Minicolumn detection methods for aflatoxin in raw peanuts: collaborative study.

The Holaday-Velasco method and a modified Holaday method have been compared. The former method combines the speed and simplicity of the Holaday extraction and cleanup with the sensitivity of the minicolumn originally described by Velasco. The combination method has been approved by the AOAC and the AACC for determining aflatoxin in corn. The Holaday method was modified by substituting toluene for benzene in the solvent partition, and methylene chloride for chloroform in the minicolumn development to eliminate use of hazardous solvents. The neutral alumina in the Holaday minicolumn was changed from activity V to activity III to provide a more stable column. At aflatoxin levels in raw peanuts of 13-20 ng/g, the presence of aflatoxin was missed by the modified Holaday method in 4 analyses (3 laboratories) of 42 reported. There were no misses in this contamination range by the Holaday-Velasco method. There were no misses by either method with samples containing greater than 20 ng total aflatoxins/g. Analysis of uncontaminated raw peanuts by the modified Holaday method resulted in 2 false positives of 14 reports; the Holaday-Velasco method produced no false positive reports from 15 analyses of uncontaminated peanuts. The Holaday-Velasco method was adopted official first action for peanuts.

Nondestructive Quality Evaluation of Agricultural Products - Industrial Application.

Use of nondestructive quality evaluation techniques for agricultural products is steadily increasing. Reasons for increased application and refinements of techniques in processing of agricultural products are discussed, especially with regard to more automation and less labor in processing, increased processing rates, and demand for more quality and uniformity of product. Information is presented on a number of nondestructive techniques presently being used, and the need for additional development is covered. Special emphasis is given to the efficiency, practicality, and economic feasibility of various techniques. Agricultural products covered include peanuts, pecans, poultry, eggs, pork, and seeds. Nondestructive techniques discussed that are used for processing these commodities into uniform, high-quality products include visual examination, weighing, screening, gravity sorting, air classification, electronic sorting, and estimation of chemical composition. A more detailed discussion of electronic color sorting of peanuts, pecans and almonds is presented, particularly in relation to aflatoxin sampling and reduction, preparing for further processing, and evaluation of commercial sorters for speed and accuracy.

HLA antigens: rabbit antisera reacting with all A series or all B series specificities.

Papain-solubilized HLA antigens giving only two bands of 34 000 mol.wt. and 11 000 mol.wt. by sodium dodecyl sulfate (SDS) gel electrophoresis and isolated from the cultured human lymphoblastoid cell line RPMI 4265, have been used to prepare antisera in rabbits. Antisera were raised against soluble products of the A (or 1 st) series of HLA, bearing the determinant HLA-A2 (A2 substance), or against a mixture of products of the B (or 2nd) series of HLA, bearing the determinants HLA-B7 and HLA-B12 (B7-12 substances). Rabbit antisera to A2 substance reacted primarily with A2 substance on Ouchterlony analysis, showing an apparent spur of cross-reactivity with B7-12 substances. Rabbit antisera to B7-12 substances reacted primarily with B7-12 substances, giving a spur of cross-reactivity with the A2 material. Neither antiserum precipitated beta-2microglobulin. Both types of sera reacted with membrane molecules of 43 000 mol.wt. and 11 000 mol.wt. by immune precipitation and gel electrophoresis in SDS of detergent-solubilized radiolabeled membranes from cultured cell lines, as predicted for sera directed towards HLA antigens. F(ab')2 fragments of the antibodies blocked the complement-mediated cytotoxicity of all HLA alloantisera tested for human peripheral blood lymphocytes. After absorption with B7-12 substances, F(ab')2 fragments of antisera to A2 substance only blocked the cytotoxicity of HLA alloantisera to A series specificities. After absorption with A2 substance, F(ab')2 fragments of rabbit antisera to B7-12 substances only blocked the cytotoxicity of HLA alloantisera to B series specificities. The results prove the existence of shared antigenic determinants between all members of the same series. These findings support the genetic evidence that A series HLA antigens are allelic products of a single locus, while B series HLA antigens are allelic products of a separate locus, by establishing some invariance of structure, presumably amino acid sequence, between members of the same series. The apparent cross-reactivity between A2 substance and B7-12 substances, and the ability of the unabsorbed F(ab')2 preparations to block the cytotoxicity of all HLA alloantisera, suggests that some determinants are common to both HLA loci. This may be considered to support the hypothesis that the two loci arose by gene duplication.