A.A. Franke

Measurement oftrans and other isomeric unsaturated fatty acids in butterand margarine

A procedure is described for gas liquid chromatographic determination of cis andtrans isomers of unsaturated fatty acids after fractionation of the saturated, monenoic, dienoic, and polyenoic fatty acid methyl esters by argentation thin layer chromatography. To test its reliability, the procedure was used for quantitative measurement of transisomers of unsaturated fatty acids in a known mixture of simple triglycerides containing saturated fatty acids from 4:0 to 24:0 andcis andtrans isomers of 14:1. 16:1, 18:1, and 18:2. Results of the analyses of five margarine and five butter samples are presented, together with results of infrared spectrophotometric analyses fortrans fatty acid concentrations, ultraviolet spectrophotometric analyses for conjugated fatty acid concentrations, and enzymatic analyses forcis-cis-methylene interrupted fatty acid concentrations. The combined argentation thin layer and gas Chromatographic procedure is suitable for determination of the principal fatty acids in complex food lipids such as milk fat.

Iodine in Cow's Milk Produced in the USA in 1980–19811

In 378 samples of milk collected from farms and silos outside California, iodine varied from 30 to 3484 μg/kg and averaged 499 μg/kg. In a previously reported study, iodine in 1021 samples of milk collected from farms in California varied from 22 to 4048 μg/kg and averaged 328 μg/kg. Of samples collected outside California, 68.0% were below 500 μg/kg; of samples collected in California 83.4% were below. Volume weighted averages were calculated for both sets of samples. The volume weighted average outside California was 438 μg/kg and inside California was 316 μg/kg. While some farms do produce milk containing high (more than 500 μg/kg) concentrations of iodine, dilution of that milk with milk lower in iodine results in finished fluid and manufactured products low in iodine; thus it is unlikely that any population group purchasing processed dairy foods at the retail level in the USA will be exposed to excessive concentrations of iodine in the dairy products they consume. However, it is possible that some farm families using only the milk produced on their farms might be at risk.

Iodine in California Farm Milk: 1985–19861

Iodine has been measured in 1572 California farm milk samples, representing 2,725,000 gallons of milk, or about 54% of daily production. The mean iodine concentration in the analyzed samples was 173.3 μg/kg milk, with a standard deviation of 115.8 μg/kg- The volume-corrected mean iodine concentration for all samples was 188.3 μg/kg. Of the farms examined, 13% used neither an iodine teat-dip or backflush; the milk iodine concentration on these dairy farms averaged 147.8 ± 90.2 μg/kg. Of the farms examined, 73% used iodine teat-dip only; milk iodine concentrations averaged 166.7±109.4 μg/kg. Less than 1% of the farms used iodine only in their backflush systems; their milk iodine concentrations averaged 202.3±107.2 μg/kg. Thirteen percent of the farms used both iodine teat-dip and iodine in their backflush systems; their milk iodine concentrations averaged 251.3±153.9 μg/kg. While the concentration difference between farms using iodine in both the teat-dip and backflush system and farms in the other three groups was statistically significant, the mean concentration was still well below the maximum limit of 500 μg/kg imposed by health agencies in some countries. Overall, 30.7% of samples measured has less than 100 μg iodine/kg; 70.1% had less than 200 μg/kg; 88.8% had less than 300 μg/kg; 94.4% had less than 400 μg/kg; and 98.1% had less than 500 μg/kg.