Vegetable in can has the longest shelf life. It is safe to consume for one year, and much longer. Part of the whole process is thermal treatment - blanching, so canned vegetables are very similar to vegetables cooked. Recently, preservation procedures have been developed without heat treatment to maintain texture and nutrient levels at the highest level.
Although conserving occurs when compared with freezing to greater nutrient losses, during storage, losses are lower than for fresh or frozen vegetables. Lycopene, an antioxidant in tomatoes, raised attention when the level of tomatoes was higher than that in fresh tomatoes. This may be due to the fact that it is more relaxed when preserving, but remains stable. Mineral substances and fiber are also stable in processing, so the level of these nutrients is very similar in all three types of vegetables.