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A. H. Bloksma and I. Hlynka. Copyright 1960 by the American Association of Cereal Chemists, Inc. If unleavened doughs are tested in the Brabender extensigraph according to the structural relaxation procedure, they yield hyperbolic structural relaxation curves irrespective of whether they are or are not remixed before shaping. However, remixing causes a decrease in the structural relaxation constant and in the asymptotic load. The effect increases with increasing duration of remixing. The effect on the structural relaxation decreases when the time interval between remixing and shaping increases from 3 to 20 minutes; this is called recovery. Recovery may or may not be complete in 20 minutes, but under the conditions of the present experiments it does not proceed beyond that time interval. Doughs to which 35 p.p.m. N-ethylmaleimide are added are least sensitive to remixing, closely followed by doughs with 12.5 p.p.m. iodate. Doughs with 20 p.p.m. bromate and doughs without additions but mixed in an atmosphere of oxygen show a large effect of remixing. With bromated doughs the effect of remixing increases considerably with reaction time. After recovery the rank order of doughs with different additions has remained essentially the same. Recovery of doughs with N-ethylmaleimide is even complete for reaction times shorter than 60 minutes. Doughs mixed in an oxygen atmosphere and remixed in nitrogen hardly show any recovery; if the remixing is done in an oxygen atmosphere, however, recovery is considerable. Results obtained with the Brabender and Halton extensigraphs show that at least part of the effect of remixing is due to interference with subsequent structural activation during shaping of the test piece. Possibly differences between flour improvers that change rheological dough properties rapidly and slowly are more important than differences between oxidizing and thiol-blocking reagents. |
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