O branqueamento dos grãos de café

Abstract

An extensive investigation was carried in the years 1952/53 to study the importance of rainfall distribution on coffee yields. Fourteen coffee counties were selected to represent the different soil and climatic conditions prevalente in the State of São Paulo, for the purpose of correlating official estimates of coffee yields and monthly precipitation for the period 1945 up to 1953, known to have had quite dry spells. Linear correlation was shown ta decrease with the average coffee yields of the counties, losing its significance for the counties with lowest yields. Closer linear correlation was found for the drier period of April-to-September, as well as for July-to-September, this period appearing to be the most important as there is the coincidence of coffee blooming with the driest period in the year. Linear correlation studies were also made with soil water defficiences determined by using Thornthwaite's method. The results obtained paralleled those of the rainfall-yield studies previously mentioned. The data best suited for the linear correlation studies were found to be progressive two years averages of the years tn and tn + 1 for yield data, and tn-1 and tn for rainfall dato, which appeared to minimized the biennial bearing effect on coffee yield. The high degree of correlation obtained might suggest the possibility of improving the method for the purpose of yield estimates. However, the law values obtained for the regression coefficients show that the importance of rainfall distribution is minimized by the biennial bearing effect not completely eliminated and other factors not considered in this study, as shown by the results with counties of lowest yields. Higher values of the regressions coefficients for counties of highest yields may indicate the method will prove better when applied to coffee of high yielding capacity.

Same time after being milled and stored, green coffee becomes normally subject to a phenomenon of discoloration or whitishness of the grains, which causes a considerable loss of its commercial value. In the present paper, which is the first to be published on this question, are reported the results of various experiments carried out in order to investigate the cause of this phenomenon and the influence of some factors on its manifestation. According to these results it may be clearly concluded that the injuries to the grains, such as those which normally result from their mechanical milling, are the indirect cause of the coffee discoloration. Among the studied extrinsic factors, the relative Humidity of air showed to be the most effective of them. The higher the air humidiry, especially on levels above 80%, the more rapid and intense was the manifestation of the phenomenon.