Modeling the alcoholic fermentation of cocoa by a selected ...
1
Conception: Cirad, Martine Duportal,, October 2018- © photos: C. Kouamé The growth of a S. cerevisiae strain (LM, Lallemand) was modeled by mobilizing the Rosso primary model (Eq.1) and the gamma concept (Eq.2). The parameters of the models were determined by growing LM in synthetic liquid medium, by varying the parameters independently. The model was implemented under Matlab-Simulink and two validations mimicking the natural fermentation conditions (pH, temperature profile, initial glucose content) were performed. Experimental approch CHOCOLATE is a pleasure-food consumed mainly for its aromatic quality directly related to that of the fermented and dried cocoa beans. The fermentation of the beans is a key step led by a wild microflora, poorly controlled, that sometimes leads to beans of undesirable quality. Its smooth running depends on multiple factors (Figure 1). To control the quality of the beans, a mathematical model of alcoholic fermentation has been developed; it can be used to predict and optimize the behavior of a yeast strain according to the fermentation control parameters (inoculum level, T ° C, pH , PO2). Modeling the alcoholic fermentation of cocoa by a selected yeast strain Christelle Kouamé 1 , Gérard Loiseau* 1, 2 , Joël Grabulos 1 , Renaud Boulanger 1 , Christian Mestres 1 1 CIRAD, UMR Qualisud, F-34398 Montpellier 2 QualiSud, Univ Montpellier, CIRAD, Montpellier SupAgro, Univ Avignon, Univ Réunion, Montpellier, France *Contact: [email protected] tél. : +33-04-67-61-57-13 Yeast γ pH γ T°C γPO 2 γ [Acetate ] γ [etoh] γ gluc. γ N Ethanol Nitrogen O 2 water … Glucose Bacteria Acétate pH Temperature Equation 1 : dNt / dt = 0 si t ≤ λ dNt / dt = µ max Nt (1- Nt / N max ) si t ≥ λ Equation 2 : µ max = µ opt . γ T°C . γ pH . γ[Gluc] . γ[Etoh] . γ[Azote] .γ PO 2 . γ[Acétate]. avec 0 < γ < 1 Rosso et al ., 1995. Convenient model to describe the combined effects of temperature and pH on microbial growth. Appl. Environ. Microbiol. 61, 610–616. Zwietering et al ., 1993. A decision support system for prediction of microbial spoilage in foods. J. Ind. Microbiol. Biotechnol. 12, 324–329 Figure 1. Schematic representation of bean fermentation. References • Model predicts LM growth and growth arrest quite well. • Inoculation at 10 4 CFU/mL: when the temperature reaches 41°C, the γ-temperature drops to 0, and the growth of LM stops. There is still glucose in the environment. • Inoculation at 10 6 CFU/mL: the growth stops when the glucose level and γ-glucose reaches 0 (≈ 20h); there is no more glucose in the medium. The Tmax is reached later ≈ 35h. Conclusion • A mechanistic model predicts yeast growth during cocoa fermentation. • The model predicts growth cessation depending on inoculation level. • For low inoculation level, yeast growth stops with increased temperature of cocoa. • For high inoculation level, depletion of glucose stops yeast growth. •The model explains that depending on the quality of the raw material (glucose content), the conditions of inoculation and temperature maintenance, the quality of the cocoa will vary. •The model is a tool to define the inoculation level of yeast for cocoa fermentation. Results: modeling yeast growth in "real" conditions γ-glucose γ-T°C T°C --- Model 10 6 Expe 10 6 γ-T°C --- Model 10 4 Expe 10 4 --- γ-glucose glucose
Transcript of Modeling the alcoholic fermentation of cocoa by a selected ...
Con
cept
ion:
Cira
d, M
artine D
uport
al,,
Oct
ober
201
8- ©
pho
tos:
C. K
ouam
é
The growth of a S. cerevisiae strain (LM, Lallemand) was modeled by mobilizing the Rosso primary model (Eq.1) and the gamma concept (Eq.2). The parameters of the models were determined by growing LM in synthetic liquid medium, by varying the parameters independently. The model was implemented under Matlab-Simulink and two validations mimicking the natural fermentation conditions (pH, temperature profile, initial glucose content) were performed.
Experimental approch
CHOCOLATE is a pleasure-food consumed mainly for its aromatic quality directly related to that of the fermented and dried cocoa beans. The fermentation of the beans is a key step led by a wild
microflora, poorly controlled, that sometimes leads to beans of undesirable quality. Its smooth running depends on multiple factors (Figure 1).
To control the quality of the beans, a mathematical model of alcoholic fermentation has been developed; it can be used to predict and optimize the behavior of a yeast strain according to the fermentation control parameters (inoculum level, T ° C, pH , PO2).
Modeling the alcoholic fermentation of cocoa by a selected yeast strain
Christelle Kouamé1, Gérard Loiseau*1, 2, Joël Grabulos1, Renaud Boulanger1, Christian Mestres11 CIRAD, UMR Qualisud, F-34398 Montpellier
2 QualiSud, Univ Montpellier, CIRAD, Montpellier SupAgro, Univ Avignon, Univ Réunion, Montpellier, France
*Contact: [email protected] tél. : +33-04-67-61-57-13
Yeast
γ pH
γ T°C
γPO2 γ [Acetate ]
γ [etoh] γ gluc.γ N
Ethanol
Nitrogen
O2
water …
GlucoseBacteria Acétate
pH
Temperature
Equation 1 : dNt / dt = 0 si t ≤ λ dNt / dt = µmax Nt (1- Nt / Nmax ) si t ≥ λ
Equation 2 : µmax = µopt . γ T°C . γ pH . γ[Gluc] . γ[Etoh] . γ[Azote] .γ PO2 . γ[Acétate]. avec 0 < γ < 1
Rosso et al., 1995. Convenient
model to describe the combined
effects of temperature and pH on
microbial growth. Appl. Environ.
Microbiol. 61, 610–616.
Zwietering et al., 1993. A
decision support system for
prediction of microbial spoilage in
f oods . J . I nd . M i c rob io l .
Biotechnol. 12, 324–329
Figure 1. Schematic representation of bean fermentation.
References
•Model predicts LM growth and growth arrest quite well.
• Inoculation at 104 CFU/mL: when the temperature reaches 41°C, the γ-temperature drops to 0, and the growth of LM stops. There is still glucose in the environment.
• Inoculation at 106 CFU/mL: the growth stops when the glucose level and γ-glucose reaches 0 (≈ 20h); there is no more glucose in the medium. The Tmax is reached later ≈ 35h.
Conclusion•A mechanistic model predicts yeast growth during cocoa fermentation.
•The model predicts growth cessation depending on inoculation level.
•For low inoculation level, yeast growth stops with increased temperature of cocoa.
•For high inoculation level, depletion of glucose stops yeast growth.•The model explains that depending on the quality of the raw material (glucose content), the conditions of inoculation and temperature maintenance, the quality of the cocoa will vary.•The model is a tool to define the inoculation level of yeast for cocoa fermentation.
Results: modeling yeast growth in "real" conditions
- - - Model 104
Expe 104
- - - Model 106
Expe 106
γ-glucose
γ-T°C
glucose
T°C
- - - Model 104
Expe 104
- - - Model 106
Expe 106
γ-glucose
γ-T°C
glucose
T°C
- - - Model 104
Expe 104
- - - Model 106
Expe 106
γ-glucose
γ-T°C
glucose
T°C
- - - Model 104
Expe 104
- - - Model 106
Expe 106
γ-glucose
γ-T°C
glucose
T°C
![Cocoa and Coffee Fermentation [MyeBookShelf]](https://static.fdocuments.in/doc/165x107/55cf93e7550346f57b9eba04/cocoa-and-coffee-fermentation-myebookshelf-569cc6d6a4250.jpg)