Vintner's Corner

Vol.16, No. 4 July - August, 2001


Bruce W. Zoecklein

Department of Food Science and Technology

VPI & SU - 0418

Blacksburg, VA 24061


Web site:

Table of Contents

I. Formulating a HACCP-like Plan 1

II. Regulatory Issues and Winery Tax Reporting Seminar 4

III. Student Achievements 4

IV. American Society for Enology & Viticulture 4

V. Winery Planning and Design Workshop Proceedings 5

VI. Enology Notes 5


I. Formulating a HACCP-like Plan

Formulating a HACCP-like Plan. In several previous editions of the Vintner's Corner I have discussed the importance of establishing a viticultural and enological HACCP-like (hazard analysis critical control point) plan. Such plans are designed to help assure that you reach and maintain your quality and stylistic goals. A unique feature about the wine industry is that each winery, regardless of size, is a specialized operation with different varietal, production practices and philosophies. Therefore, each winery must establish its own plan. The following, in outline form, are some questions and thoughts to aid in establishing a red wine HACCP-like plan. In some cases topics have been elaborated either in my newsjoural, the Vintner's Corner (VC) or my electronic Enology Notes (EN). Both are available on my web site at (HACCP-like plans VC 12:6,15:1, 15:2, EN#8, EN #19).

Key questions in regard to red wine quality include the following (VC 14:5). What are the key natural processes that effect the formation and accumulation of aroma/flavor and phenols in fruit? What vineyard management tools are available to influence aroma/flavor and phenols? What are the key natural processes that affect vineyard management tools in the wine and their modification during processing? How can we monitor the quantitative and qualitative changes in aroma/flavor and phenols in the fruit and the wine? What are appropriate concentrations and proportions of aroma/flavor and phenols for specific wine styles?

Red Wine Style (VC, 11:4,12:2, 14:1 EN#4). Style and textural quality are influenced by quantity and quality of phenols, phenol maturity, extraction/management and interaction with other structural elements (acids, polysaccharides, peptides, and sugars).

Vine Nutrition (VC 12:1). Does vine nutrition influence your wine style? How are you monitoring nutritional status of your vineyard, vineyard blocks?

Training and Trellising. How does your training and trellising system influence your wine style?

Canopy Management (VC 12:1, 14:1). What is the influence of your canopy management on your wine? What is the optimum degree of fruit shading? What is the optimum degree of leaf shading?

What are the effects of light and temperature on aroma/flavor and phenols in a warm climate? With dense, shaded canopies, metabolism of both aroma/flavor compounds and anthocyanins are reduced due to low light. Aroma/flavor and anthocyanin production is low. Qualitative effects on aroma/flavor result in unripe, green and herbaceous 'notes' which dominate the resultant wine. With moderately open canopies, metabolism of both aroma/flavor compounds and anthocyanins is maximized. The aroma/flavor profiles tend toward the riper end of the spectrum. With very open canopies, high berry temperatures may result in overripe and/or undesirable aroma/flavor and less color formation. Completely open canopies favor the production of phenols which can add harshness to wines. Opening canopies too many days following bloom can result in sunburning and the significant loss of desirable aroma/flavor and color.

What is the influence of asymmetric vine, cluster and/or berry ripening?

What is the influence of row orientation? Should both sides of the canopy be managed the same way?

Defining Optimum Crop Load (VC 12:1, 15:5).

Are your vines balanced? How are you determining optimum crop load? Do you understand the detriment of too much and too little crop?

Fruit Ripeness Indicators (VC 11:4,12:1,12:5, 12:6, 16:1).

Are you using maturity indices which will allow you to attain your stylistic goals? Your indicators should correlate to aroma/flavor and phenol suppleness.

Are you using adequate fruit sampling methods?

What is the degree of asymmetric ripening: clusters, berries? Sugars are usually fairly uniform (small coefficient of variance, secondary metabolites can be much greater).

Are you using sensory evaluation of skin, stem, pulp and seed phenol maturity?

Are you using seed maturity-color, texture and brittleness as a ripening index?

Are you evaluating crushing ability, berry softness?

What is the relationship between berry weight, shriveling and engustment (the increase in varietal aroma at the end of the season)?

What is the relationship between berry weight and physiological maturity?

Are you using an estimation of berry size/weight to help make stylistic winemaking decisions? (EN#23)

Do you understand the relationship between sugar per berry and Brix?

What is the relationship between days post-bloom and fruit maturity?

Do you understand that Brix level is usually not strongly correlated to wine quality in a warm growing region like Virginia(EN#6)? Brix and aroma/flavor, phenol development are not the same.

Changes in pH are not necessarily a function of berry 'age' and relate to levels at K+ and vigor.

Do you know the Brix to alcohol conversion rate for your vineyard and the importance of the alcohol content to the structural balance of wine?

Do you understand the relationships between phenol maturity, TA and potential structural balance?

Harvest Methods.

Hand vs mechanical: is there a difference in wine quality?

Processing (VC 14:1).

Are your processing methods vineyard driven?

Are your processing methods goal driven? Those goals should include integration and balance of structural elements, conversion of monomeric anthocyanins to large polymeric anthocyanins, integration of methods that reduce the level of ethanol soluble hard tannings that are extracted.

De-stemming/crushing/whole cluster press.

When planning maceration, know the extent of mechanical resistance from various parts of the fruit.

Understand the importance of gentle fruit handling, the role of low non-soluble solids to wine integration.

Understand the relationships between the degree of berry breakage and your stylistic goals.

Cap Management Procedures

Is cold soak consistent with your stylistic goals(VC 13:2)? It enhances 'bright fruit' character, increases color stability. Variables include time/temperature, with or without enzymes, sulfur dioxide and oxygen.

Is bleeding and /co-fermenting consistent with your goals(EN#3)? How are these judgments made? Juice that has been bled has a lower arginine/proline ratio which will influence fermentation. Bleeding also increases the pH evolution of the must.

Fermentation (VC 14:2, 14:4, 15:4).

What is the Brix to alcohol conversion rate? Is chaptalization desirable?

What are the relationships among alcohol, TA, tartaric/malic, pH, phenols and the potential wine structural balance?

What are the desirable TA adjustment methods?

Is the pre-fermentation addition of tannin desirable? It can add mid-palate depth.

Fermentable nitrogen content is not simply a matter of sticking(VC 13:4,14:2, 14:4). It influences the ratio of esters to fusel alcohols. The nitrogen content is dependent upon a number of things including yeast strain.

Which yeast(s) are optimum for your wine styles? How are you making this decision? What is your yeast volume?

Will you add sulfur dioxide to the must? How much? What is the role of polyphenol oxidase and phenol polymerization (VC 13:4)?

What is the role of oxygen (VC 16:3)?

What is the optimum size and shape of fermentation tanks?

open vs closed?

What is the relationship between your must temperature and wine style, liquid and cap?

MLF? strain(s)? timing and volume of inoculation?

Fermentation with wood (VC 14:3)?

What cap wetting procedures are the best; punch down, pump over, irrigation systems, sweeper tanks, delestage (VC 15:3, EN# 8)?

What is the alcohol at time of dejuicing (VC 13:2) and how do you make this determination? Post-fermentation maceration? For how long?

Do you combine free run with press run?

Cellar Management.

Wood(s): sources, seasoning age, fill age, barrel type, etc.

Are you storing red wines sur lie (VC 14:3, EN #6)? Lees storage can be very helpful for structural integration.

What level of sulfur dioxide? Keeping sulfur dioxide levels low (15 mg/L free) for first year increases phenol polymerization(VC 12:2, 13:5, 14:6).

What level of oxygen exposure is desirable? During the first year process oxidatively, thereafter, anaerobically. Every premium wine producer should measure oxygen pick-up (VC 12:3, 13:5, 14:3).

Post-fermentation blending.

How does filtration influence your wine quality (VC 16:2)?


How does your bottling influence wine quality?

Some Additional Notes:

Maceration enzymes may be desirable, particularly if you have a lot of whole berries in the fermenter. These contain pectinase, hemicellulases and cellulases which, like native enzymes, aid in the diffusion and association of anthocyanins, tannins and polysaccharides.

Yeasts. Species and strain have a significant influence on grape and wine phenols as a result of both binding and polysaccharide liberation. Desirable strain features include: 1) low color adsorption, 2) a high production of mannoprotein polysaccharides available during fermentation and autolysis, and 3) a low production of volatile sulfur compounds (some of which can enhance the perception of astringency).

Cap Management should occur to limit the formation of non-soluble solids and seed tannin extraction. Process to encourage phenol polymerization and stabilization (oxygen exposure and low sulfur dioxide). Delestage reduces seed extraction, while at the same time enhancing enzyme activity and oxidative polymerization.

Tannin Management and Textural Quality. Tannin quality (suppleness, creaminess) is the result of :1) the quantity and quality of phenol components in the fruit, and 2) the interaction and stabilization of anthocyanins, tannins and certain polysaccharides.

Integration. During fermentation, yeast species and strain, oxygen and maceration influence the stability of phenols and their resulting mouth feel. What is the sensory significance of specific phenols including specific tannins? All phenols are both bitter and astringent. Bitterness is the result of access to membrane bound receptors and is likely limited by molecular size.

Bitterness and astringency increase with increased molecular weight. Polymerization increases astringency due to an increased number of possible hydrogen binding sites.

With concentration, the bitterness of monomeric flavonoids increases at a faster rate than the astringency. This is in contrast to the astringency of polymeric seed tannins which increase more rapidly than bitterness, with increases in concentration. Astringency masks bitterness, an extremely important concept to understand as it relates to fining.

Hard vs Soft Tannins. The ratio of bitterness to astringency helps to explain the concept of hard vs. soft tannins. The interaction of phenols and other wine components are an important feature in wine texture:

Sweet --- Acidity + Bitterness and Astringency

Suppleness Index = Alcohol-(Acidity + Tannin)

Even experienced tasters have trouble differentiating between bitterness and astringency. Suggest running in-house trials: Astringency-alum, gallic acid, tannic acid, citric acid and mixtures.

Bitter-caffeine, quinine sulfate.

II. Regulatory Issues and Wine Tax Reporting Seminar

The Department of Alcoholic Beverage Control is pleased to offer a seminar on Regulatory Issues, Wine Tax Reporting and Product Registration Procedures:

Date: November 14, 2001 10:00 a.m.

Location: ABC Central Office, 2901 Hermitage Rd., Richmond, VA

This will be a one-day seminar during which the Board's regulations and the provisions of the Code of Virginia governing the operation of a Farm Winery will be reviewed. In addition the staff of our Tax Management Section will explain the Wine Tax Reporting and Product Registration Procedures.

The target audience for this seminar is those farm winery licensees who have recently received their license and those licensees who have had a recent change in management staff.

To register please contact:

ASAC Roger Stevens (540) 332-7800 or email

Ms. Ernestine Mack (804) 213-4555 or email

III. Student Achievements

Danielle LoGiudice, a student of ours working under the direction of Dr. T. Wolf received the award for the best oral presentation in viticulture at the American Society for Enology and Viticulture - Eastern Section annual meeting. Mr. Samir Masri, a student in the Enology-Grape Chemistry Group was awarded a scholarship from the Society.

Anna Katharine Mansfield, an M.S. student in the Enology-Grape Chemistry Group was awarded her degree in July. Anna has accepted the position of Enology Project Leader at the University of Minnesota. She will be working with plant breeders in evaluating the wine potential of new cultures. Anna received regional and national scholarships from the American Wine Society and the American Society for Enology and Viticulture. She excelled as a student and will no doubt excel in her professional career. We wish her well!

IV. American Society for Enology & Viticulture

The American Society for Enology and Viticulture - Eastern Section is designed to support the growth and technical development of our industry through educational/technical programs and scholarships. The Society has supported the growth of the Virginia industry by helping to support our students. Each wine producer in Virginia should be a member of the professional organization of the industry. For information on the society contact my office or go to

V. Winery Planning and Design Workshop Proceedings

I have a limited number of proceedings available from the Winery Planning and Design Workshop held July 21st. Send a check made payable to "Bruce Zoecklein Foundation" for $45.00 and mail it to Bruce Zoecklein, Department of Food Science and Technology - 0418, Virginia Tech, Blacksburg, VA 24061. Thanks to all of those that contributed to the highly successful event. The funds generated from the sale of the proceedings will be used to keep funding our graduate student program.

VI. Enology Notes

Enology Notes, my electronic newsjournal is available upon request at no cost. Send me an e-mail note requesting that you be added to the list serve. These electronic notes are separate and distinct from my Vintner's Corner subscription newsjournal.