What is the most essential instrument in the brewery laboratory? A pH meter is high on the list but a microscope should be first considering its value in checking routine beers and solving brewing problems.

Ideally we are looking at a compound microscope. Not a toy plastic one from a gift shop but a real solid body instrument with finely calibrated movements, internal light source and high-quality lenses. In some senses it is still a toy but certainly one with purpose and providing added value to your future operations.

Microscopes have reduced in cost considerably in the past 20 years and good quality makes are now available for a few hundreds of pounds compared to thousands in the past. This has inevitably reduced second hand prices so giving a much more accessible range of options for the busy brewer. At the other extreme computer connections are now relatively inexpensive to couple a camera so you can display and capture images for future comparison.

In selecting your instrument consider the following options:

• Do I want strained eyes and headaches after peering into the lenses? If not then choose binocular eyepieces so you can comfortably search around the field of view and not squint over your assessment.

• Do I want poor and varied illumination from a distant bulb or window so making images indistinct resulting also in strained eyes and headaches? If not then select a built-in bulb automatically focused into the light path.

• Do I want poor quality resolution making it hard to distinguish between yeast and bacteria and between bacteria and background clutter? If not choose good quality achromatic lenses with limited aberration. A times 40 objective and times 10 eyepiece will provide the 400 times magnification needed to distinguish both yeast and bacteria. Other lenses may be useful to view barley or hop materials but a single 40 times objective will do most of your heavy work.

• Do I want a high-resolution image to ensure that you can identify protein haze material from bacterial contamination in a reject sample? If so ensure that the microscope has an under-stage condenser. Some cheap instruments have a simple ring of holes to limit the light level reaching the sample. This option is poor economy. A focusable condenser is important to give the required quality of light and highest resolution.

• Do I want slides to fall off the stage or skim widely out of position when trying to locate a sample? If not choose a mechanical stage. Moving slides with your hand requires very fine control – not easy if you have just shovelled a ton of spent grain. A screw ratchet with suitable gearing provides easy movement and accurate positioning. Storing and maintaining your instrument are simple but important considerations. Leaving a microscope exposed to moist air, steam and dust will inevitably encourage corrosion leading to poor movement of parts, lens aberrations and confused images. Avoiding these conditions in a brewery is difficult so it may be necessary to locate your microscope in part of the general office, construct a small laboratory or use it at home in a last resort.

The tracking rods and gears of the various movements on a microscope are particularly sensitive to dust which will embed in the lubricating oil and act to wear away the finely tuned mechanisms. Eventually the focus system will run through its movements under gravity so preventing you obtaining a stable image. The stage movements will slacken making positioning difficult and the condenser lens will slide from position to give poor illumination.

These difficulties may already be present in a second-hand instrument so check before you buy particularly if the microscope is standing on an open shelf in a second hand shop. Ideally store your microscope under a plastic cover or in a wooden box and handle with care to avoid jarring the lenses and knocking out of focus. They are also heavy items to drop on your foot.

Additional extras to consider are a computer connection so you can record your images and incorporate into your quality assurance scheme. Useful options to consider are programmes which automatically count cells and provide measurements of sizes and aspect ratios – length / width.

Even more extensive analysis is possible if your budget stretches to a florescence system whereby you can stain cells for specific components – but cost does escalate with these options.

Using your microscope requires a few accessories particularly slides, cover slips, pipettes and stains. A haemocytometer to allow cell counting and viability assessments is essential for day to day use. A 5% solution of sodium hydroxide is also useful to test samples for protein haze which dissolves in strong alkali. All these are relatively cheap and can be bought in bulk to ensure you don’t run out at a critical moment.

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