ANTIOXIDANT ACTIVITIES OF ENZYMATIC EXTRACTS FROM AN EDIBLE SEAWEED SARGASSUM HORNERI USING ESR SPECTROMETRY

The antioxidant activity of water-soluble natural extracts from an edible seaweed , Sargassum horneri, was evaluated by examining the radical scavenging activities of the extracts of hydrolyzates from S. horneri on 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and alkyl radicals. A spin-trapping electron spin resonance (ESR) spectrophotometer was employed and the results were compared for their ESR signal intensity. The brown seaweed S. horneri was enzymatically hydrolyzed to prepare water-soluble extracts by five carbohydrases (AMG, Celluclast, Termamyl, Ultraflo and Viscozyme) and five proteases (Alcalase, Flavourzyme, Kojizyme, Neutrase, Protamex). The extracts so prepared exhibited strong scavenging activity on DPPH, hydroxyl and alkyl radicals. The scavenging activity of the radicals increased with increased concentration of the extracts. The scavenging results were higher or similar for hydroxyl and alkyl radicals, and lower for DPPH radical compared with vitamin C as a reference. Viscozyme and Alcalase extracts were superior and scavenged radicals examined better than the extracts prepared by other carbohydrases and proteases.     

Application of Laminated Edible Films to Potato Chip Packaging

The effects of various stearic-palmitic acid blend concentrations in films, storage temperatures and storage times on potato chip quality were evaluated using Response Surface Methodology. Storage temperature and time affected the quality of potato chips. The maximum storage times for acceptable potato chip quality were: 30 to 43 days, 23 to 25 days, and 11 to 12 days for storage temperatures of 15, 25 and 35°C, respectively. Results were independent of stearic-palmitic acid blend concentrations.     

亚临界和超临界状态下甲苯-多环芳香烃体系的气液相平衡

The phase behaviors of toluene/polycyclic aromatic hydrocarbon mixture systems were investigated with a continuous-flow type apparatus at 573.2,598.2.623.2 and 648.2K,while the pressure changed from 1 tp 5 MPa,The pseudo-binary phase behaviors were predicted with the Peng-Robinson equation of state with interaction parameters between toluene and pseudo-components considered.The phase diagrams of the system have been classified following the category of phase boundary diagram models.The extraction selectivity and efficiency of toluene as a solvent was discussed by comparing with that of hexane .The prediction model for selectivity was also suggested.     

Fabrication of cast carbon steel with ultrafine TiC particles

The carbon steels dispersed with ultrafine TiC particles were fabricated by conventional casting method. The casting process is more economical than other available routes for metal matrix composite production, and the large sized components to be fabricated in short processing time. However, it is extremely difficult to obtain uniform dispersion of ultrafine ceramic particles in liquid metals due to the poor wettability and the specific gravity difference between the ceramic particle and metal matrix. In order to solve these problems, the mechanical milling (MM) and surface-active processes were introduced. As a result, Cu coated ultrafine TiC powders made by MM process using high energy ball milling machine were mixed with Sn powders as a surfactant to get better wettability by lowering the surface tension of carbon steel melt. The microstructural investigations by OM show that ultrafine TiC particles are distributed uniformly in carbon steel matrix. The grain sizes of the cast matrix with ultrafine TiC particles are much smaller than those without ultrafine TiC particles. This is probably due to the fact that TiC particles act as nucleation sites during solidification. The wear resistance of cast carbon steel composites added with MMed TiC/Cu-Sn powders is improved due to grain size refinement.     

High-Protein Texturized Products of Defatted Soy Flour, Corn Starch and Beef: Shelf-Life, Physical and Sensory Properties

Selected mixes consisting of Bf [high-beef (29%) low-fat (2.96%)], bf [low-beef (20%) low-fat] and BF [high-beef high-fat (5%)] which incorporated raw beef, defatted soy flour, and corn starch were extruded in a single-screw extruder. The products had no flavor additives and trained sensory panelists detected hay-like, beany or grainy flavors. Bf extrudate was more expanded than BF extrudate and rated least hard by the sensory panel, whereas bf extrudate was least susceptible to lipid oxidation. Bf and bf extrudates showed microstruc-tures with large air cells. All three showed advantages of beef and soy flour in amino acid and fatty acid compositions, respectively, and were microbiologically safe during prolonged storage at 37°C.     

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.     

Linear Heating Rate Affects Gelation of Alaska Pollock and Pacific Whiting Surimi

Shear stress of Alaska pollock surimi gels with and without beef plasma protein (BPP) increased as heating rate decreased, but shear strain was unaffected. An increase in shear stress was accompanied by an increase of cross-linked myosin heavy chain. Slow heating rates increased proteolysis in Pacific whiting surimi as shown by degradation of myosin heavy chain and low shear stress and shear strain. Proteolysis of whiting surimi was lessened by BPP to a greater extent at rapid heating rates (20 and 30°C/min) than at slow heating rates (1 and 5°C/min).