone and lead acetate together apparently catalyzes the relactonization of flatoxins B1 nd G1 and leads to essentially quantitative recovery of aflatoxin B1 and somewhat lower recovery of G1 added to alkaline or acidulated soapstock.