I have made the mistake of adding post-boil hops to the boiler at 104 °F (40 °C). I think that I should have added the hops at 176 °F (80 °C) after flame out. Will adding hops at 104 °F (40 °C) spoil the beer?
The one very important thing that all brewers should know about hops is that they are not a source of beer spoilage organisms when added to normal beer. My definition of normal beer means that the beer contains at least 3% alcohol by volume and some hops to add bitterness. Normal beer is prone to spoilage by certain organisms generally called "beer spoilers," including Lactobacillus and Pediococcus bacteria (both lumped together as lactic acid bacteria) and wild yeasts like Brettanomyces. But normal beer is not a good growth medium for the microflora that is found on hops. In practical terms this means that brewers can feel free to add hops to wort or beer at any stage of the process used to produce normal beer without having to worry about introducing beer spoilers.
This does not mean that brewers simply add hops without any real plan. If you want to impart bitterness to your beer it is important to add hops to wort and boil for at least 45 minutes. During the boil, alpha acids present in hops dissolve into wort and isomerize into the much more soluble and bitter iso-alpha-acids. Hops added later in the boil are usually added for their aroma contribution because the shorter boil time limits isomerization, yet the heat of the wort does extract hop aromatics. There is also some aroma removal when hops are added to hot wort and many of the "high notes" that you smell when hops are added to the kettle are lost to the environment. This is why brewers wanting those pungent and fresh hoppy notes add hops after the boil either to their hot wort or to their beer as "dry hops."
It sounds to me that your recipe called for some late kettle hops that were intended to impart some of these high notes, but maybe not as much of the hop high note as one would get from dry hopping. Or perhaps the person who wrote the recipe did not like messing around with dry hopping and formulated their recipe so that all of the hops would be added on the brew day. I do not think that adding hops to 104 °F (40 °C) wort will do anything to this beer that you can detect upon tasting, unless you brewed a few batches of the same beer with the only change being the time of your last hop addition. Even in the event of this unlikely example, I bet that the differences between the brews would be minimal.
Food-grade CO2; is that a thing? How do you know what you're buying?
This is an interesting question that has a less than satisfactory answer. When brewers discuss carbon dioxide purity the elephants in the room often include oxygen, oil and sulfur compounds. While all of these compounds may have no effect on food safety (oils may if they are derived from petroleum distillates, for example) they do all have the potential to damage beer. So in practical terms there is a very real difference between food-grade and high purity carbon dioxide.
The fact is that all companies I know who sell carbon dioxide carry one stock gas and sell this gas to various customers who in turn use the gas in a wide variety of applications, brewing and soda dispensing being just two of many. When it comes to food grade, the primary difference lies not in the gas, but the gas container. If liquid carbon dioxide is transported from a gas supplier to a brewery that in turn adds the gas to beer, the supply chain from the gas company to beer must all be clean, sanitary and compliant with standards that are consistent with "food grade." If this last clause seems ambiguous, it is. Since local health codes differ across the world, and often times within the confines of small regions, there is not a great definition of food grade.
In the broadest sense of the term, food grade simply means that a product is processed, handled, stored, transported and used in a manner that does not permit spoilage or the introduction of substances that may be injurious to the consumer. So let's look at this from a practical point of view. Bottles used to transport compressed/liquid gases can potentially be used for multiple purposes. A bottle used to transport liquid propane could subsequently be used to transport carbon dioxide. This practice is not acceptable because the residual propane would contaminate the carbon dioxide. One very important thing that is done to prevent this sort of contamination is defining what types of gases are filled into bottles.
Another thing that goes along with handling gases intended for human consumption is cleaning of containers and the segregation of tools, fittings and hoses that may serve as vectors. Again, this is all fairly approximate from what I have seen. When it comes right down to it, I really doubt there is much oversight by US health inspectors when it comes to carbon dioxide because this ingredient does not have a history of causing health problems and does not draw the attention from regulators. In my opinion, this is a good thing.
But your question is really about brewing and we still have the elephants lurking in the corner. Let's start with oxygen. Oxygen in ubiquitous on planet earth, is detrimental to beer and is almost always present in carbon dioxide gas at some level. Typical levels are between 0.05–0.5% and this amount of oxygen is sufficient to oxidize beer. This is a very broad topic and I will resist commenting more about oxygen and carbon dioxide. The important thing is for brewers to recognize this fact. Carbon dioxide can also contain sulfur compounds because of some of the sources that gas suppliers use for carbon dioxide. Fuel ethanol, fertilizer and petroleum processing all yield carbon dioxide as a byproduct and most of the carbon dioxide gas that we buy originates from these sources, and all of these sources can contain sulfur contaminants that brewers do not want in beer. And finally, there are oils from compressors that may be present in carbon dioxide.
Larger breweries treat carbon dioxide like any other ingredient and carefully monitor carbon dioxide purity for a number of obvious reasons. As with water, carbon dioxide is often filtered to remove flavor-active compounds. This is often performed as a prophylactic measure to simply guard against the possibility of stinky gas causing a problem. A common place to use these filters is between carbon dioxide bottles and beer kegs tapped in bars and restaurants.
I recently attended the 2014 Brewing Summit in Chicago, a joint meeting of the Master Brewers Association of the Americas (MBAA) and the American Society of Brewing Chemists (ASBC). During a break between meetings I had a great conversation with a fellow brewer about some of the hoopla stirred up by bloggers regarding ingredients in food and beer. My friend made a great point about carbon dioxide. In a nutshell, his point was that many brewers have a lackadaisical approach to carbon dioxide. For example, when asked to talk about the "four ingredients" of beer most brewers could easily gnaw the ear of most beer consumers. But the same brewers often times do not know anything of substance about their carbon dioxide supply. My friend's point was that the carbon dioxide supply question is very easy to answer when beer is naturally carbonated during tank or bottle conditioning.
Thank you for asking this question. I feel like a captain who just felt a little bump on the bow and peered into the water to see a great berg lying beneath the surface. This topic is one that is infrequently discussed among homebrewers and small craft brewers, and it also lacks any real coverage in most of the books, magazine articles and blog posts written for this group of brewers. I sense an article on this topic in the works for a future issue of Brew Your Own!
I am working on an all-electric HERMS system for my homebrew setup. One of the components I have read about on some setups involves utilizing a mash stirring motor. I've seen some guys pull them out of bread machines or ice cream makers (high torque, low RPMs). Do you think there is any benefit to this? I was considering doing this and then stirring down to a certain level, but leaving the bottom 4-6 inches unstirred so as not to disturb the filter bed. Some brewers I've seen stir for the duration of mash, and then stop the stirrer for a final recirculation period before draining, but I would think this would promote channeling along the stirring mechanism. One more consideration: Do you think there is considerable risk of hot side aeration using a stirring mechanism during the mash, and should a homebrewer be concerned about this?
This is a pretty weighty topic because stirring the mash does a few things to the mash. To avoid a geeky treatise I will cover this from a treetop level. So why are mashes stirred? Like all brewing subjects the answers to questions like this almost always involve commercial practices because brewing technology was developed for commercial brewing, not homebrewing. Mashes are stirred in commercial breweries because that is the method that allows brewers the most flexibility with ingredient selection and with mash temperatures.
The most flexible brewhouse configuration in my view of brewing includes a mash mixer and a lauter tun. While I do not believe there are many tangible reasons to use decoction mashing using today's malts, there were certainly some real benefits to this mashing method when poorly modified malts with less than stellar enzymatic strengths were the norm. Decoction mashing, even the revered triple decoction, can be mastered if the transfer piping between the mash mixer and lauter tun is designed to permit mash to be pumped from the lauter tun to the mash mixer.
As malt quality improved over last century through the successes of barley breeding programs, advances in farming practices, and a better understanding of the biochemistry of malting, the need for intensive mashing methods waned. Exceptional beers are brewed today using step mashing or infusion mashing methods. Indeed, many of the great European lager breweries no longer use decoction mashes, and have replaced these methods with step mashing techniques. Step mashing gives brewers more control over the enzymatic reactions that occur during mashing in comparison to infusion mashing. And if a brewer wants to use step mashing in a commercial-sized brewery, a stirred mash is required.
Another reason to stir during the mashing process is to improve extract yield. Stirring has a pronounced effect on yield and for this reason many breweries using single temperature holds for conversion use mash mixers. What is essentially an infusion mash is further improved when conducted in a mash mixer because the mash temperature can be increased following conversion. This "mash-out" or "mash-off" step has the primary benefit of reducing wort viscosity and improving extract recovery during wort collection. Another benefit to the mash-off step is the ability to stop enzymatic conversion.
When you build a system based on external mash heating with a heat exchanger, there are a few key changes to how the mash behaves during mashing in comparison to stirred mashes. The most significant difference is how the heat is transferred into the mash. With a HERMS system you are pumping wort from the mash tun, through a heater and back into the mash tun. In a mash mixer, the heat is applied to the mash from the exterior surface of the vessel. Since the goal of step mashing is to exert control over the conversion of starch into fermentable and unfermentable sugars, it is vital to uniformly heat the mash, not just a part of the mash. I believe stirring the mash is really quite important for these systems to properly function and have the intended effects on the finished beer.
I understand why you are considering not stirring the entire mash, but my concern is that if you only stir the upper half of the mash that the lower portion will not have a uniform temperature and this will result in inconsistency between batches. While consistency between batches is not important to all homebrewers, I think it is an important consideration for those who want to build more complex mashing systems. Consistency with this process allows brewers who want to perform mashing experiments the ability to evaluate their data with confidence.
Regarding hot side aeration ... my answer is no. I do not believe that stirred mashes contribute to hot side aeration. My primary justification for this belief is that the design of most mash mixers allows for mashing without splashing.
I recently made a blueberry Weizen. After a bit of research, we decided to add the blueberries to the secondary fermenter. We defrosted them, ran them through a blender, then poured the crushed berries into the secondary. The resulting brew is nicely bluish-purple, tastes nicely of the blueberries, and is a very refreshing beer. I like it a lot. The issue is that the beer is very cloudy, millions of tiny particles of blueberries in the liquid, in spite of draining the berries through a muslin bag to get out the solids. I suspect the particles I see are too tiny to be caught in the bag. We added Irish moss during the boil, but wonder if there's something we should do next time for a clearer result.
I think the problem with this beer is that you placed your blueberries into a blender. By doing this you broke down insoluble compounds in the blueberry skins into millions of tiny bits that have a density not much greater than beer. The result is fairly stable, hazy emulsion that is difficult to filter and not effectively removed by straining or fining (Irish moss helps with wort clarity in the kettle, but has no effect on ingredients added after the boil). Some fruit beers, like Abita's Purple Haze, are intended to be hazy and using fruit purees help achieve this sort of appearance. But if you want clearer beer, different techniques work better than the one you employed in your blueberry weizen.
I suggest taking a lesson from winemakers and begin with crushed, not pureed, fruit. Add the crushed fruit to the secondary and allow the yeast to completely ferment the fruit sugars. During this process the fruit pulp tends to break down and the insoluble fruit matter associated with the skins and pulp will sink to the bottom of the beer after activity has ceased. You are still likely to have some haze because tannins from the berries react with proteins in the beer. These hazes may settle over time, but if you want to move things on a bit finings like Bentonite, PVPP and silica gel can work quite well.
Another method that is appealing to food geeks like me is to make blueberry juice syrup from your fresh fruit. If I did this I would be very tempted to add pectinase to the juice before reducing to prevent gelling. This sort of syrup will have nice color, flavor and sweetness. Add it to your weizen for a sweeter, fruitier preparation than adding fruit to the secondary. I hope these simple tips help you out in your quest for great fruit beer.