Nicht-destruktive Erkennung von Berostung bei Birnen
Matthias Klemm,Olga Röttger,Lutz Damerow,Michael Blanke
Erwerbs-Obstbau 59(1): 1-11
The objective of the present study was to investigate possibilities of non-destructive examination of russet on pome fruit using a luster sensor (Mukhtar et al. 2014) including varietal, colour and positional influences. Therefore, pears of three varieties from the local market in December, were investigated by three means, visual observation of the type and spread of russet, 3D colour microscope and sensor technology. Visual oberservation showed that pears of cv. 'Conference' from Belgium exhibited the most severe russet, particularly in the spherical part of the fruit, but also with speckled russet at the elongated stalk end of the fruit. Pears of cv. 'Alexander Lucas' from Germany had the least russet localized at the calyx end of the fruit and those of cv: 'Abate Fetel' from Italy showed an intermediate level of russet at the calyx end. Three-dimensional colour microscopy at x200 magnification. showed that russet, i. e. suberinisation of the fruit peel, on cv. 'Conference' caused a 2.5-fold increase in roughness of ca. 50 µm compared with ca. 20 µm on russet-devoid peel sections of cv: 'Alexander Lucas'. Scarcely russeted peel of cv. 'Alexander Lucas' showed significantly larger luster levels and those of cv. 'Abate Fetel' the tendency of larger luster levels with a smaller variation than russet devoid fruit peel. Russet was more difficult to detect on the elongated part of the pear fruit next to the pedicel. These first results indicate that this sensor-based russet detection is based on a combination of peel roughness and colour; but require further investigations. The results of larger luster levels on russeted pears are in line with those on plums (Mukhtar et al. 2014) where polishing during harvest and postharvest handling doubled luster levels compared with the undisturbed natural amorphous fruit surface.