Winemaker’s Bookshelf


Somemicroscopic answers to the question: ‘What are those lumps in the bottomofmy wine glass?’


S


ooner or later, all winemakers experience the “joy” of finding sediment in a bottled wine. Some, such as wine diamonds (potassium bitartrate) are easily identified, are a common occurrence, and cause little concern. Others, which are accompanied by a spritzy palate, can be disastrous for the batch.


Then there is a wide range of things that cause haze in the night. These are the marginal things where you aren’t quite sure what went wrong. Is it cardboard dust that remained in the bottles because they weren’t sparged before filling? Is it unstable protein that didn’t precipitate during fining? Did your filter develop too much pressure drop and rupture part way through the run?


Now there’s a book to help you track down the cause of sediments. All you require is a microscope and a copy of Charlie Edwards’ book, Illustrated Guide to Microbes and Sediments in Wine, Beer and Juice. ISBN: 0- 9772522-0-5.


The book is essentially an atlas of wine sediments, with captions in Chinese, French, German, Italian, Spanish, and English. The languages reflect the international nature of winemaking and the universality of its problems.


Many wine sediments can be identified with a wet mount specimen at, say, 400 diameters magnification with brightfield microscopy. Bacteria, fixed with a gram stain, are viewed more easily at 1,000 diameters with an oil immersion lens.


With phase contrast microscopy, slides can be viewed at up to 1,000 diameters with a wet mount. Edwards also illustrates colony morphology of a wide range of pure culture bacteria and yeasts on various agar media. Most of his examples have been drawn from the American Type Culture Collection and are identified by their ATCC number. Others have been drawn from


British Columbia FRUIT GROWER • Fall 2011


By Gary Strachan Travel guide for a sedimental journey


the UC Davis collection or from the author’s collection. Edwards


photographed a wide range of sediments,


ranging from the ubiquitous


bitartrate crystals,


cardboard box residues, cork pieces, and diatomaceous earth, to oak dust. I would have liked to


slides. I liked the inclusion of a mixed culture slide, because this is typically the way sediments occur. I would have liked to have seen more slides with mixed


sediments of various species


plus wine sediments typically seen in tank or barrel samples. The question of what to do next after you find the sediment is another story.


GARY STRACHAN


Sporulating wine yeast, Saccharomyces cerevisiae. Yeast spores in tetrads are stained green with Malachite Green. Vegetative cells are counterstained red with Safranin.


have seen some of the typical phenolic complexes of red wine, and perhaps some of the mixed sediments that occur in unfiltered wines.


The guide is a good introduction to wine microscopy, but those who have not taken microbiology may find the instructions lacking in detail, especially in the preparation of media and stained


Microbiology on a shoestring is quite possible. Edwards has given the formulations of most common media. They can be prepared on a kitchen stove and sterilized in a household pressure cooker for 15 minutes after the pressure cooker has reached temperature. Even simpler is to purchase pre-poured plates. Inoculating loops can be purchased to inoculate the plates or spread slides. A Bunsen burner can be improvised from a propane torch. Many digital cameras can capture the image from the eye piece of a microscope by simply prefocusing the microscope and then holding the camera lens next to the eye piece. I know it’s kind of hokey, but it works.


— Gary Strachan is on LinkedIn.


Since the beginning of BC Wines, Flory Bosa has devoted her talents to ensuring the best supplies for her customers. Flory joined the industry in 1989, and worked with the BC Amateur Winemaker Association. Today she serves the needs of small, medium and large wineries. If you want to get the best from your grapes, come to Bosa. Where wine, and winemakers, matter.


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