A Gravity Penetrometer for Measuring Flesh Firmness in Citrus Fruits

Abstract

Abstract Investigations on a widely distributed variant Navel orange led to the need for reproducible, quantitative measurements of flesh firmness of orange fruits. Previous work using pressure devices on the surface of transversely-cut citrus fruits had resulted in erratic results. Whole fruit compression tests failed to show significant differences between samples of the variant and normal fruits (Table 1). In preliminary trials, dropping a pointed rod a given distance through a guide tube onto the transversely-cut fruit gave reproducible results. On the basis of the preliminary results, the present instrument, Fig. 1, was constructed and used in subsequent tests comparing variant Navel oranges with normal Navel oranges. In all plantings tested, the variant trees could be identified by means of the differences in the penetrometer measurement. The absolute values varied from planting to planting and on different sampling dates, but the differences between the two fruit types were always detectable. Results from the first plantings sampled are given in Table 1.