EFFECT OF STARCH GRANULE SIZE ON THE THERMAL AND PASTING PROPERTIES OF MAIZE

Abstract

The kernel of maize (Zea mays L.) is mainly composed of starch, whose size varies among races. The knowledge of the starch gelatinization process provides important information about the functionality, energy requirements, and end use of this cereal. The aim of this paper was to investigate the relationships between starch granule size, and thermal and rheological properties of 71 pure corn races from México, the Caribbean, Central and South America. Imagens of starch granules were obtained by means of environmental scanning microscope from soft and hard endosperm samples. Gelatinization temperatures and enthalpies were determined by differential scanning calorimeter. Pasting properties were measured with a rapid visco analyser. Moisture, protein, lipid and amylose content, as well as kernel hardness were also determined. Small starch granules gelatinized slowly and showed higher temperature and enthalpy values. Soft grains showed larger starch granules in the soft endosperm, and smaller ones in the hard endosperm, while the opposite was observed in hard grains. Hardness also correlated to temperature, range, and enthalpy of gelatinization. Starch granule size was inversely correlated to time and temperature to peak viscosity. The starch granule size was proportional to the moisture and amylose content and inversely correlated to protein content in soft endosperm samples.