ACTA ALIMENTARIA VOL. 17 (An International Journal of Food Science, 1988)
1988 / 1. sz. - KAFFKA, K. J.: Determination of amino acids in lupine by near infrared reflectance spectroscopy
1* Acta Alimentaria, Vol. 17 (J), pp. 3—11 (19S8) DETERMINATION OF AMINO ACIDS IN LUPINE BY NEAR INFRARED REFLECTANCE SPECTROSCOPY K. J. KAFFKA Central Food Research Institute, H-1022 Budapest, Herman Ottó út 15. Hungary (Received: 16 January 1986, revision received: 13 October 19S6; accepted: 17 October 1986) Preliminary studies were carried out to determine if NIR spectroscopy could be used to estimate the concentrations of amino acids in lupine. Seventeen amino acids were analyzed in the lupine calibration samples. The chemical analyses were performed with an ion exchange amino acid analyzer type OE 914 Aminochrom II. The log (1/R) spectra of the ground lupine samples were obtained and recorded in the 1100—2500 nm wavelength range on the NEOTEC (Pacific Scientific) Research Composition Analyzer, Model 6450. The relationship between concentration data and values of the second derivative spectra measured at different wavelengths was determined by multiple linear regression analysis using two different equation forms (two mathematical models). Results as characteristic wavelengths, multiple correlation coefficients, standard errors of calibration and coefficients of variability for seventeen amino acids in lupine are summarized in Tables 2 and 3. For lysine, isoleucine and threonine (limiting acids) the correlation coefficients were around 0.85, the SEC values around 0.08 and the CV values around 5.5. The higher CV value for methionine determination may be related to the inherent higher error of methionine analysis by ion exchange chromatography due to hydrolysis losses. These results prove that NIR technique can be used as a rapid, nondestructive method for determining the amino acid concentrations in lupine. Keywords: amino acid analysis, near infrared spectroscopy, lupine, nutrition The determination of amino acid concentrations of animal and plant materials is of major interest to those involved in the food and feed industry. From the point of view of nutritional physiology the most important amino acids are considered to he the ten essential ones. These include : lysine, methionine, threonine, tryptophan, isoleucine, arginine, leucine, phenylalanine, valine and histidine. The first five amino acids listed are limiting ones. In many plant materials one or more of them are present in a minor concentration limiting the nutritive value of the protein. The standard chemical determination of amino acid concentration involves hydrolysis of the proteins followed by purification and ion exchange chromatography. This is a fairly complicated and time consuming process, hindering the efficiency of the research programs in food and feed industry. The promising results of the NIR technique in the different fields of agriculture and food industry have encouraged us to extend our research work to determine the amino acid concentration by this technique. Provided Akadémiai Kiadó, Budapest Kluicer Academic, Publishers, Dordrecht