Abstract
This work studied the effect of drum-rotation frequency, drum temperature, and water-to-pulp ratio in a double-drum drier on the content of sulforaphane, glucoraphanin, total phenolic compounds, ascorbic acid, and antioxidant activity of broccoli pulp through a multilevel factorial design with one replicate. Drum-drying conditions did not significantly affect sulforaphane content, unlike glucoraphanin, however the poor adherence of broccoli pulp resulted in a final product with undefined shape and heterogeneous color. On the other hand, antioxidant activity was unevenly affected by drying conditions; however, drum-rotation frequency affected it in the same way that phenolic compounds and ascorbic acid, showing a concordant behavior. The ascorbic acid content decreased significantly after drying, and it was highly dependent on the experimental factors, resulting in a regression model that explained 90% of its variability. Drum-rotation frequency of 5 Hz, drum temperature of 125 °C, and water-to-pulp ratio of 0.25 resulted in an apparent increase of sulforaphane and phenolic compounds content of 13.7% and 47.6%, respectively. Drum drying has great potential to fabricate dehydrated broccoli-based foods with functional properties. Besides, since drum drying has low investment and operation costs, it represents a very attractive option for the industrialization of broccoli derivatives.
Highlights
Broccoli (Brassica oleracea var. italica) offers many health beneficial effects due to its high content of bioactive compounds, such as polyphenols, ascorbic acid, sulforaphane, and high antioxidant activity
The effect of drum-rotation frequency, drum surface temperature, and water-to-pulp ratio was evaluated on the content of moisture, sulforaphane, glucoraphanin, total phenolic compounds, ascorbic acid, and antioxidant activity (FRSA and FRAP) in the dried product
Our results suggest drum drying as a promising dehydration process to preserve sulforaphane content in dehydrated broccoli, with lower operation and investment costs in comparison with freeze drying
Summary
Broccoli (Brassica oleracea var. italica) offers many health beneficial effects due to its high content of bioactive compounds, such as polyphenols, ascorbic acid, sulforaphane (and its precursor, glucoraphanin), and high antioxidant activity. Italica) offers many health beneficial effects due to its high content of bioactive compounds, such as polyphenols, ascorbic acid, sulforaphane (and its precursor, glucoraphanin), and high antioxidant activity. Sulforaphane gained great attention because of its outstanding health-promoting properties, such as acting as indirect antioxidant at cellular level and as a powerful cancer preventing agent, by inducing phase II detoxifying enzymes. The formation of sulforaphane occurs through the hydrolysis of glucoraphanin mediated by the enzyme myrosinase (EC 3.2.1.147), processing conditions greatly influence the health benefits of broccoli. This encouraged research on exploiting these healthy properties by optimizing culture, harvest, and post-harvest processing conditions of broccoli [1].
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