I highly recommend the following steps to be taken before freezing vegetables such as broccoli, cauliflower, carrots and zucchini.
1. Cut off the vegetables in the same size.
2. Cook for one minute in salted boiling water.
3. Move the vegetables to a bowl filled with ice cold water, this stops the cooking immediately.
4. Place on paper towels to remove as much water as possible.
5. Spread on a tray and place in the freezer for half an hour.
6. Store in plastic bags and freeze completely.
Can last between 3 to 6 months.
This is the method I personally use to freeze my vegetables.
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