Compositional Differences of Stem and Floral Portions of Broccoli Heads

ABSTRACT Edible portions of broccoli (Brassica oleracea L. var. italica Plenk) consist of immature fully differentiated flower buds and tender portions of the upper stem. Differences in the developmental stage of the above tissues may be reflected in a different composition that may also be a result of environmental conditions. Dry matter (DM), soluble solids (SS), reducing sugars (RS), water soluble carbohydrates, ascorbic acid, total soluble phenols, nitrates, pH and titratable acidity (TA) in the stem and floral portions of the head were determined in two broccoli cvs. Marathon and Samurai, harvested from fields of two planting dates. The head portion, but not the planting date, had a significant effect on all compositional constituents measured with the exception of ascorbic acid in both cultivars and water soluble carbohydrates (on a dry weight basis) in ‘Samurai’. In both cultivars, the floral portion of the heads had higher values for DM, SS, water-soluble carbohydrates (on a fresh weight basis), total soluble phenols and TA and lower values for RS, nitrates and pH, than the stem portion. The largest differences between the head portions were observed on the nitrate and total soluble phenol content. More than 90% of the nitrate content of the heads was found in the stem, while about 70% of the total soluble phenol content was found in the floral portion. Therefore, the floral portion of the broccoli head is equally prized with the stem portion for its ascorbic acid content, but it has higher values for total soluble phenols (an antioxidant and anticancer constitute) and lower values for nitrates an anti-nutritional constitute), than the stem portion.