A bioassay procedure for the evaluation of the nutritional quality of the protein in foods is described. This method involves measurement of the protein efficiency ratio (grams gain per gram protein consumed) under standardized conditions. Male rats of the Wistar strain 20–23 days of age are fed ad libitum an otherwise adequate reference diet containing 10% protein supplied by a standard sample of casein. Foods to be assayed are added to the diet as the sole source of protein at the expense of the casein and corn starch to maintain a protein level of 10%. Protein efficiency ratios (P.E.R.'s) are calculated after 4 weeks and are adjusted to a constant value of 2.5 for casein. Although influenced by the age of rat and subject to certain inherent criticisms, determination of P.E.R. values was found to be a simpler method for evaluating protein quality than determination of net protein retention or net protein utilization and equally sensitive.

A bioassay procedure for the evaluation of the nutritional quality of the protein in foods is described. This method involves measurement of the protein efficiency ratio (grams gain per gram protein consumed) under standardized conditions. Male rats of the Wistar strain 20–23 days of age are fed ad libitum an otherwise adequate reference diet containing 10% protein supplied by a standard sample of casein. Foods to be assayed are added to the diet as the sole source of protein at the expense of the casein and corn starch to maintain a protein level of 10%. Protein efficiency ratios (P.E.R.'s) are calculated after 4 weeks and are adjusted to a constant value of 2.5 for casein. Although influenced by the age of rat and subject to certain inherent criticisms, determination of P.E.R. values was found to be a simpler method for evaluating protein quality than determination of net protein retention or net protein utilization and equally sensitive.

The apparent piperine contents of black and white peppers were determined b y both a spectrophotometric method and a colorimetric procedure. The piperine contents by the latter procedure were consistently higher than that indicated b y the ultraviolet measurements. The variables causing these discrepancies in results were investigated using column fractionation of pepper extracts as well as by paper and thin-layer chromatography. Analogs of piperine with less than two conjugated ethylenic linkages could not be found in pepper extracts. However, all black and white peppers contained the piperine analog with three conjugated ethylenic linkages, piperettine. Measurements of the ultraviolet absorbances at 343 mp for piperine and at 364 mp for piperettine and calculation of the ratio of these two biochemically related constituents gave results for true piperine and piperettine contents which served to some extent as an indication of the geographical origin of a pure pepper.

Use of the 5-liter modified Schóniger combustion flask has been extended to the combustion of potatoes, cherries, onions, cabbage, and oats for the determination of residues of arsenic, bromide, chloride, manganese, and nickel.

No abstract