 Have you ever had a delicious tasting chocolate bar or even had a nice hot cup of chocolate on a cold winter day? Have you ever wondered where your chocolates came from? Hi my name is David Gropulsion and I'm a research fellow at the University of Nottingham and I'm interested in understanding the fermentation of cocoa beans and finding ways to improve the flavor and quality of chocolates. Our story starts thousands of miles away close to the equator. Greetings from Colombia. You see cocoa is the principle ingredient used to make chocolate and cocoa is made from cocoa beans. The beans are the seeds from the mature fruits of the cacao tree, a tropical plant native to the Amazon rainforest. Over the centuries humans have brought cocoa to other continents and today it's cultivated in many tropical countries close to the equator. Most of our cocoa about 70% comes from West Africa with Ivory Coast and Ghana by far being the two largest producers. But Latin America, the Caribbean, Asia and Oceania are also important producing regions and about 5 million tons of cocoa are produced globally each year. About 5 to 6 million farmers grow cocoa with more than 90% of the world's cocoa beans are grown and harvested on small family-run farms. Growing cocoa is no simple task. The cocoa tree is a delicate and sensitive plant. It requires high rainfall and temperatures to grow as well as shade trees to protect it from too much light and damage caused by wind. Because the trees are so sensitive to these conditions they only grow best in tropical regions around the equator where the climate is suitable. Farmers must protect the trees from wind and sun, fertilize the soil and watch for signs of disease or distress. With proper care, most cocoa trees can mature to bear fruit by the 4th or 5th year after the seedlings are planted and this can continue for another 30 years. A typical pod contains 30 to 40 beans and a tree can produce about 30 pods every year. Approximately 400 beans are required to make one pound of cocoa. Most countries have two periods of peak harvest, a main harvest and a smaller minor harvest. When the fruits are ripened, the farmers use long handle steel tools to reach the pods and cut them without wounding the soft bark of the tree. The pods are then collected and cracked open to extract the cocoa beans together with the creamy white sweet mucilage covering them called the pulp. After the beans have been removed from the pods, they are packed into boxes, baskets or heaps and then covered with mats or banana leaves for up to seven days. During this time the beans ferment and many of the desirable flavor compounds are formed while undesirable ones are broken down. This process has a huge impact on cocoa quality and taste. After fermentation the beans are dried, usually by leaving them in the sun for seven days. The dried beans are packed into sacks and the farmers would sell the beans to buying stations. The buyers transport the beans to warehouses where they are inspected and stored. Once enough beans have been collected, usually from many different trees and farms, they are shipped to a chocolate manufacturer. Wow, this is a lot of beans. Cocoa is among the most important agricultural crops. However, unlike the large agribusiness farm models that produce many of our major crops, cocoa farming remains a small family enterprise much as it was a hundred years ago. The challenges of low productivity, pests, diseases and low farmer incomes all limit the development of cocoa farming communities. By giving farmers information to make better quality tasting beans, we will give them more control over their harvest and ultimately their livelihoods. So we've seen how cocoa beans are growing, but it's important to realize that at harvest these beans don't taste anything like chocolate. In fact, they're quite bitter, they're astringent and a little bit slimy. Now, whilst all stages of processing have an influence, fermentation, drying and roasting have the biggest impacts on cocoa flavor development. In fact, cocoa that isn't fermented will never develop a chocolate-like taste or aroma. Now, the global market for beans is currently worth around 12 billion US dollars, but cocoa farmers still face problems like low wages and low productivity. If we can help farmers to get the very best flavor out of every single harvest, they can make their beans more valuable and together we make chocolate that is both tastier and fairer. More than 600 volatile compounds have been identified in chocolate, but none of these are unique. And what we perceive as chocolate flavor is really a combination of a large number of different compounds acting in concert. So to understand how this flavor develops, we must start with the chemistry of the cocoa bean. On a dry basis, unfermented beans contain about 50% fat, 10 to 15% carbohydrate, 12 to 18% polyphenols, and anywhere between 9 and 24% protein. Let's take these one by one. Now, fat is vital to the eating quality of finished chocolate. Fat gives chocolate its glossy finish. It's snap. It's melt in the mouth quality. All that is gooey about chocolate, its ability to coat the inside of our mouth when we eat it. All of this comes from fat. However, the composition of fat doesn't really change during fermentation. It's quite stable. And as far as we're aware, fat doesn't really directly contribute to chocolate flavor. However, fat may act as a repository for all of the volatile aroma compounds that we generate. And this may actually protect them from loss during roasting. Now the main change to the carbohydrate content within the beans is a breakdown of starch and sucrose. And this leads to reducing sugars like glucose and fructose. These are vital substrates for the generation further flavors on roasting. However, if we're talking about sugar, we should also remember the pulp. Fresh cacao pulp is a sweet sticky mass. It's an ideal media for a wide variety of microbial species. And it supports three distinct phases of fermentation. In the first phase, yeasts dominate the microbial profile, producing a variety of boozy alcohol flavors. The yeast also break up the pulp gel, which means liquid starts to drain away as what's called sweatiness. And this allows air to circulate between the beans. This in turn allows lactic acid bacteria to grow. This brings flavors like yogurt and then acetic acid bacteria, which bring a variety of sour and fruity flavors. All of these microbial end products will slowly seep into the bean. And as the pH and the temperature changes, this all drives a wide variety of other reactions. For example, cocoa polyphenols are very potent antioxidants. They can protect the plant from UV damage from fungi from parasites. They're quite bitter, which prevents animals from feasting on the plant. But also it's the same compounds that gives dark chocolate, it's bitter and slightly astringent flavor. You know that puckering sensation on the tongue. During fermentation, many of these compounds are oxidized into larger polymers, which reduces the overall bitterness, making the cocoa more palatable, and also gives it a beautiful red brown color. Finally, the protein content of beans is significantly changed during fermentation. Specifically, a globular storage protein known as a vasillin is broken up into a mixture of hydrophilic peptides and hydrophobic free amino acids. These can be converted into a wide range of aldehydes, alcohols, acids and acetates during fermentation and drying, or can combine with reducing sugars on roasting to form an even wider range of flavors and colors through the Maillard reaction. Cacao vasillin is responsible for the heart of what we know as chocolate flavor. And across different varieties of cocoa, the profile of this vasillin is nearly identical. However, when we compare the flavor and peptide profiles from fermented cocoa beans around the world, they can be hugely different, often with flavors that are unique to each farm. We think a big reason for this is differences in fermentation. At the University of Nottingham, we are mapping out how different fermentation practices and profiles influence the flavor of cocoa beans. To do this, a trained sensory panel characterizes the flavors associated with samples from several different farms. We then use next generation high throughput genetic sequencing tools to give us a profile of the microbiome across the fermentation process. We also use a variety of analytical techniques, including high resolution LC mass spectrometry to correlate changes in the chemical profile of the beans with microbial action and resulting flavor. The end result is that we can start to optimize cacao fermentations towards generating desirable fruity and spicy flavors, and we can empower cacao farmers to produce consistent, high value and delicious cocoa.