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The Effect of Application Rates of Nitrogen, Phosphorus, and Potash on Some Chemical Constituents in Two Varieties of Hops 1
Author(s) -
Keller Kenneth R.,
Magee Robert A.
Publication year - 1954
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1954.00021962004600080008x
Subject(s) - potash , mathematics , phosphorus , agriculture , agricultural science , horticulture , agronomy , chemistry , environmental science , history , archaeology , fertilizer , biology , organic chemistry
THE market value of hops, in the past, has been primarily dependent upon such physical characteristics as uniformity of color, color and condition of the lupulin, aroma, amount of seed, and leaf and stem content. Although these characteristics may still serve as selection criteria in the purchase of hops in the future, there has been a recent trend by several brewers to evaluate hops on the basis of the percentage of total soft resin content and its components, alpha acid and beta fraction. The brewing or preservative value of a sample of hops has been employed by English workers but has received limited attention in the United States. The formula for preservative value is sometimes expressed by the following equation: P.V. — W (% alpha acid + 1/n (% beta fraction) . The denominator for beta fraction percentage may vary from 3 to 9 depending upon the worker. The preservative values therefore may be interpreted only when the denominator in the equation is known. The formulae do provide an estimate of the relative importance of alpha acid as compared to beta fraction as a measure of the inhibitory effect of the soft resins of hops on the growth of certain lactic acid-forming bacteria in beer or wort. Since the percentage of alpha acid is considered to be more important than the percentage of beta fraction in computing brewing or preservative value, it was of interest to determine the effect of various application rates of nitrogen, phosphorus, and potash on these components of the total soft resin content in two varieties of hops.