Relationship of starch changes to puffing expansion of parboiled rice

‘Intan’ variety of paddy (Oryza sativa) was test-
ed for puffing. It was parboiled under a wide range of paddy
moisture content, steaming pressure and time, as also tem-
perature and time of sand heating. The resulting milled rices
were studied for their diverse properties including puffing.
Indices of starch changes in the samples were calculated as:
(1) gelatinisation index from the solubility of amylose in 0.2
N KOH; (2) amylopectin retrogradation from the post-pro-
duction drop in room-temperature hydration power of the
parboiled paddy during air-drying, (3) thermal breakdown
of starch from the drop in gel permeation chromatographic
fraction I of starch; lipid-amylose complexation indirectly
from (4) drop in rate of water uptake during cooking and (5)
cooked-rice firmness. It was found that the puffing expan-
sion was very highly correlated with the combined above 5
indices of starch changes, as much as 90% of the variation
in puffing being explainable on that basis. Puffing was pro-
moted by gelatinisation as well as lipid-amylose complex-
ation, but was retarded by amylopectin retrogradation and
probably starch breakdown.