The image shows an important test required to produce high quality, stable white and Rosé wines.
All wines contain proteins which have a tendency to precipitate out with storage producing a hazy appearance. While not noticeable in red wine, to many consumers a haze is aesthetically unacceptable in white or Rosé wines.
To remove these proteins (and potential haze), one can add a powdered clay called Bentonite to the wine before it is bottled. The charged clay particles attract the oppositely charged protein molecules which “fall out” and settle to the bottom of the tank.
This benefits the appearance of the wine but, like all good things, there is a downside, namely the removal by the Bentonite of important aroma and flavour compounds. Hence, the dose of Bentonite needs to be kept to a minimum.
Back to our photograph: each bottle contains 100 mL of either Sauvignon Blanc or Rosé plus Bentonite added in incremental doses from zero to more than 2 grams per litre. After a day or two of settling, a small volume is withdrawn from the top of each bottle, filtered and transferred into a test tube. These tubes are then subjected to severe heat stress; 80 degrees Celsius for 6 hours. Normally, one would do this in the laboratory using a thermostatically controlled water bath designed for the purpose. However, Lindsay’s purpose design is a large frypan of water on the stovetop with himself acting as the thermostat, adjusting the stove setting and water level every 10 to 15 minutes. Not great fun really – especially when he has a dinner party underway and has to excuse himself regularly, much to the chagrin of his charming co-host and wife and his bemused guests!
After 6 hours of heating and, hopefully, the departure of the guests, the tubes are cooled and observed under a bright light The samples from the bottles with zero or the lowest doses of Bentonite will be cloudy due to the persistence of wine proteins. Along the line of tubes (representing increasing doses of Bentonite,) one should see a progressive reduction in the degree of haze until, ultimately, a tube with no haze. That tube tells us the exact Bentonite dose that we need to add to the wine in our tank to ensure a haze free, stable wine after bottling.