Document Type: Original Article


Department of Food Science and Technology, College of Applied Food Sciences and Tourism, Michael Okpara (Federal) University of Agriculture Umudike, Abia State, Nigeria


Purpose: The aim of this study was to investigate the effects of ambient temperature storage condition (27-29°C) and domestic cooking on contents of carotenoids, chlorophylls, vitamins and minerals in the leaves of Gnetum africanum.  Research method: Carotenoids were separated and analyzed by HPLC. Total-carotene content, vitamins and minerals were assessed spectrophotometrically. Main findings: Results indicated that G. africanumwas rich in lutein (528.87 µg g-1 (dry weight basis) and total β-carotene (248.10 µg g-1). There was no statistical increase in total β-carotene content due to cooking, but there was a decrease due to storage. Total β-carotene isomerized more during thermal processing than in storage. Cooking decreased (p>0.05) the contents of chlorophylls, water soluble vitamins and minerals. Cooking and storage of G. africanum resulted in significant losses in ascorbic acid, riboflavin and niacin. Cooking also reduced the potassium, calcium, magnesium and zinc. Iron contents of cooked and stored samples were higher than that of the raw sample. Research limitations: We had to travel over 600 km to use facilities for carotenoid analysis. Originality/value: The concentrations of lutein, β-carotene and certain micronutrients in G. africanumare much higher than typical contents in conventional edible leafy vegetables. The results of this study therefore provide evidence that G. africanum leaf could be an important contributor for improving the nutritional status of rural and urban people.


Main Subjects

Agtel, V.V., Tarwadi K.V., Mengale, S., & Chiplonkar, P. (2009). Potential of traditional cooked green leafy vegetable as natural sources for supplementation of eight Micronutrients in vegetarian diets. Journal of Food Composition and Analysis, 13, 885-891.

Akwaowo, E. U. Bassey A. N. & Ekaete U. E. (2000). Minerals and anti-nutrients in fluted pumpkin (Telfairia occidentalis Hook F). Food Chemistry, 70, 235-246.

Ali, F. Assanta., M.A. & Robert. C. (2011). Gnetum africanum: a wild food plant from the African forest with many nutritional and medicinal properties. Journal of Medicinal Foods, 14(11), 1289-97.

AOAC. (2005). Official Methods of Analysis. Association of official Analytical Chemists. 18th ed. Washington, D.C., 242-268.

Bauernfeind, J.C. (1972). Carotenoid vitamin A precursors and analogs in foods and feeds. Journal of Agricultural and Food Chemistry, 20(3), 456-473.

Bergström, L. (1994). Nutrient losses and gains in the preparation of food. NLG Report, National Food Administration, Sweden, Reports No 32/1994.              

Biswall, B., 1995. Carotenoid catabolism during leaf senescence and its control by light Photochemistry and Photobiology, B30, 3-14.

Brown, P., Lumpkin, T., Barber, S., Hardie, E., Kraft, K.H., & Luedeling, E. (2005). Global horticulture assessment. Scripta Horticultura, 3, 1-134.

Casternmiller, J. J. M., & West C. E. (1998). Bioavailability and bioconversion of carotenoids. Annual Review of Nutrition, 18, 19-38.

Chandler, L.A. & Schwartz S.J. (1987). HPLC Separation of cis-trans carotene isomers is fresh and processed fruits and vegetables. Journal of Food Science, 52, 669-72

Damodaran, S., Kirk P., & Owen F. (2008) Food Chemistry 4th Edn. C.R.C. Press Taylor & Francis Group. Boca Raton, London New York.

Damon, M., Nancy, Z., Zhang, D. B., Haytowitz, S., & Booth, C. (2005). Phylloquinone (Vitamin K1) content of vegetables. Journal of Food Composition and Analysis, 18, 751-788.

Deming A., & Erdman, J.W. (1999). Mammalian carotenoid absorption and metabolism. Pure and Applied Chemistry, 71(12), 2213-2223.

Dias, M.G., Filomena, M., Carnoes, G.F.C., & Oliviera, L. (2009). Carotenoids in traditional portugese fruits and vegetables. Food Chemistry, 113(3), 808-815.

Dietz, J.M., & Erdman J.W. (1989). Effects of thermal processing upon vitamins and proteins in foods. Nutrition Today, July/August, 6-15.

Ekpedeme, U., Bassey, A. N. & Ekaete, U. E. (2000). Minerals and antinutrients in fluted pumpkin (Telfaria occidentalis Hook). Food Chemistry, 70(2), 235-240.

Faber, M., Olelofse, A., Van Jaarsveld, P.J., Wenhold F.A.M., Jansen & Van Rensburg, W.S. (2010). African leafy vegetables consumed by households in the Limpopo and Kwaszulu-Natal Provinces in South Africa. South African Journal of Clinical Nutrition, 23(1), 30-38.

FAO/WHO Joint Expert Consultation (1988). Requirements of Vitamin A, Iron, Folate and Vitamin B12: FAO Food Nutr. Sci. No 23 Rome: Food Agric. Org. 107.

Faulk, S., & Southan, R.M. (2005). Challenges to understanding and measuring carotenoids bioviality. Biochemica et Biophysica Acta, 174(2) 95-100.

FBN (2003). Food and Nutrition Board, Institute of Medicine (I.O.M), 2003. Dietary Reference intakes for vitamin A, Vitamin K., Arsenic, Boron, Chromium Copper, Iodine, Iron Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. National Academy Press., Washington D. C.

Federico, G.G., Werner, H., Vasilis, G., & Ingrgard, S. (2004). Factors affecting quality and postharvest properties of vegetables. Integration of water relations and metabolism. Critical Review in Food Science and Nutrition, 14, 139-154.

Fennema, O. (1988). Effects of freeze preservation on nutrients. In Nutritional Evaluation of Food Processing, 3rd. Ed. E. Karmas and R. S. Harris (Ed.), 133-170 Marcel Dekker. Inc. New York.

Ferrente, A., Incrocci, L., Maggini. R., Serra, C., & Togoni, F. (2004). Colour changes of Freshcut leafy vegetables during storage. Journal of Food Agriculture and Environment, 2, 40-44.

Granado, F., Olmedulla, B., Blanco, I., Gil-Martinez, E., & Rojas-Hidalgo, E. (1997). Variability in the inter comparison of food carotenoid content data; a user’s point of view, Critical.Review in. Food Science and Nutrition, 37, 621-633.

Grassmann, J., Hippeli, S., & Elstre, E.F. (2002). Plant’s defense mechanism and its benefits for animals and medicine role of phenolics and terpenoids in avoiding oxygen, stress. Plant Physiology and Biochemistry, 40, 471-478.

Gregory. J. (1996). Vitamins In Food Chemistry, O. Fennema (Ed.), 531-567. Marcel Dekker, Inc. New York.

Howards, L.A., Wong A.D., Perry A.K., & Klein B.P. (1999). β-carotene and ascorbic acid retention in fresh and processed vegetables Journal of Food Science, 64, 929-936.

Howe, J.A., & Tanumihardjo, S.A. (2006). Evaluation of analytical methods for carotenoid extraction from biofortified maize (Zea mays sp) Journal of Agriculture and Food Chemistry, 54, 7992-7994.

IPGRI, (2001-2005). International plant Genetic Resources Institute. Conserving and increasing the use of Neglected and under-utilized crop species. Retrieved October 15, 2015 from

IPGRI, (2008). Neglected no longer: a fact sheet on neglected and underutilized species in Sub-Sahara Africa (online). Available http://news.bioversity (Accessed; 20 July 2016).

Jaworska, G., & Kmiecik, W. (1999). Effect of the date of harvest on the selected traits of the chemical composition of Spinach (Spinacia olearceae) and New Zealand Spinach (Tetragonia expansa Murr). Acta Agraria et Silvestria, 37, 15-26.

Kao, A., Randall, A., Yang, Y., Patel, V.R., Kandur, W., Guan, S., Rychnovsky, S.D., Baldi, P. & Huang, L. (2012). Mapping the structural topology of the yeast 19S proteasomal regulatory particle using chemical cross-linking and probabilistic modeling. Molecular & Cellular Proteomics, 11(12), 1566-1577.

Kimura, M., & Rodriguez-Amaya D.B. (2003). Carotenoid composition of hydroponic leafy vegetables. Journal of Agriculture and Food Chemistry, 51, 2603-2607.

Kopsell, D. A., Kopsell, D. E., Curran-celentano, J., & Wenzed, A. J. (2009). Genetic Variability for Lutein concentrations in leafy vegetables crops can influence serum carotenoid levels and macular pigment optical density in human subjects. Acta Horticulturations, 841, 113-117.

Kumari, M., Gupta, S., Lakshmi, J., & Prakash, L. (2004). Iron bioavailability in green leafy vegetables cooked in different utensils. Food Chemistry, 88, 217-222.

Landrum, J.T., & Bone, R.A. (2001). Lutein, Zeaxanthin and the macular pigment. Archives of Biochemistry and Biophysics, 385, 28-40.

Lefsrud, M.G., Kopsell, D.A., Wenzel A., & Sheehan J. (2009). Changes in Kale (Brassica oleracea L. Var Ocephala) carotenoid and chlorophyll pigment concentrations during leaf ontogeny. Scientia Horticulture, 112, 136-141.

Luciane, M., Kawashima, L.M., & Valente, S. (2003). Mineral profile of raw and cooked leafy vegetables consumed in Southern Brazil. Journal of Food Composition and Analysis, 16, 605-611.

Mayne, S. T. (1996). β-carotene, carotenoids and disease prevention in humans FASEB Journal, 10, 690-701.

Marx, M., Stuparic, M., Schieber, A., & Carle, R. (2003). Effects of thermal processing on trans-cis-isomerization of b-carotene in carrot juices and carotene-containing preparations. Food Chemistry, 83, 609-617.

Mepba, H.D., Eboh, L., & Banigo, D. (2007). Effect of processing treatments on the nutritive composition and consumer acceptance of some Nigerian edible Leafy vegetables. African Journal of Food Agriculture and Nutrition, 7(1), 1-18.

Moreira, M.D.R., Ponce, A.G., Valle, C.E.D., & Roura S.I. (2006). Ascorbic acid retention, microbial growth, and sensory acceptability of lettuce leaves subjected to mild heat shocks. Journal of Food Science, 71, 188-192.

Negi, P.S., & Roy S.K. (2000). Effect of blanching and drying methods on β-carotene, ascorbic acid and chlorophyll retention of leafy vegetables. LWT-Food Science and Technology, 33(4), 295-298.

Nyambaka, H., & Ryley J. (1996). An Isocratic reversed-phase HPLC separation of the steroisomers of the pro-vitamin A carotenoids ( - and β-carotene) in dark-green vegetables Food Chemistry,. 55(1), 63-72.

Oboh, G. (2005). Effect of some post-harvest treatments on the nutritional properties. Pakistan Journal of Nutrition, 44, 226-230.

Oladunmoye, O.O., Ojeniyi S., & Bankole A.O. (2005). Mineral composition of tender and matured cassava leaves after home cooking procedure. Proceedings: 29th Annual conference of the Nigeria Institute of Food Science and Technology, Ebonyi State University, Abakaliki. (pp. 151-152).

Prabhu, S., & Barett, D. (2009). Effect of storage condition and domestic cooking on the quality and nutrient content of African leafy vegetables (Cassia tora and Corchorus tridens) Journal of the Science of Food and Agriculture, 89, 1709-1721.

Rickman, J.C., Barret D.M., & Brulin C.M. (2007). Nutritional comparison of fresh, Frozen and canned fruits and vegetables. Part I Vitamin C and B and Phenolic Compounds. Journal of the Science of Food and Agriculture, 87, 930-944

Rodriguez-Amaya, D.B. (2002). Effects of processing and storage on food carotenoids.  Sight and Life Newsletter. 3(Special Issue), 25-35.

Rodriguez-Amaya, D.B., & Kimura, M. (2004). Harvest Plus Handbook for Carotenoid Analysis. Harvestplus: Washington, D.C., and Cali, Columbia.

Schonfeldt, H., & Pretorius, B. (2011). The nutrient content of five traditional South African dark green leafy vegetables. A preliminary study. Journal of Food Composition and Analysis, 24(8), 1141-1146.

Schwartz, S.J., & Von Elbe J.H. (1983). Kinetics of chlorophyll degradation to pyropheophytin in vegetables. Journal of Food Science, 48(4), 1303-1306.

Selman, J.D. (1994). Vitamin retention during blanching of vegetables. Food Chemistry, 49, 137-147.

Shiembo, P.N. (1997). Domestication of Gnetum spp. by vegetative propagation techniques. In: Schippers, R.R. & Budd, L. (Editors). Proceedings of a Workshop on African Indigenous Vegetables, Limbe, Cameroon, 13-18 January 1997. Natural Resources Institute/IPGRI, Chatham, United Kingdom. (pp. 31-35).

Simpson, K.L., Tsou, S.C., & Chichester, C.O. (1985). CarotenesIn Methods of Vitamin Assay, 4th ed., Augustin, B.P., Klein, D. Berker, & P.B. Venugopal (Ed.) p. 185. John Wiley & Sons. New York.

Sobowale, S.S., Olatidoye, O.P., Olorodo, O.O., Sokeye O.K. (2010). Effect of preservation methods and storage on Nutritional quality and sensory properties of leafy vegetables consumed in Nigeria. Journal of Medical and  Applied Biosciences, 2, 46-56.

Souzan, S.L., & ABD EL-AAl. (2007). Mineral profile-Shelf Life Extension and Nutritive value of Fresh Green Leafy Vegetables consumed in Egypt. African Crop Science Conference Proceedings. 8, 1817-1826.

Stahl, N., Baldwin, M.A., Teplow, D.B., Hood, L., Gibson, B.W., Burlingame, A.L. & Pruusiner, S.B. (1993). Structural studies of the scrapie prion protein using mass spectrometry and amino acid sequencing. Biochemistry, 32(8), 1991-2002.

Usuwazo, A.B., & Tanulo, B. (2006). The Vitamins. Journal of Food Science, 23, 54-57.

Uusiku, N.P., Oelofse, A., Duodu, K.G., Bester M.J., & Faber, M. (2010). Nutritional value of leafy vegetables of sub-Sahara Africa and their potential contribution to human health. A review. Journal of Food Composition and Analysis, 23, 499-509.

Van Poppel, G., & Galdbohm, R.A. (1995). Epidemological evidence for β-carotene and cancer prevention. American Journal of Clinical Nutrition, 62, 1493-1503.

Vina, S.Z., & Chaves, A.R. (2003). Texture changes in fresh cut celery during refrigeration storage. Journal of the Science of Food and Agriculture, 83, 1308-1314.

Wisniewska, A., & Subczynski, W.K. (2006). Accumulation of macular xanthophylls in unsaturated membrane domains. Free Radical Biology and Medicine, 40(10), 1820-1826.

World Cancer Research Fund, American, Institute for Cancer Research. Food Nutrition and thePrevention of Cancer, American institute for Cancer Research, Washington D.C. (1997).

Zechmeister, L. (1949). Stereoisomeric Provitamin A. Vitamins & hormones, 7, 57-81. Academic Press.

Žnidarčič, D., Dean, B., & Helena, S. (2011). Carotenoid and chlorophyll composition of commonly consumed leafy vegetables in Mediterranean countries. Food Chemistry, 129, 1164-1168.