Cereal Chem. 71:87-90 | VIEW
Variation for Thermal Properties of Starch in Tropical Maize Germ Plasm.
J. Li, T. G. Berke, and D. V. Glover. Copyright 1994 by the American Association of Cereal Chemists, Inc.
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 thermal variation of maize starch in normal maize genotypes. Inter- and intrapopulation variability for thermal properties of laboratory-isolated starch from 35 tropical and semitropical maize populations, representing 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 ([Delta]H), peak onset (To), peak maximum (Tp), and peak conclusion (Tc) temperature. The temperature range of gelatinization was calculated as (Tc minus To). Among 35 populations, highly significant differences (P less than or equal to 0.01) for all measured thermal properties were observed. Means of To, Tp, and Tc were 63.0, 71.0, and 77.8 C, respectively; ranges were 64.3-69.6 C, 70.1-73.9 C, and 76.8-79.6 C, respectively. Temperature ranges of gelatinization varied between 9.8 and 13.0 C. Average enthalpy ([Delta]H) was 10.5 joules per gram with a range of 8.2-12.3 J/g. Within each population, highly significant differences were noted in the To values of endotherms in all populations; highly significant differences were also noted in the Tp, Tc, and temperature range in most populations. Within each population, there were few significant differences in the (Delta)H. There was little relationship 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 properties of maize starches exists in tropical and semitropical maize germ plasm. Compared to the range of starch thermal properties found in maize endosperm mutants, the range of variability in this germ plasm was limited.