The purpose of the present research has been the highlighting of the correlation between the protein content, the wet gluten content and the gluten index of flours, and some characteristics of bread, such as volume and the ratio height / diameter (H / D). In this respect, were analysed 19 samples of flour obtained from Romanian wheat, determining the protein content, wet gluten content and gluten index. At the same time were carried out baking tests corresponding to the 19 loaves of bread and were determined the parameters volume and the height / diameter ratio (H /D).
The results showed that the best predictor for the bread quality parameters: volume and H / D ratio, is the gluten fraction of the gluten index parameter which remains on the sieve (highly significant positive correlation r = 0.79***, respectively r = 0.73***). Gluten index parameter correlates insignificantly with bread volume (r = 0.18) and significantly with the height / diameter ratio (0.51*). In conclusion, the parameter Gluten index itself, is not relevant for the baking qualities of flour; these quality parameters could be better predicted by remaining fraction of gluten on the sieve.
The correlation of the analysis methods of flours quality with their technological performance has always represented a major interest for the experts in the field. The technological performance of flours depends on complex factors which are only partially revealed by the usual assessment tests for the flours quality. These factors are consisting of both physical and chemical parameters, such as protein content, ash content, wet gluten content, gluten index etc., as well as a range of parameters concerning the flours behavior in gel or dough stage, namely: falling number, amylografic viscosity, extensibility, resistance, strain energy, elasticity, development time, stability, softening, etc. [3, 5, 7, 10, 12, 14, 18, 19].
Besides this factors also the variability of the analysis methods by which these factors are determined, which can be very high, has to be considered.
The mixer, farinograph, extrudograph, mixograph, valorigraph, rheograph, give us indications about dough behavior during mixing.
The extensograph, alveograph, extensometer and glutograph give indications about dough behavior to stretch.
The fermentograph, the maturograph, the microclimate room, the zimotachigraph, the rheofermentometer, give indications about the behavior of dough during fermentation.
The amylograph, the viscograph, the rheotron, the consistometer, the penetrometer, the viscometer, give indications of penetration, viscosity and so on .
Several studies showed that the best predictor for bread volume is the protein content of wheat or flour [1, 4, 11].
R. Koppel and A. Ingver (2004) demonstrated interesting correlations for the flour processed from the Estonian wheat cultivated in the 1999 – 2003 period. Specifically, the researches focused in this case, on the linkages between physical and chemical parameters, extensographic and farinographic parameters and the volume of the bread .
Gaines et al. (2006) tested 33 wheat samples of some varieties cultivated in the United States. Three of the parameters taken into consideration were proven to be superior with respect to predictability of technological characteristics: the alveographic mechanical work (W), the height of the mixographic peak and the capacity of retention of the solvents (Solvent Retention Capacity, AACC Method 56 – 11), against the gluten index ant the sedimentation indices (SDS).
Similar investigations have been made by Bettge et al. (1989), Kostyukovsky and Zohar (2004), Rashed et al. (2007) [2, 9,15].
Różyło and Laskowski (2011 ) showed that the best predictors of bread quality on the volume and core are combinations of alveographic, physical and chemical parameters, namely: Zeleny sedimentation index , falling number, and alveographic work ( W) or protein content, the falling number and alveographic extensibility  .
Sapirstein and Suchi (1999) obtained some results showing that the height of flour gel, obtained after centrifugation, in certain conditions of the flours dispersed in sodiumdodecilsulphate (SDS), correlates very strongly with bread volume (r2 between 0.89 and 0.95 ) .
The purpose of the present research was to highlight the level of correlation between various parameters of flours (protein content, wet gluten content, gluten index) and some qualitative characteristics of bread, such as volume and the ratio height / diameter (H/D).
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