Ihei Iwata

Thermal Degradation Products of S-Alkyl-L-cysteine Occurring in the Allium Species with D-Glucose

Thermal treatment of a mixture of S-alkyl-l-cysteines (alkyl: methyl, MCS; allyl, ACS; propyl, PCS; cis-1-propenyl, PeCS) occurring in the Allium species and d-glucose (Glc) gave rise to volatile products which are responsible for characteristic food flavors. Flavor evaluations due to thermally treating mixtures MCS–Glc, ACS–Glc, PCS–Glc and PeCS–Gilc indicated pickled radish-like, garlic and rice cracker-like, roasted onion-like, and rice cracker-like flavors, respectively. The major volatile products from MCS–Glc, ACS–Glc and PeCS–Glc were sulfur compounds generated from the thermal decomposition of MCS, ACS and PeCS, respectively. Interestingly, the compounds contributing to the good aroma of PCS–Glc were alkylpyrazines as well as sulfur compounds. Furthermore, novel compounds—2,4-bis(propylthio)butanal and 2,4-bis(propylthio)but-2-enal, which were thermally generated from an equimolar mixture of PCS and Glc, were isolated and identified by MS, IR, 1H-NMR and 13C-NMR.

Lipids of Algae:Part V. Fatty Acids of Chlorella and Scenedesmus

The saturated and unsaturated fatty acids of the algae Chlorella and Scenedesmus were examined by paper chromatography, alkali isomerization and gas chromatography. Free fatty acid obtained by saponification was about one half in amount of the total lipid. The solid fatty acid amounting to about 13% of the total fatty acid was found to be palmitic acid. Linolenic acid was nearly 40%, while the sum of stearic acid and oleic acid was less than 4%. Tetraenoic acid was found to be present in all the samples used in this experiment. Tetraenoic acid of Chlorella was found to be Cl6-acid and amounted to 15~26%, though it was not found in C18-acid. Hexadecamonoenoic acid was about 10% and it was separated by column chromatography using a silica gel: Celite (2: 1) column. Its double bond was found to be at the 3 position, because tridecanal was the product of its ozonide cleavage.

Lipids of Algae: Part III. The Components of Unsaponifiable Matt r of the Algae ChlorellaPart IV. Carotenoid Pigments of Scenedesmus

A fresh cake of Chlorella cells was extracted with hot methanol and ether. The extracted lipid was saponified. The unsaponifiable substance, 2.7% of the dried Chlorella cells, was extracted with petroleum ether to separate hydrocarbons and higher alcohols. The extract was fractionated by the vacuum distillation, and each fraction was further separated by the solubility difference of the urea adducts followed by column chromatography. Small amounts of n-hexadecane and n-hexacosene were isolated besides phytol which was the major component of the unsaponifiable substance. Another unsaturated hydrocarbons with straight and branched chain were also found. The residue of the petroleum ether extract was extracted with ether to separate sterols, the major component of which was found to be ergosterol.