Brewer Quality Control & Testing Flashcards

Which microorganism is most commonly responsible for 'ropy' or 'sick' beer characterized by an unpleasant sliminess?

Answer: Pediococcus damnosus producing exopolysaccharides

Pediococcus damnosus produces beta-glucan exopolysaccharides that cause beer to become ropy or viscous — a spoilage condition called 'sick beer' that can recover with continued conditioning.

When should a TTT (Time-Temperature-Turbidity) test be performed in the brewing process?

Answer: To evaluate chill-haze formation potential in finished beer at cold temperatures

The TTT test chills beer samples to near freezing and measures turbidity development over time, predicting the beer's susceptibility to chill haze in retail cold storage.

What is the function of PVPP (Polyvinylpolypyrrolidone) in beer production?

Answer: Adsorbing polyphenols to improve colloidal stability and prevent haze

PVPP selectively adsorbs polyphenols (tannins) responsible for protein-polyphenol haze formation, improving colloidal stability and extending shelf life clarity.

A master brewer is investigating high foam stability complaints in a finished lager. Which compound would most likely be contributing to excessive foam retention?

Answer: Lipid transfer proteins (LTP1) and glycoproteins from malt

LTP1 and other foam-positive proteins from malt form stable foam structures — while usually desirable, excessive levels from high-protein malt or certain conditions can create overly persistent foam.

Which on-site rapid test kit is commonly used by brewers for detecting Lactobacillus and Pediococcus contamination in 24–48 hours?

Answer: Iso-sensitest broth with actidione and nalidixic acid (selective medium)

Selective broths containing actidione (cycloheximide to suppress yeast) and nalidixic acid (to suppress gram-negatives) allow rapid detection of lactic acid bacteria in brewery samples.

What does the term 'apparent extract' (AE) refer to in brewery analysis?

Answer: The gravity reading of beer measured directly without removing alcohol

Apparent extract is the direct refractometer or hydrometer reading of beer including alcohol, which artificially lowers the reading — real extract is calculated by correcting for the alcohol's low density.

A QC manager establishes a control chart for monitoring dissolved oxygen at packaging over 30 days. A sudden shift of 8 consecutive data points above the mean (but within control limits) indicates what?

Answer: A special cause variation suggesting a systematic process change

The 'run of 8' rule in statistical process control (SPC) signals a non-random pattern indicating a systematic shift — even within control limits, this warrants investigation of a process change.