Comparison of the Degree of Proteolytic Modification in Wheat Malts Obtained from Wheat Grain Produced at Different Nitrogen Fertilization Rates

The degree of proteolytic modification in wheat malts significantly affects their quality, determining their suitability for use in brewing. Nitrogen fertilization at doses of 60 and 80 kg N·ha−1 applied during 3-year field experiments had a positive effect on the content of protein compounds in the analyzed wheat malts. The total protein content of the malts obtained averaged 9.9–10.1% d. m., depending on the cultivar, and from 9.1 to 10.8% dry matter, depending on nitrogen fertilization. The soluble protein content and Kolbach index value were at similar levels (4.60% dry matter and 46.07%, respectively, on average) except for malt obtained from the Elixer cultivar, for which significantly lower values were obtained (by 7.39% and 6.66%, respectively). In contrast, the highest free amino nitrogen value was obtained for malts derived from the Elixer and Gimantis cultivars. The least variation in the quality of malts derived from grains obtained in the three growing seasons during the field experiments was in the cultivar Gimantis. In 2-year commodity field experiments (in commodity farms), under 60 kg N·ha−1 nitrogen fertilization, the cultivar Lawina was characterized by the best indices of the degree of proteolytic modification.