Just because it looks good, is it still good for you?
J. Heyes , T. Carlyon , D. Woollard, L. Green and G. Taylor
Proceedings of 26th International Horticultural Congress. Volume of Abstract . Toronto, Canada, 11-17 August, 2002. Abstract S09-P-175. pp. 264-265.
2002
บทคัดย่อ
Nutrition scientists sometimes appear to regard fresh fruit and vegetables as having a fixed complement of dietary nutrients. As post-harvest scientists we are well aware that this is not eh case. Vitamin C levels are greatly affected by both pre- and post-harvest factors, a fact which has been used in a marketing campaaign for frozen peas in New Zealand (“freezing at harvest locks in the nutrients…”). Our research has investigated the effects of good and bad storage regimes on the retention of some vitamins (A, C and E) and dietary polyamines in a wide range of fresh vegetables. Capasicums are a rich source of vitamin C (higher content than orages per gram fresh weight) and we found that, unlike in peas, vitamin C level were maintained even after three weeks’ storage and four days’ shelflife (maximum ten percent loss). Vitaminas A and E were also stable throughout this period, which is less surprising as the lipid-soluble vitamins are regarded as less labile. Dietary polyamines are not universally recongised as nutrients; they are essential for cell division but the body is normally capable of producing adequate quantities for itself. However in the elderly or in recuperating patiends, dietary polyamines may be critically required for normal cell devision in e.g. the intestinal epithelium. Only the polyamines, spermine and spermidine, are useful in the diet; putrescine is a diamine and is broken down in the stomach. We found that the polyamine content of red, yellow and orange capsicums rose during storage but this was entirely accounted for by an increase in putrescine. Broccoli had a much higher level of polyamines at harvest than capsicums, in keeping with the fact that this is an immature tissue; polyamine contents generally decline with maturity of fresh produce; putrescine was rapidly metabolised in the first 24 hours after harvest, but spermine and spermidine were more stable. Our work with lettuce, tomatoes, silver beet, snow peas, pak choy, asparagus, broccoli and capsicums is shedding light on the complex interaction between storage regimes and vitamin and polyamine retention in vegetables and demonstrates that it is not enough to know that fresh produce still looks good after storage and shelflife; to know whether it is still good for you, you must measure its content of dietary nutrients.