A question I hear often is are frozen fruits and vegetables as nutritious as fresh? The simple answer is yes, and sometimes even more so.
When in season, fresh is the best choice for local produce. A side note that my sister wanted me to point out, some of the local produce stands may shine their produce with oil so they look prettier.
Whether it's because of a bad crop or the roads being closed, during the winter fresh produce may not be available, and what is might not be the best selection.
Produce at the grocery store can be transported any where from 7 - 14 days, which diminishes and degrades vitamins and other nutrients in the fruit and vegetables. There is some diminishing of nutrients when fruits and vegetables are frozen as well. The only way to avoid this would be to buy direct from a local farmers market or roadside stand, if there are any in the area.
Most fresh produce is picked right before fully ripening, since it has to be shipped. Produce that is to be frozen is usually harvested at it's peak and then frozen within a day, if not a few hours. This is why frozen veggies can be more nutritious compared to imported 'fresh' out-of season produce.
Freezing foods can also alter the texture and taste of some produce, so it would be best to use frozen fruits and veggies as part of a meal rather than eat them as is once thawed. Frozen produce also has a much longer shelf life, so you can always have your favorite strawberries or sweet corn on hand no matter what time of the year it is.
Another plus for eating frozen produce, is that often it's on sale. I once bought 20 bags at the store because they were $1 each, and my freezer is still overflowing.
A few frozen food companies add chemicals/preservatives, like sodium, to their products, but it isn't necessary to the freezing process. If the produce is frozen immediately after harvesting there is no need for preservatives.