THE COMPOSITION AND VITAMIN A VALUE OF THE CAROTENOIDS OF PUMPKINS OF DIFFERENT COLORS

The carotenoid pigments of the yellow and orange flesh varieties of the pumpkins Cucurbita moschata and C.maxima were identified and quantified, α-Carotene, β-carotene, ζ-carotene, β-carotene 5,6-epoxide, β-cryptoxanthin, lutein, taraxanthin, zeaxanthin, luteoxanthin and auroxanthin were detected in the pumpkins. The difference was that the yellow variety of C. moschata had no zeaxanthin. The quantitative patterns of the two varieties were similar. Although some quantitative variation was observed, lutein, β-carotene and luteoxanthin predominated. The difference in the color between the two varieties resulted from these quantitative differences in carotenoid composition. The vitamin A activity of the C. moschata variety with yellow flesh was higher than that of the C. maxima, which had many oxygenated carotenoids.     

MILK BASIC PROTEIN ENHANCES THE BONE STRENGTH IN OVARIECTOMIZED RATS

We studied the effects of milk basic protein (MBP) on bone metabolism in ovariectomized (OVX) rats. Five‐week‐old female Sprague‐Dawley rats were ovariectomized and fed a low‐calcium diet (0.009% Ca) for 5 weeks. The OVX rats were divided into three experimental groups: Control group (20% casein), MBP‐L group (19.9% casein, 0.1% MBP), and MBP‐H (19% casein, 1% MBP) of six animals. The rats were fed each experimental diet for 3 weeks. The bone breaking strength and energy of femur in the MBP‐H group were significantly higher than those in the control group. The bone breaking energy of femur in the MBP‐L group was also significantly higher than those in the control group. There were no differences in the amount of femoral calcium and phosphorus among the three groups, however, the amounts of femoral proline, hydroxyproline and hydroxylysine (typical amino acids of collagen) in the MBP groups were significantly higher than those in the control group. These data indicate that MBP in the whey protein increases the amount of the bone collagen and enhances the bone strength.     

Gel Strength Enhancement by Addition of Microbial Transglutaminase during Onshore Surimi Manufacture

Surimi from Alaska pollock flesh was manufactured onshore with Microbial transglutaminase (MTGase). Effect of MTGase was investigated by evaluating breaking strength and deformation of gels from MTGase-treated surimi with and without setting at 30°C. Quantitative analysis of ε-(γ-glutamyl)lysine (GL) crosslink was also carried out to monitor the MTGase reaction. In set gels, breaking strength and GL crosslink increased, and myosin heavy chain decreased correspondingly with MTGase concentration. These changes were smaller in gels prepared without setting. Results suggest that surimi gel could be improved through the formation of GL crosslinks by added MTGase in surimi.     

Changes of soy protein under ultra-high hydraulic pressure

High pressure (<500 MPa) was applied to soy milk and the protein changes were examined. Soy milk remained a liquid within the range of examined pressures, although its viscosity increased when the time of pressurization was less than 10 min. However, the soy milk changed from a liquid to a sol after treatment at 500 MPa for 30 min. the liquid soy milk showed improved emulsifying activity and stability but reduced emulsifying capacity. Sulfhydryl content of this soy milk was increased slightly after anaerobic pressurization. Harder tofu could be made from pressurized soy milk with CaC1₂ than could be made with unpressurized soy milk. Electrophoresis and isoelectrofocusing revealed that soy proteins were dissociated and some of them coagulated by high pressure. Fluorescence analysis also revealed that soy proteins were modified by high pressure to have larger hydrophobic regions. After pressure treatment, soy milk showed a higher affinity for beany flavour components and saponins which would lead to better use of soy milk in soy foods.     

Microbial Transglutaminase and ε-(γ-Glutamyl)lysine Crosslink Effects on Elastic Properties of Kamaboko Gels

Kamaboko gels from Alaska pollock surimi (SA? and 2nd? grades) were prepared by setting at 10 or 45°C with Microbial transglutaminase (MTGase) and its effect on gel properties was investigated. At 10 and 45°C, gels from 2nd? grade surimi paste showed increases in breaking strength, without decline in deformation. Gel from SA? graded surimi paste showed an increase in breaking strength with no changes in deformation in 45°C setting, up to 0.03% MTGase. Crosslinking of myosin heavy chains through ε-(γ-glutamyl)lysine bonds was observed and a possible correlation was shown between ε-(γ-glutamyl)lysine content and gel strength (breaking strength X strain). ε-(γ-Glutamyl)lysine content up to 3 μmol/100g or MTGase 0.03% or higher improved gel properties.     

PARTIAL PURIFICATION AND PROPERTIES OF PUMPKIN LIPOXYGENASE WITH CAROTENE-BLEACHING ACTIVITY

From locally grown pumpkins, an active lipoxygenase preparation with an active carotene-bleaching factor was partially purified by ammonium sulfate fractionation, gel filtration, and ion-exchange chromatography. The enzyme had a pH optimum at 6.5 and was inactive at pH below 3 and above 10. The maximum activity occurred at 30°C. The apparent K_m determined in the presence of linoleate was 0.33 × 10^?3 M. The heavy metals Hg²⁺, Cu²⁺, Co²⁺, and Fe³⁺ were effective inhibitors of this enzyme. Cyanide, fluoride, and L-ascorbic acid also inhibited lipoxygenase activity. Carotene-bleaching activities operated strongly on the lipoxygenase fraction and slightly on the denatured lipoxygenase and hemoproteins treated with heat.