Craft Beer Yeast Handling (2/3) - Biological Sampling

There are several areas of minimum sampling to identify beer spoilage organisms. The main goal is to evaluate cleaning procedures and update methods to remove contaminants.

Table 1 - Proposed Sampling Procedure

• Forced Wort Test

A forced wort test is a determination of the cleanliness of the wort chiller. If the wort chiller has been appropriately maintained and cleaned to the proper degree, there should be no growth in a sample that has no inoculate.

• Materials

• Sample Port
• Isopropyl Alcohol
• Butane Torch
• Sterile Sampling Container

• Method

• Thoroughly clean hands and forearms; apply gloves and personal protection equipment.
• During wort transfer to the cellar, prepare materials.
• Apply isopropyl alcohol to sampling port and sterilize with the butane torch.
• Collect a sample in the sterile container.
• Leave the container in an isolated warm location.
• Inspect for haze formation (Jones, 2018).

Table 2 - FWT Haze Results (Jones, 2018)

• Clean-In-Place Swab Test

A cleaning verification method is a swab test; it can identify growth not removed by clean-in-place or clean-out-place procedures. Sampling areas that encounter beer will ensure a stable product. Several example areas are fermenter connections, hard-piping ports, the wort chiller, or any filters.

• Materials

• Dry or wet swabs
• Sterile saline
• Sterile wort samples, 10mL in transport tubes.
• Incubator
• Microscope with slides
• Gram Stain Reagents

• Method

• Thoroughly clean hands and forearms; apply gloves and personal protection equipment.
• With dry swabs, remove the packaging and apply sterile saline. With wet swabs, remove from container ensuring no contact with the container rim.
• With a substantial amount of pressure apply the swab to an area less than 10cm2.
• Place swab in wort sample and enclose.
• Incubate the sample at 30°C for three days and monitor for growth.
• If growth occurs, prepare for gram staining and mount to a wet slide (Manufacturing.net, 2014).

• Hsu's Lactobacillus Pediococcus (HLP) Test

HLP media detects Lactobacillus and Pediococcus and designed to simplify procedures. It is a low-cost preparation that contains the yeast inhibitor Actidione and an oxygen scavenger. It is semi-solid and semi-aerobic.

• Materials

• HLP Media
• Water Bath
• Erlenmeyer Flask
• Sterile test tubes
• Pipettes
• Incubator
• Microscope with slides
• Gram Stain Reagents

• Method

• Prepare HLP media as per package instructions in an Erlenmeyer Flask. Heat gently until homogeneous.
• Seal and store at 45°C in the water bath.
• Transfer 15mL of media into test tubes. Media must be above 25°C for use.
• Gather 1mL of beer sample and pipette into the media, disperse across the media.
• Seal and incubate at 28-30°C for 48-72h. Check for growth.
• If growth occurs, prepare for gram staining and mount to a wet slide (Pellettieri, 2015).

• Rapid Methods
  • ATP Bioluminescence

A swab method that uses light to detect biological activity but cannot identify the organisms present. A sample is collected and inserted into a monitor giving near-instantaneous results. The reaction involves ATP from the microorganisms reacting with Luciferin and oxidizing to produce bioluminescence which is measured. ATP bioluminescence provides a quick pass/fail analysis of cleaning procedures and can be used to prior to disinfecting or for ensuring the equipment is safe for beer (Bolton and Quain, 2013).  

Craft Beer Yeast Handling (1/3) - Types of Brewery Organisms 

Craft Beer Yeast Handling (2/3) - Biological Sampling 

Craft Beer Yeast Handling (3/3) - Pilot Batch Propagation 

References

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Manufacturing.net. 2014. How to Swab For Bacterial Contamination in Your Brewery. [online] Available at: https://www.manufacturing.net/operations/blog/13190255/how-to-swab-for-bacterial-contamination-in-your-brewery [Accessed 16 Nov. 2019].

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