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Causes of the changes of the marc content

  • Autor/in: Kenter, C., C. Hoffmann
  • Jahr: 2008
  • Zeitschrift: Proc. 71. IIRB-Kongress
  • Verlag: Brüssel
  • Seite/n: 183-187
  • Stichworte: Markgehalt, Zuckerrübe, Sorte, Standort, Schnitzel

Abstract

Beet marc is the part of the beet root which remains after full extraction of all soluble parts from brei. It forms the beet pulp and is thus the second most valuable product in the sugar beet after sugar. In Germany, the pulp output of a sugar factory is estimated and paid using a general factor, since no routine method for marc determination in the factory exists. This figure was derived in the 1980s. However, calculations from the sugar industry for the past decade show that the pulp output was in many cases lower than estimated. The aim of the present study was thus to identify which factors influence the marc content of sugar beet and to investigate if marc content has changed in recent years. In 2006, field trials at 3 locations in Germany with 6 current varieties and 3 levels of N application showed a positive correlation between marc and sucrose content. In another field trial, older (registration 1964 and 1987) and current varieties were grown. The results show that breeding progress led to slightly higher sucrose content and lower marc content in the beet. Thus, the positive correlation between marc and sucrose does not hold if older and current varieties are compared. Meanwhile, the figures to assess the pulp output were adjusted downwards. To study whether the selection for higher sugar yield has changed the cell structure in the beet root, number and diameter of the cambial rings in the beet were determined. For the 6 current varieties, both marc and sucrose content decreased significantly with increasing ring diameter. The comparison of older and current varieties also showed a negative correlation between ring diameter and marc content, but no relationship between ring diameter and sucrose content was found. Thus, breeding may have increased the optimal cell volume for sucrose storage. Current, higher-yielding have larger rings which include less cell wall material than older varieties and thus, constant or increasing sucrose content is associated with low marc content.
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