Verneal R. Bruce

Incidence of Toxigenic and Other Molds in Green Coffee Beans

The mold flora of 944 green coffee bean samples from 31 coffee-producing countries was determined before and after surface disinfection with 5% NaOCl. Molds were detected on 99.1 % of 47,200 beans not surface-disinfected and in 47.9% of 47,200 disinfected beans. Although the percentage of differences in occurrence of mold before disinfection was minimal (93.4 to 100%) on a country-by-country basis, after disinfection the beans from Asiatic and African countries showed more internal invasion (80.5%) than those from Central and South America (49.4%). Aspergillus spp., which dominated the mold flora of 944 samples before and after disinfection, included the toxigenic A. ochraceus , A. flavus and A. versicolor as well as A. niger , A. tamarii , A. wentii and species of the A. glaucus group. The genus Penicillium , including the toxigenic P. cyclopium , P. citrinum and P. expansum , was detected regularly, although its occurrence was substantially lower than that of the aspergilli, especially after surface disinfection. The rare detection of Alternaria and Fusarium indicated that toxigenic species of these genera do not readily invade green coffee beans. A. flavus and A. tamarii were prevalent in Central and South American beans, whereas other aspergilli were prevalent in Asiatic and African beans. The penicillia were prevalent in Central and South American beans.

Molds and tenuazonic acid in fresh tomatoes used for catsup production.

The mold flora was determined for 146 samples of fresh but visibly moldy tomatoes collected from sorting belts in tomato catsup processing plants in California and in Midwestern and Eastern United States. Mold found in 141 of the samples included at least 22 genera, principally Alternaria , Aspergillus , Cladosporium , Fusarium and Penicillium , and 51 species. The California tomatoes were dominated by Geotrichum candidum and species of Aspergillus and Penicillium ; Midwest and East tomatoes were dominated by Alternaria . This suggested that the predominant molds in tomatoes may differ, depending on geographical source. Tenuazonic acid (TA), a toxic metabolite of Alternaria spp., was found in 73 of the samples at a range of 0.4 to 69.7 (average 4.94) μg/g of moldy tissue; however, Alternaria spp. were not found in 35 of the 73 TA-positive samples. It is possible that other molds may produce TA or that the toxin-producing Alternaria died off before our sampling.

Incidence of Toxic and Other Mold Species and Genera in Soybeans

The mold flora of 385 unprocessed soybean samples was determined before and after surface disinfection of the beans with 5% NaOCl. Molds were detected in 99.4% of the 19,250 non-disinfected soybeans examined, and in 52.8% of the 19,250 surface-disinfected soybeans examined indicating that contamination was primarily at the surface, although internal invasion also was substantial. The mold flora, both before and after surface disinfection, was dominated by species of the Aspergillus glaucus group, Asperigillus flavus , Aspergillus candidus , Penicillium cyclopium , plus species of Alternaria and Cladosporium . The toxicogenic species A. flavus , Aspergillus nidulans , Aspergillus ochaeceus , Aspergillus versicolor , Penicillium citrinum , P. cyclopium , and Pencillium viridicatum were encountered regularly in non-surface-disinfected soybeans. Except for A. flavus and P. cyclopium , the occurrence of toxicogenic species Aspergillus melleus , soybeans was sporadic. The toxicogenic species Aspergillus melleus , Pencillium expansum , and Penicillium urticae were encountered occasionally, but only in non-surface-disinfected soybeans. Penicillium chrysogenum , the penicillin-producing organism, was encountered regularly in non-surface-disinfected soybeans, but less frequently in disinfected soybeans.

Recovery of Salmonella from high-moisture foods by abbreviated selective enrichment

Five high-moisture foods were used to evaluate both the effect of a 6 h, rather than the standard 24 h, selective enrichment incubation period, and the efficiency of Rappaport-Vassiliadis (RV) medium relative to the use of selenite cystine (SC) and tetrathionate (TT) broths for the recovery of Salmonella . Cheese and lettuce were artificially inoculated with a pool of two serotypes, whereas the other foods were naturally contaminated. Significantly higher numbers of Salmonella -positive test portions were obtained at 24 h with the following food and media combinations: cheese (TT and RV media), lettuce (SC, TT, and RV media), raw chicken (RV medium), and pork sausage (SC, TT, and RV media). There were no significant differences between the two incubation periods in recovery of Salmonella from turkey. Overall, more Salmonella -positive test portions were obtained from samples of lettuce, chicken, and pork sausage selectively enriched in RV medium than in SC or TT broths. The results of this study indicate that not all high-moisture foods can be selectively enriched for 6 h without a significant loss in recovery of Salmonella . RV medium was superior to SC and TT broths for recovery of Salmonella from some meats and was at least as productive in its recovery from the other high-moisture foods tested.

Abbreviated Selective Enrichment, Post Enrichment and a Rapid Immunodiffusion Method for Recovery of Salmonella from Instant Nonfat Dry Milk

Recovery of Salmonella from instant nonfat dry milk was studied by determining the efficiency of 6 and 24 h selective enrichment incubation periods, the productivity of Rappaport-Vassiliadis (RV) medium relative to selenite cystine and tetrathionate broths, and the potential enhancement of post enrichment with GN and M broths. Efficiency of the immunodiffusion method recently approved by the Association of Official Analytical Chemists (AOAC) for recovering Salmonella was also determined. Samples of artificially contaminated instant nonfat dry milk were selectively enriched for 6 h without compromising recovery. There was no advantage in using RV medium, and post enrichment did not enhance recovery. For the evaluation of the immunodiffusion method, three analysts independently read the test kit reactions. Of the 220 samples examined, 42.7-45.5% were positive by the immunodiffusion and the AOAC/Bacteriological Analytical Manual (BAM) culture methods, 42.3-43.2% were negative by both methods, 11.4-14.1% were negative by the immunodiffusion test and positive by the AOAC/BAM culture method, and 0-0.9% were negative by the AOAC/BAM method and positive by the immunodiffusion method.

Recovery of Salmonella from Fluid Milk

Methodology was developed for isolation of Salmonella from skim milk, 2% fat milk, whole milk and buttermilk. Lactose broth, lactose broth plus brilliant green dye, buffered peptone water and each milk type plus brilliant green dye were evaluated as preenrichment broths. Incubation temperatures of 35 and 43°C were compared for use at the preenrichment stage. The recovery of Salmonella was determined after selective enrichment in selenite cystine, tetrathionate and Rappaport-Vassiliadis broths. Results indicated that fluid milk should be examined for Salmonella by being preenriched in lactose broth, subcultured to selenite cystine and tetrathionate broths and streaked to selective agars, with 35°C as the incubation temperature throughout the analysis.

Recovery of Salmonella from frozen shrimp : evaluation of short-term selective enrichment, selective media, postenrichment, and a rapid immunodiffusion method

Frozen shrimp was used as a high-moisture food matrix to evaluate the effect of the following conditions and media on the recovery of Salmonella : comparative efficiency of 6 and 24 h selective enrichment incubation periods; efficiency of Rappaport-Vassiliadis (RV) medium relative to selenite cystine (SC) and tetrathionate (TT) selective enrichment broths; need for postenrichment; and reliability of the immunodiffusion method ( Salmonella 1-2 TEST) as a rapid screening procedure. From a total of 244 Salmonella -positive, samples, recoveries at 6 h for selective enrichments SC, TT, RV(1) receiving 1 ml of inoculum, and RV(2) receiving 0.1 ml of inoculum, were 147, 149, 200, and 169, respectively; at 24 h, recoveries were 148, 142, 193, and 205, respectively. As a selective enrichment, RV medium was generally more productive than either SC or TT broths. Postenrichment reduced method sensitivity. Test kit reactions were read independently by three analysts to evaluate the immunodiffusion method. Examination of 200 shrimp samples by standard cultural and 1-2 TEST methods detected 52.5-57% and 56.5-60.5% positive samples, respectively.

Evaluating Illicit Marihuana for Aflatoxins and Toxigenic Fungi

The illicit use of marihuana as an in toxicant by a proportion of the American population has been a major issue of national concern since the early 1960’ s. Marihuana has been reported to be the most widely used nonlegal psychoactive drug, including cocaine and heroin (Miller and Cisin, 1983). Since marihuana is considered an illegal substance which has a high potential for abuse, and there is no acceptable medical use in the United States (Schedule 1 Drug), it is not regulated by governmental standards; therefore it may be more susceptible to possible contamination.