6 December: Where does the vanilla flavour in Danish rice pudding come from?
Danish rice pudding with almonds, AKA “risalamande”, is a Yuletide staple across Denmark. However, the vanilla that many people think that they are adding to their Christmas pudding is often a chemically synthesized product called vanillin. Today’s researcher is Birger Lindberg Møller, Center Director at the Centre for Synthetic Biology “bioSYNergy”, part of the Department of Plant and Environmental Sciences’ Biochemical Plant Laboratory. Together with Postdoc Nethaji Gallage and the company Evolva, he has developed a sustainable alternative to chemically synthesized vanilla.
Without realising it, many everyday substances are plant derived. But whether you are using powdered vanilla sugar for a Danish rice pudding or spoiling your guests with real vanilla, you might not really know all that much about vanilla production.
Vanilla is a mixture of hundreds of complex flavours and fragrances that originate in the pods of vanilla orchids. It is what you get when buying one of the long, blackish brown vanilla pods. But, there is a complicated process that precedes a vanilla pod purchase, a process that makes the bean’s price as robust as its flavour.
Vanilla orchids lack natural pollinators. So, between its early morning blooming and withering by night, the flower must be pollinated, by hand, using a small brush or toothpick. If not, the flowers die and no pod develops. If pollination is a success, the pod is harvested after about nine months. The pod is then cured for approximately a half-a-year, under varying conditions that promote a complicated fermentation process, during which the vanilla’s characteristic fragrances and flavours are developed.
The most important flavour in vanilla is vanillin, the substance most associated with Christmas and the aroma of vanilla cookies. During fermentation, vanilla pods become blackish brown and lose three-quarters of their original weight, eventually becoming the dark pods that we know as consumers.
Chemically synthesized vanilla cookies
Vanilla pods contain between 1-2% vanillin. So, to produce a single kilo of vanillin from pod requires for roughly 40,000 vanilla flowers to be hand-pollinated. From an industrial perspective, replacing natural vanilla with chemically synthesized vanillin makes enormous sense. And globally, less than 1% of vanilla flavouring actually comes from vanilla orchids as a result. Unfortunately, chemically synthesized vanillin is not a particularly sustainable alternative to natural vanilla.
“For example, vanilla can be produced through the chemical breakdown of wood (lignin). The production of one kilogram of vanillin using this method produces 160 kg of environmentally damaging waste,” explains Birger Lindberg Møller, Head of the Centre for Synthetic Biology, or ‘bioSYNergy’.
Environmentally friendly vanilla
Together with the company Evolva, Birger Lindberg Møller and his colleagues aim to produce vanillin by way of a more environmentally friendly synthetic biology:
"Vanillin produced this way is now being sold as an environmentally friendly alternative to chemically synthesized vanillin. Through the project, we learned how vanilla orchids produce vanillin. This turned out to be through a very unusual enzyme, involved in an otherwise very simple process," explains Birger Møller.
“When buying a vanilla bean for cooking, know that the small black seeds aren't what provide the delicious flavour. While nice to find at the bottom of a crème brûlée, the seeds don’t contain any of the flavour substances. The vanilla pod’s flesh is where the flavours are. And this is the part that one should always be certain to scoop out and scrape at."
Yeast is the key
The researchers behind environmentally sound vanilla found that they could produce vanillin in yeast by using sugar and a classic fermentation process in an enclosed fermentation tank. By adding four genes to the yeast, the yeast was able to convert glucose to vanillin. By then adding an additional rock cress plant gene, it was possible to convert vanillin to the form locked up within the vanilla orchid. This enabled the yeast cells to release the substance, provide a longer lasting flavour and eased the process of isolating pure vanilla.
Fascination from his first year of study
As a young student interested in both chemistry and plants, Birger Lindberg Møller was gripped by an interest in natural medicines. His plant physiology lecturer, Frederik Nartey, was a Ghanaian of the Ashanti tribe. Nartey was an incredibly inspiring person whose access to Ghanaian medicinal plants was possible via family members in Ghana who happened to be medicine men. Birger Lindberg Møller’s master’s thesis was based on isolating pharmacologically strong indole alkaloids from Ghanaian medicinal plants. This was to be the beginning of his career and life with plants.
Advent Calendar 2015
The vanilla orchid flower
The vanilla orchid flower is small, greenish-yellow and fleshy, but nowhere near as striking as the other species of the same genus. Roughly nine months after the plant flowers and the flower is pollinated, a bean-like pod can be harvested. The pods are harvested while unripe, yellowish and fleshy, but without any taste or fragrance.
Photo: Nethaji J. Gallage