Maret du Toit

INSTITUTE FOR BIOTECHNOLOGY, Department of and , 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 undergoes MLF?

• Most red wines – SA: Pinotage is easy – and more difficult

• Some white wines – SA: – Other countries: wines were the acids needs to be reduced

• Base wine for sparkling wines Mechanisms to alter wine aroma

 Metabolism of 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 -

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 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 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 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