Tomato: Fresh or Processed?

World production of tomatoes for processing stands over 20 millions tons per annum, with more than 50% of that in USA. An American consumes over 12 kg of processed tomatoes per year, excluding ketchup and sauce.

Lycopene is signature carotenoid in tomatoes, giving them the deep-red colour. But tomatoes are also rich in vitamins C and E, beta-carotene, and flavonol antioxidants. 

Lycopene is predominant carotenoid in human serum and tissues. It is found circulating in the blood and also concentrates in the male reproductive system, hence its protective effects against prostate cancer. In the skin, lycopene helps to prevent UV damage from the sun, protecting against skin cancer. It is generally categorized as antioxidant.

Because of increasing clinical evidence supports the role of lycopene as a micronutrient its ability to provide protection against a broad range of epithelial cancers, it has attracted scientists attention to investigate lycopene presence and biovalibility in processed tomato products.

 There are two isomeric forms (molecules that have the same molecular formula but differ in the way their atomsare connected to each other) of lycopene: cis-lycopene and trans-lycopene. The observation has shown that serum and tissue lycopene is more than 50% cis-lycopene, whereas tomatoes and tomato-based foods contain mainly all-trans-lycopene.

 

Lycopen in processed tomatoes undergoes degradation. Thermal processing (bleaching, retorting, and freezing processes) generally cause some loss of lycopene in tomato-based foods. Heat induces isomerization of the all-trans to cis forms. The cis-isomers increase with temperature and processing time.

Dehydrated and powdered tomatoes have poor lycopene stability unless carefully processed and promptly placed in a hermetically sealed and inert atmosphere for storage.

Frozen foods and heat-sterilized foods exhibit excellent lycopene stability throughout their normal temperature storage shelf life.

Generally, the bioavailability of lycopene in processed food is higher than in fresh tomatoes. Food processing may improve lycopene bioavailability by breaking down cell walls, which weakens the bonding forces between lycopene and tissue matrix, thus making lycopene more accessible and enhancing the cis-isomerization.

Out of all the common dietary carotenoids, lycopene has the most potent antioxidant power, but combinations of carotenoids are even more effective than any single carotenoid. Single antioxidants don’t exert their protective effects alone – they work synergistically.

To sum up, lycopene is also more absorbable when tomatoes are cooked, so enjoy a variety of both raw and cooked tomatoes in your daily diet. Add fresh, juicy raw tomatoes to your salad, but also enjoy homemade tomato sauces and soups. Keep in mind that carotenoids are absorbed best when accompanied by healthy fats – for example, in a salad with a seed or nut-based dressing.

Sources:

  • Boileau AC, Merchen NR, Wasson K, Atkinson CA, Erdman JW Jr.,Cis-lycopene is more bioavailable than trans-lycopene in vitro and in vivo in lymph-cannulated ferrets, The jurnal of nutrition, 1999 Jun; 129(6):1176-81.
  • Shi J, Le Maguer M., Lycopene in tomatoes: chemical and physical properties affected by food processing, Critical Reviews in Biotechnology, 2000; 20(4):293-334
  • Thakur B.R., Singh R.K., Nelson P.E., Quality atributes of processed tomato products: a review, Food Reviews International 1996; 12(3):375-401 
  • Heat, Shape and Type: Increasing Lycopene Absorption, AICR’s Cancer Research Update, October 14, 2015
  • World Cancer Research Fund International. Diet, Nutrition, Physical Activity and Prostate Cancer. November 2014.

 

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