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Improvement of quality and shelf-life of wheat bread by using bacterial starter cultures

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Strain specific influences on sourdough properties were evident. Ash content of the flour was most efficient in adjusting titratable acidity(TTA), lactate content and acetate content. Dough yield had a minor, positive influence on TTA and lactic acid production and in the case of heterofermentative strains, acetic acid production was negatively affected by dough yield. The effect of temperature depended on the strain. Addition of dried yeast had no remarkable effects. Fructose supply was most effective in adjusting fermentation quotient and temperature had no significant influence on the quotient. Under conditions practiced for sourdough preparation, sourdoughs do not prevent bread becoming stale. Their effect on delaying microbial spoilage depended on the strain of lactobacilli and on the use of yeast. Only Lactobacillus brevis 25a with yeasted sourdough extended shelf-life of bread more than 30%. Improving acetic acid production also extended shelf-life but consumer acceptance decreased. Sourdough addition increased bread volume but it was decreased when bran or rye was added. Sourdough addition improved bread texture especially when yeast was added in high amounts. Sensory evaluation showed that the heterofermentative strain L62 gave an odd flavour, 25a gave higher sensory scores. When yeast was added L73 gave a better taste than 25a. Sourdough addition at 10% was the maximum acceptable dose. Higher dosage gave bread with more acidity, but less bread smell and taste. Higher ash content in sourdough increased acid smell and taste, which is not appreciated. Yeast has a positive influence on taste. Toasting the breads decreased the sensory score.