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Protocols for detecting picogram quantities of aflatoxin M1 in dairy products were established. Milk samples were subjected to a reverse phase Sep-Pak C18 cartridge treatment before analysis by an enzyme-linked immunosorbent assay (ELISA) according to previously published procedures. M1 in yogurt, brick cheddar, and ripened Brie cheese was extracted by a modified Pons method, subjected to a normal phase silica cartridge treatment, and analyzed by ELISA. The detection limits for M1 in milk, yogurt, cheddar, and Brie were 10, 10, 50, and 25 ppt (ng/kg), respectively. Recovery for M1 added to these products was in the range 70-110%. Good agreement was found for M1 levels in several naturally contaminated milk samples analyzed by both ELISA and liquid chromatography.

The active antitumor component of yogurt obtained by dialysis was further fractionated by ion exchange chromatography into acidic, basic, and neutral fractions, which were analyzed for activity by in vitro agar diffusion, cell culture, and in vivo mouse assay. Neither dialysate nor fractions showed any antitumor activity when tested by agar diffusion or cell culture techniques. When tested by in vivo mouse assay, the dialyzate as well as the anionic fraction showed significant inhibitory activity. The cationic fraction showed no activity. There was no direct relationship between stage of purification and antitumor activity. Moreover, the response of the dialyzate or anionic fraction was not linear with concentration. The antitumor activity of the yogurt fraction(s) may be related to a host-mediated immunological reaction or "activation" of the "inactive" component(s).

Synthetic dyes were extracted from yogurt by different methods, but all methods had in common a liberation of dyes from the food followed by ion-pair formation with tri-n-octylamine. Extraction with pH 5.5 phosphate buffer gave high recoveries for 5 of the 7 dyes investigated and was relatively fast. Precipitation of proteins followed by polyamide adsorption and desorption gave high yields for all the dyes but was tedious and long.

Because of autodigestion of lactose by its endogenous bacteria, the lactose in yogurt is better absorbed than other sources of lactose in lactase-deficient subjects. To investigate possible differences among brands of yogurt in this autodigesting capacity, we challenged eight lactose-malabsorbing subjects with 20 g oral lactose and three different brands of yogurt (Borden, Dannon, and Royal Maid). As a quantitative measure of carbohydrate absorption, end-alveolar breath samples were collected for 8 h and assayed for hydrogen gas. Symptoms were scored by questionnaire every 30 min for 8 h. The cumulative breath H2 and the area under the discontinuous curve of breath-H2 concentration decreased relative to lactose results after ingestion of Dannon and Royal Maid but not after Bordon yogurt. no correlation of symptoms with the degree of carbohydrate malabsorption was demonstrated. We conclude that the lactase activity of yogurt cultures varies among brands.

A technique for the simultaneous determination of sorbic acid, benzoic acid, dehydroacetic acid, p-hydroxybenzoic acid esters (ethyl, isopropyl, n-propyl, isobutyl and n-butyl p-hydroxybenzoate) and saccharin sodium using ion-pair reversed-phase high-performance liquid chromatography is described. The nine food additives were separated on a Nucleosil 3C18 (3 microns) column (75 x 4.6 mm I.D.) using methanol-acetonitrile-0.05 M aqueous acetonic acid solution (pH 4.5) (1.5:1:3.1) containing 2.5 mM cetyltrimethylammonium chloride as the mobile phase at a flow-rate of 1.0 ml/min, and detected at 233 nm. The food additives were separated within 18 min and their calibration graphs were linear between 2 and 200 ng.