The measurement of mannitol in beet sugar factories to monitor deterioration and processing problems*

Abstract

The major (but not sole) contributor to beet deterioration in many countries, particularly when warm and humid conditions prevail, is infection by hetero-fermentative Leuconostoc mesenteroides lactic acid bacteria. In recent years it has emerged that mannitol is a major product of L. mesenteroides deterioration of sugar beet and a sensitive marker that can predict processing problems. How mannitol and dextran formation are related is described. An enzymatic factory method that is rapid, simple, accurate, and inexpensive is now available to measure mannitol in juices and is also applicable to downstream products. The method recently became an Official ICUMSA Method GS8-12. Numerous factories in Europe, including France, Germany, Belgium, and Poland are now using the method to monitor for Leuconostoc activity in beets, press water, raw, and thin juices. In two Belgian factories steam disinfections of juice/cossettes heat exchangers are applied when critical levels (>160 mg/L) of mannitol are detected. At a German factory, heat exchangers are treated regularly with sodium hydroxide when mannitol content becomes greater than 50–60 mg/L. In numerous French factories, mannitol levels are helping to control filtration difficulties. Mannitol balances undertaken by Groupement D’Exchanges Techniques during the 2009 beet campaign are discussed.