Determination of Riboflavin in Low-Potency Foods and Feeds

Abstract

A, Figure 4, shows that the results are entirely reproducible. After one sample had been brought to constant weight at 100°, it was redissolved in benzene. Removal of the benzene by the same technique yielded the same weight of polymer. When this polymer was redissolved in benzene and the solvent removed by the distillation technique, the same weight of product was obtained if the heating time was sufficiently long (A, Figure 2), showing that moisture or solvent adsorption on the porous polymer was negligible.The following details should be of assistance in applying the frozen benzene technique.Pyrex Erlenmeyer flasks have been used because they give fairly large, flat cakes of polymer. Less than 1% of the 125-cc. flasks collapse under vacuum.

Determination of Thiamine and Riboflavin in Presence of Reduced Iron

“…They carried out this reduction with hydrogen in the presence of a catalyst, zinc in acid solution, sodium thiosulfate, hydrogen sulfide in alkaline solution, and titanous chloride. Sodium hydrosulfite also effects complete reduction to the leuco compound, which is easily oxidized to riboflavin by air, a reaction which is commonly used (11,15,16) in riboflavin assay procedures. With an acid solution of stannous chloride, however, Chaves and Guimaraes (4) found that riboflavin was only partially reduced and could not be completely reoxidized by aeration.…”

“…Contrary to the findings with premixes, hot acid extraction caused no loss of thiamine or riboflavin when applied to enriched flour (80% extraction). The claimed values were obtained for thiamine by both the short and the complete thiochrome procedures, for riboflavin by the complete fluorescence method (16).…”

Excessively High Riboflavin Retention during Braising of Beef. A Comparison of Methods of Assay

“…The fluorometric method which Tucker had used in her braising studies was a slightly modified procedure of that described for vegetables by Brush, Hinman, and Halliday (3), further details of which are reported under "Experimental Methods". It included a digestion of the samples with Clarase; adsorption on Florisil, originally suggested by Ferrebee (7) and Conner and Straub (4); oxidation of eluates with potassium permanganate as described by these authors; determination of individual eluate blanks made by exposure to light as suggested by Najjar (15) and applied to assays of cereals by Wright and Booth (27); and determination of "internal" standards as employed by a number of workers when determining fluorescence in digests directly (S, 13, 16, 19) or in eluates (1,2,12).…”

Feedstuffs Assay, Liberation and Determination of Riboflavin in Natural Feedstuffs

“…Autoclaving in decinormal acid is widely accepted (9, 14. 15), although digestive release with papain and takadiastase is often employed (3,12).…”