Flour Properties of Milky-white Rice Mutants in Relation to Specific Loaf Volume of Rice Bread

Abstract

Starch content, starch damage, particle size distribution, pasting properties measured using a rapid visco analyser (RVA properties) of rice flour, and their relation to specific loaf volume (SLV) of rice bread with gluten were examined in rice cultivar Koshihikari and its milky-white mutant lines. Two different milling methods were used: jet-milling under semidry condition after pectinase treatment and pin-milling under dry condition. Jet-milled and pin-milled milky-white mutants and jet-milled Koshihikari produced flour with low starch damage, fine particle size, low pasting temperature, high final viscosity, large setback, high trough, and long peak time. Such flour resulted in high SLV rice bread. SLV of rice bread from pin-milled milky-white mutant was equivalent to that from jet-milled Koshihikari. Using milky-white mutants, rice flour suitable for bread-making would be produced by dry pin-milling.

Properties of Floury Rice Mutant and its Utilization for Rice Flour

“…Pin-milled Koshihikari was shown to have a shoulder at around 15-20 µm, a peak at around 130 µm, and MPS of about 90 µm. On the other hand, jet-milled floury mutant rice showed two peaks at around 15-20 µm and 40-50 µm, and MPS of about 20 µm in six mutant lines 4 . The distribution pattern of pin-milled floury mutant rice was given to have two peaks around 15-20 µm and 100 µm, and MPS about 40 µm.…”

“…Jet-milled Koshihikari reportedly has a shoulder at around 15-20 µm, a peak at around 50-60 µm, and median particle size (MPS) of about 40 µm 4 (Fig. 2).…”

“…Experiments using six floury mutant lines showed that the specific loaf volume (SLV) of rice bread with gluten made from jet-milled flour exceeded that of pinmilled flour in both Koshihikari and floury mutant rice 4 ( Fig. 4).…”

“…4). Therefore, the production of rice flour suitable for high-SLV rice bread would be possible by pinmilling when using floury mutant rice 3,4 .…”

“…Six floury mutant lines were developed by γ-irradiation or ethyl methanesulfonate treatments applied to a japonica rice cultivar "Koshihikari" during 1986-1987 3,4 . Koshihikari is a non-waxy cultivar with a translucent kernel (Fig.…”