Technical Papers
Here you can purchase technical papers I have authored on very specific, advanced topics. The contents are based on my knowledge of winemaking and extensive literature research over the years, and my own experience in making wine commercially and as an amateur as well as from analyzing wine in my laboratory. There are many, many references cited to support the content and for further reading.
These 3-5 pages papers are for those interested in furthering their knowledge on advanced wine chemistry, the application and use of specialized instrumentation, wine microbiology, and many more topics — topics which you will not find in any of my books or other publications.
Cost is US$9.95 per paper.
PLEASE READ CAREFULLY.
You can only purchase one paper at a time. Once your payment has been processed, you will be provided with a link to a page to view the paper. You will also receive a confirmation email with the link. A paper can only be viewed in your browser, and this for a period of one (1) month, after which time access expires. Papers cannot be downloaded.
Saccharomyces Yeast in Winemaking – Part I
Date of Publication: coming soon
The role of Saccharomyces cerevisiae yeast in winemaking goes well beyond just converting fermentable sugars into ethanol—and vast amounts of carbon dioxide (CO2) gas in the process. S. cerevisiae yeast’s complex metabolic engine uses a whole host of specialized enzymes in transforming not only sugars but various other substrates into a plethora of compounds that give wines their wonderful aroma and flavors, all the while performing under stressful conditions in an increasingly hostile environment of high-osmotic pressure from high sugar concentration and of increasing alcohol.
This paper describes the metabolism of various classes of compounds of S. cerevisiae yeast, the major intermediates involved, and metabolites secreted into the wine medium, and how aroma and flavor compound are created and transformed.
Saccharomyces Yeast in Winemaking – Part II
Date of Publication: coming soon
This paper discusses the many growth, stress and survival factors in Saccharomyces yeast in winemaking. Specific topics include: fermentation temperature, osmotic stress, oxygen needs and oxidative stress, nutrient availability, minerals, acidity and pH, SO2, killer systems, competition with other microorganisms, mechanical and hydrostatic, and many more.
Measuring and Managing Residual Sugars in Wine
Date of Publication: March 9, 2024
Residual sugars, either remaining after completion of the alcoholic fermentation or from any addition of sweetening sugars, can referment spontaneously under favorable conditions if wine is not properly stabilized with preservatives or by sterile filtration. Refermentation risk can be assessed by measuring the amount of residual, potentially fermentable sugars. Although hydrometers are used to assess completion of fermentation, they cannot be used to measure or estimate residual sugars. And inexpensive methods, such as the Rebelein Method, commonly used by winemakers, measure fermentable and non-fermentable reducing sugars, that is, those that act as reducing agents (e.g., glucose and fructose), but do not measure non-reducing sugars, such as sucrose. Measurements using these methods require making some assumptions to estimate the real amount of fermentable sugars remaining. More advanced enzymatic, HPLC, and voltammetric techniques and instrumentation are used in wine analysis laboratories to measure glucose and fructose concentrations to confidently confirm end of fermentation and microbial stability.
Color and Tannin Analysis in Red Wine
Date of Publication: January 30, 2024
Color and tannins have significant impacts on quality and appreciation of red wine. By routinely measuring color and tannins, winemakers are able to better understand and assess the impacts of processing techniques and the evolution of their wines during cellaring and aging. Color and tannins can be quantified using a spectrophotometer capable of measuring wavelength absorbances in the visible (VIS) and ultraviolet (UV) ranges of the electromagnetic spectrum. Their quantification also allows winemakers to objectively describe color and degree of bitterness and astringency more accurately.
Turbidity: A Process Control Parameter for Improving Winemaking and Wine Quality
Date of Publication: January 27, 2024
A wine’s clarity, or limpidity, is an important quality control parameter but which is often only assessed by visual inspection. And perfectly clear wine can suddenly and unexpectedly develop a haze and become cloudy, especially under storage conditions of increasing temperatures, a phenomenon due to the instability of proteins. Analytical tests to assess protein (heat) stability only provide qualitative results. Winemaking processes and quality can be greatly improved by monitoring and controlling turbidity with an easy-to-use turbidimeter. This process control parameter can be used to improve fermentation kinetics, to assess protein stability and determine more accurately the amount of fining agent needed to treat proteins, to select a most suitable grade of filter medium, and to assess bottling readiness.
Redox Potential: Principles and Applications in Red Wine Fermentation
Date of Publication: January 16, 2024
Punchdowns, pump-overs, and other traditional techniques of aerating red wine ferments are used to polymerize phenols to enhance mouthfeel and stabilize color, and to mitigate the production of foul-smelling, reductive volatile sulfur compounds, such as hydrogen sulfide, which can otherwise compromise wine quality. These winemaking techniques are seldom practiced in controlled, rigorous fashion, and their benefits are short-lived, leading to varied, inconsistent results, and winemakers often faced with having to deal with reductive aromas. Oxidation–reduction potential (ORP) is an emerging control process parameter to improve fermentation kinetics while minimizing—or eliminating—the risk of reductive aromas. Specialized platinum sensors can be used to monitor fermentation and control the injection of air or oxygen repeatedly as needed to keep fermenting wine above a pre-programmed threshold, away from the reductive danger zone.