A simplified alternative to the AOAC official method for cholesterol in multicomponent foods.

An AOAC official method for quantitating cholesterol in multicomponent foods, which was first published in the 13th edition of the Official Methods of Analysis, is rarely used. The method includes so many operations and manipulations--all described in excruciating detail--that most laboratories shun it altogether. Intent on finding an alternative, laboratories have developed their own methods for specific foods. As a result, new methods have proliferated, but still no practical method has been developed for the broader categories of multicomponent foods. The aim of AOAC, which is to promote greater accuracy and uniformity of analytical results primarily through collaborative testing, has not been well served under these circumstances. A different approach guided the work reported in the present paper. This approach was directed toward updating and dramatically simplifying the existing AOAC official method. The method's chloroform-methanol-water mixed-solvent extraction is preserved; however, all the remaining steps have been streamlined, updated, or eliminated by using newer technology. Cholesterol is quantitated with highly specific capillary gas-liquid chromatography using the internal standardization technique. The lipid extract is prepared for the chromatography step by a brief saponification carried out in a culture tube. The resulting method has been validated by using Standard Reference Materials and the standard addition method. Because a simplified method is now available for quantitating cholesterol in the lipid extracts, the expectation is that more attention can be given to the development of improved and efficient extraction methods. This step remains as the central difficulty in any number of methods of analysis for lipid analytes.

Weight increase of cotton fibers during swelling in alkali as a sensitive measure of cellulose degradation in ruminal fluid.

Weight increase of cotton fiber in an 18% NaOH solution, termed "alkali-centrifuge" or "AC" value, was measured after incubation of either 1 g or 100 mg of the fiber in ruminal fluid. The AC response was a sensitive measure of cellulolytic activity. Thus, fiber incubated at 21 and 51 degrees C exhibited major AC increases even when direct weight losses of the unswollen fiber were less than 2%. Similarly, progressive additions of acetic acid to ruminal fluid progressively depressed both AC response and direct weight loss, but the former was still easily measurable when the latter was not. In tightly closed, completely filled vials with high ratio of ruminal fluid to sample, AC increased greatly and rapidly, i.e., in 6 h. This time could be further reduced to 2 h by overnight "preincubation" of the ruminal fluid with cotton fiber before starting the test incubation. Certain surfactants used to aid wetting of the fiber had a low but measurable potency in inhibiting cellulose digestion, but other surfactants were non-inhibitory. The AC response was maintained when ruminal fluid was diluted with an equal amount of McDougall's "artificial saliva" solution.

Fungi that infect cottonseeds before harvest.

As a part of an investigation of aflatoxins and other mycotoxins in cottonseeds at harvest, samples of seeds collected from the 1971 crop at locations across the U.S. Cotton Belt were examined to determine the kinds of microorganisms causing internal or seed-coat infection in the field. Aspergillus flavus infection was absent from all seeds examined from most areas but was present in some samples from Arizona, California, and Texas. Fusarium spp., Alternaria sp., and A. niger caused internal infection at many locations; Colletotrichum gossypii and Rhizopus stolonifer were present in seeds from some areas but were generally much less common. Many of the infections with A. niger were in the seed coat. Bacterial infections were fairly frequent. In a series of commerical samples from Arizona. A. flavus infection was found in 61% of seeds, with fiber showing the bright, greenish-yellow (BGY) fluorescence that is diagnostic for A. flavus boll rot. Aflatoxin contamination was also concentration in the same seeds. The above findings agree with previous data showing that aflatoxin contamination of cottonseeds before harvest occurs rarely, if at all, in most parts of the U.S. Cotton Belt and that when such contamination does occur, it tends to be concentrated in seeds with the BGY fluorescence in their fiber and seed fuzz.