Isinglass: Is It a Type of Glass?

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Fishes inhabit the underwater world and make the ocean life amazing. They are awesome in a real sense as they have acquired a number of adaptations to live in the dangerous environment of water. Their number varies in millions in the ocean world. They are not only beautiful but are also very important to us as they provide us very valuable items that are useful for us in our day to day life. Isinglass is one such valuable stuff obtained from the swim bladders of fish and is of high economic importance. It is a form of a protein known as collagen which is widely used for the clarification of wine and beer. It can be processed in the form of a paste to make glue which is used in commercial purposes. Isinglass was in general prepared from the swim bladder of sturgeon fishes particularly the Beluga sturgeon. In 1795 William Murdroch prepared isinglass from the swim bladder of cod which was a cheap substitute for the isinglass obtained from the swim bladder of sturgeon. The isinglass prepared from cods was chiefly used in Britain not in Russia. The bladders once taken out from the body of fishes is processed and dried and then moulded in different shapes depending upon the usage.

Isinglass was earlier used in the production of the confectionery like fruit jellies and blancmange but is now replaced by gelatin which is cheap and inexpensive. Isinglass finings are widely used in Britain for beer and wine clarification. They are widely used in the production of fine beers known as real ale. Although there are some cask ales which are not clarified by using isinglass. The finings of isinglass flocculate the live yeast present in beer in the form of mass that settles at the bottom of the cask. If beer is left undisturbed then it undergoes clarification by its own but use of isinglass accelerates the process. Isinglass is sometimes mixed with an auxiliary fining which further accelerates the process of sedimentation of beer. Beers that are prepared for kegs, cans and bottles are often pasteurized and filtered. The yeast present in these beers settles at the bottom of the production tank by its own so the use of isinglass is not required. However, some breweries often use isinglass for the production of non-cask beers.

Some remains of isinglass still remain in the beer even after clarification so some vegetarians consider such type of beers unfit for their consumption. A beer fining agent known as Irish moss is considered suitable for vegetarians. Irish moss is actually a type of red alga also identified by the name carrageenan. This carrageenan is however used in the boiling and post-fermentation process but for the removal of yeast isinglass is finally used. Both these fining agents act differently and are not interchangeable but some breweries make use of both these agents together in beer clarification. Isinglass finings are also used in the production of kosher wines but for this purpose the isinglass is not derived from the Beluga sturgeons as they are not kosher fishes. They are also used in repair parchment. The pieces of the best Russian isinglass are soaked overnight and allowed to swell and then dried. This dried material is then slowly cooked in bain marie at 113ºF with regular stirring. A small amount of gum tragacanth dissolved in water is added to this mixture which finally acts as an emulsifying agent. When the repairing paint flakes from the parchment then isinglass can be directly applied to that area which has been made wet by ethanol application. Generally a very tiny drop of isinglass is applied with the help of binocular microscope.

Isinglass can be used to coat tissue or goldbeater’s skin. But here isinglass is used in the form of adhesive that can be reactivated by the use of moisture. For making adhesive isinglass is cooked with few drops of glycerin and honey. This adhesive is used for parchment repair where minimal amount of water is required and the strength of this adhesive is much more as compared to other adhesives used for parchment repair.