Big QC Day #2

Read below for results 
(Come back soon for a breakdown by region)

The most comprehensive and economical way to test beer, QC Day allowed brewers to send in two or more beers, each of which were tested for such factors as IBUs and total VDK. Breweries can compare their results to others, including by style and region. By conducting the tests in a concentrated time and for many breweries at one time, each customer saved nearly $400.

Big QC Day, which began in 2007, is the only large-scale, independent testing of craft beer. Brewers learn about their beers and quality control issues at an affordable costs. The tests provided a picture of the status of craft beer in general.

As in the past tests, Big QC Day 2008 involved the following tests, among others: aerobic bacteria, alcohol, anaerobic bacteria, color, density, IBUs, Real Extract, total VDK, wild yeast, microbiological analysis overall, microbiological analysis by test.

New for 2008: Calories per 12 oz, pH, and real and apparent attenuation.

2008 Results

Below: Aerobic bacteria

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. Positive aerobic bacteria results can be from sample collection, follow up tests are usually done to confirm contamination of product.

Below: Alcohol

Alcohol: We use an Anton Paar Density Meter DMA 4500 and Alcolyzer Plus. Results are reported as percent vol/vol. 

Below: Lactic acid bacteria (or 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 the IBU value, 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 is measured on our Perkin Elmer Clarus 500 Gas Chromatograph and Headspace Sampler. VDK (vicinal diketones) consists of diacetyl and 2,3-Pentanedione. The test includes heating the sample, which drives diacetyl precurses 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 Brit ish strains and some lager strains. 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 84 percent of the the beer was bacteria-free (up from 80 percent in Big QC Day #1). 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

Below: Calories

Calories: Calories are calculated from the data and reported as cal per 12 oz serving of beer.

Below: pH

pH: The pH of beer is an important indicator of quality and consistency. A high pH can result in flavor problems and make the beer more prone to contamination. We use a pH probe to measure the pH of each beer. Typical pH values are 4.2 to 4.6.

Below: Apparent attenuation

Apparent attenuation: Attenuation is expressed as a percentage of the difference between the original and final gravities of the beer. Apparent attenuation is before accounting for ethanol, which has less density than water.  Attenuation will vary by beer and yeast strain, typical ranges for apparent attenuation are 65-90%. We include apparent attenuation and apparent extract in your results so you can compare in house brewery data.

Below: Real attenuation

Real attenuation: Attenuation is expressed as a percentage of the difference between the original and final gravities of the beer. Real attenuation accounts for ethanol, which has less density than water. Attenuation will vary by beer and yeast strain, typical ranges for real attenuation are 65-80%.