Characterization of Water States in Canola Seeds With Varying Moisture Contents Using Differential Scanning Calorimetry.

Characterization of water status in grains is essential for grain drying, storage, and handling. A state diagram of canola seeds was developed incorporating the freezing curve, glass transition line, and critical moisture content (MC) at which freezable water first appears using differential scanning calorimetry. Cooling and heating rates of 1, 2, 5, 10, and 20°C/min were tested, and 1°C/min was used to determine the freezing and melting parameters such as peak temperature, onset temperature, and enthalpy. Below 17.8% MCs, the freezing point varied, and the minimum was about -26°C, whereas, beyond 17.8% MC, the freezing point increased to -6.72 ± 0.18°C at 35.8% MC. The critical MC was about 16%. Below this threshold, all remaining water exists as unfreezable water. Multiple glass transitions were observed across all tested MCs, with the first glass transition becoming undetectable above 6.2% MCs. As MC increased, the temperatures of the second and third glass transitions decreased, reaching 63.46 ± 0.39°C and 73.38 ± 0.98°C, respectively, at 35.8% MC. The developed state diagram will be useful for understanding effects of MC and temperature on the water state, and it will offer guidance for drying, handling, and storage strategies for canola seeds. PRACTICAL APPLICATIONS: The state diagram aims to elucidate changes in water state as a function of MC and temperature, ultimately informing the selection of suitable conditions for handling and storage of canola. In addition, the state diagram will be used to determine the material state and knowledge about the material state is necessary for selecting suitable drying conditions.