Tecnological and sensory properties of traditional sourdough bread

Namen diplomskega dela je s pregledom strokovne literature raziskati razvoj tradicionalnih droži in spoznati lastnosti kruha pripravljenega z drožmi. Droži so mešanica vode in moke fermentirane z mikroorganizmi, ki pridejo v mešanico s surovinami ali pa iz okolja. V drožeh prevladujejo heterofermentativne mlečnokislinske bakterije, ki proizvajajo v glavnem organske kisline, etanol in CO2. Kvasovk in homofermentativnih mlečnokislinskih bakterij je v drožeh bistveno manj. Razmerje mikroorganizmov je odvisno od različnih dejavnikov. Nekateri izmed teh so pH, temperatura, surovine, prisotnost kisika, mikrobiota surovin in okolja, dohranjevanje in mikrobne interakcije. Ob spremembi posameznega dejavnika vplivamo na stabilnost in sestavo mikrobne združbe droži. Z različnimi kombinacijami dejavnikov lahko dosežemo želene lastnosti droži in končnega izdelka. Priprava kruha z drožmi zahteva več časa predvsem zaradi daljše fermentacije. V tem času združba mlečnokislinskih bakterij in kvasovk ustrezno poveča volumen pekovskih izdelkov in zagotovi značilne senzorične lastnosti. Spremembe glutenske frakcije, upočasnjena retrogradacija škroba, tvorba eksopolisaharidov in podaljšana trajnost so nekatere od glavnih pozitivnih tehnoloških lastnosti pekovskih izdelkov pripravljenih z drožmi. Značilne senzorične lastnosti so rezultat tvorbe aromatičnih spojin med pripravo droži, fermentacijo in peko. Delna razgradnja škroba, glutena in fitatov so lastnosti, ki vplivajo na izboljšano prebavljivost in prehranske lastnosti pekovskih izdelkov z dodatkom droži.The purpose of the diploma work is to study the production of traditional sourdough and characteristics of bread prepared with sourdough through a literature review. Traditional sourdough is a mixture of water and flour, fermented by microorganisms introduced by raw materials and house microbiota. Heterofermentative lactic acid bacteria that produce mainly organic acids, ethanol, and CO2 dominate in traditional sourdough. Homofermentative lactic acid bacteria and yeasts are much less present in traditional sourdough. The ratio of microorganisms depends on several factors. Some of them are pH, temperature, raw materials used, presence of oxygen, house microbiota, backslopping and microbial interactions. Single parameter change can destabilise sourdough microbiota. With different combinations of factors, we can achieve the desired characteristics of traditional sourdough and the final product. Production of sourdough bread takes longer than conventional bread production, mainly because of the longer fermentation. During this time, the association of lactic acid bacteria and yeasts correspondingly increases the volume of baked goods and provides a characteristic aroma. Changes of gluten fraction, slowed starch retrogradation, exopolysaccharide formation and prolonged shelf life are important technological characteristic that improve the final product made with addition of sourdough. Characteristic sensory properties are the result of formation of aromatic compounds during traditional sourdough preparation, dough fermentation and baking. Partial degradation of starch, gluten and phytates are part of changes that improve digestibility and nutritional properties of bakery products with the addition of traditional sourdough