The Microbial Spoilage of Konnyaku

Abstract

A brief survey on the microbial spoilage of Konnyaku (a traditional gel food in Japan made from konjac mannan) and on the factors affecting the spoilage was carried out in advance of the study on microorganism control of Konnyaku manufacture. Total microbial count was predominantly used as an indicator of the spoilage in this work. The count for Konnyakus on the market was in the range of 0-1.1×10³/g. The level of spoilage was reduced by prolonging the storage period and elevating the temperature. The count for Konnyaku paste (prepared by dispersing konjac flour and pulverized algae in water), which was practically responsible for those of raw materials at the begining (10³/g), increased with the progress in processing until just before the alkali treatment (10⁴×10⁶/g). The increment was mostly attributed to the microbial spoilage of the apparatus such as pumps used for feeding of Konnyaku paste. The count decreased remarkably by addition of alkali and considerably by heating (10¹-10³/g). The spoilage level of konjac flour and pulverized algae were in the order of 10³/g and 10⁶/g, respectively, both including the heat-resistant microbes approximately 10% of the count. The pulverized algae, in addition, was considerably spoiled by coliform organisms. The results showed that the microbial spoilage of Konnyaku is largely attributed to those of feeding pump and pulverized algae. It is, therefore, necessary to establish a useful method for reducing the microbial spoilage of them from the hygienical and preservative viewpoint.