Characterization of lipoxygenase-1 null mutants in barley

This study describes the discovery and characterization of lipoxygenase-1 (LOX-1) null mutants in barley. Six lines did not exhibit any significant LOX activity in the silenced seed extract. Immunological analysis showed that these lines lacked the authentic LOX-1 protein. Genetic analysis of the F2 population revealed that this trait was governed by a single recessive gene located at the LoxA locus on chromosome 4H. The six LOX-1 null mutants shared similar features and the same unique polymorphism in a structural gene region, implying that these mutants might be derived from the same ancestral origin.

Behavior of Mono-, Di-, and trihydroxyoctadecenoic acids during mashing and methods of controlling their production

The behavior of mono-, di-, and trihydroxyoctadecenoic acids was investigated during laboratory-scale mashing under various conditions with a view to controlling their production. Using a malt in which the lipoxygenase activity was at only a trace level (less than 0.01 U/g) or starting the mashing at a higher temperature than that conventionally used (65 degrees C instead of 48 degrees C) significantly decreased the production of these hydroxy fatty acids. Lowering the pH of the mash to inhibit lipoxygenase activity and preventing O2 uptake by the mash using carbon dioxide were also effective in reducing the amounts of these acids produced during mashing. From the viewpoint of industrial-scale beer production, the prevention of O2 uptake by the mash was selected as an appropriate method for reducing oxidation during wort production without affecting the subsequent brewing process or the taste of the finished beer. After introducing oxidation prevention procedures, the content of trihydroxyoctadecenoic acids decreased by about 30% and the foam stability and taste were improved in commercial products brewed using less than 25% malts.

[Contribution of linoleic acid to the bitter taste of poppy seeds (Papaver somniferum)]

In lipids isolated from poppy seeds which tasted "burning-bitter" the off-taste was associated with the free fatty acids fraction. In this fraction linoleic acid predominates, while oxidized fatty acids were among the minor constituents. The taste threshold of linoleic acid emulsified in water with monolinolein lies in the range of 4.0-6.0 mumol/ml. On the basis of its high concentration and relatively low taste threshold we conclude that free linoleic acid contributes significantly to the "burning-bitter" off-taste in poppy seeds.