rowth temperature and photoperiod were found to affect the content of fatty acids before cold acclimatisation. For α-linolenic acid (18:3) and stearic acid (18:0), a day length × temperature interaction was observed. The content of α-linolenic acid (18:3) at low growth temperature/24 h day length was 13% lower compared to low growth temperature/12 h day length. Oleic acid (18:1) and behenic acid (22:0) had the highest level at short day. The highest content of stearic acid (18:0) was found at high growth temperature and 12 h day length and 15/9 °C and 24 h day length. For hexadecatrienoic acid (16:3) the content at high growth temperature was 17% higher with a long photoperiodic regime. A difference in ratio between unsaturated fatty acids vs. palmitic acid (16:0) + stearic acid (18:0) was evident in the growth treatments, by having the highest ratio at 21/15 °C-24 h and lowest at 15/9 °C-24 h day length.
The data clearly showed that the fatty acid contents were highly affected by the cold acclimatisation period. The total content of fatty acids in kale subjected to cold acclimatisation were lower (9–25%) after cold acclimatisation. Indeed the oleic acid (18:1) fatty acid content was reduced by up to 91% (12 h; 15/9 °C) after cold acclimatisation whilst the content of behenic acid (22:0) was uniformly higher (∼40%) (Table 3). The ratio between unsaturated fatty acids vs. palmitic acid (16:0) + stearic acid (18:0) had a higher portion of unsaturated fatty acids after cold acclimatisation (Table 3) for all combinations of growth temperature and day length, except the high growth temperature/24 h photoperiod. The ratio between unsaturated fatty acids and all saturated fatty acids did not appear to be impacted after cold acclimatisation, possibly due to a higher content of behenic acid (22:0) after cold acclimatisation.