Cooking is science and tradition

Cooking is all about science. In this blog our chef Peter Coucquyt will give you insights in the chemistry going on in the kitchen...

woensdag 8 juni 2011

Workshop on hydrollcoids and Foodpairing

Some months ago we started again with our course on cooking and science. The last three weeks we've talked a lot on hydrocolloids. It was time to do some practice.

Following dishes were made last week and we used our new Foodpairing website ( to create the recipes.

This dish was inspired on "The sound of sea" from Heston Blumenthal

Sea (mussel broth, iota), sand (tapiocamaltodextrine, miso oil, anchovies), clams, shrimps, mussels, different kind of algae, oyster leaves and foam of clams, fluid gel of lemon

Second dish was a deconstruction on a classic crab cocktail 

Cannelloni of crab and ketchup (mayonnaise + crab meat, tomato ketchup gel) tomato foam and croquant, grapefruit fluid gel, guacamole

Next was also a deconstruction: Fôret Noir

Chocolate flan, cherry crumble, cherry cream, cherry croquant, vanilla ice cream, Kirsch gel

Fourth recipe is a combination of two classic dishes (asparagus with orange and asparagus with smoked salmon) with a twist

Gnocchi of asparagus (made with kuzu), pickled asparagus, asparagus dashi, smoked salmon, orange fluid gel and fresh grounded coffee

As second dessert we made a recipe based on strawberry

Strawberry gel, strawberry/bell pepper cream, strawberry croquant (obulata with freeze dried strawberry and palatinose, basmati rice soup flavored with cardamom

dinsdag 17 mei 2011

Foodpairing workshop

Last week, we had a workshop on the new foodpairing website. Following dishes were made:
(ingredients in bold in the tree, were used in the dish)

Foodpairing with tomato

Tomato - Philadelphia cheese ice powder - Darjeeling

Tomato salad with different kinds of fresh tomatoes and preparations thereof (raw, pickled, seeds, ...). Tomato bouillon infused with Darjeeling tea. For the tomato bouillon we used ginger and bay leaf. Ice powder of Philadelphia cheese, milk and a pinch of salt.

Foodpairing with asparagus

Asparagus gnocchi and  broth - smoked salmon
orange fluid gel - coffee

A combination of 2 classic dishes, asparagus with orange (asparagus 'Maltaise') and aspargus with smoked salmon, finished with some fresh ground coffee, orange fluid gel and grated orange peel.
The gnocchis were made with kuzu. The broth was made in a pressure cooker (skin of the asparagus, kombu and salt, finished with some butter)

Foodpairing with chicken

Chicken breast in hay - leek - clams
white chocolat crème - black olives

Chicken breast cooked sous vide with hay at 62°C, afterwards smoked on hay and briefly coloured in butter. The clams were prepared in a microwave oven. White chocolate ganache with yoghurt. Dried black olives and braised leek.

Foodpairing with carrot

Yoghurt espuma - carrot - grapefruit
basil - saffron

Yoghurt espuma sweetened with honey. Different textures of carrot: pickled, sponge cake and puree. Fresh grapefruit and meringue of grapefruit. A broth made of fresh grapefruit, tomato and saffron. The ingredients for the broth were put sous vide with soma water and sugar and cooked for 1 hour at 70°C. The result is a clear jus with all the flavours of the ingredients.

Foodpairing with strawberry

Strawberry - bellpepper - almond crème - elderflower beignet

For the gel we cooked some strawberries with water and sugar in the microwave. Afterwards we made a gel of it. The gel is garnished with a cream of strawberry and bell pepper (bell pepper cooked in a light sugar syrup), fresh strawberry, strawberry croquant (obulata with freeze dried strawberry and palatinose), elderflower beignet and cream of almonds (almonds cooked in water, afterwards frozen with milk in a pacojet vessel)

Obulata: tiny papers of potato starch, can be used as a base of croquants
Palatinose: sugar with low sweetness (0,4) made of saccharose. Out of this sugar they make isomalt

maandag 21 februari 2011

Raisin-like caviar

In our post on osmosis we explained how the principle works and which changes occur in food. We also briefly mentioned that this phenomenon could take place on alginate caviar. If so what could we obtain?
Osmosis is the movement of water molecules through a selectively permeable membrane. The membrane is usually an intact cell membrane, present in many food products, but it can also be artificially created, e.g. when making alginate caviar. Water will move from an area of low solute concentration to an area of high solute concentration.
This is the reason why alginate caviar should be stored in the encapsulated fluid. In this case there is no difference in solute concentration so there will not be movement of water from or to the alginate capsule. When capsules are stored in pure water, the solute concentration in the capsule will be higher than in the storage liquid. So the capsules will take up water and swell, this will also dilute the concentration of solutes and the flavor in the capsule. This process goes on until equilibrium is achieved.
What if we now put the alginate caviar in salt or sugar?
Pickling products in salt or sugar was once a popular method. Salt and sugar extract moisture from the food, which increases the shelf life. The same will happen with the alginate caviar. The withdrawal of water from the fluid center of the caviar is an osmosis reaction. The result is a raisin-like caviar. Yet the caviar itself will not take up the sugar or salt. So the raisin caviar will not taste like the pickling fluid. Although the content of the caviar will be concentrated.
So now we know that by osmosis water can flow from the center trough the membrane. We just need to use a highly concentrated storage liquid, or even pure salt or sugar. What if we uses some energy like heat, could we than obtain the same results? 

pumpkin caviar in alginate bath

pumpkin caviar before drying

pumpkin caviar after drying

The results of the drying test are similar as pickling in salt or sugar, but faster. Drying till a fruit leather-like texture gives better results by pickling in sugar. Drying gives a tough result.

zondag 20 februari 2011

Brining or pickling

One of the new trends in kitchens is brining or pickling. What is brining and what happens during this process?
Originally this method was used as a preserving method and not so much for altering or enhancing the flavor and texture. This was just an unavoidable side effect. By putting food in a jar with salt, sour, alcoholic beverages or sugar you could preserve it. (For example: pickles, pickled onions, anchovies, herring, cherries in alcohol, ...).
A high content of salt, a high acidity or low humidity inhibits the growth of microorganisms, which extends the shelf life of products. Brining or pickling will result in microbiological stability, but not in chemical stability. In all cases there will be chemical changes in the food products, resulting in new flavors, textures and colors. Osmosis and diffusion are displacement phenomena that take place in a brined or pickled food product. These processes are mainly responsible for the microbiological stability, while the high concentration of salts, acids and/or alcohol will cause the  chemical changes. Yet these substances are also responsible for the displacement phenomena.
Osmosis is the movement of water molecules through a selectively-permeable membrane. The membrane is usually an intact cell membrane, present in many food products, but it can also be artificially created, e.g. when making alginate caviar. Water will move from an area of high solute concentration to an area of low solute concentration. This process does not require any energy so it occurs naturally and goes on until an equilibrium is achieved. This is the essence of osmosis and is life critical in the cells of all living organisms. Yet osmosis can still occur after the death of the organism, if the cells remain intact.
Osmosis can be and is being utilized in the kitchen.  All plants consist of cells, surrounded by a cell wall that gives strength to the plant. The fluid in the cell is under pressure, providing a crisp and fresh texture. When bitten, the cells snap. Older vegetables lose their moisture (carrots, beans, ...). The pressure in the cells decreases and the vegetable loses its crispness. However, this process is reversible with the aid of osmosis. Soak old vegetables (peeled carrot, limp lettuce, ...) in cold, clean water. They will soak up the water like sponge. After an hour or so, they are crisp again. Since the concentration of solutes in the washing water is lower than in the cells, there will be water movement from the washing liquid to the cells, resulting in a recovered pressure in the cells.
When cleaning lettuce in salted water, there will be water movement from any organism, like bugs, to the salted water. This will essentially dehydrate the bugs causing them to die and release the lettuce. But there will also be water movement from the lettuce to the salted water, causing a drop of cell pressure which we will experience as a reduction in crispiness. In most cases this in not desirable. The effect can again be reversed by washing the lettuce afterwards in clean ice water. Now the lettuce will take up water since the concentration of solutes is higher in the cells than in the ice water.
Diffusion is the movement of solutes, like salts or dissolved sugars, from an area of high solute concentration to an area of low solute concentration. This movement does not require an intact membrane, which is critical for osmosis. Yet diffusion can occur through a membrane if the solutes can pass through it. Diffusion is greatly involved in the marination of a food product. The substances, like salts and flavors in the marinade will move in the food product by diffusion.
When brining or pickling. Water will be extracted from the food product by osmosis, resulting in a concentration of solutes in the food product. Meanwhile, diffusion will cause the food product to enrich itself with solutes in the brining solution. It is also possible that substances in the food product leach out to the brining solution. Consider the curing of a piece of meat, say bacon. Over time, the salt concentration of the bacon will be equal to the salt concentration in the bath.  Water is drawn out of the meat by osmosis and diffusion makes the meat saltier, all because the salt concentration of the bath is higher than in the meat. The meat will also lose acidity, acids migrate by diffusion from the meat to the brine, this is because the latter contains no acid.
Brining or pickling will preserve food microbiologically. It will actually make water unavailable for any living organism in the brine or brined food product. Since the concentration of solutes, in this case the concentration of sodium and chloride is far greater outside the cell of any bacteria, or other harmful organisms, than inside. The result is that bacteria will not be able to uptake water, which is essential to remain alive, on the contrary, water will be forced out of the cell, causing the bacteria to dehydrate and eventually  die. The same happens in a pickling solution, with added pH effects.
Brining or pickling will not preserve food chemically. In fact brining or pickling will promote chemical changes in the food product. Today this is one of the main reasons why foodstuffs are pickled in gastronomy. By brining or pickling, new flavours will arise, the texture and color will also be modified. Acid, alcohol and high salt concentrations have a similar effect on proteins as heat does. Hervé This established the term for the increase in strength without heat, in 2003. He called it “cocteren”. Acids will strengthen cell walls of plant cells while salts will weaken them. Brining vegetable will lead to a loss of crispiness, because the weakened cell walls can not support the pressure, adding to that, the pressure is also lost due to osmosis. 
By brining and pickling, we can alter following properties of the food.
- The water balance: The water balance of the food product will be altered by osmosis.
- The taste and flavor: Diffusion will cause of movement of odorants and tastants from and to the food    product. The substances in the brining or pickling solution will cause chemical reactions, creating or destroying flavors.
- Texture and color: The substances in the brining or pickling solution will cause chemical reactions, altering color and texture.
- Shelf life: Brining and or pickling creates an environment that is inhospitable for food pathogens. 

donderdag 3 februari 2011

Sous-vide cooking

Low temperature cooking, is there a difference with sous-vide cooking? Why should we cook some products at low temperature?
Can one compare sous-vide cooking with low temperature cooking? No, both terms are often mixed but they have different meanings. Sous-vide cooking does not always happen at low temperatures.
Sous-vide cooking or “under vacuum” cooking is a technique in which food products are put in a vacuum bag. The bag is then put under vacuum and sealed. The product is usually cooked at temperatures between 90 and 100 ° C
Cooking at low temperatures is mostly done in a vacuum bag like sous-vide cooking, but can also just happen in oil, butter, broth, ... without sous-vide. The temperatures used are below 90 ° C. and take more account of the structure, composition of the product. Cooking at the right temperature might be a better description. Low temperature cooking refers to the temperature of the cooking medium, not to how the food product is placed in that medium. It’s a technique where the cooking temperature is at, or close, to the desired internal temperature of the food product
Cooking of food products.
There are 4 specific reasons for cooking food:
  • Cooking promotes the accessibility of some nutrients such as starch in potatoes (starch granules are available for digestive enzymes) and colour pigments. So the food will be more digestible
  • The food products become tender, so it is easier to eat. (e.g. connective tissue in meat)
  • Cooking eliminates potentially harmful microorganisms and leaches out some toxins.
  • Heating food launches a series of chemical reactions, breaking down big, tasteless molecules into small molecules detectable by our taste buds.
When we cook, we usually use heat. The methods are varied and each way has its own impact on the product. The medium in which we heat is also important. (e.g. papilotte, can be cooked in the oven or placed on the barbecue. Inside the food, the reactions are the same; the products will cook in a humid vapor atmosphere).
Apart from stews, most cooking processes occur at high temperatures: 100 ° C for boiling water,   160 ° C or more for frying, 200 ° C in an oven, 250 ° C or more on the plancha, ... All these temperatures are much higher than the temperatures whereupon proteins denature and coagulate with significant effects: dry crust around meat, disintegrated fish tissues,... . As the cooking time proceeds, those effects occur more and more.
The “Roner” and other devices
By scientific studies of the chemical and physical phenomena during cooking of food, we learn to understand the changes food undergoes during cooking: changing of colour and texture, development of flavour and aroma. This knowledge and especially with regard to the behaviour of the proteins, led to the determination of the optimal temperatures that should be achieved in the core of food products. The aim is not only cooking the products, but also retaining its shape, making it soft, tender and give it an excellent flavour.
By technical progress, one is able to make very accurate temperature controlled equipment. With the right equipment, one can achieve cooking circumstances that are consistent and reliable. In the beginning of the nineties, a commercial device was placed into the market allowing us to cook at very controlled temperature, called “Roner”.
The Roner is developed by Joan Roca of the restaurant “El Celler de Can Roca" and Nora Caner of the restaurant "La Fonda Caner", both from the province of Gerona (Cataluña).
The Roner is a water bath with a thermal circulator, ensuring that the water maintains a uniform, controlled temperature. Also, it ensures that we can cook, with precision, sous-vide at lower temperatures (mostly between 38 ° and 85 ° C). Now days there exist a lot more devices than the Roner to cook this way (e.g. Noon pro, Sous Vide Professional of Polyscience,…).
These temperatures are not a coincidence. They depend on the composition of the product (e.g. ratio of muscle tissue and connective tissue, starchy vegetables,...). As said, cooking at the right temperature is a more correct expression After all it refers to the best cooking temperature for the product.
The principle of cooking at low temperature in a vacuum bag is clear. Also important is the accuracy over the entire duration of the cooking process. Water is one of the best media for heat transfers by which the temperature can be adjust with the greatest accuracy to one tenth of a degree. (heats up quickly and the transfer of heat is 23 times faster than in a traditional way e.g. conventional oven), While a steamer is precise, his cooking area does not guarantee total uniformity.
Devices like a Roner are often used in laboratories. These thermostats are immersed in water, therefore called thermostat bath. Elbow of a thermostats are heat pumps providing water circulation. They are equipped with a temperature probe. Thermal bain-maries give a fixed temperature and don’t fluctuate a hundredth of a degree.
The technology of a thermostat bath can also be used without sous-vide. One can cook at low temperature directly in oil or melted butter. These fats do not penetrate into the product because the cooking temperature prevents the release of the cell fluid from the product. The fat sticks on the surface in the form of droplets. During cooking both the product and the fat are in contact with each other, making the fat spoil quickly.
Most food products can be successfully cooked sous-vide at low temperature. Although some ingredients can’t be cooked at low temperature such as: green vegetables, cereals, rice,... . Below a brief overview and their advantages on low temperature, sous-vide cooked products.
  • Tender pieces of meat: exact core temperature, uniform cooking and temperature throughout the whole piece
  • Hard, tougher pieces of meat can be softened over time and still look pink. Traditionally confit is done in a large amount of fat. By confit made sous-vide, less fat is used and obtains the same result. In both ways you can cook the meat until it falls apart or just simmer it so one can cut it into slices.
  • Fish: pure flavour and even cooking. Some textures can’t be obtained on traditional way, such as salmon cooked at low temperature. A less flavoured liquid for a more and better taste can now replace cooking in a broth.
  • Other seafood such as lobster, octopus and squid become quickly tough at high temperatures. Low temperature cooking can soften them.
  • Hard vegetables: good results in terms of texture and colour (even cooking of potatoes with not to far cooked outsides, carrots are brilliant orange)
  • Other vegetables: they are soft without being cooked too far or breaking up
  • Fruits: like vegetables. Fruits sensitive of oxidation such as apples and pears retain their colour and gloss
For sous-vide cooked products or dish, we distinguish two methods
  • Indirect cooking
  • Direct cooking
Direct cooking is applicable in restaurants or at home. It replaces other direct cooking techniques and provides a specific core temperature. For fish we speak of 40 to 50 ° C and 50 to 65 ° C for meat. One can cook at a much higher temperature than the desired core temperature where a core thermometer is essential.
Indirect cooking is a kind of mise-en-place preparation, often for products with a long cooking time, such as collagen rich meat. The indirect cooking is similar to pasteurization.
The students made following dishes, using sous-vide technics
Apple, 9h at 85°C, salted butter caramel, vanilla ice, muscovado sugar foam, crumble of hazelnut
Beef 53°C, broccoli florets, broccoli puree, truffle caramel, triple cooked potato, silver onions, onion croquant
Veal sweetbread, 3h at 62°C, braised chicory, liquorice foam, coffee sauce
Pork loin 58°C, cauliflower (puree, couscous, pickled), stalk of the cauliflower, cream of piccalilli
Cod 53°C, spinach, mussel, mussel juice foam, crispy onion
Pineapple 70°C, vanilla ice, mango cream, bourbon caramel, hazelnut crumble
Pheasant breast 62°C, pumpkin (puree, pickled) truffle, trompette de la mort mushrooms, pecan
Venison 52°C, Jerusalem artichoke (puree, cooked sous-vide in microwave), pear (pickled and fluid gel), chocolate crumble
Filet of hare 51,5°C, parsnip puree, apple (pickled, jelly), black pudding cream
Cod 53°C, chervil root (puree, pickled, cooked sous-vide in microwave) bacon crumble

dinsdag 11 januari 2011


Have you ever thought about the fact that some ingredients goes very well together and other combinations are bad?
When we say that tastes good, we mostly talk about how something smells rather than tastes. One has discovered that 20% of what we sense when eating is taste and 80% is aroma. Our tongue has about 9000 taste buds detecting tastes as sweet, sour, bitter, salt and umami. Meanwhile we have between 5 to 10 million cells that can absorb aromas in the nose. We are able to distinguish more than 10000 different odors. This science is the base of Foodpairing
What is Foodpairing?
In the early nineties Heston Blumenthal was working on reducing the bitterness of dark chocolate by adding salty ingredients such as cured ham, anchovies, aged cheese, blue cheese and caviar. By tasting the combination of chocolate and caviar, he was surprised about the perfect match. He asked a friend, Francois Benzi of Firminch to do analyses on the chocolate and the caviar. They found that chocolate and caviar have major flavour molecules in common. At that moment they hypothesized if we find ingredients or drinks with major flavour molecules in common, we could combine them in a dish or drink.
In 2004 Sense for Taste took the initiative to research the fundamentals of this hypothesis, what we now refer to as Foodpairing. Over the last five years, we have created a database containing more than 1000 ingredients with their corresponding flavour profile
The Foodpairing process starts with a flavour analysis of a product. Once the flavour components of a product have been analysed, they are compared to a database of several hundreds other food and drink types. Products with flavour components in common are retained. The results are then represented graphically on a Foodpairing tree, a visual aid for chefs and cocktail makers indicating which ingredients match from a flavour perspective. The shorter the branch, the better the match to the choose product or drink.
More info and Foodpairing trees on
The following dishes, made by the students are based on foodpairing.

Yoghurt soup, milk chocolate mousse, pickled pumpkin, pumpkin croquant, orange, yoghurt meringue and granite of pumpkin and orange.
Pumpkin has major flavour molecules in common with milk chocolate, orange and yoghurt
Flexible chocolate ganache, popcorn ice, roasted sesame croquant, coffee cream, crumble of coffee and chocolate, passion fruit caramel and a mango sphere.
In this example we made some “bridges”. Some ingredients don’t have flavour components in common. Therefore you should search a third ingredient containing major flavour molecules of both other ingredients. Roasted sesame has major flavour components in common with popcorn and mango while popcorn has also flavour components in common with chocolate and coffee. By using popcorn you can combine chocolate and coffee with the roasted sesame
Pomegranate, goose liver ganache, smoked eel, beetroot, red wine vinegar gel.
An other example of making “bridges”, where we started with pomegranate, who has major flavour molecules in common with beetroot and smoked eel, while the eel has also flavour components in common with the goose liver.

woensdag 8 december 2010

Crystallization of sugar

When making a caramel or candies we want a smooth texture and not a grainy one. Large sugar crystals will cause a grainy texture in confectionary products. How can we prevent the over-crystallization of the sugar and thereby prevent unwanted grainy textures?
Dissolving sugar in a liquid results in a sugar syrup. Most of the time the dissolution of the sugar is promoted by heating the mixture. When the solution starts to boil, water evaporates and the solution becomes more concentrated. Crystals start to form only when the sugar solution reaches a certain concentration. This state is called a supersaturated solution. Now the solution is in a state where not all of the sugar can be solubilised. So the sugar goes out of solution and forms crystals. The saturation point (the maximum concentration of sugar in water without crystal formation) is influenced by the temperature of the solution. It is possible to cool an unsaturated solution to a state of supersaturation. And vice versa, it is possible to heat a supersaturated mixture to an unsaturated solution. Far less sugar can be dissolved in cold water than in warm water, this is also the reason why we heat the mixture to obtain a fast and complete dissolution of the sugar. When boiling the solution, water will evaporate and the sugars will get more concentrated. It is possible to supersaturate the boiling solution, this can be observed when crystals form in the solution while boiling. In most cases this is unwanted. Better results will be obtained when the boiling solution is kept unsaturated and subsequently cooled down to a supersaturated state.
If you want to make a candy, like fudge, you need a creamy texture. This creamy texture comes from the formation of tiny sugar crystals. So when preparing fudge, you need to steer the crystallisation towards the formation of tiny crystals and avoid the growth of these crystals, because big crystals result in a grainy texture.
Agitation, stirring or beating supersaturated syrup incorporates air and promotes the formation and growth of sugar crystals due to the rapid movement of the molecules. If the solution is allowed to cool before it is beaten, only tiny crystals forms, which are not allowed to grow. This results in a creamy mass. So when making candy, like fudge, you should allow cooling the sugar syrup to 38°C before beating it, otherwise you will end up with crystals that are too large, resulting in a grainy texture. The beating must also continue until the formation of the tiny crystals is complete, otherwise the excess molecules, the sugar that is still in solution, will migrate to already formed crystals and increase their size. These large crystals will again produce a grainy product.
supersaturated sugar solution
supersaturated solution beaten above 38°C
supersaturated solution beaten below 38°C
Impurities in the sugar syrup may also result in the formation large sugar crystals. Impurities promote premature crystal formation, which will grow to big unwanted crystals. Some products can be added prevent the formation and growth of crystals. These products such as cream, butter, egg white, … are called interfering agents. The agents coat the crystals and prevent the growth of large crystals. Boiling the sugar syrup to the exact temperature is also very important, complete solution of the sugar is very important. Undisolved crystals can also grow out to big crystals, even at room temperature. That is what occurs when we make a “meringue italienne” with bad cooked sugar syrup. The present crystals will grow and result in a grainy texture.
Some sugars as glucose do not form large crystals that easily. By adding some glucose to the sugar for the preparation of sugar syrup or caramel, the glucose will prevent the growing of large crystals.
Sugar, sucrose, is formed from one molecule of glucose and one molecule of fructose. By adding some lemon juice or cream of tartar to the sugar for the preparation of sugar syrup or caramel, we speed up the break-up of the sucrose in glucose and fructose and so decrease the formation of large crystals.