Active oxygen species, e. g., hydrogen peroxide (H₂O₂), superoxide anion radical (O₂-), hydroxyl radical (·OH) and lipid hydroperoxides, have been implicated as mediators of oxidative cell injuries in a variety of clinical conditions. Some metabolites of carcinogenic compounds, cigarette smoke and glucosone, an intermediate of the Maillard reaction, were found to produce H₂O₂ in their autoxidation processes, and to induce both cytotoxicity and DNA single-strand breaks in mammalian cells. Inhibition of these cell injuries by catalase indicated that H₂O₂ was the critical species. In contrast to the above prooxidant effects, antioxidant effects of food ingredients on H₂O₂-induced cytotoxicity were also investigated. Polyphenols, e. g., caffeic acid ester and flavonoids, were effective for suppression of H₂O₂-induced cytotoxicity on mammalian cells. A study of the structure-activity relationship revealed that the affinity of polyphenols for cell membranes and the presence of an ortho-dihydroxy moiety in their structure were essential for their protective action.

View full abstract

An experiment was performed to evaluate the effect of calcium supplementation on bone mineral maintenance. Under the conditions of a low-calcium diet, lactating rats were fed with calcium phosphate or eggshell calcium. The wet weight, dry weight and density of bones in the rats receiving the low-calcium diet without calcium supplementation were significantly lower than those in rats given the calcium phosphate or eggshell calcium supplement. In the eggshell calcium-supplemented rats, these parameters were higher than those in the calcium phosphate-supplemented rats. Furthermore, the eggshell calcium-supplemented rats exhibited a low level of alkaline phosphatase activity. These results suggest that lactating rats require an adequate amount of calcium, and that eggshell calcium is more effective for bone mineral maintenance than calcium phosphate.

View full abstract

The effects of mulberry leaves on lipid metabolism were investigated in male rabbits fed a hypercholesterol diet containing 1% cholesterol. Fresh mulberry leaves (ML) were dried using a tea machinery, and mulberry extract (ME) was prepared from the ML using hot water. ML or ME ranging from 1.25% to 10% was added to the 1% cholesterol diet (Ch) or a normal diet. The rabbits were fed the Ch diet containing 2.5% or 10% ML (2.5ML·Ch and 10ML·Gh) for 16 weeks. Increases in the concentration of serum tatal cholesterol and levels of other lipids were significantly suppressed in the 2.5ML·Ch and 10ML·Ch diet groups compared with those in the Ch group. Furthermore, suppression of hepatic enlargement and fat deposition in the hepatic cells was observed in both the 2.5ML·Ch and 10ML·Ch groups. However, the hypolipidemic effects were more prominent in the 2.5ML·Ch diet group than in the 10ML·Ch diet group. When rabbits were fed the ML·Ch or ME·Ch diet for 12 weeks after receiving the Ch diet for 4 weeks, suppressive effects were also observed. These findings suggest that mulberry leaves exert hypolipidemic effects in hypercholesterolemic rabbits.

View full abstract

The effects of supplementing the rations of laying hens (Dekalb XL-L) with linseed oil on the lipid composition of egg yolk were investigated. The hens were fed rations containing five different levels (0%, 1%, 2%, 4% and 5.9%) of linseed oil for more than 35 days. Variations in the level of linseed oil had no effect on the contents of total lipid, neutral lipid and polar ligid in egg yolk. However, analysis of the fatty acid composition of the total egg yolk lipid showed that, with increasing levels of dietary linseed oil, the contents of α-linolenic acid (18: 3, ω3) and eicosapentaenoic acid (20: 5, ω3) increased, while the contents of oleic acid and arachidonic acid (20: 4, ω6) decreased. The egg yolk from the 1% linseed oil group contained a higher concentration of docosahexaenoic acid (22: 6, ω3) and a lower concentration of linoleic acid (18: 2, ω6) in comparison with the 0% linseed oil group; a further increase in the level of dietary linseed oil gave the same values as those in the 1% group. Consequently, the ratios of ω3 and ω6 fatty acids in the total egg yolk lipid in the 0%, 1%, 2%, 4% and 5.9% linseed oil groups were 0.11, 0.31, 0.44, 0.69 and 0.92, respectively. The concentrations of α-tocopherol in egg yolk from the 0% and 1% linseed oil groups were similar, but linseed oil suppiementation at levels of more than 2% significantly reduced the α-tocopherol contents. The ω3/ω6 ratio of fatty acids in the feed containing 1% linseed oil was 0.43.

View full abstract

Water-soluble dietary fiber was prepared by alkali extraction from corn hull, a by-product of corn starch manufacturing. The fiber was shown to be composed mainly of arabinose and xylose. Four-week-old male Wistar rats were fed experimental diets containing 5% cellulose or soluble dietary fiber. A fiber-free diet was used as a control diet. There were no differences in food intake or body weight gain among the three dietary groups. The soluble-fiber diet lowered the serum cholesterol concentration compared with both the fiber-free and cellulose diets in both groups fed cholesterol-free and cholesterol-containing diets. Hepatic total lipid and cholesterol contents were lowered only in the group fed the atherogenic diet. These results show that water-soluble fiber from corn hull has excellent characteristics as a dietary fiber.

View full abstract

A study was conducted on the effects of several kinds of commercial processed foods, which were brown-colored due mainly to enzymatic or non-enzymatic browning, on the activity of α-amylase from human saliva. The investigated foods included 4 types of soy paste, 5 types of soy sauce, 5 types of sauce, 5 types of tea and 5 miscellaneous other products. Starch Azure, which is chemically modified and insoluble potato starch, was used as a probe substrate for digestion in the presence of food components. The enzymatic reaction medium was 0.1M NaCl-0.04M sodium/potassium phosphate buffer (pH 7.0) containing 1mM CaCl2. The reaction solution was incubated at 37°C. The blue pigment solubilized from the solid substrate into the supernatant on digestion by α-amylase was determined by differential spectrometry using its absorption at 595nm. Some foods below the concentration normally eaten were found to exert an adverse effect on the activity of α-amylase with the following relationship: log (A/100) =-α·F.F: conc. of food component, A: relative activity, α: coefficient corresponding to inhibitory efficiency. In this experiment, a correlation between inhibitory effect and coloredness of food components was not confirmed, and the involvement of complex factors in the inhibition was suggested.

View full abstract

Mushrooms have occasionally been used for cooking pot-steamed hotchpotch (tyawanmushi), but solidification has not been possible following the addition of Grifola frondosa. Therefore, proteinases in Grifola frondosa may degrade egg white protein. Ovalbumin (OVA) was digested with an extract of G. frondosa at acid, neutral or slightly alkaline pH, judging from SDS-PAGE patterns. After DEAE-cellulose column chromatography and gel filtration on Sephadex G-75, three proteinases and an acid proteinase from G. frondosa were identified. The molecular weight of proteinase A was about 18, 000 and its enzymatic properties were essentially the same as those of alkaline metal proteinase, reported by Hashimoto et al. However, proteinase B appeared to be a new proteinase because of its high molecular weight of about 44, 000, and neutral optimum pH. Proteinase C was present in the smallest amount and could only be poorly characterized. Acid proteinase was a carboxyl proteinase inhibited by pepstatin. Each proteinase digested OVA, but the SDS-PAGE patterns of the digestion products indicated hydrolytic specificity towards OVA. No proteinase alone could prevent OVA and egg white gelling, but a mixture of the three proteinases prevented gelling. Proteinases present in G. frondosa would thus appear to degrade egg white protein and prevent its gelling.

View full abstract

In order to obtain egg yolk oil by a method other than roasting, interactions between lipids and proteins in the egg yolk were split off by partial hydrolysis with acid protease preparations i. e. Kokurase SS (reaction: 50°C, 3h), and addition of glacial acetic acid followed by heatirlg at 100°C for 10min. After centrifugation, the sum total of the separated oil and the same amount of water was transferred to a separating funnel and then shaken vigorously several times in order to remove the odor of acetic acid. The yolk oil obtained in this way was light yellowish and not as viscous as that obtained by roasting of egg yolk. The yield of yolk oil was about 20-23%. The fatty acid composition of the separated yolk oil was found to have a higher content of linoleic, linolenic and arachidonic acids than yolk oil obtained by roasting. The vitamine E content of yolk oil was found to be about 3.4-4.3 times higher than that of egg yolk.

View full abstract

Lactic acid bacteria (3 strains of cocci and 10 strains of bacilli) and lactose-fermenting yeasts (18 strains) were isolated from a 24 h cultured of kefir milk. The lactococci and yeasts were identified as Streptococcus lactis and Kluyveromyees marxianus var. marxianus, respectively. The lactobacilli were of the heterofermentative type but had no ability to ferment lactose, and were considered to correspond to Lactobacillus fruetivorans (4 strains), Lactobacillus hilgardii (1 strain) and their closely related strains (3 and 2 strains each). The characteristics of the yeast and streptococci, such as lactose decomposition, oxygen consumption, and ethanol, carbon dioxide and acid production, were considered to promote the growth of the Lactobacillus strains, the main fermenters of kefir.

View full abstract