Maret du Toit
INSTITUTE FOR WINE BIOTECHNOLOGY, Department of Viticulture and Oenology, Stellenbosch University Winemakers perspective on MLF and aroma
• Do you do MLF for aroma contribution?
• What aromas are important for you from MLF, which cultivars or styles?
• What descriptors do you associate with MLF?
• What factors do you experience influence MLF and aroma?
Which wines undergoes MLF?
• Most red wines – SA: Pinotage is easy – Merlot and Pinot noir more difficult
• Some white wines – SA: Chardonnay – Other countries: wines were the acids needs to be reduced
• Base wine for sparkling wines Mechanisms to alter wine aroma
Metabolism of grape constituents − Sugars − Amino acids − Citric acid Modification of grape- or yeast-derived secondary metabolites − Glucose bound precursors Adsorbing of flavour compounds to bacterial cell walls
General impact on wine sensory attributes • Aroma – Improved fruitiness – Butteriness – Reduced vegetative character • Taste – Less acidic – Creamier and fuller pallet – More complex • Mouthfeel – Better structure – More balanced wine Descriptive aroma terms associated with MLF
– Buttery – Lactic/yoghurt – Nutty Sequential Co-inoculation – Yeasty – Oaky – Vanilla – Fruity – Caramel/toffee
Impact of wine yeast on MLF
Longer lag phase Neutral towards MLF
Yeast 1 Yeast 2
Mix Mix
Yeast 3
Mix Stimulatory towards MLF Impact of wine yeast - Esters
Merlot 2011 250
225
200
175
150
125 Concentration (mg/L) Concentration
100
75
50 yeast Control
Mix O. oeni 2 O. oeni 1
Impact of O. oeni strains
Pinotage 2008 Esters
ethyl decanoate Pinotage 2008 3.0 diethyl succinate 2.5 ethyl hexanoate 2.0 1.5 hexyl acetate 1.0 ethyl octanoate 0.5 0.0
ethyl phenylacetate ethyl propionate
ethyl-3-hydroxybutanoate ethyl-2-methylpropanoate
ethyl-2-methylbutyrate
Before MLF A V O C Pinotage 2008
diacetyl isobutyric acid 10 2
decanoic acid butyric acid 5 1 trans-2, cis-6- trans-2, cis-6- acetoin nonadienalnonadienal 0 0 octanoic acid isovaleric acid
hexanoic acid valeric acid E-2-hexenal 2,3- pentanedione
esters 500 400 Before MLF 300 200 A aldehydes higher alcohols 100 V 0 O C
carbonyls fatty acids
Correlation between chemical and sensory
(a) PRUNE_A SOUR_T BODY/MOUTHFEEL WINE_A FRUITY_T
WINE_O NUTTY_A SMOOTHNESS YOGHURT/BMILK VEGETIVE_T BUTTER_A VEGETIVE_A WINE_V BERRY/BERRY JAM_A CONTROL FLORAL/ROSE_A FRUITY GENEAL_A BUTTER_T
WINE_C
Vegetative Fruity Lactic/Butter Impact of MLF scenario on Riesling aroma
Simultaneous Time safed: 25 – 50 Days
24 h 40 % 60 % Sequential AG 100 AG 3,1 2,9 3,0 O. oeni 3,1 R1124 O. oeni R1105
entration (%) 50 relative Sugar conc Sugar
0 Winemaking AG– alcoholic fermentation Impact of MLF scenario on Riesling aroma
1400 24h24 h 1200 a AFEndSequentiell
1000 b
[µg/L] 800 a
600 a b
Concentration Concentration 400 b a b 200 a b
0 Essigsäure-3-methyl- Essigsäure-2-phenyl- Bernsteinsäure- Essigsäure- Buttersäure- butylester ethylester diethylester hexylester ethylester (Bannana) (floral) (fruity) (fruity / floral) (Appel) Impact of MLF scenario on Riesling aroma
Acetate-3- methylbuthylester (Banana) 24h
40% AF No MLF Other Ethylester 60% AFF (fruity) Succinic acid Diethylester (fruity) Acetate ethylester Sequential MLF (Apple, acetone) 24hCo -inoculation
Nitrogen source
Control DAP Complex Amino Control DAP Complex Amino acids acids
• Co-inoculation strategies produced higher total ester concentration than sequential inoculation fermentations • Esters not impacted significantly by nitrogen source • Higher alcohols impacted with amino acids
What can be used to drive MLF aroma?
• Choose your yeast strain to compliment MLF • MLF scenario: co-inoculation vs. sequential • Decide on LAB strain to be used • Use wine parameters such as pH