Most food is flash frozen at the peak of ripeness.
Berries – These have a very short season, so frozen is the best way to get ripe strawberries, blueberries, raspberries 10 months out of the year. Thaw them overnight in the refrigerator.
Spinach – Greens freeze very well. You can thaw these in the fridge overnight, or place them in a bowl of water for 30 minutes. Leaf for leaf, frozen spinach costs quite a bit less than fresh as well.
Tomatoes – These don’t freeze well so should be canned, or bought canned or sun dried and placed in oil.
Vegetables – Frozen peas are much better frozen than canned. They are frozen at the peak of ripeness. The canning process can tend to make them mushy. Thaw them overnight in the fridge in a bowl of water.
Lemon juice – Don’t buy that plastic lemon shaped container, or even the green bottles of juice. Squeeze lemons yourself and then freeze in water bottles. Thaw in the refrigerator. There may be some separation of the juice and the pulp, so shake before using it.
Grapes – These don’t freeze or can well. Raisins can be rehydrated overnight in water.
Broccoli – This does not freeze well. It becomes mushy. It is marginally OK to use in a stir fry, but fresh is so much better.
Salmon – Of course it is better fresh, but it is also very expensive. Canned salmon is not THAT bad, and is about a fifth of the price of fresh. If budget is no matter, go fresh. For most of us canned salmon is good enough for most of what we do.