Identification of the Escherichia coli K-12 (E. coli) inhibiting substance formed by the decomposition of glycine with hydrogen peroxide (H₂O₂) or bleaching of foods with H₂O₂ were studied.
The inhibition substance zone appeared at Rf 0.2-0.4 on the bioautogram (n-butanol: acetic acid: water=60: 15: 25) of glycine oxidation products, and the substance was positive to qualitative tests of formaldehyde (Rimini test, egg albumin iron test, acetylacetone test and chromotropic acid test). Melting point, paper chromatogram, thin-layer chromatogram and infrared spectrum of yellow crystal obtained with the addition of acetylacetone reagent to the extracts from the zone of Rf 0.2-0.4 on the paper chromatogram were coincident with those of 3, 5-diacetyl-1, 4-dihydrolutidine (DDL).
Since E. coli inhibiting substance in the glycine oxidation products was proved to be formaldehyde from the above results, it was examined on the formation of formaldehyde in foods treated with H₂O₂.
Commercial foods containing 2-30ppm of formaldehyde were bleached with 3% hydrogen peroxide under the following conditions (10g of the samples were treated with 50ml of 3% H₂O₂, and kept at 50°C for 1 hour). Formaldehyde was produced in these samples at the level of 16-34ppm, while its concentration in soaking solutions was within the range of 10-68ppm. Further, the amounts of formaldehyde were determined after standing at room temperature for a week, and 40-68ppm of formaldehyde was found in the foods. In case distilled water was used as soaking solution, no increase in formaldehyde content was observed.