General Description: Isohop CO2N is an aqueous solution of potassium salts of isomerized alpha acids that have been separated in a pure state from a liquid CO2 hop extract. It is intended for post-fermentation addition to beer to provide tight control of bitterness. It provides a means to control accuracy and consistency of beer bitterness, whilst at the same time reducing costs. ISOHOPCO2N is devoid of hop essential oils and hence contributes no aroma or flavors other than bitterness.
Uses and Advantages in Brewing: ISOHOPCO2N is designed to be added to the beer after conditioning and just before final filtration of fining. Alternatively, it may be added after primary fermentation but slightly lower levels of utilization will result. The method of addition is similar whether all or part of the bitterness is to be derived from ISOHOPCO2N. The major advantages of using ISOHOPCO2N are twofold.
- Utilization: It is well known that utilization rates of leaf hops, pellets and whole extracts are relatively low and even lower with high gravity brewing. Under such conditions, and with a knowledge of current brewery utilization rates, it is possible to compute the optimal balance of kettle and post-fermentation bittering to minimize the overall cost of bitterness in any brewing situation. Experience indicates that it can be economically advantageous to add up to 60% of beer bitterness as ISOHOPCO2N when high gravity brewing. By replacing a proportion of hop bitterness with isomerized extract, not only is there a direct saving because of the high efficiency of ISOHOPCO2N but the remaining bitterness source used in the kettle will also show a greater utilization.
- Consistency: Since ISOHOPCO2N is added to beer at the end of the brewing process fine adjustments can be made to bitterness levels. The bitterness quality derived from this isomerized extract will be uniform as it is due solely to iso-alpha acids.
Method of Uses: ISOHOPCO2N is best used then injected directly into the beer stream just before final filtration. The amount of ISOHOPCO2N (at 30% w/v) to inject is easily calculated as follows:
I = (B x V x 0.01) / 30
where I = amount of ISOHOPCO2N in liters
B = bitterness units required
V = volume of beer in hectoliters
If the volume of beer to be bittered is known in U.S. barrels rather than hectoliters simply replace the factor 0.01 with the value 0.0117. The required amount of ISOHOPCO2N is still calculated in liters.
The calculated volume of ISOHOPCO2N should be adjusted for any losses during secondary filtration. If there is no firm knowledge about losses assume an efficiency of 90% and adjust later based on analysis or taste tests.
Example: It is required to supply 50% of the bitterness to 1,000 bbl beer using 30% ISOHOPCO2N. The final bitterness is to be 18 IBU.
I = (9 x 1,000 x 0.0117) / 30 = 3.51 liters
At 90% efficiency the ISOHOPCO2N required = 3.51 / 0.9 or 3.91 liters
In evaluating the total bitterness units by the standard ASBC analysis the absorbance of the initial beer should be multiplied by the standard factor of 50. The incremental absorbance provided by ISOHOPCO2N should be multiplied by the factor 75 as discussed earlier. The true bitterness units are the sum of these two readings.
The total amount of ISOHOPCO2N required for addition to a brew should be added with stirring to about 5-10 times the amount of water. Preferably, distilled or deionized water should be used for this purpose, although brewery softened liquor would be acceptable. Beer or hard water must not be used. The working solution of ISOHOPCO2N should ideally be metered into a stream of beer flowing from the condition tank to a holding vessel just before filtration. Addition should be made over at least 75% of the beer transfer time. Alternatively, after dilution with water, ISOHOPCO2N may be mixed into beer in a conditioning tank. Where this is carried out, however, it is essential that adequate mixing of the tank contents is effected.
ISOHOPCO2N should be added to beer before any redox treatments are made since materials, such as ascorbic acid, if mixed with a solution of ISOHOPCO2N will interfere with is solubility in water. Additions of ISOHOPCO2N should also be made before finings are added. The use of hop oil, dry hops and dry hopping emulsions do not affect the use of ISOHOPCO2N.
Typical brewing performance: When injected just before final filtration, and when the appropriate corrections to the ASBC equation are made, ISOHOPCO2N exhibits utilizations of between 85 and 95%. It increases bitterness without affecting any other taste, flavor, aroma or beer quality characteristic. Head retention may even be improved.
