Swiss chard (Beta vulgaris) produced under greenhouse conditions – effects of water content in the growing media on the content of bioactive compounds and the microbiology of the leaf surface

Moderate drought stress was applied during growth of baby leaf Swiss chard (Beta vulgaris L.) and known concentrations of the human pathogens E. coli and L. monocytogenes were applied at the last irrigation event before harvest. The content of ascorbic acid in the leaves and the survival/growth of bacteria on the leaf surface were studied. A small increase in ascorbic acid was observed in the drought stressed leaves on a fresh weight basis, but it was absent on a dry weight basis. No significant effect on either of the two bacteria could be found between the treatments. The conclusion is that drought stress will decrease the yield while not improving the food safety or the healthiness of Swiss chard baby leaves.