Deutsch 
English
Isinglasss for wine clarification
Composition
Isinglasss is a natural product. Thus, only approximate values can be provided:
| Moisture level | 10 - 25% |
| Ash | max. 1 % |
| Protein Content | 75 - 85% |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Originally, Isinglass was obtained from the swim bladder of the fish species Beluga, found primarily in the Caspian and Black Sea basins. The swim bladders of many other fish, mostly from India and Brazil, are also known as Isinglasss.
The swim bladder is processed by eviscerating it from the dorsal portion of the fish and cut lengthways. It is then softened in hot water followed by separation of the outer muscle layer and blood. The swim bladder is then stretched for drying.
The quality of Isinglass for wine clarification comes from its high content on native (high molecular) collagen. Native collagen consists mostly of L-amino acids and therefore dissolves readily under acidic conditions in cold water. It retains entirely its tertiary structure in contrast to gelatine. At typical pH values of wine, the protein molecules are positively charged and coacervate with other negatively charged particles, e.g. yeast, leading to quick clarification of wine. There is no distinct difference in the amino acid composition between gelatine and Isinglass.
The highest content of native collagen is found in the swim bladders of the caviar fish Beluga and Sturgeon, which is often regarded as premium-quality. This quality is also referred to as Isinglass.
Preparation of the solution
Usually, solution concentrations of 1% to 5% are prepared. For this purpose, the previously weighed Isinglass is treated 1 to 2 times with water and soaked until it becomes soft. The Isinglass is then plucked diagonally to the fibre direction into small pieces.
Since native collagen is only soluble under acidic conditions, wine with a high acid content should be used for preparing the solution. Whenever possible, 0.1 parts of tartaric acid should be added for every 1 part of Isinglass. If the addition of tartaric acid is not possible, an aged sour wine can be recommended alternatively.
The small pieces of Isinglass are then dissolved at 20 °C in the acidic solution/ wine for approximately 24 h under occasional stirring. A high-shear mixer can be used to accelerate the disintegration process of undissolved pieces . To avoid a rise in solution temperature, the mixing should be stopped after 1 minute. If necessary, the process can be repeated after a cooling phase. After 2 to 3 days the Isinglass has become a viscous, opaque solution with a limited shelf life.
Advantages of wine clarification with Isinglass
1. Removal of colloidal turbidities before filtration.
2. Fast settling of yeast, forming a compact sediment.
3. Removal of astringent, strong tasting components and polymeric phenols without influencing esters and the fruity bouquet.
4. Enables better performance of sterile filtration.
5. Higher selectivity and less material material needed during wine clarification compared to gelatine.
Combined wine fining
To accelerate the clarification process, it is recommended to combine Isinglass with silica sol. Silica sol is always added separately after the Isinglass.
Furthermore, Isinglass can be combined with gelatine and bentonite, in which case, a preliminary testing is required to optimise the fining effect.
Usage
For wine clarification usually 1 g of Isinglass is sufficient for 1 hl (10 ppm). The optimum amount has to be assessed in a preliminary trial, because an excess amount can lead to overfining. In order to do so, aliquot samples (10 x 25 ml) of the wine and mix it with increasing amounts (2 - 20 ppm) of the clarification solution. After 2 - 24 h, the concentration leading to the largest sediment and best clarity is considered the optimum amount.
The determined amount of the clarification solution is then pre-mixed with a small portion of the wine and subsequently added to the entire amount. A good mixture is obtained, when the clarification solution is added during transfer of the wine from one tank to another. Filtration can be done after 8 to 14 days.
IMPORTANT: Dissolution and storage of the Isinglass should be performed at low temperatures (not above 20 °C). Higher temperature leads to degradation of the native collagen. A solution of Isinglass prepared at higher temperatures would result in a gelatine solution. The viscosity of the solution is a suitable indicator for the quality of the Isinglass, with higher viscosity reflecting a higher amount of native collagen. During storage, the content of native collagen, viscosity and its clarification efficiency will decrease.
