STRESS DISTRIBUTION IN A STATOR VANE UNDER BENDING

The stress distribution on the surface of a stator vane loaded statically as a cantilever has been obtained by means of brittle coatings, strain gauges and three-dimensional photoelasticity. A metal prototype was available for the determinations and from this an epoxy model was made by casting. The combination of methods used suggests the most efficient way of stress analyzing this type of structure.     

ANGIOTENSIN I-CONVERTING ENZYME (ACE) INHIBITORY PEPTIDES FROM WHEY FERMENTED BY LACTOBACILLUS SPECIES

From 2% (w/w) whey powder in growth media, inhibitory peptides against angiotensin I-converting enzyme (ACE) were studied with nine Lactobacillus species. Lb. brevis, Lb. helveticus and Lb. paracasei were proved to be the most effective strains in liberating ACE inhibitory peptides from whey protein. The inhibition rates of these peptides against ACE ranging from 93.3 to 100%. Several distinct peaks were eluted when the whey proteins were fractionated on a Delta Pak C₁₈ column by reversed phase-high performance liquid chromatography (RP-HPLC). Among ACE inhibitory activities of 14 peptides purified by dialysis and by fractionation using RP-HPLC, two peptide fractions (H5 and H7) of Lb. helveticus showing IC₅₀ values of 5.3 and 7.8 were the most potent ACE inhibitors.
All of these peptides including some other peptides (H1 and B1), having strong inhibitory activities against ACE were pentapeptides positioning with Ala at their N-terminal and these petapeptides had mostly hydrophobic (Pro, Val and Leu) or aromatic (Phe) amino acids at the C-terminal.

PRACTICAL APPLICATIONS

There is a significant amount of research and interest in developing and charactering the peptides that inhibit angiotensin I-converting enzyme (ACE) activity as these natural products may have a role in blood pressure control in man. This study revealed that the identification of peptides, mostly composed of pentapeptides following fermentation of whey protein in growth medium with different strains have the ACE inhibitory activities. These peptides may have antihypertensive effect as natural and safe nutraceutical/functional ingredients, though the exact potency of the pentapeptides isolated in this experiment has not been determined.     

植物乳杆菌中胆盐水解酶的研究现状及展望

益生菌的降胆固醇作用与它们所产的胆盐水解酶(bile salt hydrolase,BSH)有关,这使得胆盐水解酶成为近年来研究的热点之一。文中主要对植物乳杆菌中胆盐水解酶的克隆表达、生化特性以及降胆固醇作用等方面的研究现状进行了综述,并展望了它未来的发展方向。以期对植物乳杆菌胆盐水解酶的研究及其相关制品的开发利用提供一定的指导意义。     

AN INVESTIGATION ON THE DEFORMATION AND CRACK FORMATION OF METALS IN CROSS FORGING AND CROSS ROLLING

在200—300毫米輥径的横軋机上于不同溫度、速度、变形程度、变形区长度与直径之比以及外端等条件下,用金相法和硬度法对各鋼种的圓棒的变形分布和中心破裂进行了研究。在冲床上用端面画有同心圓的鋁棒和鉛棒进行了常溫的旋轉橫鍛試驗,以了解横鍛横軋时金属的变形分布。試驗結果表明: 1.一次横鍛时,表面层的变形最大,越靠中心变形愈小。当压縮率不大时,中心处可能只发生弹性变形。 2.旋轉橫鍛时,表面层和中心区的塑性变形較大,过渡区的变形最小。当变形率很小时,塑性变形亦可能不致于深入到中心区。 3.横軋时金属的变形規律与旋轉橫鍛时相似,但在压縮很小时,断面中心只发生弹性变形。 4.横軋时,軋制溫度、軋制速度增高,压縮率及变形长度与直径比越大,外端越小,中心破裂愈易产生。     

The Role of Biotechnology in Modern Food Production

ABSTRACT: Modern food production technology is given great challenges by the emerging fields of biotechnology and molecular biology. Knowledge of conventional fermentation technology is upgraded by the gene level explanations of enzyme actions and physiological functions of biomaterials derived therefrom. The use of genetically modified organisms (GMOs) and their products in food widens the availability of resources while also raising public interest about safety and labeling. As an example of the application of molecular biology in conventional fermentation technology the selection of proteases from a Bacillus species grown in Korean traditional soybean fermentation starter, Meju , and the production of peptides with blood cholesterol lowering effect, obtained from soybean protein hydrolysate, are presented. Recent developments in the Korean bioindustry are reviewed as an example of the role of biotechnology in the food industry. The present status of GMO enzymes in food production is reviewed and safety issues about GMO use in the food system are discussed.     

CONTENT AND STABILITY OF HEXANE EXTRACTABLE LIPID AT VARIOUS STEPS OF PRODUCING MACARONI CONTAINING GROUND FLAXSEED

Research was conducted to determine changes in content and stability of hexane extractable lipid during processing of macaroni containing 15% (w/w) ground whole flaxseed and ground flaxseed hull. Dry mixture, hydrated mixture, extruded macaroni, dried macaroni and cooked macaroni were evaluated. Results were similar for macaroni containing ground whole flaxseed or ground flaxseed hull. Hydration decreased extractable lipid. Hydration decreased the amount of α-linolenic acid (ALA) and free fatty acid (FFA) and increased the amount of conjugated diene in the extracted lipid. Little or no conjugated triene was detected in lipid extracted from samples containing flaxseed, regardless of the processing step. Extruding, drying and cooking had little or no effect on the stability of lipids in macaroni containing flaxseed. The low levels of FFA, conjugated diene and conjugated triene indicate that lipid remained relatively stable during processing and cooking of macaroni containing ground flaxseed.