Effects of post-harvest storage conditions on the levels of glucosinolates in broccoli sprouts (Brassica oleracea var. italica) grown under different temperature regimes

Broccoli sprouts have been recognised as a rich source of glucosinolates, particularly 4-methylsulphinylbutyl glucosinolate, the precursor of the potent anti-cancer compound, sulphoraphane. Previous results have shown that temperature can significantly affect the levels of glucosinolates. In this study, we showed how sprout age and storage temperature affected glucosinolate levels in broccoli sprouts grown under different temperature regimes. Experiments were conducted in growth cabinets with day/night temperature regimes of 30 degrees/15 degrees C, 22 degrees/15 degrees C and 18 degrees/12 degrees C. At 9, 10 and 11 d after sowing in the first temperature regime, 10, 11 and 12 d in the second, and 12,13 and 14 in the third, sprouts were submitted to VC or 20 degrees C to simulate refrigerated and room temperature storage. Sampling was done after 1 d or 2 d of exposure to these conditions. The results showed that total glucosinolate levels and the potential health effects of broccoli sprouts depended on the growth temperature regime (P < 0.05), the age of the sprouts (P < 0.001), and the storage conditions (P < 0.01). The highest total glucosinolate levels (65.7 mu moles g(-1) dry weight) were obtained under the 30 degrees/15 degrees C temperature regime for the youngest sprouts (harvested 9 d after emergence), after being submitted to a storage temperature of 4 degrees C for 24 h. However, these levels were much lower than in 3-d-old sprouts. Consuming old sprouts provides less health-protective effects due to reduced levels of glucosinolates.