Volatile compounds in whole meal bread crust: The effects of yeast level and fermentation temperature.
The influence of fermentation temperatures (8°C, 16°C, and 32°C) and yeast levels (2%, 4%, and 6% of the flour) on the formation of volatile compounds in the crust of whole meal wheat bread was investigated. The fermentation times were regulated to optimum bread height for each treatment. The volatile compounds were extracted by dynamic headspace extraction and analyzed by gas chromatography-mass spectrometry. The results were evaluated using multivariate data analysis and ANOVA. In all crust samples 28 volatile compounds out of 58 compounds were identified and the other 30 compounds were tentatively identified. Higher fermentation temperatures promoted the formation of Maillard reaction products 3-methyl-1-butanol, pyrazine, 2-ethylpyrazine, 2-ethyl-3-methylpyrazine, 2-vinylpyrazine, 3-hydroxy-2-butanone, 3-(methylsulfanyl)-propanal, and 5-methyl-2-furancarboxaldehyde whereas at lower temperature (8°C) the formation of 2- and 3-methylbutanal was favored. Higher levels of yeast promoted the formation of 3-methyl-1-butanol, 2-methyl-1-propanol and 3-(methylsulfanyl)-propanal, whereas hexanal was promoted in the crust fermented with lower yeast level.
Crust formation and its role during bread baking.
The final properties of the crumb and crust differ according to their heat–moisture dynamics. Compilations of heating and drying rates reported in the literature are discussed and will serve to validate future models of baking. Their impact on the structural elements in dough films and the porous network are discussed, highlighting the lack of data and the need to reproduce these dynamics inside the instrument of analysis. Some roles of the crust setting during the whole baking process are also presented, suggesting further research in this area. Finally, as the region covered by the crust should be defined as a starting point to future studies, definitions proposed in the literature are discussed.
Predicting colour kinetics during cracker baking
Abstract The topic of this investigation covers the study of the kinetics of colour formation during the baking of crackers in a static electrically heated oven. Methods for measuring the kinetics of variation of product temperature, water content and surface colour (assessed in CIE 1976 (L ∗ , a ∗ , b ∗ ) system) are described. An appropriate experimental set-up was developed and experiments with increasing baking times were realised in order to reconstitute the whole baking profiles. The validity of this method was proved using continuous temperature recordings. Experimental recordings of cracker surface lightness during baking show first an enlightenment and subsequently a darkening phase. The darkening phase is initiated when the product temperature reaches a critical value in the range of 105–115 °C. A kinetic model was developed in order to predict the lightness variation of the cracker surface using the product temperature and moisture content variations during baking. The evolution of lightness appears to follow a firstorder kinetic influenced by these two parameters.