Experimental approach to optimize the use of alpha-Amylases in breadmaking.

alpha-Amylases from different origins (wheat, malted barley, fungi, and bacteria) are used extensively to improve breadmaking. However, the enzyme activities, in addition to the differences associated with their origins, are strongly affected by the process conditions and the presence of other compounds in the medium. The activity of different alpha-amylases was tested under different conditions (pH and temperature), and in the presence of some bread ingredients (salt and sugar), some breadmaking additives (ascorbic acid and sodium propionate), and some metabolites (organic acids and saccharides) generated during the fermentation step, to envisage the behavior of these alpha-amylases during the breadmaking process. The alpha-amylase activities were affected to a different extent by the addition of these compounds depending on the enzyme origin. In general, the alpha-amylases from cereals (wheat and malted barley) were less sensitive to the presence of some ingredients, additives, and metabolites. These results show the great variation of the alpha-amylase activity with the process conditions and the importance of its knowledge in the selection of the appropriate alpha-amylase for a specific breadmaking process.

Effect of processing conditions on acidification properties of wheat sour doughs.

The pH, total titratable acidity (TTA) and lactic and acetic acids production have been investigated for wheat sour doughs with and without yeast addition, inoculated with two strains of Lactobacillus plantarum (B33, B39). To study the effect of flour extraction rate (0.54, 11.11 and 1.68% ash content), dough yield (DY) (160, 200 and 240 of sour dough/100 g flour), and fermentation temperature (25, 30 and 35 degrees C) a response surface regression, factor analysis and K-means clustering analysis were used. Results from factor analysis point out that the extraction rate of fluor governs TTA and acetic acid content; this factor accounts for the 53% of variability of the data. Dough yield is highly correlated with lactic acid content, explaining 27% of the total variance. Finally, temperature explains the remaining 16% of variation, but it is not related to any analytical variable. From K-means clustering analysis, flour extraction rate of 1.68% ash content leads to the highest TTA and acetic acid values, whereas DY of 240 g sour dough/100 g flour gives the greatest lactic acid content, and DY of 160 leads to the lowest levels of TTA and organic acids.

Headspace flavour compounds produced by yeasts and lactobacilli during fermentation of preferments and bread doughs.

Production of volatile flavour compounds during fermentation with pure cultures of Saccharomyces cerevisiae and Candida guilliermondii, Lactobacillus brevis and Lactobacillus plantarum have been investigated, using wheat doughs and several preferements as substrates. For yeast, preferments consisted of 10% (w/v) glucose, maltose and sucrose solutions, whereas for lactobacilli they consisted of supplemented and unsupplemented (3% and 10% (w/v)) glucose solutions, and a 10% (w/v) wheat flour slurry. Seven volatile compounds (acetaldehyde, acetone, ethyl acetate, ethanol, hexanal+isobutyl alcohol, and propanol) were detected when using yeasts. All these compounds, except propanol, appeared for all the substrates assayed, with ethanol as the predominant component. Generally, S. cerevisiae produced higher amounts of the different components than C. guilliermondii. Both yeasts produced larger amounts of volatile flavour compounds during fermentation in glucose and sucrose solutions than in maltose or wheat dough. In general the yeasts examined produced more flavour components than the lactobacilli. For the lactobacilli the highest number of volatile flavour compounds were observed for substrates containing flour.