Day 159

For the past few weeks in Sensory Evaluation, we have been looking at setting up tasting panels and the types of tests that can be used. Today we looked at open and blind tests. An open (non-blind) test is where both you the tester and your subject(s) are aware of the beer being tested.  This might be used for your brewery’s daily quality control check tasting–everyone knows the beer you are tasting, you are only interested in finding out if a problem has cropped up in the latest batch of beer.

Then there is the single-blind study: you know what beer is being tasted, but your panelist only sees glasses coded with “Sample A”, “Sample B”, etc. This works well if you are able to refrain from passing on info to the taster through speech intonation or body language–for instance, unconsciously sighing and rolling your eyes as you hand your panelist a sample of something you believe tastes like water (or worse).

To prevent this, there is the double-blind study: neither you the tester, nor your panelists know which beers the panelist is tasting. First you need to have a “cut-out” person who sets up the samples for you, marked by codes, and then leaves. When you arrive, you have no idea what you are serving–only the cut-out person holds the “key” to which samples are which. A double-blind is less frequently used, simply because it is more complicated to set up and run.

Once you have run your tests, you need to be able to turn the raw data into results. Instructor Mark Benzaquen quickly ran through some very basic statistical principles (that still left left me scratching my head at times. Stats were never my strong suit in math class.) However, Mark did mention that there were spreadsheet programs available that would analyze your data and deliver a summary of results. (“I’ve got to find me one of those!” I thought to myself.)

Okay, so you’ve run the tests and you have results. Lastly, you need to be able to communicate the results of your tests to your client–no use in organizing a tasting panel and running a bunch of tests if the results just sit in a folder on your desk.

On to Chemistry. Today, it was all about enzymatic activity during the mash. First of all, what is an enzyme? Let’s start small, with a measly little amino acid–a standard structure in the chemical world that has an amine group (nitrogen and some hydrogens) and a carbon group (some carbons and oxygens), both joined together like the two wings of  a capital “T”, with another group of molecules joined to them like the downstroke of the T.

The last group of molecules varies from amino acid to amino acid, and defines the amino acid’s function. Think of amino acids as Swiss Army knives–every Swiss Army knife has a red case–the amine group–and a fold-out knife blade–the carbon group. It’s the other fold-out tools like screwdrivers, nail files and scissors–the third group of molecules– that varies from model to model and defines how a particular Swiss Army knife can be used.)

Now, put two of these amino acids together and you have a peptide. Put many peptides together and you have a protein–a structure that is dozens if not hundreds of molecules long. Some of the atoms in that structure have negative or positive charges, and the attractions and repulsions of the various atoms and molecules start to bend the molecule chain this way and that, resulting in a very abstract-looking collection of helixes and wavy bits. However, if you heat up a protein too much, the energy unwinds this unique shape, and possibly even breaks up the protein into its component peptides and amino acids.

Okay, so what is an enzyme? An enzyme is a protein that acts as a catalyst, breaking apart or joining together other molecules, while remaining unchanged by the chemical reaction that it has enabled. For instance, an enzyme called beta-amylase can attach itself to the end of an amylose starch chain and break off a maltose unit (two glucose molecules). Then it reattaches to the chain and breaks off another unit… and then another and another, until the chain has been completely broken up into maltose.

Various enzymes with various tasks are designed to operate most efficiently at various temperatures and pH concentrations. The purpose of the mash is to provide the proper temperature and pH for several enzymes so that they can break down the proteins and starches in the barley kernels into sugars and other substances needed by the yeast.

Whew. That was something of a review of concepts we had covered last semester in Ingredients, but more quickly and in more detail.

On to Microbiology. The topic was how to crop yeast–that is,  how to save some yeast from a batch of beer that has finished fermenting and immediately use it to start another fermentation.

Why immediately? It turns out that yeast has an internal energy supply called glycogen. If you haul the yeast out of the fermenter but then leave it sitting in a bucket for a few days, the heat of the room and the oxygen in the air will kick-start yeast growth, forcing the yeast to use its glycogen reserves. When you go to use it, your yeast won’t have the energy reserves needed to get the fermentation process going. Good luck with that beer thing.

Of course, leaving the yeast in the fermenter after it’s done fermenting is just as bad–the yeast is actually being poisoned by the alcohol and carbon dioxide that the yeast itself made. Leave it in the fermenter, and the yeast will build a kind of armour to protect itself–which again will use up its glycogen reserves.

So get your yeast out of the old fermenter as soon as fermentation has ended, and immediately get it back to work in a new batch of wort. If you do have to store it for a few hours or days, remove the CO2 from the slurry (with gentle agitation), then put it in a fridge, and protect it from oxygen.

That was it for the week. Thankfully it is a long weekend in Ontario–and that extra day will come in handy for studying. Even though next week is only 4 days long, we have 3 mid-term exams and 2 tests scheduled, and one major assignment due. I sense this is one long weekend where I  will be cracking open more books than beers.

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