Pre-harvest applications of pulsed light increases vitamin C, chlorophyll, carotenoids and proteins in alfalfa sprouts

The possibility of using pulsed light (PL) pre-harvest during the cultivation of alfalfa sprouts to reduce microflora and simultaneously enhance the bioactive concentration was presented. Different fluences were compared, and the effect of PL direction on sprout quality was determined. PL application up to 12 J/cm2 per day resulted in an increased accumulation of bioactive components (vitamin C, proteins, chlorophyll, and carotenoids), in response to the stress resulting from PL emission. More interestingly, the direction of incidence was found important, with different trends observed for different bioactive components depending on whether only leaves were illuminated, or both leaves and roots were illuminated. Pulsed light directed solely towards the cotyledons (24 J/cm2) reduced the level of total microbial counts by about 0.7 log cfu/ml, and yeast and mold counts by about 1 log cfu/ml. It was found that an excessive amount of PL directed towards the roots might damage the root system, which promotes the growth of bacteria and will lower increases in the accumulation of chlorophylls, carotenoids, vitamin C, and proteins. The work will guide the development of photo-energized cultivation chambers for the production of agricultural and food products.