Different moisture contents of tempered hulled and hull-less barley grains prior to milling : 1. effect on extraction rate, color and characteristics of flours

الملخص EN

The purpose of this work was to study the effect of different moisture contents(12, 14, 16 and 18%) of conditioned hulled and hull-less barley grains prior to milling on extraction rate, color and characteristics of flours.

flour extraction rate was decreased as the tempering moisture of grains prior to milling increased.

in all conditioning treatments, the flour yield was lower in hulled than in hullless variety.

the flour color was significantly improved (become white) as the conditioning moisture of hull-less barley grains before milling increased, while the hulled barley showed slight improving.

the chemical composition of flours including protein, fat, crude fiber, ash, pentosan, β-glucan, bond and total phenolic compound and phytic acid contents showed decreasing, whereas starch, reducing sugar and free phenolics contents were raised as the conditioning moisture of grains prior to milling in both varieties increased.

a slight raise in solubility of protein and starch with substantially increasing in the solubility of pentosan and β-glucan was observed in all flours from both barley varieties as the tempering moisture of grains before milling increased.

the solubility of β-glucan was higher in flours from hulled than that corresponding flours from hull-less variety and this reflected the higher values of relative viscosity of flour water extract from the former than the latter.

the rapid visco analyser (rva) measurements for the flours obtained from hull and hull-less barley indicated that the values for pasting temperature, time to gelatinization, time to peak, peak viscosity, trough viscosity and final viscosity were decreased as the moisture content of barley grains prior to milling increased.