Silvia L. Resnik

Proposed Theoretical Water Activity Values at Various Temperatures for Selected Solutions to be Used as Reference Sources in the Range of Microbial Growth

This paper compiles recent data on the theoretical prediction of the water activity (aw) of selected saturated salt solutions, unsaturated NaCl and LiCl solutions, and H2SO4 solutions. These results are presented in tabular form in such a way that they can be safely used as reference sources for aw determination in the range of microbial growth (i.e. about 0.57-0.97) and at different temperatures.

Effect of fermentation on naturally occurring deoxynivalenol (DON) in Argentinean bread processing technology.

The stability of naturally occurring DON was evaluated during the fermentation stage of the bread-making process on a pilot scale. Two different products, French bread and Vienna bread, were prepared with naturally contaminated wheat flour (150mg kg -1) under controlled experimental conditions. Dough was fermented at 30, 40 and 50°C according to standard procedures employed in Argentinean low-technology bakeries. When the dough was fermented at 50°C, the maximum reduction was 56% for the Vienna bread, with French bread being reduced by 41%. DON reduction during bread-making occurs not only in the bakery due to thermal decomposition, but also during the fermentation step. The Argentinean traditional bread-making process might reduce DON levels during the fermentation stages if the dough is leavened at temperatures >30°C.

A survey of the natural occurrence of aflatoxins and zearalenone in Argentine field maize: 1983-1994.

A survey was carried out from 1983 to 1994 to determine the natural occurrence of aflatoxins and zearalenone in maize samples from Buenos Aires and Santa Fe provinces, Argentina. Among 2271 samples analysed, 1214 (53.5%) were contaminated with mycotoxins. Aflatoxin B1 was identified in 445 samples (19.6%), aflatoxin B2 was identified in 92 samples (4.1%) and zearalenone was identified in 676 samples (29.8%). Aflatoxin G1 was detected in only one sample and none of the samples contained detectable amounts of aflatoxin G2. Aflatoxin contamination was not detected in the 1988, 1993 and 1994 harvests and, in the other years, with the exception of 1989, the contamination levels were low. Zearalenone was found in every year.

Natural co-occurrence of fumonisins, deoxynivalenol, zearalenone and aflatoxins in field trial corn in Argentina.

Corn samples collected from the main production area in Argentina in 1995 were surveyed for the natural occurrence of Fusarium mycotoxins and aflatoxins. Fumonisins B1, B2 and B3 and zearalenone were found in all samples. A positive relationship was found between fumonisins B1, B2 and B3, B1 and B3, and B2 and B3. Deoxynivalenol and aflatoxins were not detected. Mycological survey has also revealed the predominance of Fusarium moniliforme. This is the first report on the simultaneous occurrence of fumonisins and zearalenone in corn from the main production area in Argentina.

Alternaria alternata prevalence in cereal grains and soybean seeds from Entre Ríos, Argentina.

A mycological survey was carried out at Entre Ríos province, Argentina, on sorghum grain, maize, rice, soybean seeds and on freshly harvested and stored wheat. The isolation frequencies and relative densities of species belonging to genera Alternaria, Aspergillus, Fusarium, Penicillium and other fungi were calculated. Alternaria alternata was the major fungal species isolated from sorghum, rice, soybean seeds and on freshly harvested wheat, and a low incidence of Fusarium species was observed on the same substrates. In maize the major fungal species isolated was Fusarium verticillioides. The high incidence levels of A. alternata observed,suggest that it may be necessary to determine, among other mycotoxins, if Alternaria toxins occur in these commodities.

In vitro effect of phenolic antioxidants on germination, growth and aflatoxin B1 accumulation by peanut Aspergillus section Flavi

Aims:  The effectiveness of the food‐grade antioxidants butylated hydroxytoluene (BHT), trihydroxybutyrophenone (THB), propyl paraben (PP) and butylated hydroxyanisole (BHA) at 1, 10 and 20 mmol l−1 concentrations on germination, growth, and aflatoxin B1 (AFB1) production by Aspergillus section Flavi strains was determined.

Natural occurrence of deoxynivalenol in wheat, wheat flour and bakery products in Argentina.

The objective of this study was to evaluate the natural occurrence of deoxynivalenol (DON) in wheat, wheat flour and different kinds of breads and pastries widely consumed by the population in Argentina. Of 60 wheat samples analysed, 93.3% were contaminated. The average DON contamination level over all samples was 1798 micrograms/kg, and the minimum and maximum values were 100 micrograms/kg and 9250 micrograms/kg, respectively. The wheat flour samples (61 samples) were contaminated with DON at levels ranging from 250 micrograms/kg to 9000 micrograms/kg with an average of 1309 micrograms/kg. The frequency of DON contamination over 42 samples of different bakery products was 92.8%, with levels ranging from 200 micrograms/kg to 2800 micrograms/kg with an average of 464 micrograms/kg. These results suggest a high risk for consumers of wheat products and the need to monitor final products before consumption.

Production of trichothecenes and zearalenone by isolates of Fusarium spp. from Argentinian maize.

Fusarium cultures (27 isolates of Fusarium graminearum, 5 of F. sporotrichioides, 5 of F. semitectum, 2 of F. solani, and one isolate of F. equiseti, F. heterosporum and F. oxysporum respectively, from maize ears) were screened to determine their ability to produce different trichothecenes and zearalenone. Twenty of 27 F. graminearum isolates produced deoxynivalenol (384-5745 micrograms/kg), 7/27 produced 3-acetyl-deoxynivalenol (322-1840 micrograms/kg), 3/27 produced neosolaniol (199-898 micrograms/kg), 5/27 produced diacetoxyscirpenol (205-3095 micrograms/kg), 4/27 produced HT-2 toxin (278-1377 micrograms/kg) and 13/27 produced zearalenone (200-35045 micrograms/kg). No isolate of F. graminearum produced either nivalenol, 15-acetyl-deoxynivalenol, T-2 tosin, T-2 triol or T-2 tetraol. Only chemotype IA (deoxynivalenol and 3-acetyl-deoxynivalenol) was observed. F. sporotrichioides isolates produced deoxynivalenol (5/5), T-2 triol and T-2 tetraol (1/5) and zearalenone (1/5). One F. semitectum isolate produced diacetoxyscirpenol and F. equiseti and F. oxysporum isolates produced only deoxynivalenol. Thus, three of the toxins studied, deoxynivalenol, zearalenone and 3-acetyl-deoxynivalenol are most likely to appear as contaminants in freshly harvested maize.

Fungi associated with food and feed commodities from Ecuador

Freshly harvested soybean, rice and corn from farms and corn-based pelleted feeds were collected from ranches from the coastal and mountain regions in Ecuador during 1998, and assessed for fungal contamination. The most prevalent fungi on pelleted feed were Aspergillus flavus and Fusarium graminearum. The prevalent fungi recovered from soybean were F. verticillioides, F. semitectum, Aspergillus flavus and A. ochraceus. In rice, F. oxysporum was the most prevalent toxigenic fungal species recorded, followed by F. verticillioides and A. flavus. In corn, F. verticillioides was the most prevalent fungus isolated in both the coastal and mountain regions, with high isolation frequencies of A. flavus and A. parasiticus at the coast. Based on the toxigenic species recovered, ochratoxin A may pose a contamination risk for soybean. A higher probability of aflatoxin contamination of corn was found in the coastal samples compared to those of the mountain region, while a risk of fumonisin contamination of corn exists in both regions.

Distribution of fumonisins in dry-milled corn fractions in Argentina

Corn samples and different dry-milled fractions collected from an industrial mill in Argentina were analysed. Average contaminations were FB1 1540 µg kg−1, FB2 716 µg kg−1 and FB3 152 µg kg−1 in whole corn; FB1 135 µg kg−1, FB2 39.1 µg kg−1 and FB3 10.2 µg kg−1 in corn grits; FB1 358 µg kg−1, FB2 122 µg kg−1 and FB3 45.9 µg kg-1 in ‘C’ flour; FB1 148 µg kg−1, FB2 52.5 µg kg−1 and FB3 28.3 µg kg−1 in corn meal; and FB1 4210 µg kg−1, FB2 2010 µg kg−1 and FB3 447 µg kg−1 in germ and bran together. The fumonisin contamination level was approximately three times higher in germ and bran than in whole corn, 13 times higher than in ‘C’ flour and 29 times higher than in corn meal and corn grits. Taking into account the distribution of fumonisins in commercial dry-milled corn fractions and corn meal consumption in Argentina, a theoretical whole corn level of 6640 µg kg−1 maximum of total fumonisins could be processed to obtain products considered safe for human health.