Molecular Weight Distribution of Water-soluble Pectin in Citrus Juice

Abstract

Molecular weight distribution of water-soluble pectin in Satsuma mandarin (Citrus unshiu Marc.) juices was measured by using Sepharose CL-4B gel filtration. This investigation was done for the following juice samples; the juice which happened to clarify, juices from the common Satsuma and the early-ripening variety (Wase Satsuma), from later-picked fruit and the unheated one. Watersoluble pectin showed the wide distribution of molecular weight from 10⁴ to 2×10⁶. In the clarified juice, the amount of the pectin larger than 10⁵ decreased and water-insoluble pectin increased. This finding suggests that it is the pectin of larger molecular weight than 10⁵ that is insolubilized and brings about the clarification of citrus juice. Some differences were observed in the molecular weight distribution between the juice from the common and from the early-ripening variety, while the distribution was neither affected by the difference in the time of picking fruit nor by heating juice.