Leafy greens vegetables are increasingly grown through hydroponics, sometimes under protective structures, said Mr. Arvin Lau from Vegfor Cooling Technology Limited.
After working in the the fresh produce industry for several years, he saw a clear development in the process of growing leafy green vegetables in China. “Compared with plants grown in the field, vegetables grown in this way have fewer leaf diseases but are more likely to wither. When the temperature is low and the plants are fully hydrated, wilting can be reduced by harvesting.”
Mr. Lau explains further: “To avoid wilting, they are best picked while cool and fully hydrated – such as early in the morning. They should be cooled below 5℃ as quickly as possible after the harvest. Vacuum cooling is the best cooling method that can cool down field temperature rapidly from maybe above 25℃ to 5℃ or lower. Furthermore, it is one of the best ways to reduce water loss, as during vacuum cooling most water will be retained.”
As Mr. Lau mentioned that vacuum cooling is essential to maintain leafy greens’ quality. Though only using a vacuum cooler is not enough, you should also understand your crops very well to know which kind of temperatures you need and for how long.
Mr. Lau explains: “Before you use vacuum cooling or any other cooling method to cool down your leafy greens, you should really do your homework on the local freeze point of your product. If you don’t know this, you cannot reach the most optimal conditions for your fresh produce. A precise temperature control is thus critical to leafy greens’ cooling. At 2–4℃ and relative humidity of > 90%, Asian leafy vegetables are still acceptable for up to 4 weeks without the risk of damage. Needless to say, leafy greens vegetables are extremely easy to freeze, as long as you do it at the right temperatures.”
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Vegfor Cooling Technology Limited