Starch barley: influence of growing conditions

LÓPEZ, OLIVIA VALERIA; LÁZZARI, MARÍA AURORA; RODRÍGUEZ, MARÍA SUSANA

Rosario

Conferencia; Conferencia Internacional de la ICC "Cereales y Productos de Cereales. Calidad e Inocuidad"; 2007

ICC, INTA, SAGPyA y Bolsa de Comercio de Rosario

It has been demonstrated that some environmental and growing conditions may affect the concentration, chemical composition, granule size and physicochemical properties of starch in different cereals. The objectives of this work were: a) to isolate and to quantify the starch of barley grains; b) to characterize isolated starch and c) to study the relation between the conditions of growth (nitrogenous fertilization, growing sites and years and weather conditions during grain filling) and physicochemical characteristics of the isolated starch. Grain barley samples from Quilmes Palomar cultivar were considered in this study. They were selected from 6 experimental sites located in the province of Buenos Aires (Argentina) cultivated in 1999 and 2000. Two samples were obtained from each of places and years: one of them without any fertilization treatment and the other, fertilized with 60 kg N ha-1 in the form of urea, applied at the emergence of the crop. The starch was isolated using a modified version of Morrison Method. The range of starch concentration (53.2-63.3 %) found in grain samples was similar to the levels reported in the bibliography. The isolated starch samples were characterized physicochemically. The low concentrations of lipids, phosphorus and nitrogen found allow us to conclude that the method used to isolate the starch led to highly purified samples. The apparent and total amylose concentrations found were correspondent with the data in the bibliography. The electron scanning microscopy (SEM) showed that all starch samples presented a bimodal granule size distribution, evidencing small granules (type B) and large granules (type A). Some of the Type B granules present irregular shape, while all Type A granules have a lenticular shape. The gelatinization temperature - determined using a Differential Scanning Calorimetry - coincided with the data reported in the bibliography. X-ray diffraction spectroscopy determined that amylopectine is the responsible of the crystallinity in the starch granule and all starch samples exhibited a typical cereal (A) diffraction pattern. A statistic study was carried out in order to establish relationships between the concentration and the physicochemical characteristics of barley starch and the set growing conditions. The findings of this statistic research are as follows: a) the starch concentration in barley grain is not affected by the nitrogenous fertilization; b) the nitrogenous fertilization can only affect the concentration of the total amylose; c) the X–ray diffraction pattern obtained from the starch in fertilized barley presents a greater correlation with the amylopectine pattern than starch in non-fertilized barley; d) no relationship is found between the concentration and physicochemical characteristics of starch and the different growing sites and years and e) the concentration of amylose increases as rainfall, during filling grain, becomes higher.   References: Bremner, J.M. (1996). Nitrogen-Total. In: Sparks et al. (eds.). Methods of soil analysis. Chemical Methods. Part 3. Am Soc. Agron. Inc., Madison, Wisconsin, USA. 1085-1123. Mc. Donald, A. M. L. and Stark, J. R. (1988). A critical examination of procedures for the isolation of barley starch. Journal of the Institute of Brewing, 94. 125-132. Myllärinen, A. H., Schulman, H., Salovaara, H. y Poutanen, K. 1998. The Effect of Growth Temperature on Gelatinization Properties of Barley Starch. Acta Agric. Scand., Sect. B, Soil and Plant Sci. 48, 85-90.