(663a) Mathematical Modelling of Cocoa Bean Fermentation and Sustainable Land Use Analysis for Cacao Plantations

Authors: 
Poolworaluk, C. - Presenter, University of Bath
Samsatli, S., University of Bath
The global chocolate market was estimated at GBP 130 billion in 2017 and is expected to grow at a compound annual growth rate (CAGR) of 7% between 2017 and 2024. The basis of chocolate is cocoa beans, which are the dried and fully fermented seeds of Theobroma cacao trees. The industrial applications of cocoa beans include functional food and beverages, confectionery and cosmetics. Recently, the health benefits of cocoa, such as regulation of fatigue syndrome, outstanding anti-oxidant properties and reducing the impact of hypertension, have been receiving attention.

Fermentation of cocoa beans is considered the most important step in cocoa processing and defines the chocolate’s flavour and aroma. This process is performed on the pulp and seed after the cocoa pods are harvested and cut open. Spontaneous fermentation occurs instantaneously due to natural inoculation, where the pulp and bean undergo the process with the successive action of yeasts, lactic acid bacteria and acetic acid bacteria. A combination of acetic acid and ethanol produced, along with the rise in temperature in the pulp during fermentation causes some cells in the beans to rupture, which results in the following: 1) the penetration of the flavours formed in the pulp to the beans; 2) the breaking down of the sucrose and proteins into simple sugars and amino acids, respectively, which will aid in the production of aromatic compounds during a future roasting step; and 3) the formation of less astringent compounds upon the mixing of phenolic compounds with each other as well as with proteins and oxygen. The cocoa beans that emerge from this step are flavourful and less astringent than the unfermented ones.

Despite the huge industrial significance of this process, mathematical modelling of cocoa bean fermentation is very limited. Mathematical modelling can provide an enormous understanding of and insights into the underlying mechanisms of a physicochemical process. It can save significant development costs by replacing the majority of expensive laboratory experiments with much cheaper computer simulations. Especially for complex processes, such as cocoa bean fermentation, mathematical modelling provides a systematic and rigorous approach for optimising the design and operating parameters of a process. Therefore, this project aims to further understand cocoa bean fermentation through mathematical modelling.

Furthermore, cacao plantations and the practice of cocoa farming is far from being sustainable. Expanding or establishing new cacao plantations involves clearing forests, which forces indigenous people habiting those forests to relocate or biodiversity to be lost. Cocoa farmers are paid as little as $0.50 to $0.84 a day, which is lower than the poverty line determined by the World Bank. Lack of government support, in conjunction with a lack of knowledge from farmers in maintaining and improving their plantations, leads to deforestation and a myriad of other environmental issues. Therefore, land use planning in conjunction with the correct policies implemented is imperative to determine which land areas are the most sustainable and suitable to locate cacao plantations.

Geo-spatial analysis can be used to assist in land use planning. For forestry, land use planning involves analysing land to be used for different purposes by considering the economic, social and environmental implications to determine the best use the land in the forested landscape. However, in practice, many countries have not adopted land use planning successfully and this is taking a toll on the planet.

Asia has been receiving increasing attention lately as Asia’s location on the cocoa belt makes it an attractive area for locating cacao plantations. More specifically in Southeast Asia, countries like Vietnam and Malaysia are turning to grow cacao trees, following on from the success of Indonesia in growing cacao. Moreover, Asia is the fastest-growing chocolate market globally due to a rapid increase in wealthy middle-income earners. Hence, this research aims to identify suitable areas in Southeast Asia to locate cacao plantations to shorten the cocoa supply chain and increase transparency between farmers and consumers.

The methodology involves the following steps:

  1. Conducting a review of the biochemistry and microbiology of the cocoa bean fermentation process, as well as the advances and challenges in this area.
  2. Surveying existing mathematical models for fermentation processes.
  3. Developing a mathematical model for cocoa bean fermentation by deriving the set of differential equations that best represent the physical system.
  4. Examining and categorising the drivers of tree cover loss in Southeast Asia, such as commodity-driven deforestation, urbanisation, shifting agriculture and forestry.
  5. Determining land areas in Southeast Asia that are suitable to locate cacao plantations sustainably.

Overall, the proposed model fits the experimental data relatively well. The average percentage error calculated for all microbial and metabolite concentration profiles is less than 10 %, except for the yeast concentration profile. The discrepancy for this profile could have arisen from the assumption that only one strain of yeast exists in the fermentation pile, but numerous strains are present in reality. Moreover, the abiotic factors are assumed not to influence the model’s parameters but experimentally, the growth and death of yeasts are heavily dependent on the temperature and pH of the fermentation pile.

The proposed model could potentially be used as a kinetic model for cocoa bean fermentation. To further validate the model, more detailed experimental data with a higher sampling rate could be used. For future research, it would be useful if the model’s parameters could reflect changes in abiotic factors to optimise the cocoa bean fermentation process.

Regarding the land use analysis of Southeast Asia, lands that are deforested for commodity purposes appear to be the most suitable to plant cacao trees, as farmers can adopt the intercropping practice. This allows farmers to gain more income from the same plot of land by growing and selling more than one crop at one time. Moreover, farmers have previous transferable skills that can be easily applied to growing cacao trees. Although cacao plantations are not suitable to be grown in urbanised areas, locating cacao plantations near urbanised areas has its benefits. Harvesting and processes cocoa beans are labour-intensive, therefore it is beneficial if there are many workers available nearby. On the other hand, lands that have gone through shifting agriculture and forestry are not suitable for cacao plantations. These practices cause soil to become infertile and water resources to be polluted, making it hard for foliage to develop.

To ensure sustainable cocoa farming in Southeast Asia, suitable policies need to be implemented. Currently, there is no definite sustainable network in Asia as the focus on improving the sustainability of the cocoa supply chain lies predominantly in Ghana and Ivory Coast. Community forests were promoted as a method to regenerate degraded forests; however, this was met with varying degrees of success. Therefore, in the future, more research should be taken into improving the sustainability of the cocoa industry in Southeast Asia by considering the economic trade-off with a greener and shorter cocoa bean supply chain.