engleski

Effect of various types of acidification and carboxymethylcellulose on quality parameters of fresh and frozen breads

Effect of biological and chemical acidification and carboxymethylcellulose (CMC) on dough properties, and bread quality was examined, the dough being made of two wheat flour types. Biological acidification was done with freshly prepared sourdoughs from two strains of lacticacid bacteria (Lactobacillus plantarum and Lactobacillus brevis) and dry sourdough. On the other hand, chemical acidification process involved lactic acid. Rheological properties of dough were monitored by the basic rheological methods. Changes of total titration acidity (TTA) and pH values during fermentation were also examined, as well as, changes of HMW glutenins after fermentation by SDS-PAGE electrophoresis. Thermal changes of wheat starch during baking were tested by differential scanning calorimeter (DSC) as an oven. Specific volume, penetration depth, water share, pH value and TTA were determined in fresh bread samples and bread that had undergone freezing and frozen storage (one, five and nine weeks), and subsequently microwave reheating. Rheological examination results showed that each of the examined additions had various effects on certain rheological parameters. The effect extent depended on chemical composition of flour. CMC buffer effect was proved regardless of acidification or flour type. There was a high correlation between the parameters of dough acidity (pH and TTA) and specific rheological parameters (pharinographic dough development, stability, resistance and softening degree, dough extensibility, amylographic maximum viscosity and Falling number). Electrophoretic analysis proved that chemical and biological dough acidification had an effect on specific protein degradation, which significantly changed gluten structure after fermentation. Simulation of bread baking on DSC showed that parameters of wheat starch gelatinization in dough after fermentation depended significantly on chemical composition of flour. Besides, dough acidity significantly influenced gelatinization capacity of starch, as well as melting of the more stable crystalline structure of starch. CMC addition had a positive influence on specific volume, hardness and water share in bread. On the other hand, lactic acid did not change specific volume of breads with regard to the control sample. While outstanding decrease of specific volume and water share occurred, there was an increase of hardness of all examined bread samples after freezing and microwave reheating. All research, apart from electrophoretic analysis, showed differences regarding two flour types.

wheat flour; sourdough; dry sourdough; rheological properties; pH values; SDS-PAGE; frozen bread; microwave reheating; DSC

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