Sample preparation for aflatoxin assay: The nature of the problem and approaches to a solution

Cases have been reported of individual peanuts, cottonseeds or Brazil nuts so highly contaminated with aflatoxin that, for a 50 g portion to be representative of the whole, the sample preparation procedures should grind each unit to a large number of particles and distribute them uniformly throughout the sample. Assuming uniform contamination of the individual kernel, each 50 g sample should contain 1/100 of that kernel. Even though these extreme cases may be encountered only infrequently, the more usual situation still presents difficulties because of great variability in individual kernel contamination. However, if the extreme can be handled, one can expect to handle the more usual situation. Equipment and procedures to achieve this distribution goal are described. The equipment studied includes a food chopper (Hobart), a nut mill (Thomas Mills), a disc mill (Bauer), a hammer mill (Fitzpatrick Model D comminuting machine), a hammer mill designed specifically for peanut samples (Dicken’s subsampling mill), a Polytron homogenizer (Bronwill Scientific), a vertical cutter-mixer (Hobart), and a sample splitter (Jones riffle). Commodities examined were shelled peanuts and in-shell Brazil nuts, walnuts, pecans and almonds. Comminution and mixing effectiveness were determined by particle size analysis, by distribution of kernels made radioactive by neutron activation and by aflatoxin analysis of naturally contaminated products. From the results we conclude that the ultimate in sample uniformity can be achieved with a disc mill, solvent addition to obtain a fluid system and mixing and grinding of the fluid with a dispersion mixer-grinder. A practical uniformity can be achieved in a vertical cutter-mixer with less expenditure of time and effort for the commodities studied. Presented in part at the AOCS-AACC Joint Meeting, Washington, D.C., April 1968.     

An investigation of oven methods for determining the moisture content of shelled peanuts

Air-oven methods, using ground, sliced, and whele shelled peanuts, were investigated. The use of ground samples was found to be unsatisfactory. Slightly more accurate results were obtained with whole nuts than with sliced nuts. The method of heating 50-g. samples of whole shelled peanuts for 3 hrs. at 130°C. in a foreed-draft oven gave results agreeing closely with those obtained by the Karl Fischer method for samples of low moisture content.     

Textural,Rheological and Sensory Properties and Oxidative Stability of Nut Spreads—A Review

Tree nuts are rich in macro and micronutrients, phytochemicals, tocopherols and phenolic compounds. The development of nut spreads would potentially increase the food uses of nuts and introduce consumers with a healthier, non-animal breakfast snack food. Nut spreads are spreadable products made from nuts that are ground into paste. Roasting and milling (particle size reduction) are two important stages for the production of nut spreads that affected the textural, rheological characteristic and overall quality of the nut spread. Textural, color, and flavor properties of nut spreads play a major role in consumer appeal, buying decisions and eventual consumption. Stability of nut spreads is influenced by its particle size. Proper combination of ingredients (nut paste, sweetener, vegetable oil and protein sources) is also required to ensure a stable nut spread product is produced. Most of the nut spreads behaved like a non-Newtonian pseudo-plastic fluid under yield stress which help the producers how to start pumping and stirring of the nut spreads. Similar to other high oil content products, nut spreads are susceptible to autoxidation. Their oxidation can be controlled by application of antioxidants, using processing techniques that minimize tocopherol and other natural antioxidant losses.     

Comparison of the observed distribution of aflatoxin in shelled peanuts to the negative binomial distribution

Suitability of the negative binomial distribution for use in estimating the probabilities associated with sampling lots of shelled peanuts for aflatoxin analysis has been studied. Large samples, called “minilots,” were drawn from 29 lots of shelled peanuts contaminated with aflatoxin. These minilots were subdivided into ca. 12 lb samples which were analyzed for aflatoxin. The mean and variance of these aflatoxin determinations for each minilot were determined. The shape parameterk and the mean aflatoxin concentrationm were estimated for each minilot. A regression analysis indicated the functional relationship betweenk andm to be:k=(2.0866+2.3898m) × 10⁻⁶. The observed distribution of sample concentrations from each of the 29 minilots was compared to the negative binomial distribution by means of the Kolmogorov-Smirnov test. The null hypothesis that each of the true unknown distribution functions was negative binomial was not rejected at the 5% significance level for all 29 comparisons. Journal Series Paper of the North Carolina State University Agricultural Experiment Station, Raleigh, N.C.     

Influence of decreased sample size on cone calorimeter results

Cone calorimeter sample size sensitivity and the influence of sample size on the results were studied in order to investigate the possibility to use smaller samples than prescribed by the standard. The influence of the position of the sample on the sample holder of the decreased samples was also studied. Samples of birch plywood, industrial two‐component polyurethane adhesive and polypropylene wax were tested. The results from standard size sample experiments, 100 cm ², and decreased sample size, 50 and 25 cm², were compared, in order to investigate the sample size influence on the results. The experiments were performed using an external heat flux of 50kW/ m². The results show differences between the sample types. The measured heat release rates for plywood and polyurethane adhesive indicate that the sample size is possible to down‐scale, while the polypropylene wax results show the opposite. All sample types and sizes show constant results for the effective heat of combustion, indicating down‐scalability. For in‐house testing and screening of materials, downscaling can be used for most sample types. However, results from experiments carried out with decreased sample size should not be compared to results from experiments executed according to the standard procedure. Copyright © 2011 John Wiley & Sons, Ltd.     

Fat‐soluble bioactives in nuts

The levels and compositions of fat‐soluble bioactives such as fatty acids, tocols, phytosterols, and sphingolipids present in 12 nut oils (almond, Brazil nut, cashew, chestnut, hazelnut, heartnut, macadamia, peanut, pecan, pine nut, pistachio, and walnut) are reported and compared. Meeting the recommended daily intake of vitamin E and phytosterols by consuming nuts is discussed. The health benefits of fat‐soluble bioactives in nuts have been thoroughly reviewed. Research findings from over 88 references, many of which published only within the last 10 years, have been compiled and reported.     

Macadamia Nut Consumption Modulates Favourably Risk Factors for Coronary Artery Disease in Hypercholesterolemic Subjects

Macadamia nuts are rich source of monounsaturated fats (oleic and palmitoleic acids) and contain polyphenol compounds, therefore, their consumption can be expected to impart health benefits to humans. This study was conducted to examine the effects of consuming macadamia nuts in hypercholesterolemic male individuals on plasma biomarkers of oxidative stress, coagulation and inflammation. Seventeen hypercholesterolemic male subjects were given macadamia nuts (40–90 g/day), equivalent to 15% energy intake, for a period of 4 weeks. As expected, monounsaturated fatty acids (16:1n-7, 18:1n-9 and 20:1n-9) were elevated in the plasma lipids of all volunteers following intervention with macadamia nuts. Plasma markers of inflammation (leukotriene, LTB₄) and oxidative stress (8-isoprostane) were significantly lower (1,353 ± 225 vs. 1,030 ± 129 pg/mL and 876 ± 97 vs. 679 ± 116 pg/mL, respectively) within 4 weeks following macadamia nut intervention. There was a non-significant (23.6%) reduction in the plasma TXB₂/PGI₂ ratio following macadamia nut consumption. This study demonstrates, for the first time, that short-term macadamia nut consumption modifies favourably the biomarkers of oxidative stress, thrombosis and inflammation, the risk factors for coronary artery disease, despite an increase in dietary fat intake. These data, combined with our previous results on cholesterol-lowering effects of macadamia nuts, suggest that regular consumption of macadamia nuts may play a role in the prevention of coronary artery disease.     

Determination of the country of origin of pistachio nuts by DSC and HPLC

The laboratories of the U.S. Customs Service frequently encounter the major analytical problem of determining the country of origin of imported commodities. This is particularly challenging with natural products. This paper will describe the process for one such commodity —pistachio nuts. Two approaches were taken, high performance liquid chromatography (HPLC) and Differential Scanning Calorimetry (DSC). It was found that the results of these two techniques were complimentary and confirmatory. The HPLC data was obtained on the petroleum ether soluble fraction of the pistachio nuts while the DSC runs evaluated both this fraction and the whole nut. The HPLC results were further investigated by collecting fractions from the eluting peaks, derivatizing them to form the methyl ester of the fatty acids, and profiling by gas chromatography to confirm the triglycerides originally present. The U.S. Customs Service is currently using DSC area ratios to screen imported pistachio nuts for country of origin.     

Variability associated with testing corn for aflatoxin

The sampling, subsampling (both coarse and fine ground meal), and analytical variances associated with testing shelled corn for aflatoxin were estimated by the use of 500 g samples, 50 g subsamples, and the CB method of analysis. The magnitudes of the variance components increased with an increase in the aflatoxin concentration. Functional relationships were developed to predict the variance for a given aflatoxin concentration and any size sample, subsample, and number of analyses. At 20 ppb total aflatoxin, the coefficient of variantion associated with a 4.54 kg sample, 1 kg subsample of coarsely ground meal (passes a #14 screen), a 50 g subsample of finely ground meal (passes a #20 screen) and one analysis were 21, 8, 11, and 26%, respectively.     

Survey of aflatoxins in California tree nuts

Surveys of the California walnut and almond crops to determine incidence of aflatoxins are reported. Average proportions of contaminated nuts from the field were one in 28,250 for walnuts and one in 26,500 for almonds. It was shown that there is a high correlation of contamination with damaged nuts which are removed by standard sorting procedures. Statistical treatment of data from the surveys indicates some of the problems in sampling tree nuts for analysis.     

DETERMINATION OF MOISTURE DIFFUSIVITY OF PINE NUT SEEDS

The mechanism of drying and the diffusion of water in fresh pine nut seeds (2.5-2.62mm diameter) were successfully interpreted and modeled by using Fick's law. The initial moisture content of fresh pine nut seed was 23-24% and drying temperatures (45-60°C) were varied, but the drying air was kept at constant velocity and humidity.

The effective diffusivity was estimated from drying rate curves and expressed by an Arhenius relation. In addition, the absorption, and desorption-isotherms for fresh pine nuts were estimated at 20°C at water activity of 0.15-1.00. The isotherms of the fresh pine nuts were estimated in experimental runs.     

Non-volatile vanadium determination in petroleum condensate,diesel and gasoline prepared as detergent emulsions using GF AAS

The development of a procedure for non-volatile vanadium determination in petroleum derivative products by graphite furnace atomic absorption spectrometry (GF AAS) using sample preparation as detergent emulsion is presented. Emulsions of samples were make using concentrate nitric acid, Triton X-100, samples and water in the proportions of 1/1/2/6 respectively. Doehlert design was applied as experimental matrix to optimize the temperature program. A comparative study among the slopes of some analytical curves built in aqueous, surfactant and organic media and by analyte addition in several sample emulsions (diesel, gasoline and condensate) shows that a unique solution of surfactant in acid media can be used to make the calibration solutions. The developed procedure allows the determination of non-volatile vanadium in these samples with limit of detection (LOD) and limit of quantification (LOQ) of 14 and 45 μg L^?1, respectively. Precision, expressed as relative standard deviation (% RSD, n = 10) for 20 and 80 μg L^?1 were 6.4–2.9%, respectively. The proposed procedure was applied in the determination of vanadium in samples of petroleum condensate, gasoline and diesel. Accuracy was evaluated by spike tests in the analyzed samples. Results of recovery between 90% and 105% show that it can be successfully applied to this kind of samples.     

A study of the variability associated with sampling peanuts for aflatoxin

One lot of peanuts known to contain aflatoxin was extensively sampled to study the sources of variability. A nested design was used where sections (50 bag units), subsamples and analytical variation were the variables studied. Sample size was the most critical factor in characterizing this lot. Variability from section to section was not significant indicating random distribution of the contaminant. Three 20 lb samples were taken on a number of lots from the 1968 crop, each of which was subdivided into two equivalent subsamples. The aflatoxin was determined on each of these subsamples. The results indicated that all the significant variation came from the subsamples, further enforcing the thesis that sample size is the critical factor in variability, and not lot inhomogeneity. Analysis of 550 lots from the 1967 crop where triples and analysis were available indicates that the magnitude of the variability is a little greater than was found on the experimental lot. Using the pooled standard deviation of the 1967 crop data, operating characteristic curves were plotted to demonstrate the improvement that can be expected by increasing the sample size.     

Oxidative Stability of Cashew Oils from Raw and Roasted Nuts

Cashew nut oils, extracted from raw and roasted whole cashew nuts, were examined for their fatty acid composition, color change and oxidative stability. Fatty acids were analyzed using gas chromatography, and a spectrophotometric method was used to determine the color changes of the resultant oils. Oxidative stability was determined under accelerated oxidation conditions by employing conjugated diene (CD) and thiobarbituric acid reactive substances (TBARS) assays. The contents of monounsaturated (MUFA), polyunsaturated (PUFA) and saturated (SAFA) fatty acids were 61, 17 and 21%, respectively. Oleic acid was the major MUFA whereas linoleic acid was the main PUFA present in cashew nut oils. Oxidative stability of the oil as determined by CD values after 72 h of storage under Schall oven condition at 60 °C was 1.08 and 0.65 for the raw and high temperature roasted cashew nut, respectively. The TBARS values, expressed as malondialdehyde equivalents decreased with increasing roasting temperature. Thus roasting of whole cashew nuts improved the oxidative stability of the resultant nut oils.     

Fluorescence in pistachio nuts contaminated with aflatoxin

Bright greenish-yellow fluorescence under long wave ultraviolet light was observed on the shells of 7% of the nuts in samples from 46 aflatoxin contaminated commercial lots of Iranian pistachio nuts. Kernels from the fluorescent nuts contained 50% of the aflatoxin in the samples. No aflatoxin was found in any of the shells. When kernels and shells were cultured, toxicogenic fungi grew from only 4% of the shells and 21% of the kernels from fluorescent nuts and from 9% of the shells and 15% of the kernels from nonfluorescent nuts.     

FT-IR studies on the evolution of different phases and their interaction in ferric molybdate—molybdenum trioxide catalysts

Two samples of Fe–Mo catalysts have been prepared from ferric nitrate and ammonium paramolybdate, one following a conventional procedure and the other by a new precipitation procedure in a buffer medium. The evolution of different Fe–Mo phases, from the fresh precipitate to the aged and then to the calcined state, has been followed by FT-IR spectroscopy. All the spectral vibrations have been related to different coordination spheres of Mo and Fe ions in the samples and a comparison with a commercial catalyst of similar composition has been made. The new preparation procedure leads to small, uniform (0·3 μm size) particles and a homogeneous morphology of phases as seen by scanning electron microscopy. Additionally, a higher surface area (10·3 m² g^?1), lower bulk density (0·66 g cm^?3), a methanol conversion efficiency of > 90% and an HCHO selectivity of 95% distinguish this sample from the conventionally prepared one. Better thermal stability of this sample is inferred from the IR spectral and XRD analyses of the heat-treated (up to 800°C) samples and is related to the interaction between Fe₂(MoO₄)₃ and MoO₃ phases.     

Design and Characteristics of Novel Sensory and Nutritionally Oriented Olive,Seed, and Nut Virgin Oils’ Blendings

Virgin olive oil is considered a key component of the Mediterranean Diet, while nut and seed “cold-pressed” oils stand out as an interesting ingredient due to the growing consumer demand toward so-called gourmet and healthy oils. The main objective of this work is the development and characterization of novel virgin vegetal oils based on blendings of virgin olive oil with virgin oils obtained from seeds (sesame and flaxseed) and nuts (hazelnut and pistachio) of interest due to their peculiar nutritional and organoleptic characteristics. Oil formulations elaborated with 5% of sesame oils achieve a high content in vitamin E (842 mg kg⁻¹, 11.8 mg per standard 14 g oil dose, corresponding to an 80% of the recommended daily intake) and with 10% of flaxseed a high level in essential α-linolenic acid (6.4%, 0.90 mg per dose corresponding to a 66% of the recommended daily intake). In addition, sensory analysis shows that blends enriched with both 50% hazelnut oil and 75% pistachio oil not only maintain the typical aroma of virgin olive oil, but incorporate the characteristic nutty, roasty, seed-like, and sweet sensory attributes of nuts, providing an added value to the consumers.     

Nuts, cardio and cerebrovascular risks. A Spanish perspective

Nuts have been included in human diets for ages. They are very appreciated and used as a central component of sweets and desserts. However, during the last decades, scientific interest in those foods has increased enormously as many epidemiologic studies show protective effects of nut consumption on coronary heart disease in different population groups. To date, many clinical trials have analyzed the positive effects of nuts consumption (almond, walnut, pistachio, Macadamia nut, and pecan) on the lipid profile, decreasing total and low density lipoproteins (LDL) cholesterol. However, whether these effects are only due to their fatty acid composition or to any other bioactive compounds, such as tocopherols, phytosterols and phytoestrogens, it is still unknown. This paper, aims to review comparative composition aspects of nuts, such as the positive effects on body weight, lipoprotein metabolism, and protection against cardiovascular and cerebrovascular diseases. The inclusion of 25 g/day of nuts, mainly raw, into a prudent diet seems to be recommended. Further investigations, as actual information is still scarce, in order to dilucidate the relationship between nuts consumption and vascular diseases are proposed.     

In vitro cellular response and hydrothermal aging of two-step sintered Nb2O5 doped ceria stabilized zirconia ceramics

Niobia (1 mol. %) doped Ceria Stabilized Zirconia (NbCSZ) powders were synthesized using a co-precipitation method. The synthesized powders were uniaxially compacted and sintered in air. The two-step sintering method was adopted to sinter the samples, and the sintering schedule was optimized based on density, grain size, the phase present, and the hardness of the sintered sample. It was observed that the two-step sintering method effectively suppressed the grain growth of NbCSZ samples and helped in achieving a finer grain size of 1.57 μm along with the hardness of 1195 HV10 and optimum fracture toughness value 6.20 MPa m^1/2. The Low-Temperature Degradation (LTD) behavior of the sintered samples was estimated through an accelerated hydrothermal aging test, which revealed that the samples are highly resistant to LTD and shown no phase change even after 150 h of study. Moreover, the cytocompatibility of the NbCSZ was tested by culturing MG63 cells on the samples for 7 days. The NbCSZ was found to be highly biocompatible as evident from cell viability and metabolic activity assay.     

Antioxidant concentration effect on stability of Brazil nut (Bertholletia excelsa) crude oil

Shelled and broken Brazil nuts easily lose quality, if not properly stored. Pressing is an alternative use of these nuts and the crude oil stability was studied. Our previous studies demonstrated that TBHQ (200 mg kg-1) was very efficient to prevent rancidity development in oils bottled in brown and clear glass. As TBHQ has higher price than other phenolic antioxidants like BHT and BHA, an oven test (at 63 degrees C) was conducted to determine the economical and best concentration of TBHQ for Brazil nut crude oil. An assay at ambient temperature was conducted in brown and clear glass flasks with and without the economical concentration of TBHQ calculated (83 mg kg-1) for 90 days. Acid, peroxide, and iodine indices and the absorptivity at 232 nm were determined. TBHQ, even at this low dosage, was very efficient in both brown and clear glass flasks. Peroxide value increased from 11.5 meq O2 kg-1 to average 15 and 35, in TBHQ and control samples after 90 days. The absorptivity at 232 nm remained at 1.3 in samples with TBHQ while the control increased to 1.6.