Yosito Sakurai

Degradation of L-Ascorbic Acid and Mechanism of Nonenzymic Browning Reaction: Part II. Non-oxidative Degradation of L-Ascorbic Acid Including the Formation of 3-Deoxy-L-pentosonePart III. Oxidative Degradation of L-Ascorbic Acid (Degradation of Dehydro-L-ascorbic Acid)

L-Ascorbic acid, in an acid condition, was degraded to furfural with the formation of 3-deoxy-L-pentosone as an intermediate. Furfural and 3-deoxy-L-pentosone were isolated and identified as 2,4-di...

Studies on the Non-Starchy Polysaccharides of the Endosperm of Naked Barley: Part I. Preparation of the Water Soluble β-Glucans from Naked Barley Endosperm and their Properties

Two β-glucans were prepared from the aqueous extract of the endosperm of naked barley. The extraction was carried out under conditions which obviated enzyme action and eliminated the contamination of starch fraction. The precipitate obtained with 20% concentration of ammonium sulfate of the extract was adsorbed on DEAE-cellulose (borate form) column and fractionated into two fractions by the elutions with H2O and 0.5 N NaOH, respectively. From 5 kg. of the endosperm the yield of the former was 13.3 g. (0.27% of the endosperm), the latter was 2.0 g. (0.04%). Both showed only one peak ultracentrifugally, were slightly levorotatory, not degraded with α-amylase, and consisted of only d-glucose. These data suggest that they are both β-glucans.β-Glucan consumed in periodate oxidation 0.74 mole periodate per 1 mole of anhydro- glucose. Hydrolysate of the methylated β-glucan gave 2, 3,6-tri-O-methyl-d-glucose and 2, 4, 6-tri-O-methyl-d-glucose, and methanolysate of the methylated β-glucan gave methyl 2, 3, 6-tri-...

Studies on Flavor Components in Soybean:Part I. Aliphatic Carbonyl Compounds

Aliphatic carbonyl compounds in soybean were studied. Volatile carbonyl compounds in defatted soybean flour were identified as methanal, ethanal, n-hexanal, 2-propanone, 2- pentanone, 2-heptanone, 2-heptenal, and 2,4-decadienal, while those in raw soybean as ethanal, n-hexanal, and 2-propanone. Four kinds of non-volatile carbonyl compounds were found in defatted soybean, two of which seemed to be carbonyl ester and carbonylic acid. It is probable that the compounds in defatted soybean are mostly the secondary products derived from autoxidation of the residual fatty acids and esters in the defatting process and/or during the storage thereafter. n-Hexanal in raw soybean amounts to approximately 10 p.p.m., which is, owing to its extremely low flavoring threshold, likely to be one of the main components of the green bean flavor.

Studies on Flavor Components in Soybean: Part III. Volatile Fatty Acids and Volatile Amines

Both acidic and basic fraction of flavor components in raw soybean were investigated. The acidic fraction, having a weak but characteristic odor, contained nine sorts of volatile fatty acids, which were identified with gas chromatography as acetic, propionic, isovaleric, n-valeric, isocaproic, n-caproic, n-caprylic, n-nonanoic (pelargonie), and n-capric acid. Among those, main components were isocaproic, n-caproic and n-caprylic acid, and the others were contained in smaller amounts. Total amount of these acids, however, was so small that it would have little practical effect on soybean flavor.The basic fraction exhibited a characteristic odor just like a dried fishery product, and ammonia, monomethylamine, dimethylamine, piperidine, and cadaverine were detected in this fraction with gas and paper chromatography. Particularly, dimethylamine was isolated as 2,4-dinitrophenyl derivative.

Nutrition of Threonine: Part VIII. Actinomycin-Insensitive Induction of Rat Hepatic Threonine Dehydratase and Its Reversal by Growth Hormone

Tryptophan was found to be a factor that enhanced rat hepatic threonine dehydratase activity without resulting from increase in gluco-corticoid secretion. If rats were fed on tryptophan added diet prepared by adding 140 mg/day tryptophan to 20g/day 20% casein diet, the resulting threonine dehydratase activity was about 1.5 times as much as that observed in rats fed 20% casein diet. If adrenalectomized rats were used, the similar results were obtained. In the case of hypophysectomized rats, however, about 4 times the activity was observed. This enormous increase in the activity was mostly prevented by growth hormone. This hormone was also effective in preventing the tryptophan-aided increase in threonine dehydratase activity of intact rats. Thyroxine was ineffective in preventing the activity increase. Either actinomycin S3 or puromycin treatment on rats disclosed that the trvptophan-aided activity increase was based on de novo synthesis of the enzyme through the translational step, not through the transcr...

Studies on Changes of Protein by Dye Sensitized Photooxidation: Part II. Physico Chemical Changes of Ovalbumin by Photosensitization

Physico chemical changes of ovalbumin illuminatied in the presence of methylene blue were examined. Solubility of ovalbumin was remarkably reduced, but its extents were varied with the value of pH, that of ionic strength and illumination time. Illumination brought about aggregation of protein molecules which was revealed on the ultra centrifugal patterns. Electrophoretical patterns showed that three peaks characteristic of native ovalbumin went into one peak after 24 hr and into two peaks after 48 hr. After an illumination for 6 hr, titration curves showed that bound protons decreased below pH 8.0 and increased over pH 8.0. The spectra of illuminated ovalbumin were displaced upward and the absorption maximum shifted toward the longer region of wave length.

Studies on the Browning of KORI-TOFU Part I

(1)凍豆腐の褐変は高湿度,すなわちRH 85%以上のときに起こりやすい. (2)褐変凍豆腐のエーテル抽出物についていろいろの測定を行なった結果,脂肪酸のうちリノール酸,リノレン酸が著しく減少し,カルボニル化合物の多量の生成が特徴である.モノカルボニル化合物としてはhexanalとnon-2-enalが多い.またエーテル抽出物中の窒素含量は褐変により褐変前の8～20倍になる. (3)エーテル抽出残渣のアミノ酸分析の結果では,褐変により塩基性アミノ酸とPro, Tyrの減少ばかりでなく,他のアミノ酸もかなり減っている. (4)直接還元糖の含量が0.724 mg/gと非常に少ないことから糖による褐変はまず起こらないであろう. (5)モデル実験として行なった各種脂肪酸とカゼインによる褐変では不飽和の脂肪酸ほど褐変が早く,さらに酸化大豆油とアミノ化合物の褐変では酸化の進行が著しいほど褐変が早い.この場合も高湿度においた方が褐変は進行した.以上のことがらより凍豆腐における褐変は次のごとく考えられる.すなわち,凍豆腐に多量に含まれる脂肪のうち,不飽和度の高いリノール酸とリノレン酸とが酸化されて多くのカルボニル化合物が生じ,これが蛋白質と反応して,いわゆるアミノ-カルボニル反応を起こし褐変する.そしてこの褐変は,湿度の多い環境においたときに著しくあらわれる.なお,凍豆腐中において脂肪の酸化がどのようにして起こるかについては未詳のところが多い.また,蛋白質との反応機構についてもさらに追求を要する.

Nutrition of Threonine: Part IV. Changes in Activities of Threonine Decomposition Enzymes in Rat Liver by Exeess Feeding of Lysine and Threonine

The threonine content in blood and urine increased and threonine decomposition ability in liver decreased by feeding lower level of lysine, whereas threonine content in blood and urine decreased and the ability of liver increased gradually with increasing lysine content in diet. These phenomena were owing to the increase of threonine dehydratase activity of liver, which was measured from produced α-ketobutyric acid amount, by excess administration of lysine. The phenomena that threonine content in urine decreased and threonine decomposition ability of liver increased with increasing threonine content in diet when adequate amount of lysine was fed, were also ascribed to the increase of the dehydratase activity.One m mole of threonine was incubated with liver homogenate in presence of PALP*** at pH 8.2 for 20 and 30 min and α-ketobutyric acid produced was introduced to its 2,4-dinitrophenylhydrazone, which was chromatographed on silica-gel thin-layer plate and determined spectrophotometrically at 395 mμ und...

Degradation of L-Ascorbic Acid and Mechanism of Non-enzymic Browning Reaction:Part I. Browning Reactivities of L-Ascorbic Acid and of Dehydro-L-Ascorbic Acid

INTRODUCTION L-Ascorbic acid (ASA) is widely used in manufacture of many food products for the purpose mainly to inhibit browning, but sometimes discoloration due to ASA is observed in lemon1) or orange2) juice of high ASA content. Though some extensive studies3,4) have been reported on the subject, browning of ASA is still unknown in many respects. It is generally accepted that reductones play an important role in nonenzymic browning reaction such as sugar amino reaction, but their exact role in the reaction is still unknown. Since ASA is a typical aci-reductone,5) it is worth while to investigate the browning reaction of ASA to elucidate the mechanism of non-enzymic browning reaction. In the presence of oxygen, ASA is known to degrade to dehydro-L-ascorbic acid (DHA) in the first step. Therefore studies on browning of DHA or mixtures of ASA and DHA are needed to elucidate browning of ASA. As for browning of DHA described in some literatures, there are some discrepancies which are undoubtedly due to the impurity of DHA used. DHA used in previous studies was

Glucofructans:Part I. The Constitution of the Glucofructans from the Endosperm of Naked Barley

Glucofructans were isolated and purified from the endosperm of naked barley and their structural significances were discussed. Four unknown glucofructans (unknown 1~4) and the mixture of higher glucofructans were obtained. The results on methylated glucofructans showed that d-glucose unit in the glucofructans was present as the end group and main chain consisted of 1, 2-linked d-fructofuranose residues and that each glucofructan except unknown 1 had the branching structure comprising of 2, 6-linked d-fructofuranose residues.