Sprouts of broccoli, for example, contain large quantities of anti-oxidants as well as vitamin C and other health-promoting compounds, especially glucosinolates.
In the experiments reported here, seeds of broccoli were surface-sterilised, washed, soaked in distilled water overnight and then germinated on wet filter paper in petri dishes. After five days, the sprouts were watered either with distilled water or with sucrose or mannitol at two concentrations - 88 millimolar or 176 millimolar.
The mannitol treatment was included because, when supplied at the same concentration as sucrose, it has the same osmotic effect but without the metabolic benefits.
The sprouts were grown at 23 degsC under a 16-hour day/eight-hour night regime. Seven-day-old sprouts were harvested, frozen and then analysed. Treatment with the lower concentration of sucrose increased the contents of ascorbic acid and anthocyanin in the sprouts but not the content of glucosinolates.
However, the total glucosinolate content was substantially increased by treatment with 176 millimolar sucrose or mannitol, suggesting that the increase was a response to osmotic stress. The results indicate that the nutritional value of broccoli sprouts could be improved by supplying them with sucrose at adequate concentration.
Dr Ken Cockshull, Associate Fellow, Warwick Crop Centre, University of Warwick
Effect of Sucrose & Mannitol on the Accumulation of Health-Promoting Compounds & the Activity of Metabolic Enzymes in Broccoli Sprouts by Guo, Yuan and Wang (2011). Scientia Horticulturae 128 (3): 159-165.
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