Increasing Antioxidant Content of Broccoli Sprouts Using Essential Oils during Cold Storage

Abstract

Broccoli sprouts are natural functional foods for cancer prevention because of their high content of glucosinolate and antioxidant. Sprouts and mature broccoli are of potential importance in devising chemoprotective strategies in humans. The aim of the investigation was to study the effect of essential oils on broccoli seed germination, increase their antioxidant content and determine the glucosinolate concentration and other phytochemical parameters in 3-day-old sprouts during cold storage at 4°C and 95% RH for 15 days. The results showed that all treatments of essential oils increased germination index, seed germination percentage, seedling length, seedling vigour index, yield and the antioxidant content of broccoli sprout and reduced the microbial load compared to the control. Fortunately, the coliform bacteria was not detected in all treatments. Different essential oils of fennel, caraway, basil, thyme and sage were tested. The thyme oil was the best treatment, which increased the accumulation of the phenolic compounds and glucosinolate compared to the control at different storage periods. In the sprouts treated with thyme oil treatment and the control, at the end of cold storage, 1.98% and 28.06% of total phenolic content, 1.90% and 20.28% of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, 1.39% and 58.33% of flavonoids, 1.93% and 36.25% of vitamin C, 2.95% and 22.02% of anthocyanin and 2.18% and 49.12% of glucosinolate were lost, respectively. A slight reduction differences in all detected compound concentrations occurred between the initial content and the end of storage period because of the application of thyme oil compared to the control. Therefore, the total glucosinolate level in the sprout (27.02 μg/g F.W.) was higher than that in the florets (7.37 μg/g F.W.). Glucoraphanin was the most abundant aliphatic glucosinolate present in the sprout and reached the highest value (16.24 μg/g F.W.) followed by glucoerucin (5.9 μg/g F.W.) and glucoiberm(1.2 μg/g F.W.).