Compositional differences of stem and floral portion of brocoli heads

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Compositional Differences of Stem and Floral Portions of Broccoli Heads
Anastasios S. Siomos Parthena P. Papadopoulou Constantinos C. Dogras

ABSTRACT. Edible portions ofbroccoli (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 solublecarbohydrates (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. Morethan 90% of the nitrate content of the heads was found in the stem, while about 70% of the total soluble phenol content
Anastasios S. Siomos (E-mail: siomos@agro.auth.gr) is Assistant Professor, Parthena P. Papadopoulou is Agriculturist, and Constantinos C. Dogras (E-mail: dogras@ agro.auth.gr) is Professor, Department of Horticulture, Aristotle University of Thessaloniki, 54124, Thessaloniki,Greece. The authors would like to thank P. Tsouvaltzis and C. Roumeliotis who provided technical assistance and also the Candilidis Co. SA, Thessaloniki, Greece, for providing the seeds for the experiments. Journal of Vegetable Crop Production, Vol. 10(2) 2004 http://www.haworthpress.com/web/JVCP  2004 by The Haworth Press, Inc. All rights reserved. Digital Object Identifier: 10.1300/J068v10n02_10107

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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. [Articlecopies available for a fee from
The Haworth Document Delivery Service: 1-800-HAWORTH. E-mail address: Website:  2004 by The Haworth Press, Inc. All rights reserved.]

KEYWORDS. Brassica oleracea var. italica, ascorbic acid, total soluble phenols, carbohydrates, sugars, nitrates, antioxidants INTRODUCTION Broccoli (Brassica oleracea L. var. italica Plenk) is a popular vegetable in many partsof the world and has been considered to contribute to cancer prevention since the early 1980s (Nestle, 1998). Broccoli is one of the most nutritious vegetable since it is a vital source of essential minerals, vitamins and dietary fibre According to the relative concentration of 10 vitamins and minerals, it ranks first among 42 fruit and vegetables (Salunkhe et al., 1991). The edible portion ofbroccoli is the head consisting of immature fully differentiated flower buds (floral portion) and the tender upper part (up to 15 cm) of the stem. Harvested broccoli comprises a mass of green floral buds (florets) and thick, fleshy flower branchlets or stalks attached to the stem (King and Morris, 1994a). Information on broccoli nutritional value for flower clusters and stems is given by the USDA...