Lipase of the intestine of Tilapia nilotica was purified by ammonium sulfate precipitation, followed by ion-exchange chromatography (DEAE-cellulose), chromatofocusing (Polyexchanger PBE 94 ), and gel filtration (Sephadex G-100).The lipase was found to be a single band when examined by electrophoresis.The specific activity of the purified enzyme was 177 times higher than that of the crude extract.The lipase had a molecular weight of 46,000, showed the highest activity at pH 7.5 and 35 degreesC, and was stable at pH 6.5-8.5 and below 40 degreesC. The Km of the enzyme for olive oil was calculated to be 0.7 mM. Its activity was inhibited by Cu2+, Cd2+, Ni2+, Hg2+, PCMB, and CH2ICOOH.This enzyme specifically digested Tributyrin and Tricaproin, whereas it digested 1,2-diolein and 1-monoolein more than 1,3-diolein and 2-monoolein. The enzyme well decomposed soybean oil and coconut oil.

Lipase of the stomach of Tilapia nilotica was purified by ammonium sulfate precipitation, followed by chromatofocusing (Polyexchanger PBE 94), and gel filtration (Sephadex G-100), The lipase was found to be a single band when examined by electrophoresis.The specific activity of the purified enzyme was 19 times higher than that of the crude extract.The lipase had a molecular weight of 54,000, showed the optimum activity at pH 6.5 and 40 degreesC, and was stable at pH 5.0-7.0 and below 50 degreesC. The Km of the enzyme for olive oil was calculated to be 0.6 mM. Its activity was inhibited by Cu2+, Cd2+, Pb2+, Hg2+, Ni2+, PCMB, and EDTA.This enzyme hydrolyzed triacylglycerol more than diacylglycerol and monoacylglycerol. The enzyme hydrolyzed soybean oil well.

Effects of monoglyceride on breadmaking properties were investigated by employing three types of monoglycerides: glyceryl monostearate (GMS) as saturated monoglyceride, glyceryl monooleate (GMO) as cis-unsaturated monoglyceride and glyceryl monoelaidate (GME) as trans-unsaturated monoglyceride. Polymorphism of monoglycerides, which was considered as a factor of their dispersibility in an aqueous solution, was first examined by using X-ray diffraction and DSC analysis. In GMS and GMO, stable crystal state remained during storage at 20 degrees C, and in GME unstable crystal state was easily transformed to stable one. The unstable crystal of GME was considered to improve its dispersibility in dough as well as in the aqueous solution. The characteristics of dough with or without addition of these monoglycerides were investigated by Farinograph and Extensigraph. Breadmaking were tested according to 70% sponge-dough procedure method. Each monoglyceride was added in dough less than 1% on flour weight basis. The dough consistency decreased definitely during mixing, and the dough strength to extension increased by the addition of GMO or GME. The loaf volume increased by the addition of GMO or GME. These effects were not shown by the addition of GMS. The change in crumb firmness during storage was depressed by the addition of GMS or GME, providing a softer bread. In order to elucidate a mechanism of dough improvement, the added monoglycerides were extracted from dough much more. GMO and GME were located in the gluten fraction than GMS. It suggested that the double bonds of unsaturated monoglycerides were bound easily to the gluten fraction, so that the amount of monoglycerides in the gluten fraction influenced the dough characteristics.

The starch was prepared from kiwifruit during post-harvest ripening. (1) Scanning electron microscopies showed a gradual disintegration of tissues and a decomposition of a surface of the starch. (2) Photopastegram of kiwifruit starch showed that the initial temperature of gelatinization dropped by ripening, from 66-degrees-C to 64-degrees-C after 6 days storage, and to 62-degrees-C after 12 days storage. Decrease of transmittance was not observed prior to the drop of initial temperature of the gelatinization. (3)Kiwifruit starch showed B-pattern on X-ray diffractometry and the pattern did not change during ripening. (4) Kiwifruit starch was debranched by isoamylase and fractionated to three fractions (F-I, F-II and F-III) by gel-filtration on Sephadex G-75. By measuring of lambdamax, it was suggested that F-I was originated from amylose, and F-II and F-III was originated from amylopectin. Amylose (F-1) content increased during ripening from 8.1% to 13.0% after 6 days storage and 19.1% after 12 days storage. It was estimated that the increase was caused by decomposition of amylopectin. The degree of polymerization of F-II and F-III were in the range of 34 approximately 36 and 14 approximately 16, respectively, throughout the ripening.

Amylase of the stomach of Tilapia nilotica was purified by ammonium sulfate precipitation, followed by affinity chromatography (α-cyclodextrin-Sepharose 6B), chromatofocusing (polyexchanger PBE 94), and gel filtration (Sephadex G-75). The amylase was found to be a single band when examined by electrophoresis. The specific activity of the purified enzyme was 54 times higher than that of the crude extract.The amylase had a molecular weight of 40, 000, showed the highest activity at pH 6.0 and 35°C, and was stable at pH 5.5-7.0 and below 45°C. The Km value of the enzyme for soluble starch was calculated to be 5.8 mg/ml. Its activity was inhibited by Hg2+, Pb2+, Cu2+, Zn2+, PCMB, and DTNB. This enzyme digested not only polysaccharides such as soluble starch, amylopectin, and amylose but also oligosaccharides such as maltotetraose, maltopentaose, and maltoheptaose.

Effects of the addition of whey protein isolate (WPI) and soy protein isolate (SPI) on the texturization of rennet casein were investigated. Three types of textured casein products which were made from rennet casein alone (control), a blend with WPI, and a blend with SPI, respectively, were prepared. WPI and SPI were blended with rennet casein at a level of 5% on a dry basis. Fibrous structure of the textured product which was made from rennet casein alone tended to deteriorate during storage. Fibrous structure of the product blended with WPI was satisfactory, while that with SPI was even inferior to that of rennet casein alone. Surface hydrophobicity of each textured product was determined by using 1-anilino-8-naphthalene-sulfonate (ANS) and hydrophobic gel chromatography. Fibrousness of textured products were found to be closely related as inversely proportional to hydrophobicity. The product blended with WPI, showing the lowest hydrophobicity, revealed the highest fibrousness among the three types, while the product blended with SPI, with the highest hydrophobicity, resulted in the poorest fibrousness. It was considered that an addition of WPI to rennet casein possibly prevented mutual adhesion of fibrous structure in the resultant product due to a decrease of hydrophobicity, whereas an addition of SPI promoted the adhesion due to an increase of hydrophobicity.

Two alpha-glucosidases, I and II, of the intestine of Tilapia nilotica were purified by ammonium sulfate precipitation, followed by affinity chromatography (alpha-cyclodextrin-Sepharose 6B), gel filtration (Sephadex G-150), and chromatofocusing (poly exchanger PBE 94). Each of the two alpha-glucosidases was found to be in pure form when examined by electrophoresis.The specific activity of I was 27-fold of that of the crude extract, which was slightly higher than 21-fold for that of II. The enzymes I and II had molecular weights of 25,000 and 17,000 and showed the highest activity at a pH of 6.0 and at 55-degrees-C, respectively. Both enzymes were stable at pH 5.5-7.5 and below 60-degrees-C.The Km values for p-nitrophenyl-alpha-D-glucopyranoside of two enzymes, I and II, were calculated to be 2.61 and 1.65 mm, respectively.Both activities of the enzymes were inhibited by Hg2+ and DTNB. Both enzymes specifically digested maltose, maltotriose, maltotetraose, maltopentaose, and maltohexaose, but not amylose.

Two proteolytic enzymes designated as PA-3 and PB-3 were obtained from the intestine of Tilapia nilotica. These enzymes were purified by precipitation with ammonium sulfate and by chromatographies on trypsin inhibitor-Sepharose 4B, DEAE-cellulose, Polybuffer exchanger (PBE 94), and Sephadex G-100, up to the specific activity of 260 and 350-fold, respectively.PA-3 and PB-3 had molecular weights of 32,000 and 21,000, respectively, and showed the highest activity at 55-degrees-C and at a pH of 8.5-9.0. They were stable at pH 7.0-10.5 and below 50-degrees-C.The K(m) values for casein of two enzymes were calculated to be 0.03 mg/ml.The effect of various inhibitors on enzyme activities was examined and as a result, it was presumed that PA-3 was a serine protease and that PB-3 was a cysteine protease.

This study made it clear that specific gravity is correlative with the texture of raw potatoes and their texture changes by steaming post-treatment. Raw potatoes with high specific gravity showed high hardness, cohesiveness and gumminess. On the other hand, steamed potatoes with low specific gravity showed high hardness, cohesiveness and gumminess. As the temperature falls in steaming post-treatment, the texture of potatoes became harder and brittler. This tendency was more remarkable for the potatoes with low specific gravity.

Properties of mashed potatoes prepared from potatoes with high and low specific gravity were investigated. The numbers of bound cells and broken cells were greater in the low specific gravity samples than in the high specific gravity samples during a cooling off process in post-steaming. As the temperature falls in post-steaming soluble starch increased and pectin decreased, and this tendency was more remarkable for the low specific gravity samples. When the potato cells were separated with a hydrochloric acid solution (pH 1.3) and sodium hydroxide solution (pH 12.0) treatment, the cells in the high specific gravity potatoes were separated completely, but the separating ratio in the low specific gravity potatoes was about 70%. Pectin solubility by this treatment was greater in the low specific gravity potatoes than in the high specific gravity ones. The swelling temperature of the separated cells measured with photopastegraphy was 61-degrees-C for the high specific gravity potato and 66-degrees-C for the low specific gravity one.

Amylases of the intestine of Tilapia nilotica were purified by ammonium sulfate precipitation, followed by affinity chromatography (alpha- cyclodextrin-Sepharose 6B), Chromatofocussing (poly-exchanger PBE 94), and gel filtration (Sephadex G-75). Two different amylases were obtained in pure state and tentatively designated AA-2 and AB-2.The specific activity of AA-2 and AB-2 were 620- and 670-fold over the crude enzyme, respectively.AA-2 and AB-2 had molecular weights of 54,000 and 56,000, respectively, and showed the highest activity at 40-degrees-C and at a pH of 6.0. They were stable at pH 5.5-7.5 and below 45-degrees-C.The Km values for soluble starch of the two enzymes were calculated to be 0.48 mg/ml and 0.67 mg/ml, respectively.Both activities of the enzymes were inhibited by Hg2+, CH2ICOOH, PCMB, and DTNB. The enzymes specifically digested soluble starch, and gave maltose, maltotriose, and maltotetraose. Wheat starch was the most digested of several raw starches examined.

シロタモギタケから抽出した水溶性多糖LU-1について精製及び分画を行ない, P-1, P-2, P-3の3つの画分を得た.今回はそれらのうちP-1について構造解析を行なった.(1) LU-1は約18%のタンパクを含有する他,ほとんどが中性糖で構成されていることが分かった.その構成糖はマンノース,ガラクトース,グルコースであり,モル比は1.0:1.9:2.6であった.(2) LU-1をプロナーゼで処理し,除タンパク後,Sephacryl S-400を用いたゲルろ過により, P-1, P-2,P-3の3つの画分を得た.これらのうちP-1はゲルろ過,電気泳動,超遠心分析により, P-1は均一物質であることを確認した.(3) P-1はマンノース,ガラクトース,グルコースが1:2:5のモル比で構成され,平均分子量約470000でβ結合を優位とするグリカンであり,分子内はグルコースの(1→3)結合をcoreとし,グルコースの非還元末端と,マンノースを非還元末端に持つガラクトースの(1→6)結合の分枝を持つ構造であることを推定した.

(1) 大豆TIは精製すると耐熱性が向上する.このため共存する大豆タンパク質がどのようにTIの耐熱性に影響するかを調べた結果,大豆タンパク質中の7Sおよび15SはTIの耐熱性に影響を与えず, 11Sを添加すると著しく耐熱性が低下することを明らかにした. (2) 11Sタンパク質添加によるTIの耐熱性低下の原因を解明するため,分子内のSH基の影響について検討した.まず11Sの主要構成アミノ酸およびSH基を持つシステインをTIに添加して耐熱性を試験したところ,システインを添加した場合のみ11S添加と同様に著しい活性の低下を示し,他のアミノ酸添加では全く影響が認められなかった.このため11S添加によるTI耐熱性の低下は, 11S分子中のSH基が関与していることが示唆された. (3) 次にシステインおよび11S分子中のSH基をPCMBで修飾し, TIに添加して耐熱性試験を行ったところ,無添加と同様の耐熱性を示し, TIの耐熱性に11S分子中のSH基が関与していることが明らかとなった. (4) DEAE-celluloseによりTIを分画し,得られた5種の精製TIについて, 11S添加による影響を比較検討したところ,いずれのTIにおいても11S添加により耐熱性の低下が認められたが, TIの種類によってその失活率は異なり, 11Sの影響の程度に差のあることが認められた. (5) 11S分子表面および内部のSH基の反応性を比較検討するため, N-ethylmaleimide (NEM)により20℃および50℃で11S中のSH基を修飾し,これをTIに添加して耐熱性への影響を試験したところ,表面および分子内部のSH基はそれぞれ同様にTIの耐熱性に影響をおよぼしていた.

食用キノコ中の11種類の有機酸を分析する目的でHPLC条件及び試験溶液の調製法を検討し,市販キノコ類に応用し次の結果を得た.(1) HPLCの充てん剤はKC-811,移動相として0.1%リン酸を用いると,標準品の場合は11種類ともに相互分離が良かった.(2) HPLCの充てん剤として,ULTRON N-C18,移動相として0.1Mリン酸一カリウム(pH 2.2)を用いると,KC-811では分離できないギ酸を単一ピークとして得ることができた.また,移動相のpHを3.2とすることにより,全体的な相互分離は悪くなるが,pH 2.2では確認できなかったコハク酸,クエン酸が単一ピークとして得られた.(3) HPLCの充てん剤Unisil QC18,移動相として0.05Mリン酸(pH 2.5)は,KC-811と同程度ではあるが,酒石酸,ギ酸,リンゴ酸,酢酸,コハク酸,フマル酸が良好な単一ピークとして得られた.(4) 試験溶液のクリーンアップは,ホウ酸処理したDEAE-セファデックスA-25を用いることにより,妨害物の除去も良く,回収率はシュウ酸が80%である他は95～101%と良好な結果が得られた.(5) 本法のうち,HPLCの充てん剤をKC-811及びULTRON N-C18(移動相のpH 2.2)を用い,市販の7種類のキノコに適用した.