This 2023 study evaluated five broccoli drying methods for their effects on compounds:

“Low-temperature vacuum drying (LTVD) has shown great potential for drying vegetables. In this study, the LTVD effect on several relevant bioactive compounds, anti-inflammatory activity, and anti-proliferative activity of broccoli were comparatively evaluated with other drying methods, including vacuum drying (VD), convective drying (CD), infrared drying (IRD), and freeze drying (FD).

Higher values of TPC were found in the samples from LTVD, CD and FD, and no significant difference was determined among them (p > 0.05). Since both LTVD and FD operate under a low temperature and vacuum environment, TPCs were less affected by heating and oxygen. Higher temperatures applied during CD may have also reduced TPC degradation due to shorter exposure time of the sample to adverse effects of temperature, light, and oxygen.

Temperatures of VD, CD, and IRD methods were set at 60 °C, a temperature at which myrosinase still remained active. Although drying time of the CD method resembled the IRD method, content of SFN was diminished to a greater extent during IRD. Infrared energy absorbed by food material in different layers generates vibrating movements of water molecules and causes them to fluctuate to produce heat.

• LTVD method showed the best results in retention of heat-sensitive phenolic compounds (chlorogenic and ferulic acids), whereas CD was helpful to enhance SFN content.
• LTVD extracts performed better regarding anti-inflammatory effects on AA-induced ear edema, while CD extracts were somewhat more active against MDA-MB-231 breast adenocarcinoma cells than LTVD extracts.
• Surprisingly, FD resulted in lower anti-inflammatory and anti-proliferative activities than LTVD and CD. Probably, freeze conditions applied to FD could stop myrosinase activity, preventing formation of SFN.

Due to good functional properties and bioactive components of broccoli, both LTVD and CD (in this order) proved to be the most suitable drying methods for producing dried products with anti-inflammatory and anti-proliferative protective agents. However, the large drying time and energy consumption in LTVD are limitations that cannot be ignored, so combination with adequate pre-treatment techniques to reduce drying time needs further research.”

https://www.mdpi.com/2304-8158/12/17/3311 “Low-Temperature Vacuum Drying on Broccoli: Enhanced Anti-Inflammatory and Anti-Proliferative Properties Regarding Other Drying Methods”

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