The effects of grain temperature on breakage susceptibility in maize

To understand the viscoelastic characteristics (i.e. hardness) of the maize (Zea Mays L.) grain in relation to high-temperature drying, a breakage tester (HT-I drop tester) was developed and single-grain breakage at various grain temperatures and times after drying was determined. Both hard and soft maize hybrid varieties had minimal breakage at high grain temperatures (78-110degreesC), while decreasing grain temperature increased breakage exponentially. After drying at both 60 and 120degreesC, the percentage breakage measured at ambient temperature increased rapidly during cooling in air at an ambient temperature of 20degreesC and a relative humidity in the range 65-70%. Breakage reached a maximum after about 10 min from the start of cooling. A Mitscherlich function described the chronological development of percent grain breakage. Analysis of the function parameters for the extent (maximum) and rate of breakage indicated that there was a significant interaction between variety and drying temperature for the development of grain breakage after drying. These results indicated that grain temperature should be considered as a co-factor when assessing grain breakage susceptibility. (C) 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved.