Carol M. Weaver

Determination of totaltrans fatty acids in foods: Comparison of capillary-column gas chromatography and single-bounce horizontal attenuated total reflection infrared spectroscopy

The totaltrans fatty acid content of 18 food products was determined, after acid hydrolysis, extraction and methylation of fatty acids, by gas chromatography with a polar 100% cyanopropylsiloxane capillary column and by single-bounce horizontal attenuated total reflection spectroscopy (SB-HATR). Thetrans fatty acid methyl esters (FAME) of 9-hexadecenoate (9t-16:1), 9-octadecenoate (9t-18:1), and 9,12-octadecadienoate (9t,12t-18:2) were identified by comparison of their retention times with those of known standards and quantitated. The isomersc,t- andt,c-18:2 were identified from their published retention times and included in the quantitation oftrans FAME. Neat 50-μL portions of the FAME that were used for gas-chromatographic analysis also were analyzed by SB-HATR. This technique requires neither weighing nor quantitative dilution of test portions prior to spectroscopic quantitation of isolated double bonds oftrans configuration. A symmetric 966-cm−1 absorption band on a horizontal background was obtained from unhydrogenated soybean oil FAME as the reference material. For 9 of 11 products withtrans fat content>5% of total fat, results obtained by SB-HATR were higher than those obtained by gas chromatography. Results obtained by the gaschromatographic procedure were slightly to significantly higher than those obtained by SB-HATR for the six foods in whichtrans fat content was <5% of total fat.

Aflatoxins in ginseng roots

Ginseng roots can be infected by molds during growth, harvest and storage and result in contamination with mycotoxins. In this study, an analytical method for the determination of aflatoxins B1, B2, G1 and G2, a group of structurally similar mycotoxins, in ginseng root was developed. Test samples were extracted with methanol–water (8 + 2), diluted and passed through an immunoaffinity column packed with antibodies specific for aflatoxins. The purified extract was then derivatized with a mixture of water, trifluoroacetic acid and acetic acid. Aflatoxins were then separated and quantified by reverse phase liquid chromatography (LC) with fluorescence detection. Recoveries of total aflatoxins at 2, 4, 8 and 16 ng/g added to toxin-free 4 to 5-year old dried sliced Wisconsin ginseng were 92, 77, 91 and 83% respectively; and relative standard deviations were 3.6, 8.0, 6.9 and 2.0% respectively. A total of 11 wild simulated and 12 cultivated ginseng root samples were analysed for aflatoxins. All cultivated roots were found to be free of aflatoxin contamination. Two of the wild simulated roots contained total aflatoxins B1, B2, G1 and G2 at 15.1 and 15.2 ng/g. One moldy ginseng root purchased from a grocery store was found to be contaminated with aflatoxins at 16 ng/g.

Comparison of capillary column gas chromatographic and AOAC gravimetric procedures for total fat and distribution of fatty acids in foods

Abstract There is increasing interest in the fatty acid composition, including levels of trans fatty acids, of foods. The trans fatty acid content of American diets is increasingly studied because of reported adverse effects of trans fatty acids on risk of coronary heart disease. In this study, total fat content and fatty acid composition of 43 food products were determined after acid hydrolysis by gas chromatography using an SP-2560 flexible fused silica capillary column. Total fat content determined by the gas chromatographic method was compared with fat content determined by AOAC gravimetric method 922.06 for all food products. Total fat, saturated fat and unsaturated fat content of the foods determined by the gas chromatographic method ranged from 0.9 to 96.7, 0.2 to 16.8 and 0.5 to 89.3%, respectively. Trans fatty acids hexadecenoate ( t-16:1 ), elaidic ( t-18:1 ), and octa-decadienoate ( t , t-18:2 ) were identified by comparison of their retention times with those of known standards and quantitated. These fatty acids were present in foods at levels of 0.25 to 1.50 ( t-16:1 ), 0.87 to 268.32 ( t-18:1 ), and 0.23 to 7.92 ( t , t-18:2 ) mg/g.

Sampling and Analytical Variability Associated with the Determination of Total Aflatoxins and Ochratoxin A in Powdered Ginger Sold As a Dietary Supplement in Capsules

The U.S. Food and Drug Administration is studying the need to monitor dietary supplements for mycotoxins such as total aflatoxins and ochratoxin A. An effective mycotoxin-monitoring program requires knowledge of the sampling and analytical variability associated with the determination of total aflatoxins (AF) and ochratoxin A (OTA) in dietary supplements. Three lots of ginger sold as a powder in capsule form and packaged in individual bottles were analyzed for both AF and OTA. The total variability associated with measuring AF and OTA in powdered ginger was partitioned into bottle-to-bottle, within bottle, and analytical variances. The variances were estimated using a nested design. For AF and OTA, the within-bottle variance associated with the 5 g laboratory sample size was the largest component of variability accounting for about 43% and 85% of the total variance, respectively; the analytical variance accounted for about 34% and 9% of the total variability, respectively; and the bottle-to-bottle variance accounted for about 23% and 7% of the total variance, respectively. When the total variance is converted into the coefficient of variation (CV or standard deviation relative to the mean concentration), the CV is lower for AF (16.9%) than OTA (24.7%).

Sampling and analytical variability associated with the determination of aflatoxins and ochratoxin A in bulk lots of powdered ginger marketed in 1-lb bags

Ginger has been used as a food, dietary supplement, and condiment for centuries. Mycotoxins such as the aflatoxins (AF) and ochratoxin A (OTA) have been reported in ginger roots in several studies. It is important to design effective sampling methods that will accurately and precisely predict the true mycotoxin level in a bulk lot. The objective of this study was to measure the sampling and analytical variability associated with the test procedure used to measure AF and OTA in a bulk lot of powdered ginger using a 5-g laboratory sample and HPLC analytical methods. Twelve 5-g laboratory samples were taken from each of two lots. Duplicate aliquots were removed from each 5-g laboratory sample/solvent blend, and each aliquot was simultaneously analyzed for AF and OTA by HPLC analytical methods. Using a balanced nested design, the total variance associated with the above AF and OTA test procedures was partitioned into sampling and analytical variance components for each lot. Averaged across both lots, the sampling and analytical variances accounted for 87% and 13% of the total variance, respectively, for AF and 97% and 3%, respectively, for OTA. The sampling and analytical coefficients of variation were 9.5% and 3.6%, respectively, for AF, and 16.6% and 2.9%, respectively, for OTA when using a single 5-g laboratory sample and HPLC analytical methods. Equations are derived to show the effect of increasing laboratory sample size and/or number of aliquots on reducing the variability of the test procedures used to estimate OTA and AF in powdered ginger.

Distribution of aflatoxins in shelling and milling fractions of naturally contaminated rice

The objective of this study was to determine the distribution of an economically important class of mycotoxins, the aflatoxins, in rice milling fractions. Rice plants grown under field production conditions are frequently infected with types of pathogenic fungi that produce toxic metabolites (mycotoxins). Paddy (seeds) rice from healthy plants in the field was collected and stored on a farm under humid, poorly ventilated conditions. Samples were milled into four fractions (hulls, brown rice, bran and white rice) and analysed for aflatoxins (B1, B2, G1 and G2) using a validated method. Rice fractions from healthy plants, which contained low levels of aflatoxins (less than 1 µg kg−1), were used to determine the efficiency of the extraction method. Seeds stored under poor conditions were found to be contaminated with aflatoxins B1 and B2 as were the fractions. The sums of AFB1 and AFB2 in stored paddy rice, hulls, brown rice, bran and white rice were 141, 39, 158, 367 and 56 µg kg−1, respectively. The ratio of aflatoxin B1 and B2 was about 10 : 1. AFG1 and AFG2 were less than 1 µg kg−1. Thus, brown rice contained 92.9% of the aflatoxins in paddy rice, whereas white rice contained only 27.9%.

Determination of total fat and saturated fat in foods by packed column gas-liquid chromatography after acid hydrolysis

Abstract The new definition of total fat in FDA regulations implementing the Nutrition Labeling and Education Act of 1990 necessitates the quantitation of all lipid fatty acids and the summation of their triglyceride equivalents. A gas-liquid Chromatographic (GLC) method using a packed column has been developed for quantitative measurement of total fat and saturated fat in foods. Fatty acids are released from food matrices by acid hydrolysis, and then extracted, esterified to their methyl esters and determined by GLC. Total fat and saturated fat are calculated in accordance with the new definitions of these components. Fat content determined by the acid hydrolysis-GLC methodology was compared with fat content determined by a direct AOAC gravimetric method for 23 food products containing between about 1 and 75% fat by weight. For all food products studied, the relationship between the results obtained by the two methods was best described by a straight line that had a correlation coefficient of 0.94. Results of repeated extractions and analysis of a milk-based infant formula (SRM 1846) suggest that this material may be useful as a quality control standard.

Survey of selected materials for use as an organic nutrient standard

SummaryThere is a need for food based reference materials characterized for organic nutrient content, since very few are presently available. A series of twelve food matrices has been prepared by Agriculture Canada as Candidate Reference Materials. This paper reports a survey of the organic nutrient content of these twelve materials which include bovine muscle powder, corn starch, hard red spring wheat flour, soft winter wheat flour, white granulated sugar, whole milk powder, wheat gluten, potato starch, corn bran, durum wheat flour, whole egg powder, and microcrystalline cellulose. Whole egg, bovine muscle and whole milk powder appear to be best suited for further development as organic nutrient standards.