Abstract
The protein content of pulps of 26 fleshy fruit species from east Mediterranean habitats in Israel were estimated using two different methods: (1) the Kjeldahl procedure in which the total recovered nitrogen is multiplied by 6.25 to estimate total proteins, and (2) amino acid analysis by amino acid analyzer. The average protein content obtained by the Kjeldahl procedure was 5.75% (dry weight) while it was only 3.90% when amino acids were analyzed. The higher value of protein content by the Kjeldahl procedure is most likely the result of a relatively high proportion of nonprotein nitrogen compounds (31%) in these pulps. Therefore the 6.25 factor is not valid and a 4.05 factor may be more accurate for assessing the true protein content of these fleshy fruits. The data also suggest that the more accurate estimate of true protein (Y) from Kjeldahl total nitrogen (X) should be based on the highly significant linear regression between these two variables:Y=4.885X−0.6.
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References
Aoac. 1984. Official Methods of Analysis of the Association of Official Analytical Chemists. AOAC, Washington, D.C.
Albersheim, P. 1975. The walls of growing plant cells.Sci. Am. 232:80–95.
Barnea, A., Yomtov, Y., andFriedman, J. 1991. Does ingestion by birds affect seed germination?Fund. Ecol. 5:394–402.
Berthold, P.B. 1976. The control and significance of animal and vegetable nutrition in omnivorous songbirds.Ardea 64:140–154.
Bondi, A.A. 1987. Animal Nutrition. John Wiley & Sons, New York.
Calvert, J.J. 1985. Food selection by western gorillas (G.g. gorilla) in relation to food chemistry.Oecologia 65:236–246.
Debussche, M., Cortez, J., andRimbault, I. 1987. Variation in fleshy fruit composition in the Mediterranean region: The importance of ripening season, life-form, fruit type and geographical distribution.Oikos 49:244–252.
Ehrlén, J., andEriksson, O. 1993. Toxicity in fleshy fruits—a non-adaptive trait?Oikos 66:107–113.
Elkin, R.G., andGriffith, J.E. 1985. Hydrolysate preparation for analysis of amino acids in sorghum grains: Effect of oxidative pretreatment.J. Assoc. Anal. Chem. 68:1117–1121.
Foster, M.F. 1978. Total frugivory in tropical passerines: A reappraisal.Trop. Ecol. 19:131–154.
Gargiullo, M.B., andStiles, E.W. 1991. Chemical and nutritional differences between two birddispersed fruits:Ilex opaca andIlex verticillata, J. Chem. Ecol. 17:1091–1106.
Hansen, E. 1970. Proteins,in A.C. Hulme (ed.). The Biochemistry of Fruits and Their Products, Vol. 1, Series on Food, Science & Technology. Academic Press, New York.
Harborne, J.B. 1991. The chemical basis of plant defense, pp. 45–59,in R.T. Palo and C.T. Robbins (eds.). Plant Defenses Against Mammalian Herbivory. CRC Press, Boca Raton, Florida.
Herbst, L.H. 1986. The role of nitrogen from fruit pulp in the nutrition of the frugivorous batCarollia perspicillata.Biotropica 18:39–44.
Herrera, C.M. 1987. Vertebrate-dispersed plants of the Iberian Peninsula: A study of fruit characteristics.Ecol. Monogr. 57:305–331.
Herrera, C.M. 1989. Frugivory and seed dispersal by carnivorous mammals, and associated fruit characteristics, in undisturbed Mediterranean habitats.Oikos 55:250–262.
Izhaki, I. 1986. Seed dispersal by birds in an eastern Mediterranean scrublands. PhD dissertation. The Hebrew University of Jerusalem, Israel (in Hebrew).
Izhaki, I. 1992. A comparative analysis of nutritional quality of mixed and exclusive fruit diets for yellow-vented bulbuls.Condor 94:912–923.
Izhaki, I., andSafriel, U.N. 1985. Why do fleshy-fruit plants of the Mediterranean scrub intercept fall—but not spring—passage of seed-dispersing migratory birds?Oecologia 67:40–43.
Izhaki, I., andSafriel, U.N. 1989. Why are there so few exclusive frugivorous birds? Experiments on fruit digestibility.Oikos 54:23–32.
Izhaki, I., Walton, P., andSafriel, U.N. 1991. Seed shadows generated by frugivorous birds in an eastern Mediterranean scrub.J. Ecol. 79:579–590.
Jordano, P. 1988. Diet, fruit choice and variation in body condition of frugivorous warblers in Mediterranean scrubland.Ardea 76:193–209.
Jordano, P. 1991. Fruits and frugivory, pp. 105–156,in M. Fenner (ed.). Seeds: The Ecology of Regeneration in Plant Communities. C.A.B. International, Willingford.
Kool, K.M. 1992. Food selection by the silver leaf monkey,Trachypithecus auratus sondaicus, in relation to plant chemistry.Oecologia 90:527–533.
Levey, D.J., andKarasov, W.H. 1989. Digestive responses of temperate birds switched to fruit or insect diets.Auk 106:675–686.
Lyttleton, J.W. 1973. Proteins and nucleic acids, pp. 63–103,in G.W. Butler and R.W. Bailey (eds.). Chemistry and Biochemistry of Herbage, Vol. 1. Academic Press, New York.
Mack, A.L. 1990. Is frugivory limited by secondary compounds in fruits?Oikos 57:135–138.
Maynard, A.B., andLoosli, J.K. 1969. Animal Nutrition. McGraw-Hill, New York.
Milton, K., andDintzis, F.R. 1981. Nitrogen-to-protein conversion factors for Tropical plant samples.Biotropica 13:177–181.
Parrish, J.W., andMartin, E.W. 1977. The effect of dietary lysine on the energy and nitrogen balance of the dark-eyed junco.Condor 79:24–30.
Piper, J.K. 1986. Seasonally of fruit characters and seed removal by birds.Oikos 46:303–310.
Poddar, S., andLederer, R.J. 1982. Juniper berries as an exclusive winter forage for Townsend's solitaires.Am. Midl. Nat. 108:34–40.
Potter, D.A., andKimmerer, T.W. 1986. Seasonal allocation of defense investment inIlex opaca Ait. and constraints on a specialist leaf miner.Oecologia 69:217–224.
Robbins, C.T. 1983. Wildlife Feeding and Nutrition. Academic Press, New York.
Rogers, M.F., Maisels, F., Williamson, E.A., Fernandez, M., andTutin, C.E.G. 1990. Gorilla diet in the Lope Reserve, Gabon.Oecologia 84:326–339.
Sakai, H.F., andCarpenter, J.R. 1990. The variety and nutritional value of foods consumed by Hawaiian crow nestlings, and endangered species.Condor 92:220–228.
Sedinger, J.S. 1990. Are plant secondary compounds responsible for negative apparent metabolizability of fruits by passerine birds? A comment on Izhaki and Safriel.Oikos 57:138–140.
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Izhaki, I. Influence of nonprotein nitrogen on estimation of protein from total nitrogen in fleshy fruits. J Chem Ecol 19, 2605–2615 (1993). https://doi.org/10.1007/BF00980695
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DOI: https://doi.org/10.1007/BF00980695