raw pineapple is an excellent source of manganese (76% daily value (dv) in a one us cup serving) and vitamin c (131% dv per cup serving). mainly from its stem, pineapple contains a proteolytic enzyme, bromelain, which breaks down protein. if having sufficient bromelain content, raw pineapple juice may be used as a meat marinade and tenderizer. pineapple enzymes can interfere with the preparation of some foods, such as jelly or other gelatin-based desserts, but would be destroyed during cooking and canning. the quantity of bromelain in the fruit is probably not significant, being mostly in the inedible stalk. furthermore, an ingested enzyme like bromelain is unlikely to survive intact the proteolytic processes of digestion.