To make soup powder, vegetables are dried, losing a lot of flavor. Researcher Joanne Siccama used a different technique for asparagus, which preserves more flavor and requires fewer additives.
Conscious consumers are increasingly looking for foods made from purely natural ingredients. The more seasonings added to a product, the more suspicious the discerning buyer will be. Manufacturers are trying to respond to the changing demand.
Take a seemingly simple product like vegetable broth powder, the kind you have to add hot water to make a soup. Aromas are added in the factory to enhance the taste. Not that that taste is not naturally present in the processed vegetables, but part of it disappears due to the production process.
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Isn’t there a way to keep the natural flavor in the soup powder? Wageningen researcher Joanne Siccama was happy to respond to that question. Siccama works at the Laboratory of Food Process Engineering at Wageningen University. ‘My interest lies in ‘vegetable waste’ that is thrown away unused in the food industry. I am very concerned with sustainability: reducing waste, and reducing energy consumption and CO2emissions.’ Siccama obtained her PhD for her search for a solution to the soup powder problem.
Evaporated taste
What kills the taste of those soup powders, Siccama explains, is the way the vegetables are processed. The manufacturer uses fresh vegetables, chops them into pieces and dries the pieces at a minimum of 70 degrees in a kind of long tunnel. ‘When the vegetables are dried like this, they can be immediately ground into powder.’ That powder forms the main ingredient of the later soup.
But the big problem with this drying process is that the vegetables lose a lot of their smell and taste: they evaporate with the moisture in that tunnel. ‘Asparagus in particular seem to lose so much of their aroma.’ This is where Siccama has concentrated its research: on preserving the asparagus aroma that ends up in asparagus soup powder.
Asparagus juice
The researcher collected 220 kilos of ‘butts’ from an asparagus grower in Helden, Limburg: the back ends of asparagus, which are left over after the grower has cut them to size. She applied a completely different technique to make soup powder.
The backsides went into a press where they were wrung out. For example, they were separated into juice and – non-edible – fibres. The asparagus juice was centrifuged to eject hard particles.
Siccama then pressed the juice through an extremely fine mesh sieve, a membrane. A thick, concentrated juice remains at the front of this, while the residual water is drained at the back. She eventually obtained 28 liters of concentrate from 220 kilos of asparagus waste.
The researcher then applied a method from the food industry to that thick juice: spray drying. The juice is pumped up and atomized into very small droplets. They come in a stainless steel drying chamber in which it is 160 to 180 degrees. There the droplets dry super fast.
Siccama: ‘If you let the water evaporate, you are left with particles that consist of two thirds of sugars and one third of proteins.’ Due to the rapid drying, the particles shrink and a dry shell forms on the outside.
Processed starch, or maltodextrin, has been added to the nebulized juice. This forms a shell around the juice particles, so that the aromas cannot escape. ‘If you didn’t add the starch, you would end up with a viscous sugar mass that sticks to everything. Thanks to the starch coating, you get a powder to which you can add water, releasing the preserved aromas.’
Stronger asparagus flavour
Using a membrane to make soup powder is new: Siccama is the first to apply this fine-mesh sieving technology for this purpose. ‘It functions! And my approach uses less energy to remove the water from the vegetables than a traditional drying tunnel.’
Naturally, the researcher and her colleagues put it to the test: is the spray-dried asparagus powder really tastier than the result from the drying tunnel? A test panel thought Siccama’s variant was better. ‘And you need to add less flavorings to this powder, because the soup tastes more like asparagus.’
But as far as Siccama is concerned, this experiment does not stop with asparagus: ‘My dream for the future is that this technique will also allow us to better retain the aromas from other vegetables, so that ultimately fewer additives will be necessary.’