Yataro Obata

Studies on γ-radiolysis of sulphur containing amino acids—II : Volatile products from S-n-propyl-L-cysteine sulphoxide and S-allyl-L-cysteine sulphoxide irradiated in oxygen-free aqueous solutions

Abstract In connection with flavour deterioration accompanied by food irradiation, the volatile products from sulphoxide amino acids, S-n-propyl- L -cysteine sulphoxide (PCSO) and S-allyl- L -cysteine sulphoxide (ACSO) irradiated in oxygen-free aqueous solution were analysed. The major volatile products formed by radiolysis of PCSO were di-n-propyl sulphide and di-n-propyl disulphide, and those derived from ACSO were allyl alcohol, n-propyl allyl sulphide and diallyl sulphide, which were isolated by GLC and identified by using mass spectrometry. From the experiments with N2O or KBr addition during irradiation, i.e., from the scavenger effects, the formation processes of volatiles were partly elucidated.

Detection of Phenolic Compounds by Chromatography in Beet Sugar Molasses

Detection of phenolic compounds in beet sugar molasses was carried out by paper chromatography. Some of the phenolic compounds were identified with catechol, p-hydroxybenzoic acid, melilotic acid, salicylic acid, syringic acid, vanillin and vanillic acid and three other phenolic compounds were detected though they have not been identified.

Changes in Amino Acid Composition during Germination of Soybean:Part IV. Identification of α- and γ-Glutamylaspartic Acid

α- and γ-Glutamylaspartic acids were detected in acidic fraction of soybean seedling. RF values of both peptides were consistent with those of authentic samples with several solvent systems.

Studies on α-Alkyl-α-amino Acids:Part I. Synthesis of S-Alkyl-2-methyl-DL-cysteines

New eleven S-alkyl-2-methyI-dl-cysteines (V) were synthesized. Alkyl groups are as follows: methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, isobutyl, sec-butyl tert-butyl, n-amyl and isoamyl. 5-Alkylthiomethyl-5-methylhydantoins (IV), the synthetic intermediates, which were prepared from alkylthiopropanones (III) by Bucherer’s method are also new compounds. Alkyl groups are the same as described above. Chlorine containing two hydantoins (IVc, IVd) were also preparared.

Studies on the Constituents of Hemp Plant ( Cannabis sativa L.):Part III. Isolation of a Gibbs-positive Compound from Japanese Hemp

(1966). Studies on the Constituents of Hemp Plant (Cannabis sativa L.) Agricultural and Biological Chemistry: Vol. 30, No. 6, pp. 619-620.

Studies on the Photolysis of Sulfur Containing Compounds in Foods:Part I. Photolysis of S-Alkyl-L-Cysteines

S-Alkyl-l-cysteines in aqueous solutions were exposed to sunlight in the absence and presence of riboflavin. Ammonia, carbon dioxide, acetaldehyde and alkyl mercaptans were detected in the solutions containing a small amount of riboflavin.

Studies on the Degradation Mechanisms of Proteins and Their Derivatives in the Foods:Part IV The Decompositions of Several Mercaptals and Mercaptoles of Cysteine in Aqueous Solutions

Cysteine mercaptals and mercaptoles were prepared by the reactions of l-cystine with formaldehyde, acetaldehyde, n-butyraldehyde, benzaldehyde, furfural, pyruvic acid and levulinic acid in 6 n hydrochloric or sulfuric acid. Hydrogen sulfide released from cysteine mercaptals and mercaptoles in heated aqueous solutions (oil bath: 120°C) was determined. Although a small amount of hydrogen sulfide was liberated from l-cystine on one hour heating, its amount increased suddenly after three hours. Among these compounds l-cystine mercaptal of furfural was most unstable and a large amount of hydrogen sulfide was produced.

Isolation of a Diketopiperazine Derivative from the Soy-bean Meal Hydrolysates, Commercially Available as “AMINOSAN-EKI”

A diketopiperazine derivative isolated from the soy-bean meal hydrolysates, AMINOSAN-EKI, has been proved as l-isoleucyl-l-valine anhydride by elemental analysis, melting point, and by paper chromatography. l-Isoleucyl-l-valine anhydride must be derived from the dipeptide produced by hydrolysis of the proteins.

Anthocyanase and Anthocyanin Occurring in Eggplant (Solanum Melangena L.)

Experiments on anthocyanase and anthocyanin in eggplant were carried out by means of Warburg’s manometric method and determination of the anthocyanin. Results show that delphinidin 3-(p-coumaroylrutinoside)-5-glucoside from eggplant is oxidized by the polyphenol oxidase from mushroom, potato and eggplant flesh. The oxidative degradation of the anthocyanin is accelerated in the presence of chlorogenic acid which occurs in eggplant, and a mode of the action stimulating the degradation was discussed.In addition, an evidence was given that the existence of ascrobic acid in the enzymatic system retards the loss of the pigment, due to a coupled reaction, which is of well-known on the other o-dihydroxy phenols. Some observations on the product from the reaction mixture indicate that such decolorization of the anthocyanin progresses directly without hydrolysis of the glucosidic linkage.

Studies of the Sunlight Flavor of Beer: Part IX. Formation of Prenylmercaptan from S-Prenyl-l-Cysteine by SunlightPart X. A Comparison of Precursors of Mercaptan by Use of Sulfur-35 Compounds

The recent findings1~3) that prenylmercaptan (3-methyl-2-butene-1-thiol) is the major component of the sunlight flavor of beer has led us to investigate the pathway of its evolution. S-Prenyl-l-cys...