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The effcts of deamidation of fragmentation on the antioxidative activity of α-zein were investigated individually. Heat treatment at 70°C in 70% ethanol-0.05M HCl caused deamidation of α-zein without fragmentation. Antioxidative activity of α-zein was improved by this deamidation. α-Zein with deamidation treatment for 12 hours protected 80% of docosahexaenoic acid ethyl ester from autoxidation until 7 days. Model peptide of α-zein had a lower antioxidative activity than α-zein. Fragmentation by N-btromosuccinimide decreased the antioxidative activity of α-zein.

Heating white sauce with bovine serum albumin (BSA) at 90 °C caused the sauce to separate into aggregates and liquid phase, although this did not occur at 75 °C. Data from differential scanning calorimetry of BSA solution suggested that heat denaturation of BSA was insufficient at 75 °C but was complete at about 90 °C. Larger aggregates of BSA were formed by heating at 90 °C compared with 75 °C, as shown by gel permeation chromatography combined with a multi-angle laser light-scattering detector. Dynamic viscoelasticity measurement showed a higher storage modulus of BSA solution formed by heating at 90 °C than at 75 °C. Scanning electron microscopy revealed a random agglomerate structure of aggregates (spherical aggregates) obtained by 75 °C heating, while a well-developed network structure containing voids was observed after heating at 90 °C. These findings suggest that sauce liquid separation induced by heating at 90 °C is due to encapsulation and restriction of white sauce components by large structured aggregates of BSA containing voids. Aggregates generated at 75 °C were not sufficiently developed and structured; therefore there was no sauce liquid separation due to encapsulation and restriction of components. © 2000 Society of Chemical Industry

The present work was undertaken from the standpoint of radical-capturing ability with regard to the antioxidative ability of flavonoids, especially flavonols distributed widely in woody plants. In regard to the flavonols, six methyl derivatives were initially prepared from quercetin and its litinoside. Their radical-capturing constants were determined strictly by the stopped-flow spectroscopic method. It was proved that the radical-capturing ability of quercetin mainly involves the vicinal C3. and C4, hydroxyl groups and the C3 hydroxyl group. To clarify the reaction mechanism begun at the C3 hydroxyl group of quercetin, 5,7,3′,4′-tetramethylquercetin (TMQ), flavon-3-ol (F30) and so on were treated with 2,2′-azo-bis-(2,4-dimethylvaleronitrile) (AMVN). Six products (1–6) containing one depside and its two hydrolytic products, two valeronitrile adducts, and others were isolated from the reaction mixture of TMQ and their structures determined by instrumental analyses. Similarly, F30 gave four products, 7–10, which corresponded to the above products 1–3 and 5 (one depside, its two hydrolytic products, and one adduct), respectively. 3,5,7,3′,4′-Pentamethylquercetin (PMQ) and flavon-3-O-methylate (F3M) gave no products. The quantitative change of the products with reaction time was determined spectroscopically. An initial reaction pathway for the radical-capturing reaction of flavon-3-ols with AMVN was proposed based on the products and their amounts. The main route — formation of depside and its hydrolytic products via ketohydroperoxide (3″) or ketohydroperoxy radical (4″) - was similar to that of the oxidation reaction of quercetin with quercetinase and light.

The antioxidative effects of three prolamins, α/β-gliadin, C hordein and α-zein, were investigated in powders in which the prolamin under test encapsulated peroxide-free ethyl esters of the unsaturated fatty acids, linoleic, α(γ)-linolenic, arachidonic, eicosapentaenoic and docosahexaenoic acids. All prolamins inhibited the autoxidation of ethyl esters of linoleic, linolenic and arachidonic acids, i.e. with two to four unsaturated bonds. C hordein protected an eicosapentaenoic acid ethyl ester from autoxidation in the powder system for 7 days, whereas other prolamins were less effective. None of the prolamins completely inhibited the autoxidation of docosahexaenoic acid ethyl ester.

Wheat proteins were fractionated into salt-soluble, glutenin-rich, and gliadin-rich fractions. Reactivities of these protein fractions with sera of patients with wheat-associated allergies were examined under various conditions. The relative reactivity of the fractions was generally in the order glutenin-rich > gliadin-rich >> salt-soluble fractions, although their reactivities were variable among patients and among the reaction conditions, indicating that the kind, the number and the epitope of allergens were variable among patients. To identify major allergens, alpha-, gamma- and omega-gliadin, and low-molecular-mass (LMM)- and high-molecular-mass (HMM)-glutenin genes were expressed in Escherichia coli by means of a pET vector. Recombinant gliadins and glutenins were partially purified on the basis of the solubilities of prolamin and glutelin. The partially purified recombinant proteins were reacted with the patients' sera. LMM glutenin containing many Gln-Gln-Gln-Pro-Pro motifs, which was identified to be IgE-binding epitope [Tanabe, S., Arai, S., Yanagihara, Y., Mita, H., Takahashi, K. & Watanabe, M. (1996) Biochem. Biophys. Res. Commun. 219, 290-293], exhibited the highest reactivity. The next highest reactivities were observed on alpha-gliadin and gamma-gliadin, which had not been identified as allergens.