Rheological properties of millet dough prepared with different proteins

Abstract

Millet (Panicum miliaceum L.) flour represents potential raw material for the production of gluten-free products. Since bread of satisfactory quality cannot be produced using pure millet flour, various structuring agents are used to improve its textural properties, such as different hydrocolloids, starches and proteins. Proteins from different sources have been chosen for this study because they are not considered as additives (do not possess E-number). Additionally, they improve nutritional profile of millet bread since millet flour has low protein content. Four types of proteins were used for the production of millet bread: pea protein concentrate, rice protein concentrate, pumpkin oil cake protein isolate and whey protein concentrate. Bread formulation consisted of millet flour, sugar, yeast, salt and water (110 % of hydration on the millet flour basis). Proteins were used to substitute 10 % of millet flour in bread formulation. Dough prepared without addition of yeast was used for the determination of rheological properties to avoid their change during fermentation. Small deformation dynamic oscillatory measurements of doughs were performed using a Haake MARS rheometer (Thermo Scientific, Karlsruhe, Germany) at temperature of 25 °C, equipped with a parallel plate geometry PP60 (60 mm diameter and 1 mm gap). Dough was left to rest 300 s before measurement. Frequency sweep (mechanical spectrum) was recorded over the range of 0.1 - 10 Hz at 0.1 Pa stress, which was within the linear viscoelastic region as previously determined by stress sweep test.

Proseno (Panicum miliaceum L.) brašno predstavlja potencijalnu sirovinu za proizvodnju bezglutenskih proizvoda. Pošto je nemoguće proizvesti hleb zadovoljavajućeg kvaliteta od čistog prosenog brašna, koriste se različiti agensi za poboljšanje njegovih teksturnih svojstava, kao što su različiti hidrokoloidi, skrobovi i proteini. Proteini iz različitih izvora odabrani su za ovu studiju zato što se ne smatraju aditivima (nemaju E-broj). Pored toga, proteini poboljšavaju nutritivni profil prosenog hleba jer proseno brašno ima nizak sadržaj proteina. Četiri vrste proteina korišćene su u proizvodnji prosenog hleba: koncentrat proteina graška, koncentrat proteina pirinča, izolat proteina uljane pogače bundeve i koncentrat proteina surutke. Formulacija hleba sastojala se od prosenog brašna, šećera, kvasca, soli i vode (110% hidratacije na bazu prosenog brašna). Proteini su korišćeni za supstituciju 10% prosenog brašna u formulaciji hleba. Testo pripremljeno bez dodatka kvasca korišćeno je za određivanje reoloških svojstava da bi se izbegle promene prilikom fermentacije. Dinamička oscilatorna merenja pri malim deformacijama izvedena su korišćenjem Haake MARS reometra (Thermo Scientific, Karlsruhe, Germany) na temperaturi od 25°C, uz upotrebu pribora tipa ploča-ploča PP60 (60 mm prečnik ploče i 1 mm zazor između ploča). Testo je ostavljeno da odmara 300 s pre merenja. Test pri promeni frekvencije (mehanički spektar) je snimljen u opsegu frekvencija od 0,1 do 10 Hz pri naponu smicanja od 0,1 Pa, za koji je prethodno utvrđeno u testu sa promenom napona de se nalazi unutar viskoelastičnog područja.