Showing posts with label Kitchen Sciences. Show all posts
Showing posts with label Kitchen Sciences. Show all posts
Sauces Thickened with Droplets: The principles of Emulsions
Emulsion under the microscopeOn a previous post on the principles of sauce consistency, I gave a general description of the different thickening agents. In my next few posts I am going to look into the different thickening methods: what they are, how they work and give you the general guide lines for a successful realisation of sauces using this particular thickening method.
So to start lets have a look at sauces thickened by droplets of oil or water. One very particular method to thickened sauces is to fill the water based liquid with droplets of oil. This droplets of fat are much bigger and slow moving than molecules of water. The result of this dispersion of one liquid in another, is a thick and creamy mixture called an emulsion*.
An emulsion can only be made with two liquids that don't dissolve in each other, like the oil and the vinegar in a vinaigrette. These two liquids can be seen as the container and the contained. The container is called: a continuous phase and the contained one is called the dispersed phase. So an emulsion is the dispersion of a dispersed phase in a continuous phase of water (mayonnaise) or droplets of water in a continuous of oil (vinaigrette).
As you all know it is hard work to make an emulsion. The reason that justifies these frustrating minutes of whisking, is: when two liquids, that don't mix for chemical reason, are disturbed (whisking) and let to stand, they spontaneously take a configuration that minimize their contact with each other: they coalesce. They form two separate large masses, to expose less surface area to each other (see Picture). This behaviour is the expression of the force called: surface tension. So, to make a emulsioned sauce the cook must pour a lot of energy to break this surface tension and create the droplets. The size of the droplets has a big influence on the stability of the emulsion: the smaller the droplet the more stable the sauce will be.
There are two main factors that make it easier for the cook to generate small droplets. The first one, is the thickness of the continuous phase, which drag harder on the droplets and transfers more shearing force to them from the whisk.
There are two main factors that make it easier for the cook to generate small droplets. The first one, is the thickness of the continuous phase, which drag harder on the droplets and transfers more shearing force to them from the whisk.
There is a little experiment that demonstrates this principle:
In a bottle put some water (about 1/2 pt) and some oil (about 2 tablespoons) (fig. 1), give it a good shake (fig. 2) the oil droplets are coarse and quickly coalesce (fig. 3). In another bottle put some oil but in the reverse proportions, 1/2 pt of oil and 2 tablespoons of water (fig. 4) and shake a little (fig. 5). The water breaks into a persistent cloud of droplets (fig. 6).
In a bottle put some water (about 1/2 pt) and some oil (about 2 tablespoons) (fig. 1), give it a good shake (fig. 2) the oil droplets are coarse and quickly coalesce (fig. 3). In another bottle put some oil but in the reverse proportions, 1/2 pt of oil and 2 tablespoons of water (fig. 4) and shake a little (fig. 5). The water breaks into a persistent cloud of droplets (fig. 6).
.JPG)
Fig. 1 .JPG)
Fig. 2 .JPG)
Fig. 3.JPG)
Fig. 4 .JPG)
Fig. 5 .JPG)
Fig. 6In conclusion it helps to start with as viscous a part of the continuous phase as possible and dilute in it, any of the other ingredients required in the recipe, after the emulsion has been established.
The second factor that helps the chef to form small droplets is the presence of an emulsifying agent.
An emulsifier is a molecule that lowers the surface tension of a dispersed liquid in an another. The way that emulsifiers work is that they create a coating on the droplets that shields them from the continuous phase. Such molecules are partly soluble in each of the different antagonists in an emulsion: one part of the molecule is water soluble and the other part soluble in fats. It is said that they have a hydrophobe (afraid of water) side and a hydrophile (that likes water) side.They are two kinds of emulsifying molecules:
- The first ones are, like the phospholipid lecithin in the egg, are small molecule that have an hydrophobe side that attach itself in the fat phase and an hydrophile head that is electrically attracted to the water molecules of the emulsion.
- The second one are proteins which are much larger chains of amino-acids that have a number of hydrophobe and hydrophyle regions. The yolk proteins in the eggs and the casein in dairies are the best protein emulsifying agent.
Another type of molecules that can help in the stabilization of an emulsion are: the stabilizers. They are starches and plant particles. There are many kinds of particles and molecules that can help to stabilize an emulsioned sauce once its formed. They all have in common the property of getting in the way, so that the droplets that are getting towards each others meet the stabilizer instead. Large molecules like proteins or starches are very efficient in this role, pectins, gums and particles of pulverized plants too. Ground, white mustard seeds are a very efficient stabilizer thanks to its particles and gums that are released when wetted. Tomato paste too, is a really interesting stabilizer and emulsifier with its large protein content (3% !) as well as its cell particles. There is a but, though, once the emulsion has formed, the droplets may be so crowded that they bump against each other, then the force of the surface tension may pull them together and cause them to coalesce again.
Now, after the theory the practical stuff. Always keep in mind that emulsion sauces are very fickle ones. There is always a risk that the sauce splits. Three reasons for that:the cook has added the liquid too quickly to the continuous phase, he might have added to much of the dispersed phase or he has allowed the sauce to get either too hot or too cold.
There are the basic rules that will ensure a perfect result, without the risk of the sauce separating along the way:
- The first ingredients in the bowl must be the continuous phase and at least one emulsifying or stabilizing element. The dispersed phase must, ALWAYS, be added to the continuous phase. Otherwise it cannot be dispersed.
- The dispersed phase must be added to the continuous phase very gradually, to begin with. Then, it requires an energetic and continuous whisking all the way through the making of the sauce. ONLY, when the sauce has started to thicken and become more viscous that the oil be added more rapidly.
- Finally, the proportions of the two phases must be kept in balance. The right proportion is that the dispersed phase should not exceed three times the volume of the continuous phase. If the emulsion stats looking stiff it is the sign that it is time to add more continuous phase to the sauce.
When the sauce is finished, it should not be stored at a temperature that is either too hot nor too cold. It should not be kept at a temperature exceeding 60 degrees Celsius. They should not be stored at a low temperature either, under 15 degrees Celsius the surface tension increases making it more likely to coalesce. Butterfat and some oils, solidify at room temperature or in the fridge. This results in sharp-edged fat crystals rupturing the layer of emulsifier on the droplets. Then the sauce will coalesce and separate when stirred or warmed.
In the event of the sauce separating, there are two ways to reemulsify it.
- The first one is to put the sauce in a blender to break the dispersed phase apart again. This has its limitation. It will only work if the sauce still has enough emulsifier left intact. It won't work in the event of the sauce being overheated. Especially, sauces like bearnaise or hollandaise that contains eggs, their proteins may have been cooked thus destroying their emulsifying properties.
- The second one and more reliable one, is to start with a small amount of the continuous phase, adding in an egg yolk (optional), and carefully beat the broken sauce back into it. If the proteins in the sauce have coagulated (cooked) they must be strained out of the sauce first, then it is a good idea to add an egg yolk at the beginning of the process.
*Emulsion: is a word that comes from the Latin for "milk out" and refers to the milky liquid that can be squeezed out of some nuts or plant tissues. Milk, cream and egg yolks are natural emulsions.
Relative proportion of fat in water in common food emulsion**
Food ..............Parts fat to 100 parts water
Fat-in-Water emulsion
Whole milk ..................5
Semi-skimmed milk ..................15
Light cream ................25
Double cream ................70
Double cream reduce by a 1/3 ................160
Egg yolk ..................65
Mayonnaise .................400
Water-in-Fat emulsion
Butter ...................550
Vinaigrette ..................300
**Source: McGee on food and cooking
Flour based thickeners and salt
In recent times, various research on thickeners and perceptions of flavours in sauces and food in general, have uncovered that thickeners reduce our perception of flavour molecules and saltiness. A very interesting one on viscosity and flavour perception, conducted by A. L. Ferry, J. Hort, J. R Mitchell, S. Lagarrigue and B.V. Pamies from Division of Food Sciences University of Nottingham Sutton Bonington, Loughborough in the U.K. and the division of Nestlé Product Technology Center in Germany has shown that viscosity has a huge influence on the perception of salt by our taste buds.
The first reason why the perception of salt by our taste buds is reduced, is that starch based thickeners increase the level of amylose into our mouth. Amylose has the property to trap aroma molecules and bind salt molecules thus decreasing aromatic intensity and saltiness.
Secondly, this study shows that viscosity (the property of a fluid that resists the force tending to cause the fluid to flow) influence the way our taste buds sens salt. It seems that our brain is too busy dealing with this sensation that the salt perception is decreased.
Finally, it appears that poly-saccharides (long-chain carbohydrates), like starch, are able to bind sodium ions to themselves, resulting in a reduction of saltiness.
As a result, the reduction of saltiness reduce the overall aroma intensity in our mouth, albeit the fact that the same number of aroma molecules are flowing out of the sauce and across the smell receptors in our nasal passages. So, if using flour or starch based thickeners, such as a roux or arrow root, in your sauce, you must think that its overall flavour will be diminished. It is, therefore, very important to taste your sauce and rectify, to some extent, its flavour by adding more salt at the end of its cooking process.
The Influence of Thickening Agents on Sauce Flavour
After all these basic sauce recipes that will allow you to master the different techniques used in sauce making, let's have a closer look at the influence of the thickeners on the sauce flavour elements. It is now, understood that the thicker the sauce is, the least flavour it will have.
The first explanation is that as thickeners do not or have very little flavour of their own (excepted brown roux), they only dilute the flavour already in the sauce. The second one, is that thickening agents decrease the aptitude of the sauce to deliver its flavour components. When the thickeners bind with all the elements of the sauce, they also trap some of the flavour molecules in a way that our palate never senses them. By thickening the liquid phase of the sauce, it reduces its fluidity (the speed it moves). It also slows the capacity of the sauce to release its flavour molecule so that our taste buds and nasal passages miss them as they go by.
The third reason why a sauce may feel less flavourful, is that tasty molecules tend to be more fat soluble than water soluble. So, the fat globules dispersed in the liquid phase will catch aroma molecules therefore decreasing the sauce aromatic intensity. Amylose starch molecule, also bind aroma molecules. The aroma molecules in turn make the starch molecules more likely to bond with each other into a grainy milky-coloured particles.
Finally, wheat flour has a tendency to bind more sodium than the pure starches. Long-chain carbohydrates, including starch, reduce the apparent saltiness of the sauce either by binding some of the sodium ions to themselves or by adding another sensation (viscosity) for the brain to attend to.
In general, thin sauces have a more intense and immediate flavour than the same sauce with added thickeners. In the other hand a thickened sauce will release its flavour more slowly and persistently. Each effects has its uses.Many sauces are thickened by reduction, not by adding thickeners. It removes some of the continuous phase by boiling the water off. This technique does not decrease the flavour because whatever flavour the sauce's particles or molecules can bind have already been bound. In result, the thickeners already present in the sauce as well as the flavour molecules become more concentrated, thickening the sauce and intensifying its aroma. It is this principles that are used in tomato fondues, jus, coulis and cream sauces.
And a last little thing to conclude this post, all the sauce thickened with a roux or beurre manié (handled butter) require more added salt. It may be good thing to take this into account if suffering from high blood pressure.
Sauce: The principles of sauce consistency
In this third article about sauces, I will look at the physical structure of a sauce: its consistency.
As I wrote in my last post, a sauce is made of two basic things: flavour and texture. A great sauce is the perfect balance between the two.
When it comes to consistency, several problems can arise, when making a sauce, that can make it unusable. It can congeal, curdle or separate, making your sauce either unpleasant to look at or feel in the mouth.
Lets do a bit of chemistry. A sauce is mainly made of water, even cream ones. The only exceptions are butters and some vinaigrettes. The water or the fat in a sauce is defined by physicists as a continuous phase. It means that water is the material that bathe all the other components in the sauce. All these other components that swim in that continuous phase are called dispersed phase.
Lets do a bit of chemistry. A sauce is mainly made of water, even cream ones. The only exceptions are butters and some vinaigrettes. The water or the fat in a sauce is defined by physicists as a continuous phase. It means that water is the material that bathe all the other components in the sauce. All these other components that swim in that continuous phase are called dispersed phase. So, giving a sauce some consistency is making that water based continuous phase feel less watery by adding a non-watery, dispersed phase into it. By doing that the free movement of the water molecules is obstructed, making the sauce feel thicker.
To explain what is going on when we thicken a sauce, lets imagine a pot full of individual water molecules, H2O. Left on their on, these water molecules have plenty of space to run around: they are very mobile. The water is runny and can flow easily. Now, lets add some flour (long chains of tangled molecules), some oil (droplets), tomato paste (particles) or some bubbles (air) into it. Give it a good stir. Bizarrely, our water seems less watery. The molecules in the dispersed phase that we added into the water are, now, taking some space in our pot. Our molecules of H2O have less space to run freely: we have reduced their mobility. Our liquid thickens.
On a more poetic note, now. Depending on the thickening agent used, not only its consistency will vary, but its texture too. Fat (droplets) make the sauce feel creamier, air (bubbles) make it seem, some what lighter, flour (molecules) will make it sticky or slimy, fruit purée (particles) will make it smooth, etc.
As you may have already noticed, there are 4 kinds of thickening agents: Particles, molecules, droplets and bubbles. Lets see how they interfere with our continuous phase.
Thickening with particles consists of obstructing the continuous phase (water) with tiny bits of meat, vegetables, fruits, spices or seeds. It is what happens when making a tomato sauce or a salsa for example. When these foods are pulverized in the continuous phase all the cell walls and solid cells are broken apart and put in suspension in the water. Then, they obstruct and bind the water molecules, thickening the sauce. Such a mixture is called a suspension. Depending on the size of the particles the sauce consistency will vary and its texture will be more or less smooth.
Note that suspensions have a tendency to settle and separate. Chefs will either increase the amount of dispersed phase by adding starch or reduce the continuous phase by straining the excess water.
Thickening with molecules consists of dispersing single types of molecules, such as starch, gelatin, pectin in the continuous phase. Starch, pectin and gelatin molecules are like long tangled chains of smaller molecules. When dispersed in water, they spread their long chains away taking more space. In result, the water molecules are obstructed. Then the sauce thickens. If the sauce is left to cool down, undisturbed, these molecules can bond with each other and form a loose network that trap the liquid, immobilizing it. It is called: gelation process. Such a mixture is called a gel. If you make a béchamel and let it cool down without stirring it. It will form a semi-solid mass when totally cold.
Thickening with droplets is what happens when you do a vinaigrette. This is how it works. Has you all know water and oil don't really like each other, they do not mix. But if you whisk hard enough, the large droplets of oil that you can see floating away in the water are broken into tiny little ones that block the movement of the water. Such a mixture is called a emulsion. If you want to make a mayonnaise, for example you will require a third ingredient to stabilize the whole structure of your sauce. Such ingredients are called emulsifiers. These types of molecules have the property to attach themselves to water molecules on one end and to capture molecules of fat on the other end. The lecithin in the egg yolks of your mayonnaise are such molecules.
Thickening with bubbles, in substance adding consistency with air. Very peculiar indeed. But this is what happen in the head of a beer or the foam on the top of a good espresso. If you scoop a bit of the head of a pint of Guinness, for example, it can hold its shape. In a fluid, air bubbles behave, more or less, like solid particles. They disrupt the continuous phase that is water and obstruct its flow from one place to another. Such a mixture is called a foam.The major disadvantage of such sauces is that they don't support gravity to well. They are fragile and evanescent. To delay the collapsing of such a structure, chefs thicken the liquid phase with substantial molecules or particles. It is the basic principle used to make a soufflé.
In general, most sauces that chefs make, are combinations of thickening agents. Very few sauces are simple suspensions or foams.
In general, most sauces that chefs make, are combinations of thickening agents. Very few sauces are simple suspensions or foams.
Physics and Christmas dinner!
Christmas is quickly arriving upon us. A classic problem that comes with it, is how long should I cook my turkey to get a tasty and moist roast on Christmas day.
A British doctor in physics and food lover: Peter Barham, has decided to apply Fick's law of diffusion to calculate the best timing for his traditional Christmas roast.
Fick's law says that the diffusion coefficient at different temperatures is often found to be well predicted by J= -D * D C/Dx.
Molecular scientists calculate the heat diffusion process in an animal supposing that the temperature is constant, that the bird is a cylinder and homogeneous, etc. and can achieve an accurate but complex results involving the radius of the animal, the thermal diffusion coefficient, the temperature in the turkey and the temperature in the oven.
Luckily P Braham found simplified way to apply the flick's law to cook his Christmas diner. The flick's law applied to the cooking of a turkey says that the heating time (t) required to reach a known temperature in the center of a turkey is proportional to the square root of the radius of the turkey. As the mass (M) of a sphere is proportional to cubic root of its radius we can find out how long it will take to cook our Christmas diner using this formula:
t=(M/M0)2/3t0
Now, not everybody has a PHD in physics so there are some of the results that were found:
- At 180 degrees Celsius a turkey of 5kg requires 2h25 of cooking, a bird of 7kg, 3h00.
- At 160 degrees Celsius a 5kg turkey will require 3h35 in the oven, a 7kg bird 4h30.
Why Almonds Don't Taste Like Almond Flavouring?
I don't know if you have noticed the difference in taste between the delicate nutty flavours of the common domesticated almonds and the very strong, distinctive flavouring of almond extract. I got curious and decided to investigate. This is the result of my enquiries:
The answer was very simple: the common, eating almond nuts and the almonds used to make "almond extract" are different. One is edible the second one is, potentially toxic. I am not going to focus on the first one, but one the wild bitter almond that is used in almond flavouring.
The wild bitter almonds is the original tree from almond trees family and is originated from Mediterranean and middle eastern region. The second type of almond tree, the domesticated non toxic one, seems to be a mutant of the wild bitter almond tree that has evolved to be able to grow and mature its fruits under much colder horizons.
As I said earlier the nut of the bitter almond is potentially dangerous. A study showed that just few bitter nut eaten in one sitting could kill a child. It is due to its defensive system. A bitter hydrogen cyanide* based poison that is generated when the kernel is broken. But, it turns out that one of the by-product of cyanide production is a molecule called benzaldehyde*. A volatile molecule that is the essence of wild almond flavour and a major contributor in the complex aromas of apricots, cherries, plums and peaches. The "safe" almond varieties lack of both bitterness and the characteristic aroma of the wild "unsafe" ones.
Note that in the U.S, wild bitter almonds are generally unavailable. Here, in Europe they are used in various food products, added in small amounts in marzipan (France) to bring depth to the mixture, they come into the making of amaretto liqueur in Italy as well as in the composition of amaretti biscuits, etc.
The commonest form of bitter-almond flavour is a bottled extract, which contains the aromatic benzaldehyde without its cyanide friend. The pure almond extract is benzaldehyde that is extracted from bitter almonds only, while natural almond extract contains our "B" friend produced from cassia bark (also known as cinnamon tree). Finally, the imitation extract is made with chemically synthesized benzaldehyde.
*Benzaldehyde: in simple words: oil of bitter almonds, C 6 H 5 CHO, the simplest representative of the aromatic aldehyde. It was first isolated in 1803 and was the subject of an important investigation by v.Liebig in 1837 . It occurs naturally in the form of the glucoside amygdalin (C20H27N011), which is present in bitter almonds, cherries, peaches and the leaves of the cherry laurel; and is obtained from this substance by hydrolysis with dilute acids: C20H27N011+2H20 =HCN+2C6H,206+C6H5CHO. It occurs free in bitter almonds, being formed by an enzyme decomposition of amygdalin.
*Hydrogen Cyanide: It is a molecule of the cyanogen family. They are highly toxic and volatile compounds, easily recognised by their almond like aromas. The hydrogen cyanide chemical formula is HCN, which means that it made of 1 atom of hydrogen, 1 atom of carbone and 1 atom of nitrogen. Plants have developed these poisons to warn animals and eventually kill them, in the purpose of allowing their seeds to mature and disperse. When the plant's tissue is damaged by chewing, the cyanogens are mixed with the plants enzyme that breaks them apart and release hydrogen cyanide.
Hydrogen cyanide rich-foods, such as manioc, bamboo shoots,and tropical variety of Lima beans are made safe for consumption by open boiling, leaching in water and fermentation.
Dough and Batter part I
I admit it now, but the discussion that will follow might be a bit too technical and boring for some. But I think it is important to know how ingredients in a dough or batter interact with each other and contribute to the final result. So, there is a list of the most common pastry ingredients and their components, and how they contribute to the structure of a dough or a batter.
Flour
- Glutenin: this is a type of protein that forms the interconnected gluten network and makes the dough elastic.
- Gliadin: this is another kind of protein component of the flour that bonds weakly to the glutenin network to make the dough plastic.
- Starch: It is a form of complex carbohydrate that will fill the gaps in the gluten network and absorb water during cooking. This will have for effect to tenderize the dough and set its structure during cooking.
Water
- It will allow the the gluten network to form and dilute it. Depending on its quantity the final product will be more or less tender.
Yeast and Leavening Agents
- Composed of live cells in the case of the yeasts or purified chemicals in the case of the baking powder, these ingredients have the role of producing carbon dioxide gas (CO2) in the dough or batter. This has for effect to lighten and tenderize the final products.
The Salt
- It is a purified mineral that has for effect to tighten the gluten network, thus bringing stability to the dough or batter. It make the dough more elastic.
Fats, Oils, Shortenings
- These ingredients are mainly made of lipids. They weaken the gluten network, tenderizing the final products.
Sugar
- Sugar is purely made of carbohydrates. They will have for effect to weaken the gluten network and absorb moisture, making the final products tender and moist.
Eggs
- The egg is essentially made of proteins, fats, natural emulsifiers (like the lecithin) and water. These various components of the egg will have very different, but complementary effects on the dough or batter. The first one, comes from the proteins. As the dough or batter cooks they coagulate and supplement the gluten structure with tender protein coagulum. The fats and emulsifiers weaken the gluten network, tenderizing the final products and slowing down the staling process. The other role taken by the natural emulsifier agents that are contained by the egg yolk, is to stabilize the bubbles of CO2 and the starch during the cooking process.
Milk and Buttermilk
- Essentially made of proteins, fats, natural emulsifiers and hydrogen based molecules (acids) milk or buttermilk weakens the gluten network and stabilizes the Co2 bubbles. The final products will, in effect, be tenderized and stale at slower rate.
To finish this little explanation, I would like to precise what I meant when I used the words plastic and elastic in relation to a dough.
Elastic, or elasticity and plastic, or plasticity are two qualities that are brought to a dough through the presence of gluten in the flour. It is characterized by the capacity of a dough to change shape under pressure, but still resist it and move back towards its original shape when the pressure is removed. This is why kneading bread by hand is not an easy job. I think everybody will agree with me on this! Thanks to this combination of properties, wheat dough can expand to incorporate the carbon dioxide gas produced by yeast or leavening agent, and yet resists enough that its bubble wall will not thin to the breaking point.
If you are interested in the elastic and plastic properties of wheat dough, I recommend you this study made by Dr Salme Taagepera, Lecturer and Academic Coordinator at the
Department of Developmental and Cell Biology at the University of California, Irvine, US. (Copy and paste this link in your browser) http://www.google.com/search?q=cache:DW4Ft0VszEMJ:https://eee.uci.edu/clients/staagepe/bio%25209b/powerpoints/lec15_16%2520dough%2520batter%2520c.ppt+gluten+plasticity+and+elasticity&hl=en&ct=clnk&cd=4&gl=ie
A Broad Survey of the Beneficial Effects of Chemicals in Fruits and Vegetables
It is well understood that some chemicals in fruits, vegetables, herb and spices can affect various aspects of our health. There is a very broad survey of a very rich and complex subject.
Prevent oxidative damage to important molecules in the body : antioxidants
Eye: slow cataracts and macular degeneration
Kale, many dark green vegetables.
Caroteinoids: lutein.
Citrus fruits, corn.
Carotenoids: zeaxanthin.
Blood lipids: slow the development of heart disease
Grapes, other berries.
Phenolics: anthocyanidins.
Tea.
Phenolics.
General : reduce DNA damage and the development of cancer
Tomatoes.
Carotenoids: lycopene
Carrots, other orange and green vegetables
Carotenoids: Beta-caroten
Tea.
Phenolics.
Green vegetables.
Chlorophyll.
Broccoli, daikon, cabbage familly.
Glucosinates, Thiocyanates.
Moderate the body's inflammatory response
General: slow development of heart disease and cancer.
Raisins, dates, chilis, tomatoes.
Salicylates.
Reduce the body's own production of DNA-damaging chemicals
Many fruits, vegetables
Phenolics: flavonoids.
Broccoli, daikon, cabbage family.
Glucosinolates, thiocyanates.
Citrus fruits.
Terpenes.
Inhibit the growth of cancer cells and tumors
Many fruits, vegetables.
Phenolics: flavonoids.
Soybeans.
Phenolics: isoflavones.
Grapes, berries.
Phenolics: ellagic acid.
Rye, flaxseed
Phenolics: lignans.
Citrus fruits.
Terpenes.
Mushrooms.
Carbohydrates.
Slow the body's removals of calcium from bones
Onions and parsley
Responsible agent not yet identified.
Encourage the growth of beneficial bacteria in the intestine
Onion family, sunchoke.
Inulin
Prevent the adhesion of infectious bacteria to walls of urinary tract
Cranberry, grapes
Phenolics: proanthcyanidins
Cancer and Cooking meat
A report about a technical Food and Agriculture Organization study "World agriculture: towards 2015/2030" published in 2002, shows that meat consumption in developing countries, has risen from only 10 kg per person annually in 1964-66 to 26 kg in 1997-99. It is projected to rise to 37 kg per person per year in 2030. As it seems that we are not going to become a society of vegetarians anywhere soon, let's make sure that we know the danger that a meat rich diet can have.
In the middle of the 20th century, medical researchers began to concentrate on the role of nutrition in the two main diseases which can cut our gastronomic life short: heart disease and cancer. It happens that meat and its mouth watering taste, has its downside: a diet high in meat is associated with a greater risk of developing heart disease and cancer. In our post-industrial lifestyle which consists of a lack of physical activity and an unlimited ability to indulge our taste for meat, the high consumption of meat contributes to obesity which increase the risk of various diseases.
The first contribution of meat towards shortening our life of "gastronomes" comes from the meat itself : FATS. To be more precise saturated fats. This type of fat is known to increase our blood cholesterol levels and can contribute to heart disease. And to the extent that meat displaces from our diet the vegetables and fruits that keep heart diseases and cancer at bay, it raises our vulnerability to both.
The second one comes from the way the meat is prepared. I have to say that I was probably like most, apart from the odd cremated steak. I did not suspect that the way I cooked meat could end up creating some potentially dangerous types of carcinogenic by-products. Scientist have identified three families of chemicals created during meat preparation that potentially damage our DNA and that may increase our risk of developing cancer of the large intestine.
Let's start with the Heterocyclic Amines (HCA). They form at high temperature by the reaction of some minor meat components, creatine and creatinine (women may have heard of the first compound as some cosmetics producers advertise its benefits to tackle wrinkles) with amino acids (basic elements of proteins). HCAs are generally greatest at the meat surface where the temperature is the highest and where the meat juices collect. They also appear on meats that are grilled, broiled or fried well done. Oven roast meat surfaces are more or less free of HCAs but the pan drippings can show great amounts. It is relatively easy to reduce the production of HCAs. Acid marinades, for example, decrease the creation of HCAs. Gentle cooking and aiming for a rare or medium doneness would help too. Furthermore, the consumption of vegetables, fruits and acidophilus bacteria seem to bind HCAs in the digestive tract and prevent their absorption.
The second type of carcinogenic chemical that can be created while cooking meat is called Polycyclic Aromatic Hydrocarbons or PAH. They are created when nearly any organic material, like wood or fat, is heated to their burning point. This is what happens when butter overheats and burns. This is the reason why most food authorities have simply banned the traditional "raie au beurre noir". Back to our meat, PAHs are mainly found on meats that have been cooked over a smoky wood fire that will deposit PAHs on the meat or smokeless charcoal fire which will create PAHs from the fat, if the fat is allowed to fall and burn. Small amounts of PAHs can be produced during high temperature frying. PAHs can be minimized by cooking meats over a wood fire only if it has been reduced to coals, by leaving the grill uncovered, by avoiding fat flareups and by eating smoked meat with moderation. 
Finally, there is our third bad guy. It is known by the name of nitrosamines. They form when nitrogen-containing groups on amino-acids (basic constituents of proteins) and related compounds combine with nitrite, a chemical used for centuries in salt-cured meats and prevent the development of the Clostridium Botulinum responsible for botulism. This reaction happens both in our digestive system and in a hot frying pan. Nitrosamines are well known to be a very powerful DNA- damaging chemicals, despite the lack of evidence that nitrites present in cured meats can increase the risk of developing cancer. Though, it's seems prudent to eat cured meats with moderation and cook them gently. To end this alarmist panflet about meat, I would like to quote Harold McGee in "McGee on food and cooking", Hodder and Stoughton edition, who rightly says : "It's prudent, then to temper our species' infatuation with meat. It helped make us what we are, but now it can help unmake us."
Cold cooking!
Throughout my years cooking in Ireland I encountered quite a lot of customers who would send back marinated fish dishes such as the ”mackerel” recipe that I posted on my blog, complaining that it was raw.
I always ask myself why is this. I decided then to go to have a talk with such customers to try to find an answer to my questions. I realised then that for them cooked food meant that the ingredients have been exposed to heat. This is not a misconception of the word cooking but meat, vegetables or fish can also be cooked without heat.
First of all let’s define the action of cooking. The Oxford dictionary says : “prepare by mixing, combining and heating the ingredients” or “be heated so that the state required for heating is reached”. But for the cook, cooking has two objectives, make the food easier to digest and create new flavours. For the scientist/cook, cooking means breaking down of proteins and chemical reactions.
What are the effects of heat on ingredients like fish or meat in a recipe. Heat will tenderise tough molecules and start chemical reactions that will create new aromatic compounds.
The molecule that makes meat or fish tough is called collagen. Women would be quite familiar with this type of protein as it is widely used in cosmetics. This protein constitutes a third of all animal protein. Collagen can be broken down by heat therefore making meat or fish easier to chew and digest.
But protein can also be broken down with acid such as vinegar,lemon juice or acidic compounds in wine. This will happen without heating by just placing the ingredients in a marinade for some time. So a fillet of fish placed in a marinade will be cooked with the acid in the mixture.
I came to the conclusion that the customers were mainly worried about food safety. And there are right to be concerned about it. One of the most important things is the freshness of the produce.
But there is another way of ensuring food is safe without using heat and this is where food science kicks in. The acid in a marinade acts as a preservative and there are very few strains of bacteria that would live or survive in an acidic environment. Pickles are a good example of the preservative effect of acids. Another example is ascorbic acid, more commonly named Vitamin C, is naturally present in lemon juice. The food industry make good use of this preservative, you can find it very often on food packaging under the number E300.
So feel confident, try marinated fish dishes or my simple recipe for mackerel.
I always ask myself why is this. I decided then to go to have a talk with such customers to try to find an answer to my questions. I realised then that for them cooked food meant that the ingredients have been exposed to heat. This is not a misconception of the word cooking but meat, vegetables or fish can also be cooked without heat.
First of all let’s define the action of cooking. The Oxford dictionary says : “prepare by mixing, combining and heating the ingredients” or “be heated so that the state required for heating is reached”. But for the cook, cooking has two objectives, make the food easier to digest and create new flavours. For the scientist/cook, cooking means breaking down of proteins and chemical reactions.
What are the effects of heat on ingredients like fish or meat in a recipe. Heat will tenderise tough molecules and start chemical reactions that will create new aromatic compounds.
The molecule that makes meat or fish tough is called collagen. Women would be quite familiar with this type of protein as it is widely used in cosmetics. This protein constitutes a third of all animal protein. Collagen can be broken down by heat therefore making meat or fish easier to chew and digest.
But protein can also be broken down with acid such as vinegar,lemon juice or acidic compounds in wine. This will happen without heating by just placing the ingredients in a marinade for some time. So a fillet of fish placed in a marinade will be cooked with the acid in the mixture.
I came to the conclusion that the customers were mainly worried about food safety. And there are right to be concerned about it. One of the most important things is the freshness of the produce.
But there is another way of ensuring food is safe without using heat and this is where food science kicks in. The acid in a marinade acts as a preservative and there are very few strains of bacteria that would live or survive in an acidic environment. Pickles are a good example of the preservative effect of acids. Another example is ascorbic acid, more commonly named Vitamin C, is naturally present in lemon juice. The food industry make good use of this preservative, you can find it very often on food packaging under the number E300.
So feel confident, try marinated fish dishes or my simple recipe for mackerel.
Green Blueberries!
Green blueberries ???
No, it is not an Irish specialty for the St Patrick’s celebrations. This may happen when you bake using blueberries.
Why would a deep, dark blue fruit turn green when baking it?
This could happen if the muffin mix contains too much baking soda or if the soda isn’t evenly mixed in the dough or batter. This would result in some alkaline pockets throughout the mix which could get in contact with the fruits.
Bilberries and blueberries are rich in anthocyanin pigments specially under their skin. These pigments are extremely sensitive to PH changes and are generally associated with acidic fruits. They are concentrated in cell vacuoles as in purple beans or sometimes, just in a superficial layer of cells under the fruit skin, as in grapes or blueberries.
In the fruit, these anthocyanins are surrounded by a acidic environment as the pulp of the berries is quite rich in hydrogen. When you add the berries into the muffin batter their skin may break allowing the soda in the alkaline pockets to get in contact with the pulp and the anthocyanin pigments. The result of this action will be the elevation of the PH therefore changing the pigmentation of the anthocyanin. Turning the dark blue of the blueberries into a greenish pigment.
This is not as mouth watery looking!
So, to avoid this to happen, make sure that all the dry ingredients are mixed well together before adding any liquid into your muffin or other type of cake mixes and batters.
“un homme averti, en vaut deux”
French saying
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