Reduced Kettle Extract
Reduced Kettle Extract (RKE) is an aqueous alkaline solution of the potassium salts of rho-iso-α-acids and is produced from CO2 hop extract. Reduced Kettle Extract gives protection from light-struck flavor when used as a sole source of hop-derived bittering or in conjunction with other reduced hop products. Furthermore, when added to wort or beer, Reduced Kettle Extract will act as an antimicrobial agent and is often described as having a pleasant smooth bitterness. Reduced Kettle Extract is classified as a modified hop extract that may be safely used in beer in accordance with US FDA regulation 21 CFR 172.560 (b) (1).
Description: A reddish to amber-brown, aqueous solution of reduced (rho) iso-α-acids in potassium salts form. A re-dissolvable precipitate may form during normal storage.
Concentration: 30.0% ± 0.5 of rho-iso-α-acids by HPLC
pH: 10 – 11
Density: 1.090 g/mL (approximately) at 20 °C (68 °F)
Viscosity: 20 – 40 mPas at 20 °C (68 °F)
Iso-a-acids: < 0.2%
Reduced Kettle Extract will only provide protection from light-struck flavor if a complete absence of normal iso-α-acids is achieved; therefore no other sources of non-reduced iso-α-acids should exist in the wort or beer streams. Thus, for light-stable beers packaged in clear or green glass bottles, all the hop
bitterness must be derived from reduced hop acids such as Tetra-Hydro Isomerized Hop Extract. Iso-α-acids (from equipment or yeast) must not be present in the beer. If beta extracts are used as kettle additives, ensure that the concentration of α-acids and iso-α-acids are below 0.2%
Reduced Kettle Extract is normally used as a post fermentation addition to un-hopped beer, but good utilization can be achieved through addition to the kettle so some brewers prefer to make a partial, or even complete, addition to the wort. Dosing Reduced Kettle Extract into the kettle reduces the chances of encountering bacterial growth during fermentation. For light-stable beers packaged in clear or green glass bottles, all hop bitterness must be derived from light-stable hop products such as Reduced Kettle Extract, usually in combination with Tetra-Hydro Isomerized Hop Extract. Extract should be added, without prior dilution, to the kettle or directly to beer either before or after conditioning but before the final filtration. Preferably, post-fermentation dosage should be by metered injection into a turbulent beer stream during transfer. The addition point should be well separated from that of any other additions. The dosing rate depends on the expected utilization for the chosen point of addition, and also allowing for the fact that rho-iso-α-acids are less bitter than normal iso-α-acids by a factor of 0.7. Actual utilization varies depending on plant and process conditions in the brewery. To ensure optimum performance for post fermentation addition, we recommend that Reduced Kettle Extract be warmed to 50 °C (120 °F) and then agitated to ensure dissolution of any precipitate before use. We recommend that the clear solution be injected directly into the turbulent beer stream preferably after primary filtration and gravity adjustment, but prior to final filtration (polish/trap filter). The dosing pump should be adjusted to deliver Reduced Kettle Extract over approximately 70% of the total transfer time. Following dosing, we recommend cleaning lines and dosing pumps with warm slightly alkaline de-mineralized water or ethanol immediately after each use.
The following calculations are based on the assumption of rho-iso-α-acids (Rho-IAA) being
0.7 times as bitter as iso-α-acids (IAA). The equation below factors in the adjustment in perceived bitterness and is you actual dosing rate. As mentioned for all other brewing products, trials are best to determine in-house efficiency and dosing rates for each product. We will assume 70% utilization of Rho-IAA post fermentation and 45% if used in the kettle.
Dosage = BU x 0.520
Dosage = milliliters of Rho-IAA to be added per BBL of beer
BU = is the desired amount of bitterness units imparted by RKE
Note: Use rates may vary depending on the brewing process and the desired hopping level.
** If you would like to change the efficiency from 70%, adjust the 0.70 in the equation.
75% efficiency will change this value to 0.75 and 65% efficiency will adjust to 0.65.
Kettle use – The utilization rate changes from 0.70 to 0.45 so the change is made below.
Dosage = BU x 0.520
You are going to make a beer and would like to provide all of your bitterness using Reduced Kettle Extract post fermentation. You are brewing on a 30 BBL system and want this extract addition to give you 18 IBUs in your finished beer. Assume 70% efficiency.
Dosage = 18 x 0.520 = 13.37 ml/bbl * 30 BBL = 401.1 mls RKE
You are going to make an Imperial IPA on your 30 BBL system and would like to provide some of your bitterness from Reduced Kettle Extract during the kettle boil while utilizing traditional hops throughout the boil. You decide to make a bittering addition, a flavor addition and a final aroma addition at knockout. You will also be dry hopping in the tank. Your target IBU’s for the brew are 100 from which 60 of those will come from the first bittering addition. You decide to split that bittering addition up 60/40 between Rho-IAA and Kettle Hops. Assume 45% efficiency.
Packaged in Square Polypropylene containers weighing 1 kg.
Storage and Best-by Recommendation:
Store Reduced Kettle Extract in full, closed containers at 59 - 77°F. It is normal for a precipitate of rho-iso-α-acids to separate during storage; however, warming the product to 50 °C and gentle agitation will re-dissolve this precipitate. Reduced Kettle Extract is best if used within 24 months from production date if stored as recommended. Opened containers should be used within a few days.
The concentration of reduced (rho) iso-α-acids is measured by UV Spectrophotometry
We will be pleased to offer support on the use of Reduced Kettle Extract in brewing. For assistance, please contact our knowledgeable staff at 1-800-952-4873 or e-mail firstname.lastname@example.org