Construção e avaliação de um colorímetro para produtos agrícolas.

Abstract

In order to match the color and ripening stages of fruits, a low cost colorimeter was constructed, whose operation principle consists of determining a sample reflectance respecting a White Standard and compute the coordinates of L*a*b* color space using the CIE (Comission Internationale d'Eclairage - International Illumination Commission) equations. The equipment was constructed with wood pressed, and operates with 21 LED's divided into 7 groups according to their color. The sensor is ideal to photometry applications because its responsivity is approximated to the human eye. The instrument performance was compared with the commercial model CR-10 and the linear relation of the chromatics coordinates was obtained for analysis on 60 colored samples, indicating a valid gauging. Color analysis on peel and pulps of guava, papaya and mango were made. The values found in the L*a*b* color spaces were used to calculate color indexes that were related to the soluble solids content (SSC) and pH. The results obtained permit to conclude that it is possible to estimate the ripening of papaya through the color peel, having found an accurate relation between color index of peel and SSC, expressed in terms of the third degree equation. This relation indicates that the increase on the soluble solids content is slow until all the peel becoming uniformly yellow, so that the increase is accentuated until the beginning of the degradation period. For the guava and mango there is not a relation between the color index of the peel and SSC. There is not a relation between color index of the guava, papaya and mango pulps with SSC. For all fruits studied there was not any relation between color index of the peel or pulp with pH.