Comparative protein and folate content among canola cultivars and other cruciferous leafy vegetables

Author: Rhona L. Miller-Cebert ¹, Nahid A. Sistani ^1* and Ernst Cebert ²

Received 3 January 2009, accepted 12 April 2009.

Abstract

Numerous research data support the recommendation of an increased intake of a wide variety of dark green leafy vegetables, which provide major dietary benefits in the human diet. The potential of canola (Brassica napus L.) leafy greens as a food source for human consumption is being considered to increase the variety of nutritious vegetables available to consumers. Five canola cultivars (ca), (Abilene, Jetton, Kronos, Virginia and Wichita) grown at the Alabama A&M University Winfred Thomas Agricultural Research Station in Hazel Green, Alabama, were analyzed for protein and folate composition of raw canola greens and compared to store-purchased collard greens (Brassica oleracea var. acephala), kale (Brassica oleracea var. viridis) and cabbage (Brassica oleracea var. capitata). Results showed no significant difference in the mean protein content of kale (24.85%) and the canola cultivar Kronos (22.70%). Cabbage, however, had the lowest protein content of all the vegetables tested in this study (10.15%). Among the three harvest stages (rosette, pre-bolting and blooming), the pre-bolting stage showed significantly higher protein (23.69%) compared to the rosette (20.52%) and blooming (22.27%) stages. No significant differences were observed in the mean folate content of canola and the store-purchased vegetables. Although not statistically significant, the trend from highest to lowest folate content among the Brassica species in this study was: Kale>Virginia-(ca)>Kronos-(ca)>Jetton-(ca)>Abilene-(ca)>Wichita-(ca)>Cabbage>Collard. The distribution of folate among all the samples showed variations from 0.02 mg/100 g in collard greens to 0.148 mg/100 g and 0.149 mg/100 g in canola (cultivar Jetton) and kale, respectively. Results indicated that canola greens could be a nutritionally acceptable substitute for traditional leafy green vegetables.

Key words: Brassica, cabbage, canola, collard, folate, kale, protein.