Statistical evaluation of different technological and rheological tests of Polish wheat varieties for bread volume prediction Iwona Konopka, 1 * Lucja Fornal, 1 Danuta Abramczyk, 2 Jadwiga Rothkaehl 2 & Daniela Rotkiewicz 1 1 Chair of Food Plant Chemistry and Processing, University of Warmia and Mazury, Olsztyn, Poland 2 The Central Laboratory for Grain Processing Technology and Storage, Warsaw, Poland (Received 25 July 2001; Accepted in revised form 24 April 2003) Summary Forty-two Polish wheat flour were used to establish correlation coefficients between protein content, Zeleny test, falling number value, amylograph viscosity, farinograph water absorption, bread volume and rheological properties of dough, as shown by use of a extrusion chamber and alveograph. The equations expressing the changes of bread volume and flour water absorption as a function of significantly correlated parameters were calculated. The correlations and their significance depended on wheat quality and the alveographic parameters were significantly correlated with the dough extrusion parame- ters. The dough extrusion parameters were significantly correlated only with the water absorption of soft wheats. The dough rheological tests were correlated to a greater extent with the values of the Zeleny test than to the protein content. The prediction of the bread volume as a function of flour quality parameters and dough rheological properties was best done by grouping wheat varieties into specific qualitative classes. Keywords Alveograph, dough rheology, extrusion chamber, stepwise regression, water absorption. Introduction Seeking a qualitative parameter or a group of such parameters that would determine, both fully and simply, wheat dough behaviour in the baking process has always been a challenge for scientists and industry. Currently, the most promising results can be obtained from the determination of the glutenin composition (Preston et al., 1992; Shewry et al., 1992; Czuchajowska et al., 1996; Wieser & Zimmermann, 2000) as well as the hydrophobicity of gliadin subunits (Menkowska et al., 1988). Among the glutenin subunits, x type components, especially subunit 5 with additional cysteine residue and the predominant subunit 7, are to the greatest extent positively correlated with the flour baking value (Wieser & Zimmermann, 2000). But interpretation of the wheat glutenins and gliadins separation results is difficult, because it depends on protein extraction parameters (Singh et al., 1990). This causes difficulties in the deter- mination of correlations with other flour qualitat- ive parameters (Preston et al., 1992). Dough rheological techniques are commonly used for the analysis of wheat flour baking value. The analysis of the rheological results is complex for dough and reveals both elastic and viscous properties when stress is applied (Hibberd & Parker, 1975). The different mathematical models presented in the papers of Hibberd & Parker (1975), Mackey & Ofoli (1990), Morgenstern et al. (1996), Gras et al. (2000) and others, can be applied to describe dough behaviour. The farino- graph, alveograph and mixograph are the most common equipment used for measuring dough rheological properties, both in scientific research and by plant breeders. However, oscillatory rhe- ometers and other more versatile machines pro- vide a more complete analysis of dough behaviour as affected by strain. In oscillation measurements, the dough viscosity and elasticity moduli (G¢, G¢¢), *Correspondent: Fax: +4889 523 34 66; e-mail: kropka@uwm.edu.pl International Journal of Food Science and Technology 2004, 39, 11–20 11 Ó 2004 Blackwell Publishing Ltd