Characterization and Food Application of an Amperometric Needle-Type L-Lactate Sensor

There have been increasing needs for biosensing in the food industry because it is accurate, rapid and efficient. A needle-type L-lactate sensor with a three-layer membrane system which uses lactate oxidase as the biological component was prepared. The sensor had an optimum pH around 9–10 and an optimum temperature at 45 C. The current response was stable over 40 days and specifically responded to L-lactic acid. The sensor gave accurate L-lactate measurements in kimchi and yogurt of 187.4 ± 4.1 and 734.1 ± 34.5 mg/dL, similar to those of a spectrophotometric L-lactate kit.     

EFFECTS OF OIL DROPLET AND AGAR CONCENTRATION ON GEL STRENGTH AND MICROSTRUCTURE OF O/W EMULSION GEL

The effects of oil droplet size and agar concentration on gel strength and microstructure of emulsion gels were investigated by compression test and cryoscanning electron microscope (Cryo-SEM). At all agar concentrations, the compressive stress values of emulsion gels were lower than those of the oil-free gels. Compressive stress and energy were significantly affected by oil droplet size and agar concentration, but compressive strain was not. SEM observation revealed that the overall volume of void spaces decreased and strand compactness increased with increasing agar concentration. Gels containing oil droplets had some void spaces between the gel network and the oil droplets. The strands of emulsion gels did not cover the oil globules completely, a phenomenon which was also observed for the gel with high agar concentration.     

EFFECT OF HIGH PRESSURE ON THE ACCUMULATION OF IMP AND ON THE STABILITY OF AMP DEAMINASE IN RABBIT SKELETAL MUSCLE

This study evaluated the effect of high pressure on rabbit skeletal muscle, specifically on the production of inosinic acid (IMP), one of “umami” components, and on the activity of adenosine triphosphate (AMP) deaminase, which plays a role in the conversion of AMP to IMP. By increasing the pressure (0.1 to 300 MPa), nucleotide analysis showed that IMP content in muscle increased instantly with a concomitant decrease in ATP content. The IMP content of muscle at 300 MPa was approximately 15% higher than with lower pressures (0.1–200 MPa) when stored for 1 week at 4C after pressurization. These results suggested that the metabolism of nucleotides in muscle was not significantly impaired by pressure treatment. At 300 MPa, AMP deaminase maintained approximately 70% of the activity at 0.1 MPa. In contrast, the activity of purified AMP deaminase was completely lost at 200 MPa, and irreversible conformational changes were observed by in situ fluorescence spectroscopy. These results indicated that purified AMP deaminase was irreversibly denatured under pressure as high as 300–400 MPa.     

DISTRIBUTION OF ASCORBATE OXIDASE ACTIVITIES IN THE FRUITS OF FAMILY CUCURBITACEAE AND SOME OF THEIR PROPERTIES

Activities and some other properties of ascorbate oxidases (AAO) from the fruits of family Cucurbitaceae were investigated. The peel and the flesh of seven varieties had activities ranging between 35–56500 units/mg protein and 14–1250 units/mg protein, respectively. AAO from different varieties had a similar pH optimum of around 6–6.5 and a broad pH stability ranging from pH 5 or 6 to pH 10 or 11. These properties appear to be conserved in the AAO's from the family of Cucurbitaceae. The AAO's of melon cv. andes, kinsho and papaya were more susceptible to heat denaturation than AAO from pumpkin.     

IMPLICATE FINAL CAUSES IN DEVELOPING MATERIAL SYSTEMS

Abstract

Causality in changing natural systems can be seen to involve all four Aristotelian causal categories—material, efficient, formal and final. Final causality of materialistic origin can be found in the need to maintain energy flow continuity within dissipative systems. Each interacting dissipative system acts finalistically so as to attract needed energy. In so acting, it continually disturbs its neighborhood by generating potential energy flow disruptions as results of its activities. Final causality based, in this way, on the energy requirements of dissipative systems will generate formal causes as well. In contrast, the emergence of formal causes in mechanistic systems driven solely by efficient causes is extremely unlikely. We suggest viewing the subordination of phenotypic dissipative systems by genotypic counterparts as an historical example of the emergence of formal causes out of the material necessity of maintaining flow continuity. Functional separation between genotypic and phenotypic dissipative systems can occur if the energies to be dissipated are localized, as is the chemical binding energy of molecules with respect to biological functions at a higher scalar level.     

Formation of Oligosaccharides During Hydrolysis of Lactose in Milk Using β-Galactosidase from Bacillus circulans

The characteristics of β-galactosidase from Bacillus circulans, and its suitability for hydrolysis of milk lactose were compared with those of Escherichia coli and Kluyveromyces lactis enzymes. Enzyme activity of β-galactosidase from B. circulans was not affected by major cations and proteins present in skim milk, whereas milk proteins and sodium and calcium ions decreased the activity of the enzymes from E. coli and K. lactis. The enzyme from B. circulans produced less oligosaccharides than E. coli and K. lactis during hydrolysis of lactose in skim milk at different lactose concentrations. Oligosaccharides produced by the enzyme from B. circulans disappeared almost completely at the latter stage of hydrolysis, while a large amount of oligosaccharides were still detected even at 98% conversion of lactose with enzymes from E. coli and K. lactis.     

表面波等离子体暴露下铜表面的氧化特性

Surface wave plasma(SWP) is a kind of low temperature plasma which can be utilized for material development.In this research,argon and oxygen were used as a working gas for an SWP experiment and the influence of the plasma irradiation on a copper surface was examined.Particular,relation between the spatial characteristics of SWP and wetting characteristics was examined.As a result,it was found that spatial characteristics of the SWP affected the wetting characteristics and the oxidation characteristics.     

EFFECT OF HIGH PRESSURE TREATMENT ON CYTOPLASMIC 5'-NUCLEOTIDASE FROM RABBIT SKELETAL MUSCLE

We investigated the effect of high‐pressure treatment on the properties of cytoplasmic 5′‐nucleotidase (NT), which converts inosine monophosphate (IMP) into inosine. After pressure treatment at 400 MPa, the activity of purified IMP‐NT remained at almost 100%, but the activity of partially purified adenosine monophosphate (AMP)‐NT decreased to about 40%. These data suggest that there is a difference in the pressure stability between the enzymes. In situ fluorescence spectroscopy of IMP‐NT under pressure showed that its pressure‐induced denaturation was reversible. When the pressure was reduced from the highest pressure to ambient pressure, hysteresis was observed. This suggests that high pressure treatment may lead to a partial change in the affinity of the subunits for each other once they have dissociated. The activities of IMP‐NT and AMP‐NT extracted from pressure‐treated muscles decreased remarkably between 250 and 450 MPa, but IMP‐NT was more stable than AMP‐NT.     

Effects of Polymers on Secondary Nucleation of Ice Crystals

The kinetics of ice crystallization in various polymer solutions were studied by the thermal response method in a batch crystallizer. Polymers suppress the secondary nucleation of ice crystals, depending on the kinds of polymer and concentration. The decrease of the nucleation rate constant in polymer solutions was related to the increase of viscosity. The effects of polymers on the nucleation rate were also observed in solutions containing low molecular weight compounds.