A simplified method for chloroform/methanol extraction and gravimetric determination of total fat previously published for diet composites was tested on additional foods, including milk, cheese, fried snack foods, nuts/seeds, salad dressings, baked goods, meat, fish/shellfish and fruits/vegetables. Homogenized food composites and certified reference materials (CRMs) were analyzed using the existing method involving, briefly, orbital shaking of a subsample with chloroform/methanol/buffer in specific proportions, then recovery of total lipid in the chloroform extract. For meat, fish, shrimp, cheese and fried plantains, total fat recovery was low and/or variability was high with the unmodified assay versus results from other standard total fat methods (e.g., ether extraction, acid hydrolysis) or to CRM assigned values. Reducing the sample size or adding a homogenization step during extraction resulted in relative standard deviations of <3% for all matrices and also values consistent with those generated by other standard total fat methods and within assigned ranges for total fat in most CRMs. PRACTICAL APPLICATIONS The method allows for routine batch analysis of multiple samples of a range of food types with minimized hands‐on time, using commonly available laboratory equipment. The resulting total lipid extract can be subdivided for analysis of various specific lipid analytes as well as for gravimetric measurement of total fat.

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PurposeSignificant differences may occur in the nutrient content of different edible portions of vegetables and fruits. The purpose of this study was to screen the folate content of different edible portions of some common fruits and vegetables.Design/methodology/approach5‐methyltetrahydrofolate was measured using high‐performance liquid chromatography/mass spectrometry in composites of asparagus tips and stems, broccoli florets and stems, the bulb and leaves of leeks, and the peel and flesh of apples, pears, peaches, and potatoes.FindingsFolate content was significantly higher (25 µg/100 g) in asparagus tips vs stems or whole vegetable and leek bulbs compared to leaves or the whole plant, on an as‐consumed basis. No significant difference was found in the edible portions within the other products.Practical implicationsSelective consumption of asparagus tips and leek bulbs would increase folate intake compared to the whole vegetable or the stems and leaves. Consideration should be given to possible differences in composition within other vegetables and fruits not studied.Originality/valueThere have been no previous reports on folate distribution in edible portions of vegetables and fruits that are rich sources of this vitamin.

Analytical parameters and quality control measures were optimized for standard direct gas chromatographic (GC) analysis of trans fat in unlabeled bakery products, and differences in concentrations measured in samples assayed with and without the modifications were evaluated. Total lipid was extracted with chloroform/methanol from homogenized cakes, cookies, doughnuts, pastries, muffins, and commercially available reference materials (NIST SRM 2387 Peanut Butter, LGC7103 Sweet Digestive Biscuit). Total lipid was saponified and fatty acids were derivatized to methyl esters (FAME) and analyzed by GC using a 100% nonbonded bis-cyanopropyl polysiloxane column (100 m×0.25 mm, 0.2 µm film). Total FAME entering GC was optimized to separate C18:1-12t and C18:1-13t isomers that occur at a significant level but often remain unresolved from the C18:1-9c peak in products containing partially hydrogenated vegetable oils. Silver-ion solid-phase extraction was used to validate identification of the major C18:1 cis/trans peaks. For samples assayed by the standard method and with specific sample-to-sample quality control and GC optimization, the former underestimated trans fat by 2 to 5 g/100 g (0.2-0.6 g/serving) in some products. Differences were less for foods containing <1 g/100 g, but nonetheless could have implications for labeling because trans fat levels <0.5 g/serving may be declared zero according to U.S. Food and Drug Administration regulations. The practical modifications and controls described can be implemented in routine standard GC analysis to increase the consistency and validity of trans fat measurement across a range of samples with unknown fat content and fatty acid composition.

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