Big QC Day results are in! (scroll below)
What is Big QC Day?: Each participating brewery submitted two beers, and each beer was put under various tests discussed below.
Why: Big QC Day was the first large-scale, independent testing of craft beer. Brewers learned about their beers and quality control issues at an affordable costs. The tests provided a picture of the status of craft beer in general. Breweries can compare their tests against the overall results of the test group.
What's next: Stay tuned for details about the next Big QC Day. Also, this site will continue to be updated with data. Plans include publishing charts comparing tests results for specific beer styles.
What's new: Results are in, read below.
FAQ: Click here for frequently asked questions about Big QC Day.

Thanks to all who participated in the first big QC Day. Results have been sent to all participating brewers. One of the advantages of participating in Big QC Day - besides learning about your beers as well as quality control issues - is that you can compare your beers against the other participating breweries. Each brewery sent in two beers and each beer was put through a variety of tests described below. The following results are for the group as a whole. Individual results are confidential. 

Scroll below for specific tests or follow these jumps: aerobic bacteria, alcohol, anaerobic bacteria, color, density, IBUs, Real Extract, total VDK, wild yeast, microbiological analysis overall, microbiological analysis by test.

Below: Aerobic bacteria

This test was used with Wallersteins Differential, or WLD, medium. This medium is used to check for bacteria and some non Saccharommyces-type wild yeast. Most aerobic bacteria will grow on these plates, and some anaerobic bacteria also display growth. Bacterial contamination seen on these plates is termed "wort bacteria" because they are most often associated with wort contamination, usually causing most of their damage before the onset of fermentation. As for the numbers, the same applies to aerobic bacteria as in the paragraph above about lactic acid bacteria, or anaerobic bacteria. Sometimes aerobic bacteria are already dead by the time this test is performed, after fermentation and packaging, but they could have contributed to off flavors.

Below: Alcohol

We are using a gas chromatograph machine for measuring alcohol. The detector we use is a Flame Ionization Detector (FID). Results are reported as % vol/vol. The GC method is more accurate than most other methods.

Below: Anaerobic bacteria

Anaerobic bacteria: Lactic acid bacteria (or anaerobic bacteria): This test was conducted using Hsu’s Lactobacillus medium, or HLP. This medium is used to look for the presence of Lactobacillus and Pediococcus. These bacteria are anaerobic, heat sensitive bacteria. They are called "beer spoilers" because they are most often associated with post wort production contamination. The industry standard is less than 10 colony forming units (CFUs) per ml. If it is over 10, the beer may develop flavor problems. However, any CFUs found from this test should cause concern and an evaluation of your brewing and packaging process.

Below: Color

Color: A spectrophotometer is used to measure the absorbance of a sample at a certain wavelength. The sample is separated from solids, and the absorbance at a wavelength 430 nm is measured. The number will show how light or dark the beer is. It can vary between 2 Lovibond to 100 Lovibond. A stout obviously would be high because it is dark.

Below: Density

Density: This is the specific gravity of the beer. Values depend on styles. We use an Anton Parr density meter (not a hydrometer) for this test, which gives us a higher degree of accuracy.

Below: IBUs

IBUs: The IBU scale provides a measure of the hop derived bitterness of beer. The higher number, the greater the bitterness. Porters range between 20 to 40, for instance, while India Pale Ales are 40 or higher. The American Society of Brewing Chemists International Method, bitterness units, is used. Iso-alpha acids are chemically extracted using the organic solvent iso-octane. The ultraviolet light absorbance is measured in a precision spectrophotometer, and the results are reported in bitterness units.

Below: Real Extract

Real Extract: This test shows you the sugars that are left in beer, usually non-fermentable carbohydrates. Real extract involves accounting for the alcohol, which we were able to do since we measured alcohol in the samples. Alcohol has less density than water, so if you measure straight density it does not account for the subtraction of alcohol. Results are reported in Plato.

Below: Total VDK (including diacetyl)

Total VDK (including diacetyl): VDK (vicinal diketones) consists of diacetyl and 2,3-Pentanedione. The test includes heating the sample, which drives diacetyl precursors to diacetyl. The lower the number the better, in most cases. If you are under 100 ppb you are doing well. The numbers vary depending on the yeast strain and fermentation procedure. If the number is high, perhaps in the 200 range, the brewery may not be performing an adequate diacetyl rest. Or again, it could be the yeast strain. Examples of strains with higher VDKs are the British strains and some lagers. Very high VDK levels can be an indication of contamination. Additional tests can be performed that can separate diacetyl and 2,3-Pentanedione levels.

Below: Wild yeast

Wild yeast: This test was conducted using Lin’s Cupric Sulfate, or LCSM. This medium uses cupric sulfate to inhibit the growth of brewers yeast. This medium ensures no contamination of non-Saccharomyces wild yeast. Again, the information concerning numbers is the same for wild yeast as the contaminants listed above under anaerobic and aerobic bacteria. In other words, under 10 meets the industry standard, 10 or more indicates problems. Typical off flavors produced by wild yeast would be phenolic and band-aid flavors.

Below: Microbiological testing overall

Microbiological testing overall: The above graphic show what percentage of beers tested had any level of bacteria contamination. The tests showed 80 percent of the the beer was bacteria-free. For those breweries that did have bacteria in their beer, White Labs suggests increasing quality control efforts and testing.

Below: Microbiological testing overall - by test

Look for the next test - most likely to be held in February 2008. Details will be released in the near future.