Abstract
The effects of storage conditions and cooking methods on chlorophyll, glucosinolate (GSL), and sulforaphane content in broccoli florets were investigated in this study. For the storage experiment, fresh broccoli florets were stored for 2, 4, and 6 days at 10, 4, and 0 °C with or without 1-methylcyclopropene (1-MCP) treatment. For the cooking experiment, fresh broccoli florets were cooked for 1, 3, 5, 7, and 9 min under three cooking methods, namely, steaming, microwaving, and boiling. Results showed that the contents of chlorophyll, aliphatic GSL, indole GSL, and sulforaphane in broccoli florets of two cultivars decreased with prolonged storage time. The retained contents of chlorophyll, GSLs, and sulforaphane under 0 °C storage condition were significantly higher than those under 10 °C storage condition after 6 days of storage. The sulforaphane content was increased by 1-MCP treatment but differed among varieties. The cooking experiment showed that aliphatic GSL content decreased with increased cooking time under three cooking methods, and indole GSL and sulforaphane contents had a fluctuating trend with increasing cooking time after steaming and microwaving. Sulforaphane content increased by 17.15–50.16% relative to that in fresh broccoli florets and was considerably affected by cooking time. The highest level of sulforaphane content was retained for 7 min during steaming or 5 min during microwaving. Therefore, the combination of 1-MCP treatment and 0 °C storage condition had the best performance in preserving chlorophyll, GSLs, and sulforaphane. Moreover, steaming for 7 min or microwaving for 5 min is a more effective method for preserving the quality and increasing the sulforaphane content of broccoli florets than boiling.
Highlights
Chlorophyll contents in broccoli florets of two varieties continuously decreased with increasing storage time
The contents of chlorophyll, total GSLs, AGS, indole GSLs (IGS), and sulforaphane in broccoli floret of two varieties decreased with prolonged storage time
The 0 ◦ C storage condition combined with 1-MCP treatment exerted the best effect for preserving chlorophyll, GSLs, and sulforaphane
Summary
Licensee MDPI, Basel, Switzerland.Attribution (CC BY) license (https://creativecommons.org/licenses/by/ 4.0/).Broccoli (Brassica oleracea var. italica) contains high levels of vitamins, minerals, polyphenols, and a group of phytochemicals named glucosinolates (GSLs), and it has been characterized with a high nutritional value [1]. GSLs are sulfur-rich, secondary metabolites characteristic of the Brassicales order with important biological and economic roles in plant defense and human nutrition [2,3,4]. These compounds have gained renewed interest as their major hydrolysis products, such as sulforaphane, exert chemoprotective effects through the action of the endogenous enzyme myrosinase [5]. The most abundant
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