Effect of Source and Processing on Maize Grain Quality and Nutritional Value for Broiler Chickens 1. Heat Treatment and Physiochemical Properties

Abstract

The aim of the present study was to evaluate the nutritional quality of traditional sun-dried maize grain, subjected to further heat treatment. The maize grains were obtained from three different locations, namely Moree in NSW, Emerald in QLD and Darling-Downs on the NSW-QLD border, Australia. Once received, one batch (sun-dried) was assessed without further drying. The other two batches from each source were dried artificially using a forced draught-oven at 105°C for 30 min or 24 h. The morphological structures (starch granules) of grains were changed due to heat-treatment for 30 min at 105°C and far-reaching structural changes occurred when samples were heated for 24 h. Proximate analysis of maize revealed that the DM (897.3-967.4 g kg-¹), CP (92.1-108.7 g kg-¹), EE (49.0-57.5 g kg-¹), phytate-P (1.2-2.4 g kg-¹) and ash (14.1-19.7 g kg-¹) contents of samples varied due to source and heating period. The starch, amylose, available amino acid and mineral contents increased with increasing heating duration. Variable anomeric proton peaks (H-NMR) were found with an increase in the oven drying period in all maize samples. 'In vitro' digestibility of DM, starch and CP was improved due to heat-treatment at 105°C for 30 min 24 h. It may be concluded that the chemical composition, ultra-structural characteristics and energy values of maize samples varied by source and were changed through heating of low-moisture maize over varying time periods. These changes could impact on the nutritive value of the grains and animal performance.