Relationship betweenAspergillus flavus growth fat acidity,and aflatoxin content in peanuts

The influence of fungal growth, under standardized conditions, on fat acidity in large-seeded Virginia-type peanuts inoculated withAspergillus flavus and relationships between fat acidity and aflatoxin, a toxic metabolite produced byA. flavus were studied. Fat acidity increased quadratically and was highly correlated with visible fungal growth. A lag in aflatoxin production in relation to fat acidity increase was noted; fat acidity reached 60 mg KOH per 100 g kernels before aflatoxin became detectable. This relationship suggests that a rapid method of determining fat acidity might be used to sereen peanut samples for the possible presence of aflatoxin. A rapid method of determining fat acidity is cited and compared with the official A.O.A.C. method.     

Limiting temperature and relative humidity for aflatoxin production byAspergillus flavus in stored peanuts

Sound mature kernels, broken mature kernels, immature kernels and unshelled cured Early Runner peanuts were inoculated with spores ofAspergillus flavus and incubated up to 84 days in controlled environment cabinets. In a series of experiments temperatures ranged from 8 to 49 C in combination with 98±1% relative humidity (RH); in others RH was varied from 70% to 99% at 30±1/2 C and from 83% to 99% at 20±1/2 C. Samples were removed after 7, 21, 42 and 84 days of incubation and assayed for aflatoxin, free fatty acids and peanut kernel moisture. Aflatoxin was formed in sound mature kernels at 40 C and 14 C and in broken mature kernels at 13 C, but none was formed at 41 C after 21 days or at 12 C after 84 days in 98±1% RH. The limiting temperatures for aflatoxin formation in peanut kernels with intact shells were 41 C for 21 days and 16 C for 84 days of incubation. The limiting RH at 30 C for aflatoxin production in sound mature kernels was 84%, whereas in broken mature and immature kernels it was 83% and in kernels from unshelled peanuts the limiting RH was 86% for 84 days of incubation. The limiting RH at 20 C for sound and broken mature kernels was 83%, whereas it was 86% RH for immature kernels and 92% for kernels from unshelled peanuts. Free fatty acid formation was correlated with visible growth of fungi rather than with aflatoxin production. Aflatoxin formation was generally correlated with kernel moisture contents of 10% or higher.     

Limiting temperature and relative humidity for growth and production of aflatoxin and free fatty acids byAspergillus flavus in sterile peanuts

Sound mature kernels, broken mature kernels, immature kernels, and unshelled Early Runner peanuts were heat-treated in controlled environment cabinets and inoculated with spores ofAspergillus flavus. Treatments were incubated at 97-99% relative humidity at different temperatures ranging from 5 to 55C and also at 30C with relative humidities ranging from 55 to 99%. Samples were removed after 7 and 21 days and assayed for aflatoxin, free fatty acids, and peanut kernel moisture. The limiting relative humidity for aflatoxin production byA. flavus was 85ŷ1% relative humidity for 21 days at 30C. The limiting low temperature for visible growth and aflatoxin production by the fungus was 13ŷ1C for 21 days at 97-99% relative humidity. Damaged kernels, however, developed some afllatoxin in 21 days at 12C. The maximum temperature for aflatoxin production was 41.5ŷ1.5C for 21 days at 97-99% relative humidity. Fungus growth and sporulation at 43C were equal to that at 40C, but no aflatoxin was produced. Moisture content of immature kernels was higher at equilibrium with the same relative humidity than the moisture content of sound mature kernels, damaged kernels, or kernels from unshelled peanuts. There appeared to be no proportional quantitative correlation between synthesis of aflatoxin and production of free fatty acids in nonliving peanuts, but no aflatoxin was produced without a simultaneous increase in free fatty acids.     

Effect of roasting oil composition on the stability of roasted high-oleic peanuts

Off-flavor due to lipid degradation is an important factor in the shelf life of peanut products. The use of recently developed peanuts with high-oleic acid/linoleic acid (O/L) ratio has the potential to significantly extend the shelf life of roasted peanuts. To determine the full potential for shelf-life improvement of oil-roasted high-O/L peanuts, a study was conducted to examine the effects of roasting high-O/L peanuts (O/L=30) in high-O/L (O/L=23.2) or conventional (O/L=1.5) peanut oil. Peanuts were roasted at 177°C to Hunter L values of 49±1. Roasted peanuts were stored at 30°C for 20 wk. Samples were taken at regular intervals to determine PV, oxidative stability index (OSI), moisture content, and water activity. The O/L ratio of high-O/L roasted peanuts was 27.9 vs. 13.6 for the conventional oil-roasted peanuts. After 20 wk of storage, PV of conventional oil-roasted peanuts was 10.8 compared to 5.3 for the high-O/L-roasted peanuts. OSI values were 88.5 and 52.4 immediately after roasting for the high-O/L-roasted vs. conventional oil-roasted peanuts. OSI for both decreased, but differences remained similar throughout the storage period. Shelf life of high-O/L peanuts decreased when roasted in conventional O/L-peanut oil vs. high-O/L peanut oil.     

Effect of carbon dioxide,temperature, and relative humidity on production of aflatoxin in peanuts

Effects of carbon dioxide (CO₂) in combination with reduced relative humidities (RH) and temperatures on growth and aflatoxin production byAspergillus flavus in peanuts were investigated. Sound mature kernels of Early Runner peanuts were surface disinfested, inoculated withA. flavus, and incubated at various temperatures, RH, and CO₂ concentrations. Visible growth, aflatoxin production, and free fatty acid (FFA) formation byA. flavus was inhibited at approximately 86% RH by 20% CO₂ at 17C and by 60 and 40% CO₂ at 25C. Aflatoxin and FFA levels decreased as RH decreased from approximately 99% to 92% to 86%. At a constant temperature, an increase in CO₂ concentration caused a decrease in aflatoxin and percentage FFA; and, at a given CO₂ concentration, lowering the temperature resulted in a decrease in aflatoxin and percentage FFA.     

Peanut storage studies: Effect of storage moisture on three varieties of runner peanuts

Journal of the American Oil Chemists' Society - Unshelled Dixie Runner, Early Runner, and Virginia Runner G-26 peanuts were stored 31/2 months at moisture contents ranging from 4.8 to 11.2%...     

Phosphate-inhibition of lipase activity in peanuts

Competitive inhibition of lipase activity in extracts of germinating peanuts occurred in media containing inorganic phosphate in concentrations above 10 mM. Lipase activity in germinating castor, cotton, and pumkin seeds and in quiescent castor seed was not similarly affected. Applications of this finding to peanut processing are suggested.     

Ozone Gas Antifungal Effect on Extruded Dog Food Contaminated with Aspergillus flavus

ABSTRACT

Decontamination of Aspergillus flavus spores in inoculated extruded food (Standard and Super-Premium types), through ozone (O₃) gas, was investigated at different concentrations (40 and 60 µmol/mol) and times (30, 60, and 120 min) of exposure. The gas antifungal efficiency, humidity, and lipid stability were evaluated before and after treatments. O₃ reduced A. flavus spores of the extruded food, on both types (p < 0.05). The highest reduction (98.3%) was observed for both food types, when gas was applied for 120 min, regardless of the O₃ concentration. Regarding humidity and peroxide index, there was no difference, either prior to or after the gas application for all treatments conditions. O₃ gas can be an efficient method for fungi spores’ contamination control during commercialization of extruded food in open bags exposed to the environment.     

Effect of harvest date and maturity upon free amino acid levels in three varieties of peanuts

An improved method for the extraction of free amino acids and a peptide of unknown composition with a methanol:chloroform:water mixture (60:25:15; v:v:v) was described. The largest variations were related to maturity. If the amino acids were ranked in descending order, glutamic acid, followed by asparagine (including asparagine, glutamine, threonine, and serine), topped the list in the mature and low intermediate groups, except in Valencia at 141 days. The peptide and phenylalanine were usually in the top six, while aspartic acid occurred there fairly often. Arginine was the highest in immature peanuts. Proline was found in higher concentrations in immature peanuts than previously reported. The presence of two nonprotein amino acids (γ-methyleneglutamine and γ-methyleneglutamic acid) in mature kernels was confirmed. Presented at the AOCS Spring Meeting, New Orleans, May 1973. Journal article 2635 of the Oklahoma Agricultural Experiment Station.     

Rapid method for detecting aflatoxins in peanuts

The thin-layer chromatographic procedure for detecting and quantifying aflatoxin in peanuts is too time-consuming, costly, and difficult to be practical for use by untrained personnel. A method based on millicolumn chromatography was tested and found to be both rapid and simple. Columns are prepared by filling a length of 4-mm glass tubing with silica gel to a depth of about 4.5 cm. The millicolumn is developed in a chloro-form-methanol extract of a peanut sample. If aflatoxin is present, a blue fluorescent band at the lower end of the column is observed when the column is exposed to long-wave ultraviolet radiation. Sensitivity is in the order of 5 ppb and an assay can be completed in 15–25 min. Some degree of quantification is possible by comparison with columns developed in extracts with known aflatoxin contents.     

Effect of maturity on the fatty acid composition of eight varieties of peanuts grown at perkins,Oklahoma in 1968

Eight varieties of peanuts were grown under measured field conditions. Seed obtained at five successive harvest dates and separated into three maturity levels were analyzed for fatty acid composition of oil. Mature peanuts were mostly higher in stearic (18:0) and oleic (18:1) acids, and lower in linoleic (18:2), arachidic (20:0) and behenic (22:0) acids. Oleic-linoleic ratios, which are correlated with oil stability, were higher in mature peanuts. Presented at the AOCS Meeting, Houston, May 1971. Journal Paper No. 1115 of the Georgia Experiment Station and No. 2326 of the Oklahoma Agricultural Experiment Station.     

Fatty acids in lipids of maturing wheat

Two varieties of hard red winter wheat were sampled at various stages of maturity. The lipids in those samples were fractionated into free polar, free nonpolar and bound lipids. Fatty acids of those fractions were determined. Major acids present were palmitic, oleic, linoleic and linolenic. Both wheat samples showed similar qualitative, but not quantitative patterns in distribution of fatty acids during maturation. In the free polar lipid fraction, the palmitic acid content decreased with maturation while the linoleic acid content increased. The free nonpolar fractions showed a slight increase in linoleic acid; the concentration of other acids decreased slightly as the wheat matured. The bound lipid fraction showed a marked increase in linoleic acid, accompanied by decreases in the other major fatty acids, especially linolenic. Cooperative investigations of Kansas Agricultural Experiment Station and Crops Research Div., ARS, USDA.     

Accumulation of Some Heavy Metals on Aspergillus flavus

Uranium and thorium were found to be accumulated extracellularly on the surface of Aspergillus flavus. The rate and the extent of accumulation were subjected to variations in environmental parameters such as pH, temperature and the interference of certain anions and cations. The rates of uranium and thorium uptake by Aspergillus flavus were increased by chemical pretreatment of the cells. Accumulated uranium and thorium were removed chemically from Aspergillus flavus cells. The rate of uptake of uranium and thorium at 25°C±3°C was found to be extremely rapid at pH values of 4·5±0·2 and 2·5±0·2 respectively. Electron microscopic examinations showed that uranium and thorium were accumulated in a dense layer around the surface of Aspergillus flavus cells. © 1997 SCI.     

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. Presented at the AOCS Meeting, Houston, April 1965. Honorable Mention Bond Award Competition. So. Utiliz. Res. Dev. Div., ARS, USDA.     

Elaboration of aflatoxin on cottonseed products byAspergillus flavus

In controlled laboratory experiments heat sterilized and unautoclaved glanded and glandless whole cottonseed or decorticated kernels and sterilized cottonseed meals were found to be utilized as substrates by an aflatoxin elaborating strain ofA. flavus with the production of high levels of aflatoxins B₁, B₂, G₁ and G₂. Gossypol pigments in cottonseed products are apparently not a barrier to either mold invasion or aflatoxin production. Cottonseed hulls, lint cotton, and cottonseed linters were found to be poorly utilized as substrates for either mold growth or aflatoxin production. So. Utiliz. Res. Dev. Div., ARS. USDA.     

Preparation of14C-labeled aflatoxins and incorporation of unlabeled aflatoxins in a blocked versicolorin-A-accumulating mutant ofaspergillus parasiticus

We have compared 2 methods for preparing radiolabeled aflatoxins from [¹⁴C] acetate for use in biosynthetic studies at the end of the aflatoxin pathway. The Salhab-Edwards method (SE) used a 3-day-old mycelium and a defined medium containing MnCl₂ with incubation at 28 C. The Lee-Bennett method (LB) used a 2-day-old mycelium and a defined medium containing low levels of Mn with incubation at 30 C. Generally, the LB method produced lower quantities of aflatoxin but the product had higher specific activities (sp act). The SE method produced 0.157μmol of aflatoxin B₁ and 0.028μmol of G₁ compared to the LB method with 0.058μmol of aflatoxin B₁ and 0.001μmol of G₁. The sp act (inμCi/μmol) for aflatoxin produced by the LB method were: B₁ = 1.379; B₂ = 0.130; G₁ = 5.0 and G₂ - 0.063. The sp act of aflatoxin produced by the SE method were: B₁ = 0.267; B₂ = 0.014; G₁ = 0.178; and G₂ =0.133. Unlabeled aflatoxins were presented to resting cell cultures of the versicolorin-A-accumulating mutant ofAspergillus parasiticus. No conversion of aflatoxin B, was noted. However, when aflatoxins B₂ or G₁ were presented low levels of aflatoxins B₁ and G₂ were recovered. Aflatoxins B₂ and G₁ were recovered when aflatoxin G₂ was presented. Similar low levels of recovery were obtained in experiments using autoclaved mycelia. Thus we conclude that these minor quantities of aflatoxins recovered were not produced enzymatically.     

Effect of pro-oxidants on the occurrence of 2-pentyl pyridine in soy protein isolate

Levels of 2-pentyl pyridine in hexane-defatted soybean flours prepared from Burlison, Stressland, and Probst varieties and a variety null for lipoxygenase 1, 2, and 3 were determined using an internal standard of deuterium-labeled 2-pentyl pyridine. These defatted flours contained from 0.06 to 0.51 ppm 2-pentyl pyridine. The flours from lipoxygenase-null and Stressland varieties of soybeans contained the lowest levels. Control freeze-dried soy protein isolates (SPI) prepared from defatted-flours all contained from 0.16 to 0.18 ppm 2-pentyl pyridine. Adding pro-oxidants (FeCl₃, CuCl₂) or exposing the protein slurries to ultraviolet light during SPI processing increased the level of 2-pentyl pyridine in the protein isolates by up to 1256 percent above the control Burlison, Stressland, and Probst SPI. The CuCl₂ and/or UV treatment contributed the largest increase in each case. The same pro-oxidant and UV treatments contributed no significant increases in the level of 2-pentyl pyridine in the protein isolates from the lipoxygenase null SPI.     

Seasonal variation in character of lipides in pure lines of Spanish peanuts

Summary Several strains of Spanish peanuts in four or more crop years at two locations showed very little variation in calculated oleic and linoleic glyceride values. Presented at the meeting of the American Oil Chemists’ Society, Houston, Tex., April 23–25, 1956. Published as Journal Paper 301 with the approval of the Director of Georgia Experiment Station.