Determination of food contamination by mineral oil from jute sacks using coupled LC-GC.

Jute fibers are treated with about 5-7% of a high boiling mineral oil fraction ("batching oil") to render them flexible for making fabrics. Foods transported in jute bags are contaminated by this batching oil. A method involving automated on-line LC-GC is described for determining these hydrocarbons in various foods. Complete transfer of the LC fraction to GC is presupposed for obtaining the required sensitivity. Results are given for nuts, coffee, cocoa products, and rice. Contamination ranged between about 5 and 500 ppm.

Automated aflatoxin analysis of foods and animal feeds using immunoaffinity column clean-up and high-performance liquid chromatographic determination.

A commercially available system is described for the fully automated clean-up and high-performance liquid chromatographic (HPLC) analysis of aflatoxins in foods and animal feeds. The system marketed primarily for handling solid-phase extraction columns has modified software to facilitate use with immunoaffinity columns. Sample extract clean-up followed by injection onto an HPLC column with post-column iodination and fluorescence detection is carried out completely unattended. A coefficient of variation of 5.1% for aflatoxin B1 analysis was obtained, and the accuracy of the system was demonstrated by the analysis of peanut butter certified reference material.

A further study of oxalate bioavailability in foods.

We extended the study of oxalate bioavailability by testing 7 additional food items: brewed tea, tea with milk, turnip greens, okra, peanuts and almonds. Nine normal subjects ingested a large serving of each of these items. The bioavailable oxalate was calculated from the increment in urinary oxalate during 8 hours after ingestion and bioavailability was determined as the percentage of total oxalate content in a given food item represented by bioavailable oxalate. Brewed tea and tea with milk, with a high oxalate content, had a low bioavailable oxalate level (1.17 and 0.44 mg. per load) because of the low oxalate availability (bioavailability of 0.08 and 0.03%). Turnip greens, with a satisfactory oxalate bioavailability (5.8%), had a negligible effect on urinary oxalate excretion, since oxalate content was relatively low (12 mg. per load). Okra, with a moderate oxalate content (264 mg. per load) had a negligible bioavailable oxalate (0.28 mg. per load). Only peanuts and almonds provided a moderate increase in oxalate excretion (3 to 5 mg. per load) due to the modest oxalate content (116 and 131 mg. per load) and oxalate bioavailability (3.8 and 2.8%). Thus, the ability of various oxalate-rich foods to augment urinary oxalate excretion depends not only on oxalate content but on the bioavailability.

Determination of copper, iron, and nickel in oils and fats by direct graphite furnace atomic absorption spectrometry: summary of collaborative study.

A collaborative study of a method for the determination of copper, iron, and nickel in edible oils and fats by direct graphite furnace atomic absorption spectrometry was recently conducted by the International Union of Pure and Applied Chemistry. The quantitation limits of the method are 5 micrograms/kg for copper and 10 micrograms/kg for iron and nickel. The method has been adopted official first action as an IUPAC-AOAC method.

Phospholipase activation in the cytotoxic mechanism of thionin purified from nuts of Pyrularia pubera.

Treating NIH3T3 fibroblast cells with Pyrularia pubera thionin (100 micrograms/ml) stimulated release of labelled free fatty acids from phospholipids biosynthetically labelled by incorporation of [3H]arachidonic acid. Since Pyrularia thionin exhibited no detectable phospholipase activity, it was concluded that the release response represented activation of endogenous phospholipases in the cells. The phospholipase activated by Pyrularia thionin (100 micrograms/ml) stimulated the release of 61% of the incorporated [3H]arachidonate in the presence of 1.8 mM extracellular calcium with maximum activation at 90 min following an initial lag period of about 20 min. The release response exhibited little dependence on extracellular calcium at this thionin concentration, but at concentrations 20 micrograms/ml, extracellular calcium appeared to be inhibitory to phospholipase activation. Some characteristics of the fatty acid release response are consistent with activation of a lysosomal phospholipase being part of the cellular response to Pyrularia thionin. Activation of a lysosomal enzyme can occur independently or as a result of coordinate activation of the whole lysosome, which would expose other cellular components of degradative lysosomal enzymes. Consistent with coordinate activation of lysosomal enzymes, Pyrularia thionin also stimulates the production of small, trichloroacetic acid-soluble peptides and nucleic acid fragments from biosynthetically-labelled RNA and proteins in treated cells. It is not clear from the results obtained what role, if any, activation of lysosomal enzymes plays in the overall toxic response to Pyrularia thionin in NIH3T3 cells. However, Pyrularia pubera thionin may represent a useful tool for studying the regulation of lysosomal enzymes and their roles in cells.

[Elimination of toxic compounds, biological evaluation and partial characterization of the protein from jojoba meal (Simmondsia chinensis [Link] Schneider]. / Eliminación de compuestos tóxicos, evaluación biológica y caracterización parcial de la proteína de pasta de jojoba (Simmondsia chinensis [Link] Schneider).

The purpose of this study was to establish a new methodology to remove the toxic compounds present in jojoba meal and flour. Also, to perform the biological evaluation of the detoxified products and to chemically characterize the protein fractions. Jojoba meal and seed without testa were deffated with hexane and detoxified with a 7:3 isopropanol-water mixture which removed 86% of total phenolic compounds and 100% of simmondsins originally present, the resulting products had reduced bitterness and caused no deaths on experimental animals. NPR values obtained for diets containing such products were significantly different from those obtained with the casein control (p less than 0.05). Total protein was made up of three different fractions: the water-soluble fraction was the most abundant (61.8%), followed by the salt-soluble (23.6%), and the alkaline soluble fraction (14.6%). The nitrogen solubility curves showed that the isoelectric point for the water-soluble and salt-soluble fractions was pH 3.0, while that of the alkaline fraction fell in the range of 4.5-5.0. All fractions had a maximum solubility at pH 7.0. The methodology reported here, offers a viable solution to eliminate toxic compounds from jojoba meal or seeds, and upgrades the potential use of products such as animal feed or raw material for the production of protein isolates.

[Chemical composition and content of antiphysiological factors of jojoba (Simmondsia chinensis) residual meal]. / Estudio sobre la composición química y contenido de factores antifisiológicos de la pasta residual de jojoba (Simmondsia chinensis).

Jojoba (Simmondsia chinensis) is a perennial plant with an interesting economic value by processing it for liquid wax production. By pressing of jojoba seeds, by-product which has been called "residual meal" has been obtained, and because of its high protein content, it would be a great interest to evaluate it as animal feedstuff. The results of this study showed the following. Both seed and residual meal were analyzed in regard to their chemical proximal composition: crude protein 14.03 and 25.24%; ether extract, 48.89 and 14.73%; crude fiber, 10.03 and 10.07%; ash, 1.59 and 4.72, and nitrogen-free extract, 25.46 and 45.25, the limiting amino acids being methionine, lysine and isoleucine. The trypsin inhibitor factors were 13.747 and 11,197 TIU/g; and hemagglutinins and saponins were negative for both samples. Cyanogenic glucosides were positive in both samples. It was concluded that jojoba residual meal is an alternative as an adequate feedstuff in those regions where jojoba is produced. Nevertheless, prior to consumption it must be treated so as to eliminate the toxic factors.

A survey using normal-phase high-performance liquid chromatography of aflatoxins in domestic and imported foods in the USSR.

A survey of the occurrence of aflatoxins B1, B2, G1 and G2 in Soviet domestic and imported cereals and nuts (totalling 4532 samples) collected in 1985-87, showed that 26.9% of imported peanuts, 2.2% of corn and 28.3% of cotton seeds were contaminated by aflatoxins at levels exceeding the maximum tolerated level established in the USSR (5 micrograms/kg for aflatoxin B1 in foodstuffs of all types excluding baby foods); maximum concentrations were 3650, 600 and 153 micrograms/kg, respectively. A highly sensitive normal-phase high-performance liquid chromatographic method was developed. The detection limit was 0.1 microgram/kg and the coefficients of variation were 11% and 8.5% at contamination levels 10 and 100 micrograms/kg of aflatoxin B1, respectively.

Concentration of selected heavy metals in spices, dry fruits and plant nuts.

Different spices, dry fruits and plant nuts commonly consumed in Pakistan were assayed for the heavy metals cadmium, lead, copper, zinc, iron and manganese by the potentiometric stripping analysis and AA spectrophotometry. The results revealed wide variation in heavy metal content among different biological materials. Mixed spices generally exhibited higher value for trace metals specially lead (6.6-9.2 micrograms/g), cadmium (0.65-1.34 micrograms/g), iron (142.3-285.0 micrograms/g) and zinc (64.2-65.8 micrograms/g). Dry fruits contained relatively lesser amounts of heavy metals than plant nuts. Almonds contained higher levels of lead (1.02 micrograms/g) and cadmium (0.24 micrograms/g) than other nuts and dry fruits.

Aflatoxins in domestic and imported foods and feeds.

Aflatoxins, metabolic products of the molds Aspergillus flavus and A. parasiticus, may occur in foods and feeds. These toxins cannot be entirely avoided or eliminated from foods or feeds by current agronomic and manufacturing processes and are considered unavoidable contaminants. To limit aflatoxin exposure, the U.S. Food and Drug Administration (FDA) has set action levels for these toxins in foods and feeds involved in interstate commerce. FDA continually monitors food and feed industries through compliance programs. This report summarizes data generated from compliance programs on aflatoxins for the fiscal year 1986. Commodities sampled included peanuts and peanut products, corn and corn products, tree nuts, cottonseed, milk, spices, manufactured products, and miscellaneous foods and feeds. Correlations were highest between aflatoxin contamination and geographical areas for corn/corn products and cottonseed/cottonseed meal. Higher incidences of aflatoxin contamination in corn and corn products designated for human consumption were observed in samples collected in the southeastern states (32 and 28%, respectively). A higher incidence of contamination was observed in corn designated for animal feed from Arkansas-Texas (74%) than from the southeastern states (47%). Only 3% of feed corn from corn belt states contained detectable aflatoxins. All aflatoxin-contaminated cottonseed was collected in the Arizona-California area; 80% of cottonseed meal analyzed from this area also contained detectable levels of aflatoxins.(ABSTRACT TRUNCATED AT 250 WORDS)

Action of a thionin isolated from nuts of Pyrularia pubera on human erythrocytes.

Pyrularia thionin is a strongly basic peptide of 47 amino acids isolated from Pyrularia pubera. This peptide, a member of the thionin family, is hemolytic, cytotoxic and neurotoxic. The characteristics of the hemolytic activity on human erythrocytes are as follows: (1) the peptide does not itself have any phospholipase activity in a micellar assay system with egg yolk phosphatidylcholine, as evidenced by a lack of pH change or uptake of oxygen in the presence of lipoxidase; (2) erythrocyte membranes treated with thionin, however, show a low level of oxygen uptake in the presence of lipoxidase as a consequence of fatty acid release, and this activity is synergistic with that of bee venom phospholipase A2; (3) hemolysis caused by thionin is synergistic with added bee venom phospholipase A2; (4) kinetic analysis of the hemolytic assay reveals that the reaction follows Michaelis-Menten kinetics, being saturable with thionin with a Km of 1.6 microM; (5) binding studies with 125I-thionin show by Scatchard analysis a Kd value of 2.1 microM; (6) although iodinated thionin is inactive in the hemolysis assay, it acts as a competitive inhibitor to native thionin in the hemolytic assay; the inhibitor constant, Ki, for this reaction is 7.0 microM; and (7) Ca2+ above 1 mM inhibits the reaction. All the data are consistent with thionin binding to a receptor, most likely a protein, on the erythrocyte membrane, leading to the release of free fatty acids, most likely by activation of phospholipase A2. The release of fatty acids is itself not sufficient to explain the hemolytic reaction.

Hemolytic activity of thionin from Pyrularia pubera nuts and snake venom toxins of Naja naja species: Pyrularia thionin and snake venom cardiotoxin compete for the same membrane site.

Pyrularia thionin (P. thionin) is a strongly basic peptide of 47 amino acids which is hemolytic, cytotoxic and neurotoxic. It shows the greatest hemolytic activity toward human erythrocytes. Rabbit, guinea pig and pig erythrocytes show decreasing activity in that order, and little or no activity is shown with sheep, horse, cow or mouse erythrocytes. Crotalus venoms are inactive, but the venoms from Naja naja atra, Naja naja ceylonicus and Naja naja melanoleuca and, more specifically, cardiotoxin from Naja naja kaouthia have significant hemolytic activities toward human erythrocytes. The cardiotoxin preparation used had no phospholipase activity, and was less active than P. thionin (23% compared to 35% hemolysis by P. thionin in 60 min at 10 micrograms/ml toxin). Since iodinated P. thionin is inactive, it was used as an inhibitor of hemolysis catalyzed by native P. thionin, N. ceylonicus venom and by cardiotoxin. Examination of the kinetics of the reactions catalyzed by N. ceylonicus venom and cardiotoxin in the absence and presence of iodinated P. thionin shows that both N. ceylonicus venom and cardiotoxin exhibit Michaelis-Menten kinetics, yielding apparent Km values of 7.4 micrograms/ml and 0.69 microM, respectively. These values compare to an apparent Km for P. thionin of 1.6 microM for erythrocyte hemolysis and a binding constant of 2.1 microM (Osorio e Castro, V. R. Van Kuiken, B. A. and Vernon, L. P. (1989) Action of a thionin isolated from nuts of Pyrularia pubera on human erythrocytes. Toxicon 27, 501). The inhibition constants Ki for iodinated P. thionin in the reactions with N. ceylonicus venom and cardiotoxin are 3.8 and 5.3 microM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

[Procyanidin polymers, the crucial ingredients of the almond seed coat]. / Polymere Procyanidine, die prägenden Bestandteile der Mandel-Samenschale.

The seed coat of almond (Prunus amygdalus Batsch) contains up to 30% procyanidins with different degrees of polymerisation and, in addition, fatty oils, lignin, polysaccharides and cutin. Monomer units of dimers to tetracosamers are (-)-epicatechin and (+)-catechin. Prodelphinidins could not be detected. The dimers B-1, B-3, B-4, trimers and oligomers are soluble in acetone/water. The bulk material is large polymer, that is only soluble, by thiolysis, in thioglycolic acid. The large polymer procyanidins are crucial to the structure and attributes of the seed coat.

Spectrophotometric method for determination of phosphine residues in cashew kernels.

A spectrophotometric method reported for determination of phosphine (PH3) residues in wheat has been extended for determination of these residues in cashew kernels. Unlike the spectrum for wheat, the spectrum of PH3 residue-AgNO3 chromophore from cashew kernels does not show an absorption maximum at 400 nm; nevertheless, reading the absorbance at 400 nm afforded good recoveries of 90-98%. No interference occurred from crop materials, and crop controls showed low absorbance; the method can be applied for determinations as low as 0.01 ppm PH3 residue in cashew kernels.

2-chloroethyl fatty acid esters as indicators of 2-chloroethanol in black walnuts, seasoning mixes, and spices.

Residues of 2-chloroethyl fatty acid esters (CEEs) and 2-chloroethanol (ECH), by-products of ethylene oxide fumigation, were determined in black walnuts, seasoning mixes, and spices. Extracts containing ECH and CEE were cleaned up by previously described procedures, and residue levels were quantitatively determined using a gas chromatograph equipped with a halogen-selective electrolytic conductivity detector. All food products that contained CEE residues also contained ECH. ECH residues ranged from less than 0.2 to 880 ppm and were less than 0.2-7 times the CEE levels found.

Properties, biosynthesis and processing of a sulfur-rich protein in Brazil nut (Bertholletia excelsa H.B.K.).

An abundant seed protein, which is exceptionally rich in the sulfur-containing amino acids, methionine (18%) and cysteine (8%), is synthesized in Brazil nut embryos about 9 months after flowering. This sulfur-rich protein consists of two low-molecular-mass polypeptide components, a 9-kDa polypeptide and a 3-kDa polypeptide. The two-subunit polypeptides associate through disulfide linkage(s) to form a 12-kDa protein molecule. We have demonstrated through in vitro translation studies, using RNA from 9-month-old embryos, that the sulfur-rich protein is synthesized as a larger precursor polypeptide of 18 kDa. In addition, data from in vivo labelling studies of 9-month-old Brazil nuts suggest that there are two intermediate precursors of the sulfur-rich protein, one of 15 kDa and another of 12 kDa. One of these precursors, the 12-kDa polypeptide, accumulates for a 2-month period in the developing embryos. From these data we infer that at least three stepwise cleavages are involved in the maturation of the sulfur-rich protein from its 18-kDa precursor.

Cyclopiazonic acid production by cultures of Aspergillus and Penicillium species isolated from dried beans, corn meal, macaroni, and pecans.

Ninety-five isolates of Aspergillus and Penicillium species from selected dried foods were examined for their ability to produce cyclopiazonic acid (CPA). The isolates were grown in sterile synthetic liquid medium at 28 degrees C for 8 days in the dark. The medium and mold mycelia were then extracted with chloroform. CPA was semiquantitatively determined by thin layer chromatography through visual comparison with standards. The cultures of A. flavus were also examined for their ability to produce aflatoxin. One A. tamarii and all 13 P. urticae isolates produced CPA, whereas only 19 of the 31 (61%) A. flavus isolates produced CPA, and 6 (19%) A. flavus produced aflatoxin. All 13 P. urticae isolates also produced patulin and griseofulvin. CPA-producing A. flavus was found in all food types but not in all samples. CPA-producing P. urticae was found only in dried beans and macaroni.

Lipids of high-yielding varieties of cashew (Anacardium occidentale L.).

Cashew kernel lipids from high-yielding varieties have been characterised. Neutral lipid accounted for 96% while glycolipid and phospholipid accounted for the remaining 4%. Triglycerides were very rich in unsaturated fatty acids (oleic and linoleic) while glycolipids were rich in saturated fatty acids (lauric and myristic). Varietal difference was noticed with respect to the composition of neutral and glycolipids. Composition of phospholipid did not differ among high-yielding varieties.