T. Henick-Kling and B.K. Gavitt
Department of Food Science and Technology
New York State Agricultural Experiment Station, Cornell University, Geneva, NY
The Wine Analytical Laboratory and Data Bank were implemented to create a structure for technical assistance and quality assurance for New York State wineries.
Participation by New York Wineries
This year, 48 wineries took advantage of the sample analysis and consultation program. We thank them for their support. In addition to New York State, we have had samples this year from 5 other states, which paid for analyses at the full price.
The total numbers of samples received 1 January 1996-31 December 1996 was 424. This is a 28% increase over last year, and also a record for the wine lab since it started in 1988. On the 424 samples submitted, we carried out 2,336 separate analyses.
A very important part of the wine lab's work is consultation by telephone on which we spend about 12 hours per week.
In several cases, our help with analyses and advice was of great economic benefit to the winery. We were able to return some unstable, defective wines into good quality products of high value.
The lab was also able to assist with the development of new products such as ver jus, hard apple cider, and grape seed oil.
T. Henick-Kling, C. M. Egli, C. Mitrakul and W. Edinger
Department of Food Science and Technology
New York State Agricultural Experiment Station, Cornell University, Geneva, NY
Our recent work on the fermentation performance and flavor effects of yeasts represents a fundamental re-examination of the winemaker's ability to control and direct the course of wine production and the character of the wine produced. It has generated a great deal of interest from other researchers and wine producers.
Experimental fermentations with different yeast starter cultures and grape juice treatments followed by sensory analysis of the wines have begun to provide answers to the questions that are the basis for this work: 1) how well inoculated yeasts do become instablished in a grape must; 2) what is the contribution of inoculated Saccharomyces yeasts and various indigenous non-Saccharomyces yeasts to the final wine flavor; and 3) how do we control and direct the fermentation to produce the flavor profiles we want for each wine style?
By using DNA karyotyping and Polymerase Chain Reaction, we have been able to identify the Saccharomyces yeasts present at different points of the fermentation and determine the dominance of particular strains. Our results have shown that while some commercial strains, such as EC 1118 (EC), inhibit the growth of other yeasts and are able to dominate throughout the fermentation, other yeasts show a range of vigor, including the new commercial strain Assmannshausen (AMH). This strain's much slower growth rate allows growth of a wide range of other yeasts (Fig. 1) which can dominate either adding positively to the wine or producing undesired aromas.
As an example, the sensory influence of two inoculated and an uninoculated fermentation using the same Riesling grape juice is shown (Fig. 2). Identification of the isolated strains is currently being completed, and identification and isolation of their specific flavor contributions are in the planning stages. During the 1996 crush, we distributed a number of different yeasts to winemakers in the Finger Lakes Region to compare the performance of these yeasts in a commercial setting with our laboratory results. Results from these trials will contribute significantly to our understanding of how different yeast populations affect the final product. Samples of the wines produced will be presented at the 1997 New York Wine Industry Workshop.
Fig. 1: Growth of yeasts during fermentation of
Riesling grape juices. Saccharomyces yeasts: white
circles; non-Saccharomyces yeasts: black squares.
Fig. 2: Sensory attributions of yeasts in a Riesling wine.