Volatile Compounds of Selected Raw and Cooked Brassica Vegetables

Area of Science:

• Food Chemistry
• Agricultural Science
• Plant Biochemistry

Background:

• Brassica vegetables are increasingly popular due to their health benefits.
• Consumer acceptance is sometimes limited by their distinct bitter taste and sulfurous aroma.
• Understanding their volatile composition is key to appreciating their sensory properties and health impacts.

Purpose of the Study:

• To analyze the volatile organic compounds (VOCs) in various Brassica vegetables (Brussels sprouts, kohlrabi, cauliflower, broccoli).
• To compare volatile profiles across different cultivars and between raw and cooked samples.
• To evaluate the impact of cooking and freezing on the volatile composition of Brassica vegetables.

Main Methods:

• Solid phase microextraction (SPME) coupled with comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-ToFMS) was employed.
• Analysis covered 15 Brassica cultivars, including raw, cooked, and frozen samples.
• Volatile compounds were identified and quantified, with a focus on sulfur compounds, nitriles, aldehydes, and alcohols.

Main Results:

• Significant differences in volatile composition were observed between different Brassica vegetables and even among cultivars of the same vegetable.
• Cooking generally reduced the abundance of major volatile compounds but increased the concentration of bioactive isothiocyanates in most cultivars.
• Freezing induced changes in volatile profiles, primarily affecting alcohol and aldehyde levels, linked to lipoxygenase (LOX) enzyme activity.

Conclusions:

• The study provides comprehensive data on the volatile profiles of diverse Brassica vegetables, cultivars, and preparation methods.
• Cooking can enhance the levels of beneficial isothiocyanates, potentially improving the health perception of Brassica vegetables.
• Freezing significantly alters the volatile composition, necessitating consideration in processing and analysis.