Functional characteristics of non-starch polysaccharides (NSP) obtained from native (n) and malted (m) finger millet (ragi, Eleusine coracana, indaf-15)

Non-starch polysaccharides (NSP) were isolated from a recently released, fast germinating hybrid variety of finger millet and its malt (ragi, Indaf-15), in different yields and their functional characteristics, such as viscosity, oxidative gelation capacity, foam stabilization, and their effects on various dough properties, were studied. Viscosities of hemicellulose-B (hemi-B) fractions, obtained from native and malted ragi flours, was found to be greater (N – 3.04 and M – 1.98 at 1% concentration) than all other NSP fractions. A linear increase in viscosity of this fraction was noticed with respect to its concentration; however it decreased as the temperature increased from 30 to 80 °C and it was found to be maximum at pH 6.0. Hemi-B was found to stabilize protein foams against thermal disruption and showed a high water absorption (4.4 ml at 1% concentration) compared to cold water-soluble polysaccharides (CWSP) (3.0 ml at 1% concentration). Minor variations in dough characteristics, such as dough development time (DDT), dough stability (DS), tolerance index (TI), maximum extensibility (Em) and maximum resistance (Rm) were noticed upon the addition of hemi-B polysaccharides obtained from native and malted ragi and also CWSP (N). However, a significant decrease in the above parameters was noticed upon the addition of CWSP (M). Similar patterns were also noticed in starch pasting characteristics, such as gelatinization temperature (GT), peak viscosity (PV), cold paste viscosity (CPV), hot paste viscosity (HPV), breakdown viscosity (BV) upon the addition of CWSP (N) and hemi-B (N&M). However, a visible decrease in the above parameters was noticed upon the addition of CWSP (M). Oxidative gelation studies indicated minor variations in their flow properties before and after the addition of hydrogen peroxide and peroxidase. The results obtained from this present study indicated that ragi can be incorporated as a source of dietary fibre both in the native and malted forms, in the preparation of various health foods without altering the dough characteristics or the quality of the end-product.