High hydrostatic pressure treatment induced microstructure changes and isothiocyanates biosynthesis in kale

Area of Science:

• Food Science
• Plant Biochemistry
• Food Processing Technology

Background:

• Kale contains glucosinolates (GLS) which convert to beneficial isothiocyanates (ITC) via myrosinase.
• Traditional thermal processing can degrade myrosinase activity and impact kale quality.
• Investigating alternative processing methods like high-pressure processing (HPP) is crucial for preserving bioactive compounds.

Purpose of the Study:

• To evaluate the impact of high-pressure processing (HPP) on kale's myrosinase activity, glucosinolate (GLS) content, and isothiocyanate (ITC) conversion.
• To compare HPP effects on kale quality attributes (color, bacterial count) against thermal processing.
• To elucidate the mechanism of HPP on the myrosinase-GLS-ITC system.

Main Methods:

• Kale leaves were subjected to high-pressure processing (HPP) at 600 MPa.
• Thermal processing at 100°C served as a control.
• Myrosinase activity, GLS content, ITC conversion rate, color, and bacterial count were analyzed. Scanning electron microscopy (SEM) was used to observe structural changes.

Main Results:

• HPP at 600 MPa maximized myrosinase activity and ITC conversion (70.4%), with significantly lower GLS content compared to raw or thermally processed kale.
• Thermal processing led to a gradual loss of myrosinase activity.
• SEM revealed HPP-induced damage to kale leaf structures, enhancing the myrosinase-GLS-ITC conversion. HPP resulted in less color change and comparable pasteurization to thermal treatment.

Conclusions:

• High-pressure processing (HPP) is an effective method for enhancing isothiocyanate (ITC) formation in kale by preserving myrosinase activity.
• HPP offers a superior alternative to thermal processing for maintaining kale's bioactive potential and quality attributes.
• Structural modifications induced by HPP play a key role in the improved conversion efficiency of the myrosinase-glucosinolate system.