365 AJCS 12(03):365-373 (2018) ISSN:1835-2707 doi: 10.21475/ajcs.18.12.03.pne680 Influence of nitrogen fertilization on the characteristics of potato starch Juliana Marques Ebúrneo, Emerson Loli Garcia, Thaís Paes Rodrigues dos Santos, Emerson de Freitas Cordova de Souza, Rogério Peres Soratto, Adalton Mazetti Fernandes, Magali Leonel * Center for Tropical Roots and Starches (CERAT), São Paulo State University (UNESP), Botucatu, São Paulo, Brazil *Corresponding author: mleonel@cerat.unesp.br Abstract This study evaluated the effect of nitrogen fertilization rates on the characteristics of potato starch. The experimental design was randomized block with four replications. The treatments were composed of four rates of N (0, 80, 120 and 160 kg ha -1 ). After 117 days of planting the harvested tubers were sanitized and the starch extracted. The starches of the different treatments were analyzed for the shape and distribution of size, X-ray pattern, crystallinity, amylose, minerals, pasting and thermal properties. Results showed that the fertilization did not cause alteration in the shape of the starch granules but the sizes of granules increased with the application of higher rates of nitrogen fertilizer. All potato starches had X-ray pattern B-type and crystallinity decreased when nitrogen fertilizer rates increased up to 120 kg ha -1 . Fertilization did not interfere in content of amylose. Nitrogen rates promoted a decrease in the phosphorus, calcium and magnesium contents in the starches. The starches had their initial and peak temperatures of gelatinization decreased with increasing fertilizer rates, but there was no interference of this practice in the enthalpy. The highest peaks of viscosity and breakdown were observed in starch extracted from potatoes grown with the application of 80 kg ha -1 of Entec® 26 fertilizer. These results indicated important modifications in potato starch properties grown at different rates of nitrogen fertilization and can provide information for starch applications in the food and non-food industries. Keywords: Solanun tuberosum; nitrogen; starch, minerals; thermal properties. Abbreviations: P_phosphorus; T 0 _onset temperature; T p _peak temperature; T f _final temperature; ∆T_range of temperature; ∆H_ enthalpy change Introduction Potato is a tuber that is widely distributed and highly cultivated worldwide, with the largest harvest areas concentrated in Asia and Europe (FAO, 2017). In Brazil, the oleracea variant has the highest production and is cultivated not only in the Southeast and South regions but also in the Central-West and Northeast regions. The states with the highest potato production include Minas Gerais, Paraná, São Paulo, and Rio Grande do Sul. The yield and quality of potatoes are influenced by the plant variety, environmental conditions, and cultivation practices. The potato cultivation cycle in tropical and subtropical conditions varies from 90 to 110 days depending on the cultivar. Considering its high productivity and relatively short cultivation cycle, potato consumes large amounts of nutrients that exist in a form readily available in soil. Fertilizer application has important effects on potato quality and yield. Potatoes can absorb large quantities of nutrients from the soil during the cultivation period, especially nitrogen (N), phosphorus (P), and potassium (K) (Westermann, 2005; White et al., 2007; Öztürk et al., 2010). Nitrogen (N) is the most abundant macronutrient in plants that can be absorbed in the form of ammonium (NH 4 + ) or nitrate (NO 3 - ). In potato, nitrogen availability influences the development of the aerial parts of the plant, tuber growth and differentiation, and the chemical composition of tubers (Long et al., 2004; Goffart et al.; 2008; Michalska et al., 2016). In the past decades, various research efforts have been directed towards optimizing the efficiency of nutrient utilization by plants, with the goal of reducing production costs, preventing the destruction of environmental resources, and increasing crop yields (Zebarth et al., 2009). Approximately 40% to 60% of the total nitrogen applied using fertilizers is utilized by the potato plant, and a large percentage of the residual nitrogen is incorporated into the soil organic matter, which in turn has a high risk of being leached (Zebarth et al., 2007; Goffart et al., 2008). Nitrogen losses are more pronounced in regions with high rainfall indices, because these conditions produce plants with shallow and undeveloped root systems (Heckman, 2002). The percentage of accumulated nitrogen in Ágata potato was determined to be 13% in the vegetative growth phase, 8% in the tuberization phase, 43% in the initial stage of tuber filling, 34% in the second half of the tuber filling stage, and 2% in the maturation stage. Therefore, the use of fertilizers AUSTRALIAN JOURNAL OF CROP SCIENCE | SUBMITTED: 12-APR-2017 | REVISED: 17-OCT-2017 | ACCEPTED: 27-OCT-2017