Day 128

Old Man Winter was obviously stung by my scornful observation that he was taking a vacation this year. He returned with a vengeance this morning, fulfilling all my grim expectations of winter in the Niagara Peninsula: sub-zero temperatures, intense winds, snow blowing across the highway, traffic lined up behind snowploughs… Remind me not to insult Winter again.

Fridays are all Mark Benzaquen, all day–he is the instructor for all three of our classes today.

Mark, after earning a degree in microbiology, went walkabout in Europe and ended up working for Heineken for a time. Back in Canada, he worked in Molson’s lab for a while, and now consults on building new breweries, expanding existing facilities and improving product quality.

First up on Friday morning was Sensory Evaluation II. Last semester, Roger Mittag taught us the basics of sensory evaluation of beer: the language of description, how the ingredients smell and taste, beer defects, and the various styles of beer. Now Mark would like to delve deeper, especially into sensory evaluation as quality control, using formal tasting panels, both expert and consumer for various purposes. We will also discover the different perception level for each defect that each of us has, and analyze what parts of the brewing system are contributing to the defects.

After an hour for lunch it was back with Mark for 4 straight hours. First, 2 hours of Chemistry. Obviously we’ll be concentrating on brewing chemistry, but Mark first took us over some common lab practices. This included

  • Significant figures in observations. If I am reading a column of water in a 10-millilitre graduated cylinder, and the water level is a little more than halfway between the markings for 5 and 6 mL, I might write down a value of 5.6 mL. In this case, the value of 5 mL is clearly accurate, since the water was above the 5 mL line, but the value of .6 is an approximation. So, the second-last figure in an observation is accurate; the final figure is a guess.
  • Observations have to agree in their degree of precision. Given that the final figure is a guess, if I make several observations with various instruments that have varying degrees of precision, and I have to combine those readings mathematically, the precision of all the readings has to be reduced to the level of the least precise reading. So if I take readings from three different instruments of 1.22, 5.1 and 6.311, and then have to add them together, the calculator would give the answer as 12.631. However, all the readings can only be as precise as the least precise reading–the one with the single decimal place–so the answer with the correct degree of precision is 1.2 + 5.1 + 6.3 = 12.6)
  • The difference between accuracy and precision during lab work. Using the analogy of a bullseye, where the very centre of the inner circle is the result we are striving for in an experiment, five experimental observations that are all in an outer ring but are clustered close together show a high degree of precision in our experimental method, but no accuracy–in other words, we are making a mistake in our experiment, but our work is very precise. Five observations that are all in the centre area but not near each other show a high degree of accuracy, but not of precision–we are achieving close to correct results, but our experimental method varies a bit with each iteration. Five results that are clustered very close together at the centre show both accuracy and precision, and of course five results that are all over the rings would demonstrate both inaccuracy and imprecision.
  • Reproducibility of results. We need to be able to accurately describe what we did, what we did it with, why we did it and what our results were so that the results can be closely reproduced at another lab. (Important in a brewery that is striving to produce the same beer at different locations.)

That being the end of the first Chemistry lecture, we would seem to be ready for our first Chemistry lab next week.

Mark then took off his Chemistry hat and put on his Microbiology hat. What are microbes? What effects do they have–good and bad–on brewing? What do we mean by aerobic, anaerobic and facultative anaerobic? Some cells–algae, for instance–can directly use energy; others eat inorganic substances for energy; most–like yeast–require a variety of organic compounds for energy. Some microbes are dangerous pathogens, some are not. Some have their innards neatly parcelled up into discrete parts (eukaryotes), while others just have all the innards jumbled together (prokaryotes). What can contaminate wort? And what makes wort a hostile environment for most pathogens?

Many in the class seemed to already know a fair bit of the biology, as well as cellular structures, the benefit of taking Biology in high school. I, on the other hand, eschewed the dissection of fetal pigs in favour of Chemistry and  Physics; I sense some follow-up reading will be necessary before the first Microbiology lab next week.

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