Abschlussbericht Projekt: „Verminderung der ... - BLE

Blackspot bruise formation in potato (Solanum tuberosum) tubers in relation
to the components determining tuber specific gravity
Antje Wulkow 1 , Elke Pawelzik 1 , Rolf Peters 2 , Norbert U. Haase 3
1 Quality of Plant Products Section, Department of Crop Sciences, University of Goettingen,
Germany; 2 VSD-Research Station Dethlingen, Germany; 3 Max-Rubner-Institute,
Detmold, Germany
Abstract
Table potato (Solanum tuberosum) tubers with a range of specific gravities from 1.095 kg L -1 from a three years field experiment were investigated. Genetic and environmental
factors had little influence on the development of tubers with different specific
gravities. To a greater extend the accumulation of dry matter and water during different
phases of tuberization determined the specific gravities of mature tubers of one cultivar or
plant. Mechanical impacts on harvested and stored potato tubers initiated blackspot bruise
formation. Inconsistent results occurred in many reports if intracellular membrane rupture
is necessary to form blackspot bruise or not. The presented results showed that blackspot
bruise formation might occur without membrane rupture because cell necrosis or cell
deaths were not detected. Thus presented findings compared to literature outcomes showed
that mechanical impact on potato tubers led to open mechanosensitive channels of intracellular
membranes, and therefore to blackspot bruise formation without intracellular membrane
rupture.
Keywords: dry matter, starch content, pectin
Introduction
Table potatoes are consumed worldwide, while their acceptance as food differs due to regional
habits. Additionally, convenience food becomes more accepted rather than nonprocessed
tubers (Haase 2008). This trend is noticed all over the world, especially in
Europe and North America where 20 to 50 % of the daily potato consumption consist of
processed tubers. The quality of these products depends on the available raw potato tubers
and therefore on growing conditions as well as harvesting, handling and storage operations
(Keijbets 2008). These procedures enhance the possibility to damage potato tubers mechanically
resulting in blackspot bruise, which is known to reduce tuber quality and therefore,
its utilization. Since many years the reduction of blackspot bruise susceptibility of
potato tubers is a topic of interest of scientific research. Tuber impact susceptibility include
bruise threshold and bruise resistance. Bruise threshold is the impact at which blackspot
occurs and bruise resistance is defined as the ratio of bruising energy to the resulting bruise
volume (van Eck 2007). Blackspot describes a dark discolouration of the cortical parenchyma.
After impact phenols, primarily monophenols like tyrosine and/or diphenols like
chlorogenic acid undergo a series of oxidative reactions initiated by the copper containing
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