Effect of different sub-zero temperatures and relative humidities on moisture content and germination of stored canola

Storage of high-moisture canola remains a major challenge due to mold growth resulting in seed deterioration. While equilibrium moisture content (EMC) models have been widely applied to above-zero storage and drying conditions, no research has quantified EMC isotherm and germination under sub-zero temperatures. Isotherm and germination of canola, conditioned to 14–18 % moisture contents, were tested at temperatures from −25 to +30 °C and relative humidities (RHs) between 15 and 94 %. Multiple EMC models were evaluated for their predictive accuracy across the studied temperatures and RHs. The main factor influencing EMC of canola from −5 to −20 °C was the RH, and temperature had minimal influence. Both temperature and RH influenced the EMC when temperature was ≤ −20 °C. When RH was higher than 75 %, EMC of canola had an exponential increase with the increase of RH and/or decrease of temperatures. Seed germination remained high (≥80 %) at −5 to −15 °C, and RH had a minimum influence on the germination. At −20 and −25 °C and higher than 40 % RH, canola germination was reduced to less than 40 % after EMC was reached, indicating severe damage to the canola seeds. Peleg model yielded the best fit to the isotherm data at different sub-zero temperature ranges. These findings offer essential guidance for sub-zero grain storage and drying strategies, with implications for preserving seed viability and reducing post-harvest losses. • First study to assess canola EMC and germination at sub-zero temperatures. • RH influenced EMC from −5 to −20 °C; temperature had minor effect. • Peleg model provided the best fit for sub-zero EMC across tested temperature ranges. • Canola drying occurred at sub-zero temperatures under low RH conditions. • Germination declined sharply at ≤ -20 °C and >40 % RH, indicating freeze-induced damage.