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. 2022 Mar:84:105977.
doi: 10.1016/j.ultsonch.2022.105977. Epub 2022 Mar 5.

Influence of sequential exogenous pretreatment and contact ultrasound-assisted air drying on the metabolic pathway of glucoraphanin in broccoli florets

Beini Liu  1 , Yang Tao  2 , Sivakumar Manickam  3 , Dandan Li  1 , Yongbin Han  4 , Ying Yu  1 , Dongfeng Liu  5
Affiliations

Influence of sequential exogenous pretreatment and contact ultrasound-assisted air drying on the metabolic pathway of glucoraphanin in broccoli florets

Beini Liu et al. Ultrason Sonochem. 2022 Mar.

Abstract

In this investigation, the combinations of exogenous pretreatment (melatonin or vitamin C) and contact ultrasound-assisted air drying were utilized to dry broccoli florets. To understand the influences of the studied dehydration methods on the conversion of glucoraphanin to bioactive sulforaphane in broccoli, various components (like glucoraphanin, sulforaphane, myrosinase, etc.) and factors (temperature and moisture) involved in the metabolism pathway were analyzed. The results showed that compared with direct air drying, the sequential exogenous pretreatment and contact ultrasound drying shortened the drying time by 19.0-22.7%. Meanwhile, contact sonication could promote the degradation of glucoraphanin. Both melatonin pretreatment and vitamin C pretreatment showed protective effects on the sulforaphane content and myrosinase activity during the subsequent drying process. At the end of drying, the sulforaphane content in samples dehydrated by the sequential melatonin (or vitamin C) pretreatment and ultrasound-intensified drying was 14.4% (or 26.5%) higher than only air-dried samples. The correlation analysis revealed that the exogenous pretreatment or ultrasound could affect the enzymatic degradation of glucoraphanin and the generation of sulforaphane through weakening the connections of sulforaphane-myrosinase, sulforaphane-VC, and VC-myrosinase. Overall, the reported results can enrich the biochemistry knowledge about the transformation of glucoraphanin to sulforaphane in cruciferous vegetables during drying, and the combined VC/melatonin pretreatment and ultrasound drying is conducive to protect bioactive sulforaphane in dehydrated broccoli.

Keywords: Broccoli; Glucoraphanin; Melatonin; Pretreatment; Sulforaphane; Ultrasound drying.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

None
Graphical abstract
Fig. 1
Fig. 1
The summarised metabolic pathway of glucosinolates.
Fig. 2
Fig. 2
Schematic diagram of the contact ultrasound-assisted air dryer (a: the exterior of the dryer; b: the interior of the dryer; c: ultrasonic part). 1: air inlet, 2: electric fans to recycle hot air (not used in this investigation), 3: thermocouple, 4: vibrating plate driven by ultrasound transducers, 5: air outlet, 6: ultrasound generator; 7: electric fan to remove the heat generated by the ultrasound device, 8: control panel.
Fig. 3
Fig. 3
Drying kinetic curves (A) and drying rate curves (B) of broccoli florets under the studied dehydration methods.
Fig. 4
Fig. 4
Variations of glucoraphanin content (A and B), sulforaphane content (C and D) and myrosinase activity (E and F) in broccoli florets during drying.
Fig. 5
Fig. 5
Variations in the contents of VC (A and B), Fe2+ (C and D) and total phenolic (E and F) in broccoli florets during drying.
Fig. 6
Fig. 6
Pearson correlation coefficients among different components and factors involved in the metabolic pathway of glucoraphanin. * refers to the statistical significance at p ≤ 0.05, and ** refers to the statistical significance at p ≤ 0.01.
See this image and copyright information in PMC

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