Hopback, Outdoor Fridge & Refractometers: Mr. Wizard
Q
I just acquired a hopback and now I am wondering how best to use it. Can it replace late addition hops, and if so, would the quantities be the same? What about dry hops? Will running hot wort through a hopback obviate the need for dry hopping and what would be the ratio of dry hops to hopback hops? The instructions with the hopback said use only whole hops and I can understand that but could pellets in a hop bag be substituted?
Bill Winter
Silver Spring, Maryland
A
The term hopback, or hopjack, has different meanings to different brewers. Before the advent of pelletized hops and hop extracts all brewers used whole hops. Hopbacks were used primarily to strain hops from wort after wort boiling. There were two basic designs for hopbacks; batch and continuous designs. The batch-sized hopbacks looked similar to mash tuns and were designed to hold the contents of one brew. Basically, the kettle was drained (or “knocked-out”) and the hopback acted as a strainer to remove the hops while the wort flowed through the strainer installed in the bottom of the hopback. Continuous hopjacks were designed with screw augers that moved the spent hops out of the hopback while wort flowed through the strainer and out. Both basic designs have changed little over the last century and are still used by brewers who use whole hops for brewing.
Brewers who really liked beers with pronounced hop aroma figured out that if a batch-style hopback was loaded up with hops before the kettle knock-out the resulting beer would be full of wonderful hop aromatics, but not hop bitterness. This is true because hop oils, the aroma constituent of hops, are quickly extracted by hot wort while hop bitterness requires hops to be exposed to boiling for a period of time to isomerize alpha acids into their more bitter and soluble cousins, the iso-alpha-acids. The use of the hopback in this fashion is not too different than a drip-style coffee maker or the bed of juniper boughs used in Sahti brewing.
As a brewer and beer connoisseur, I think the three methods you address in your question, late hopping, hopback hopping and dry hopping, are all distinctively different in how hop aroma is expressed in the finished beer. Late hop additions, especially when pellet hops are added to the kettle and not removed from wort until wort cooling is complete, frequently add bitterness to beer in addition to aroma. This feature of late hop additions can be avoided if whole hops are used and then separated with a hopback. As you suggest you can accomplish a similar effect by using a hop
bag and removing the bag of pellets after boiling. Late hopping and hopback hopping both extract aroma compounds from hops using hot wort while dry hopping uses beer to extract hop aroma. This makes dry hopping very different, at least to my sensitive schnoz, from these hot wort treatments.
OK, now for the subjective part of the answer. I think hopback hopping is a great substitute for late kettle additions. As far as the aroma contribution is concerned you may find that the aroma retention is better with the hopback since adding hops to the kettle does result in aroma loss if the boil extends much past the addition. However, you may end up with a slightly less bitter beer with the hopback. A slight increase to the first hop addition is an easy way to tweak any recipe you have that you want to reproduce with your new hopback.
In the “old days” of really hoppy beers, you know like in the early 1990s, simply hopback hopping or dry hopping with a pretty generous dose of hops, such as 1⁄2-ounce per gallon or roughly 4 grams per liter, was enough to make most beer drinkers say “wow, this is a really hoppy beer.” Things are different nowadays, especially since that documentary, “Hopheads Gone Wild,” inspired the ultra-hoppy tipple movement. Some of these beers use the belt-and-suspenders approach to brewing and are hopped using as many methods as possible. There are really no rules, as long as you are willing to pay to play. There is no doubt that if you hopback hop and then later dry hop the same beer that another layer of hoppy complexity will be added.
I am a fan of balance, even with big beers that are often a bit unbalanced by their very nature. Some-times it is difficult to appreciate the nuances of a technique when it is combined with others. It’s kind of like attempting to appreciate an ethereal jazz flute solo while the drummer is bashing on the kit with sticks. But if you really want to crank the dial up on the hop-o-meter the combination of hopback hopping and dry hopping can be fun. My inclination would be to balance the two methods such that neither overwhelms the other. In my experience I find that it takes about twice the weight of hops used in dry hopping to approximately equal the impact of one part of hops when hopback hopping, for example use a 1⁄2 ounce per gallon of dry hops and a 1⁄4 ounce per gallon of hopback hops. With that being said, you bought a tool, so go experiment with it and figure out what works best for your preferences!
Q
Not knowing much of anything about how a refrigerator works, i was wondering if it is possible to put one outside (central Missouri gets pretty cold) with the temperature control set at, say 68 °F (20 °C), and expect it to hold that temperature all year round? This would be home to my conical, naturally. I see soda machines outside, and the contents don’t seem to freeze during the winter.
Jim Crow
Cooper Hill, Missouri
A
The refrigeration cycle is pretty nifty and its development began in the late 1700s. The earliest use of commercial refrigeration occurred sometime in the mid 1800s by, you guessed it, breweries. The refrigeration cycle is pretty, well, um, cool, and has four main parts to the cycle.
The cycle begins by compressing a refrigerant gas, such as ammonia; this results in high-pressure, hot, refrigerant gas. The hot gas flows from the compressor into the condensing coil where a coolant, normally air from a fan (this is the thing outside of your house that blows hot air in the summer), removes heat from the hot gas, thereby converting it into high pressure liquid. This phase change occurs because the gas condenses when cooled.
The third step is where the cool begins; the high pressure gas flows through an expansion valve, which is essentially a nozzle providing backpressure to the liquid side of the system. The nozzle creates pressure drop in the system and when the high pressure liquid expands the result is a mixture of cold refrigerant gas and liquid (for more on why the mixture becomes cold read about adiabatic expansion). This mixture then flows to the heat exchanger responsible for chilling, often called “the coil” in a refrigeration system, where the refrigerant absorbs energy from the environment and is evaporated into gas. The energy absorbed by the refrigeration is removed from the system as the warm gas enters the compressor. The cycle now repeats itself and the energy removed in the condenser represents the energy absorbed in the evaporator coil.
Depending on how this system is set up, in terms of what the compressor and thermal expansion valve are doing to the refrigerant, and what type of refrigerant is being used this type of refrigeration loop works great as either a refrigerator or a freezer. The system starts and stops by activating the compressor and this is triggered using a thermostat. The bottom line is that the unit is designed to remove heat from the system, in other words make the inside of the cooler cold, when running. And when the unit is not running the inside of the cooler becomes warmer if there is a heat source inside of the cooler, such as a fermenting batch of beer, or if warm air from the outside environment infiltrates the cooler, or as the cold from inside the cooler is transferred out across the walls of the cooler.
So, what happens in the winter time when a refrigerator is placed outside and the thermostat is set to 68 °F (20 °C)? If the temperature inside is warmer than 68 °F (20 °C), the compressor kicks on and stays on until the temperature reaches 68 °F (20 °C). However, if the outside temperature is cold, let’s say it’s 20 °F (-7 °C) out and the cooler begins to drop below 68 °F (20 °C), nothing happens with respect to the compressor. The temperature inside the cooler will continue to drop as the cold from outside the cooler transfers inside. This is no different than what happens inside your house during the winter. Eventually, the contents of the refrigerator will freeze if the outside temperature stays cold for long enough. This process is slowed by insulation, but insulation does not stop it.
If you really want to have a refrigerator that does not drop below the set point, then you must install a heater and use two thermostats. The simplest heater is to use a heat lamp, but if you ferment in glass carboys you need to be careful not to damage your beer with light. Refrigerator heater kits are sold by some refrigerator manufacturers specifically to keep refrigerators located in garages from becoming too cold.
Q
I have been using both a Brix refractometer and a Hydrometer to determine the finished state of my beer. My logic is that if I measure the same Brix reading in two consecutive days, My beer is done with primary fermentation. Upon racking to secondary, I measure the specific gravity using the hydrometer for an absolute number. are there any flaws in my logic?
Todd Morgan
Olympia, Washington
A
Refractometers measure the refraction, or “bending,” of light caused when light passes through various media. The refraction of light is not the same for all media and this difference is a useful property that can be used to indirectly measure the concentration of a sugar solution, for example. This works when there are two parts to the system being measured, for example water and glucose. If there are other components of the system things become confused, especially if the components have very different refractive indices. This is why refractometers work well for measuring the sugar concentration of wort, but do not work well when fermentation begins and ethanol is present.
Hydrometers measure the density of liquids and do not depend on the nature of the liquid. In other words, if a liquid solution has a density of 1.000, the hydrometer does not behave differently if the liquid is water or a mixture of water, sugar and ethanol. Hydrometers are especially useful in brewing because they are robust tools for tracking the density of wort as it is transformed into beer.
What you want to do with your refractometer is totally valid. Since changes in the composition of beer by fermentation will change the refractive index of the beer, no changes in the refractive index imply that the composition of beer has not been changed and that fermentation must be complete. As long as you use the method as a simple indicator of activity and nothing more, you will not be mislead by the results. The key to this method is that after you determine that fermentation is complete, you then measure the final gravity of your batch. The downside, however, is that the refractive index of ethanol is greater than water, but the refractive index of sugar solutions decrease with dilution. This means that the sugar and alcohol affect the refractive index in opposing ways. At least with a hydrometer the density changes in the same direction as fermentation moves towards completion.
