PH—Postharvest Technology: 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 (78–110°C), while decreasing grain temperature increased breakage exponentially. After drying at both 60 and 120°C, the percentage breakage measured at ambient temperature increased rapidly during cooling in air at an ambient temperature of 20°C 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.