The thermal properties of starches during gelatinization are important
to the food industry, primarily because of the rapid market growth of
convenience foods. Few studies have been conducted on the amount of t
hermal variation of maize starch in normal maize genotypes. Inter- and
intrapopulation variability for thermal properties of laboratory-isol
ated starch from 35 tropical and semitropical maize populations, repre
senting a range of sources and maturity groups, was evaluated by using
differential scanning calorimetry. Starch was isolated from a bulk of
10 kernels from each of 16 plants in each population; two subsamples
from each plant were analyzed independently. Endotherms were analyzed
to determine enthalpy (DELTAH), peak onset (T(o)), peak maximum (T(p))
, and peak conclusion (T(c)) temperature. The temperature range of gel
atinization was calculated as (T(c) - T(o)). Among 35 populations, hig
hly significant differences (P less-than-or-equal-to 0.01) for all mea
sured thermal properties were observed. Means of T(o), T(p), and T(c)
were 63.0, 71.0, and 77.8-degrees-C, respectively; ranges were 64.3-69
.6-degrees-C, 70.1-73.9-degrees-C, and 76.8-79.6-degrees-C, respective
ly. Temperature ranges of gelatinization varied between 9.8 and 13.O-d
egrees-C. Average enthalpy (DELTAH) was 10.5 joules per gram with a ra
nge of 8.2-12.3 J/g. Within each population, highly significant differ
ences were noted in the T(o) values of endotherms in all populations;
highly significant differences were also noted in the T(p), T(c), and
temperature range in most populations. Within each population, there w
ere few significant differences in the DELTAH. There was little relati
onship between starch thermal properties and population origin, kernel
color, kernel weight, kernel starch content, or plant maturity group.
The results demonstrate that genetic variability for thermal properti
es of maize starches exists in tropical and semitropical maize germ pl
asm. Compared to the range of starch thermal properties found in maize
endosperm mutants, the range of variability in this germ plasm was li
mited.