PRODUCING CRYSTALS OF MONOSODIUM GLUTAMATE

I still remember fondly the first time in the seventies when we were taken on a visit to a well known seasoning manufacturing plant in Kuala Lumpur. The field trip is part of our course for those taking the subject of applied microbiology. Though the Professor then or for the matter we the students do not know much of the fermentation process and the various steps involved from substrate to the final product, memories of the visit are still remembered with fondness and perhaps drives me to study in greater detail the field of fermentation technology.
One of the most interesting points of the visit is seeing and understanding the transformation of the fermentation broth at the end of the fermentation process to become the final end product. From the huge vats containing the dark brown fermentation broth removed from the fermentors it is transformed to beautiful shiny crystals of monosodium glutamate ready for packing and distribution.
This whole process was carried out during the downstream stages of the fermentation process.
Many questions entered my mind such as:
1 Why the need to produce the crystal forms of the sodium glutamate?
2 How is the process of crystallization carried out?
In the fermentation industries everything boils down to economics. Even though the process of producing MSG crystals would add cost to the downstream processing costs but at the same time there must be more economic or even marketing benefits derived from such exercise.
In any fermentation products water form the bulk of the product. The presence of high concentration of water will not only add bulk and weight to the product but it will add costs to its packaging and transportation.
The presence of water too will increase the probability of microbial contamination as water tends to encourage microbial growth and deterioration of the products
In its crystal forms, these problems are eliminated. It is concentrated in the form of crystal and will deliver the power of the seasoning. There is also the added marketing value of the product as the crystals look clean and appealing and its purity of the product is assured
The process of forming the crystals is in simplification a kind of chemical precipitation reactions.
It is based on the salt or ionic nature of the products. Adding the Sodium to the glutamate will further stabilize the product to undergo the various harsh downstream reactions. While it is true that the process of crystallization is based on the nucleation and crystal growth of the crystal from a super saturated solution as it cools down, it is of most importance that the solution of MSG from the fermentation broth must be purified so as to produce clear and beautiful crystals.
Various downstream methods are used to obtain this clear broth such as cell separations which include centrifugation and membrane separation. This is followed by various preparatory steps such as ion exchange resin treatment, chromatography and crystallization. And in the crystallization stage there is concentration, neutralization and cooling. Ultimately the final steps include centrifugation, decantation and filtration to obtain the crude crystals
The crystallization process are usually carried out using the crystallizer


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