DIFFICULT TO FERMENT JUICES: STRATEGIES FOR

FERMENTATION MANAGEMENT

Linda F. Bisson

Department of Viticulture and Enology, UCD

Types of Difficult to Ferment Juices

• High Brix

• High Rot/High Bioload

• Vineyard Site Issues

• Varietal/Rootstock Issues

High Brix (Long Hang Time)

•High sugar means high ethanol• Increased demand for nutrients with increasing Brix,

may be as much as two-fold

•Long Hang Time means more juice seepage • Increased potential for inhibitory lactic acid bacteria

populations on surface of fruit

• Higher pH of juice, greater activity of spoilage microbes in winery

• Higher SO2 demand of juice

High Rot

• High microbial bioloads in juice• Greater competition for nutrients

• Increased production of inhibitory compounds negatively impacting fermentation progression

• Higher SO2 demands

• Nutrient level and timing of addition critical to assure feeding the right population

• Temperature critical to fostering development of right population (too warm favors bacteria, too cold favors spoilage yeast)

Vineyard Site Issues

• Poor Soils

• Chronically Nutrient Deficient Juices• Nutrient supplementation not always effective

• Complex nutrients needed

• Presence of fermentation/growth inhibitors from the vine

• High Disease/Pest Pressure• Poor fruit nutrient content

• Presence of fermentation/growth inhibitors from the vine

Variety/Rootstock Issues

• Variation in fermentation progression as a function of rootstock

• Often a soil composition component

• More severe with some varietals/clones than others

First StudyNitrogen Status and Fermentation Dynamics for Merlot on Two Rootstocks

Christine M. Stockert, Linda F. Bisson, Douglas O. Adams and David R. Smart

2013. AJEV

Outline of Study

• Compare impact of N fertilization at two seasonal time points: fall and spring on two rootstocks, 101-14Mgt and 1103P

• Merlot clone 1 used as scion

• Assessed leaf %N and fruit amino nitrogen composition

• Monitored fermentation dynamics

Questions to be addressed:

• Is Leaf %N correlated with amino acid composition of grapes?

• Can Leaf %N predict fermentation performance?

• Do rootstocks differ in uptake and utilization of N with respect to berry composition?

Details of Merlot Trial• Experiment was carried out in the UCD vineyard in Oakville,

California

• The vines were in their tenth year and trained as bilateral cordons with vertical shoot positioning (VSP)

• The trellis height was 1.6 m and the canopy was hedged to 2.2 m.

• The rows were oriented SE to NW and spaced 2.4 x 2.2 m between and within rows respectively

• Vines on 1103P were established and managed with 28 nodes while those on 101-14 Mgt were established and managed with 24 nodes

• A randomized complete block design with six blocks was used. Each block consisted of subplots of six vines per rootstock x treatment combination

Details of Experimental Design• The Spring fertilized treatment was 16.8 kg N/ha applied on 18 May

2005 and the Fall fertilized treatment was 16.8 kg N/ha applied on 7 October 2004 using potassium nitrate (36.94% K, 13.75% N) applied through the drip line

• The vines were deficit irrigated bi-weekly with 40% replacement of crop ETc, which totaled 60 mm over the course of the summer.

• Irrigation water and fertigation solution were delivered via one 3.8 L/hr drip emitter per vine, located 50 cm from each trunk.

Results

• Leaf N levels similar for both rootstocks

• 101-14 Mgt had fewer leaves, less total canopy nitrogen

• Leaf number but not nitrogen level per leaf associated with nutrient deficiency caused by rootstock

Results: Fermentation

Results: Juice Nitrogen AnalysisNitrogen 1103

Control Spring N Fall N101-14 Mgt

Control Spring N Fall N

Total Free AA, mg/L

509 565 557 228 278 249

Arginine, mg/L 85 115 111 14 22 14

Proline, mg/L 1101 1227 1191 802 967 824

YAN/YNAN 0.46 0.46 0.46 0.28 0.28 0.28

Pro/Arg 19.9 16.2 15.8 87.1 66.6 89.6

Questions to be addressed:

• Is Leaf %N correlated with amino acid composition of grapes? NO

• Can Leaf %N predict fermentation performance? NO

• Do rootstocks differ in uptake and utilization of N with respect to berry composition? YES

Conclusions

• Grape/Juice N varies by rootstock

• Nitrogen additions in vineyard might not impact juice YAN as much as thought

• Yeast YAN not predictable from Vineyard N assessments, although there is often a trend

• Sluggish juices are characterized by low YAN/YNAN and high Proline/Arginine ratios

Second Study

Difficult to Ferment Coastal Chardonnay Juices

Priyanka Dhar, Aline Cresswell, Vidhya Ramakrishnan, Gordon Walker

The Issues:

• Vineyard blocks characterized by low vine N

• Vine N less responsive to N application than other blocks in vineyard

• Chronic issues with fermentation progression

• Yeast fermentation does not respond to yeast nutrient addition

Fermentation Results: Yeast Strains Used in Study

Yeast StrainRestart Stuck

Temp. Range

Ferm. Speed

Competitive Factor

Alcohol Tolerance

Relative Nitrogen Needs

Lalvin ICV-D254

Lowest 12-28 Moderate Neutral 16 Medium

Lalvin Rhone 2226

Moderate 15-28 Fast Active 18 High

Uvaferm 43 Highest 13-35 Fast Neutral 18+ Low

Fermentation Results

Fermentation Results

Fermentation Results

Fermentation Results• Easy to ferment juices generally finished in 8 days

at fermentation temperatures of 60° F

• UV43 in Napa juice took 12 days

• In difficult to ferment juice, strains took 14-18 days to complete fermentation

Amino Acid Composition of Juices 2010 Vintage

Juice FAN YAN/YNAN Proline/ Arginine

Dry Creek 324 1.2 6.6

Napa 246.6 1.5 7.2

J Lohr Difficult

157 0.46 32.6

J Lohr Easy 341.7 0.96 8.8

KAC 522.8 1.17 5.5

Amino Acid Composition of Juices 2011, 2012 Vintages

Juice FAN YAN/YNAN Proline/ Arginine

J Lohr 2010 Difficult

157 0.46 32.6

J Lohr 2011Difficult

119.4 0.54 23.8

J Lohr 2012Difficult

216 0.76 12.4

J Lohr 2012Easy

306 0.98 9.14

Fermentation Results 2012

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2

4

6

8

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0 50 100 150 200

Wei

ght

Loss

as

CO2

Time (hours)

J.Lohr Juice

Allegro E

Allegro D

Allegro D+

Fermentation Results 2012

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0 50 100 150 200

Wei

ght

Loss

as

CO2

Time (hours)

J.Lohr juice

522 E

522 D

522 D+

Conclusions from Chardonnay Study• Difficult to ferment Chardonnay juices also show low

YAN/YNAN ratios and high Proline/Arginine ratios

• Nutrient supplementation does not affect rate of fermentation of difficult to ferment juices

• Also a rootstock effect? Difficult to ferment Chardonnay is Clone 5 on 5C

Overall Conclusions

• Difficult to ferment juices are challenging to yeasts regardless of innate nutritional requirements

• Difficult to ferment juices do not respond to typical yeast nutrient additions in winery

• Although low in N, it is not clear low N is the reason difficult to ferment juices are so difficult to ferment

• Correction of problem in vineyard may be challenging as it requires high N applications

Cause of Difficulty in Fermentation?

• Not chloride or other inhibitory ion

• Does not respond to ammonium addition

• Metabolome analysis: yeast have high concentrations of stress-associated metabolites, especially mannitol

• Not associated with wild lactic activity

• Oxidative stressors?

• Inhibitory phenolics/plant metabolites?

Acknowledgements

Funding

•American Vineyard Foundation

•USDA Viticulture Consortium

•California Grant Program for Research in Viticulture and Enology

•Maynard A. Amerine Chair Endowment

•VEN Department Scholarships