Nutritional value and staling kinetics of breads produced by bakeoff technology and sourdough addition

Cilj ove disertacije bio je ispitati mogućnosti primjene novih tehnologija za proizvodnju nutritivno vrijednog integralnog pšeničnog i bezglutenskog kruha. Razvijene su recepture za proizvodnju polupečenog smrznutog kruha s dodatkom kiselog tijesta (u koliĉini od 7,5-30%) fermentiranog pomoću definiranih starter kultura (bakterije mliječne kiseline Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus fermentum, Leuconostoc mesenteroides i kvasci C. milleri i S. cerevisiae var. chevalieri). Osim svojstava kiselih tijesta, određen je kemijski sastav, glikemijski indeks in vivo, fizikalno-senzorska svojstva kvalitete i kinetika starenja kruhova nakon skladištenja i dopečenja. Inovativni postupci kao što su proizvodnja kruha iz smrznutog tijesta ili polupečenog smrznutog kruha nisu značajno utjecali na prehrambenu vrijednost bijelog pšeničnog kruha iako je polupečeni smrznuti kruh imao za 10 % niţi GI od konvencionalnog kruha. Integralni pšenični kruh je bio dobar „izvor proteina“ i „bogati vlaknima“, no također je imao visoki GI. Dodatkom kiselog tijesta (10 %) u integralni pšenični kruh GI se smanjio na niski ili srednji, ovisno o starteru. Ovisno o primjenjenoj starter kulturi i količini dodanog kiselog tijesta, kvaliteta polupečenog smrznutog integralnog kruha se približila ili čak nadmašila kvalitetu konvencionalnog kruha. Na poboljšanje volumena, teksture, okusa i mirisa te usporeno starenje nakon dopčenja pšeničnog integralnog kruha najučinkovitije je djelovao dodatak Lb. plantarum kiselog tijesta u količini od 7,5 do 22,5 %, kao i LV4 kiselog tijesta u količini od 10 %. Bezglutenski kruh proizveden tehnologijom dopečenja bez dodatka kiselog tijesta bio je bogat vlaknima i imao je srednji GI (68). Bezglutenski kruh s 15 - 22,5 % dodanog PL3 kiselog tijesta imao je niski GI (52-54), poboljšanu kvalitetu i produljenu svjeţinu. Stoga se za „bake-off“ postupak proizvodnje pšeničnog i bezglutenskog kruha bogatog vlaknima može preporučiti dodatak kiselog tijesta u količini od 10 - 22,5 % kako bi kruh imao niski glikemijski indeks, dobru kvalitetu i trajnost, te bio prikladan za prehranu oboljelih od dijabetesa i/ili celijakije.The aim of this thesis was to investigate the possibilities of producing whole wheat and gluten-free bread of high nutritive value by bake-off technology. Newly developed bread formulations for partially baked frozen bread contained sourdough (7.5-30%) fermented by selected starter cultures of lactic acid bacteria (Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus fermentum, Leuconostoc mesenteroides) and yeast (Candida milleri or Saccharomyces cerevisiae var. chevalieri). Besides sourdough biochemical characteristics, bread chemical composition, glycaemic index in vivo, sensory and physical properties as well as staling kinetics were determined after frozen storage and final baking. Innovative processes such as frozen dough and partially baked frozen bread did not significantly affect nutritive value of white wheat breads, although partially baked frozen bread had lower GI by 10 % than conventional bread. Whole wheat bread was good „protein source“ and „high fibre“ but still had high GI (70). By adding 10 % of sourdough to whole wheat bread, glycaemic index decreased to low or medium, depending on the starter. Moreover, sourdough positively affected the quality parameters of part-baked frozen whole wheat bread. Depending on the starter culture and sourdough amount, the quality of part-baked bread was similar or even higher than of conventional bread. Addition of Lb. plantarum sourdough (15 - 22.5 %) and LV4 sourdough (10 %) the most significantly improved specific volume, texture and flavour, and retarded staling of whole wheat partially baked frozen bread. Gluten-free partially baked frozen bread without sourdough was „high fibre“ and had medium GI (68). Gluten-free breads with added PL3 sourdough ranging from 15 to 22.5 % had low GI (52-54), improved quality and delayed staling. In conclusion, 10 to 22.5 % of sourdough can be added in production of whole wheat and gluten-free breads by bake-off technology. Such breads have low glycaemic index, high quality and shelf-life, and can be recommended to diabetic and celiac patients