Posts Tagged ‘10 tips’

Ten tips for practical molecular gastronomy, part 10

Wednesday, July 30th, 2008

Finally it’s time to round up my ten tips for moleceular gastronomy with the shortest of them all:

10. Have fun!

I sincerely believe that whatever you do, you do it better if you enjoy it. This isn’t a very scientific statement, but I’m sure there are bunches of scientific papers proving this, and my excuse is that I wouldn’t know where to start searching for them ;) (perhaps anyone can help?)

If you had fun preparing the food it’s definitely going to taste better when you eat it. And if you enjoy the company of good friends it’s going to taste even better (as pointed out by Hervé This previously). In his elaboration of what molecular gastronomy is (or should be), Hervé This emphasizes that the social phenomena linked to cooking and eating are among the topics that should be studied scientifically. In the first post summing up the 10 tips I mentioned the research done at Grythyttan in Sweden which has resulted in the “Five Aspects Meal Model” which captures a little of this. And I also stated that

average food eaten together with good friends while you’re sitting on a terrace with the sun setting in the ocean will taste superior to excellent food served on plastic plates and eaten alone in a room with mess all over the place

Perhaps this is what Paul Bocuse was touching upon as well when he was interviewed by a local newspaper in Stavanger where the Bocuse d’Or Europe final recently was held. Being questioned about what his greatest culinary experiences were he answered (my translation):

- I’ve travelled a lot and been lucky to taste delicacies from many different countries, but nothing compares to simple dishes were the pot is placed in front of you on the table and where you have the opportunity to help yourself several times until the food gets cold.

Hey – I’d be happy to invite him over for dinner. He sounds like an easy guest to please ;)

One of my intentions with the “10 tips” series has been to move the focus a little bit away from what too many have come to associate with molecular gastronomy – foam, alginate spheres and cooking with liquid nitrogen to mention a few. For me it has been a great oppurtunity to research a number of topics and I’m very thankful for all the feedback from readers! And in case it sounds as if I’m going to quit blogging I can let you know that the number of drafts for future blog posts is steadily increasing… So many interesting topics, so little time … But I’ll try to finish some of them soon.


Not only do I have fun cooking – blogging is also great fun! Here’s my blog as viewed on an OLPC (shown in tablet mode) obtained through the G1G1 program. Notice the screen which in the picture shown operates in a reflective, high-resolution black and white mode that is sunlight readable!

*

There is a summary of the “10 tips for practical molecular gastronomy” posts. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (people/chefs/blogs, webresources, institutions, articles and audio/video) at khymos.org might also be of interest.

Ten tips for practical molecular gastronomy, part 9

Saturday, May 31st, 2008

9. Keep a written record of what you do!

Wouldn’t it be a pity if you couldn’t recreate that perfect concoction you made last week, simply because you forgot how you did it? Last year I made a vegetable soup to which I added garam masala and pepper. I was cooking ad lib, adding a little of this and that without taking notes… Which is annoying, because it turned out very nice! It had a remarkable aftertaste which gave me a somewhat dry feeling on the back of the tongue and it reminded me of mangoes. Even immediately after the meal I wasn’t able to recall all the ingredients.

As an undergraduate student I took an organic chemistry lab course, and I remember we were told not to use post it notes or small pieces of paper for taking notes. Everything should be recorded in a proper journal or – if necessary – small note books. Having finished my Ph.D. a couple of years later, I can only testify to this. Everything you do – be it in the lab or in the kitchen – should be recorded immediately in a journal. It’s amazing how something that was obvious one day, slips your mind a week or month later.

There is a wonderful Donald Duck story by Volker Reiche entitled “The soul of science” (the original appeared in 1981 in the Dutch Donald Duck magazine). At a point “Professor Duck”, who actually works as a janitor in a lab, utters the words “Careful notes are the soul of science” as he is caught experimenting. This is true also for the kitchen and experimental cooking. A German translation of the story was reprinted in the article “Das Leiden des cand. chem. Donald Duck” (open access) in case you want to read the whole story.


Careful notes are also the soul of kitchen science!

When taking notes it’s essential that you are able to re-cook the dish yourself. But if no one else is, the notes are of limited value. The biggest source of uncertainty in the kitchen is the widespread use of volume for measuring powders. This can best be illustrated by the question: How much does a cup of flour weigh?

I bumped into this when I began baking no-knead bread (recipe). I converted the recipe to metric units using an online calculator, but the no-knead bread wasn’t a huge success. The problem was that there is no simple answer to the question “How much does a cup of flour weigh?”. Cooking conversion online states that a cup of all-purpose flour weighs 99 g. King Arthur Mills claim that all their flours weigh 113 g/cup. USDA states 125 g/cup and Gold Medal 130 g/cup. Some cookbooks have settled at 140 g/cup (apparently because this is about half way between a loosely and densly packed cup) and if the flour is hard packed you can reach 160 g/cup. In other words – when following a recipe you would need to know how the volume of flour was measured in order to use exactly the same amount of flour. Some recipes call for “spoon and level” or “scoop and level”, but many do not include any information about this.

My recommendation is to weigh all dry ingredients (and preferably also the wet ingredients). A normal digital kitchen scale typically has a resolution of 1 g with an accuracy of +/- 5 g and they are quite affordable. Weighing liquids is also far more accurate than the average volume measurement in the kitchen. If the scale has a “tara” function it’s also much faster as you can zero the display after each ingredient you add. It shouldn’t come as a surprise that I’m not the only chemist advocating weight measurements in kitchen. And it’s not difficult finding other sites in favor of weight measurements either.

It therefore puzzles me why recipes that call for the following are still so abundant:

1 pack of instant yeast
1 envelope unflavored gelatin
1 gelatin sheet (see comment #4-5)
1 sachet powdered pectin
1 tablespoon liquid pectin
1 stick of butter
… and the list goes on

The only exception to the general advice on weighing ingredients is when very small quantities are used. This could be spices, food coloring or hydrocolloids. With normal kitchen scales, you’ll be better of using volume measurements for amounts less than 5 g (equal to a teaspoon if measuring water). Otherweise it’s worthwhile mentioning that scales with a 0.1 g and 0.01 g readout are getting cheaper and cheaper.

*

There is a summary of the “10 tips for practical molecular gastronomy” posts. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (people/chefs/blogs, webresources, institutions, articles and audio/video) at khymos.org might also be of interest.

Ten tips for practical molecular gastronomy, part 8

Sunday, February 3rd, 2008

balancing-forks-tall.jpg
Read about the physics behind the balancing fork trick.

8. Experiment!

Dare to experiment and try new ingredients and procedures. Do control experiments so you can compare results. When evaluating the outcome, be aware that your own opinions will be biased. Have a friend help you perform a blind comparison, or even better a triangle test to evaluate the outcome of your experiments.

In a scientific context, an experiment is a set of actions and observations performed in the context of solving a particular problem, in order to support or falsify a research hypothesis. In a kitchen context, the problem to solve would typically be related to taste, aroma, texture or color. And the required actions and observations would be cooking and eating.

An essential part of the scientific method is that new knowledge is gained when, based previous knowledge, an assumption is made and tested. In the kitchen, this is exactly what you do when you taste your concoctions repeatedly as you cook. And it is also what makes you an experienced cook, because you remember and learn from your previous successes and mistakes. It might sound very complicated, but here’s how it goes:

1) Observation: soup lacks flavor
2) Hypothesis: adding something with flavor might help
3) Experiment: add more spices
4) New observation: soup tastes more (or less)
5) Hypothesis is either supported (or rejected)

Of these steps, I think observation is the easiest. Coming up with a hypothesis however can sometimes be difficult. If you have lumps in your custard or a sauce that’s separating, it isn’t always easy to think of what to do. This is where books on popular food science and molecular gastronomy might help you.

balancing-forks-1.jpg

Think outside the cook book! I mentioned in previous post that you should always question authorities and cook books. And even when you have a recipe that works, remember that it’s nothing more than a suggestion. For instance, it can be useful to know when to be sloppy and when to be accurate with measurements. The smaller amount you measure, the greater the precision should be. Let’s consider a hypothetical recipe that calls for 1000 g flour and 1 g of saffron. Whether you use 999 or 1001 g of flour makes no difference, but using 1 or 2 g of saffron will be quite noticable. A good rule of thumb is that you should measure to within +/- 10% of the given amount. But again, don’t follow this blindly. Experience will show when you can be even more sloppy.

Thinking of good experiments to do requires both creativity and experience, and there are many sources of inspiration. The molecular gastronomy movement has come up with a number of books and blogs which point towards new ingredients and procedures. There are several approaches to flavor pairing (i.e. a general one based on experience and a chemical one based on impact odorants). Further more there’s a lot of inspiration to get from regional cooking – also for molecular gastronomists! Lastly, I think considering not only the food but the whole atmosphere and the setting of the meal is important, because our senses are connected!

balancing-forks-2.jpg

The best way to judge the outcome of a new procedure or ingredient is to compare it with the original. I’ve previously termed this “parallel cooking”. In scientific contexts it’s very common to do control experiments and I can’t see why this shouldn’t be done in the kitchen routinely. Im convinced that this could have saved us from many kitchen myths!

Once you’ve done your parallel cooking, you have to taste it. If you did the cooking, you’ll probably have an opnion or expectation that the new dish is better or worse than the original. The big problem here is that due to confirmation bias, if you know what you are eating, this will influence your perception of it. Therefore it’s crucial to do a blind tasting (or a double-blind tasting). Have friend help you label each dish with random three digit numbers (to avoid thinking about ranking) and give them to you. If the dishes can easily be recognized due to color, it’s important that the lights are turned down or that you are blindfolded. State which dish you prefer and have your friend reveal the identity of the dishes tasted.

A slightly more sophisticated test is the triangle test which is commonly used in the food industry. The tester is presented with three samples of which two are identical and the task is to pick the odd one out. Using statistics, it’s possible to evaluate the outcome of repeated tests. The number of correct assignments in a number of triangle tests required for you to be 95% sure there is a difference are given in the table below. Read more about simple difference tests here.

Number of tests performed Number of correct assignments required
3 3
4 4
5 4
6 5
7 5
8 6
9 6
10 7

Bionomial distribution for a triangle test (p=1/3) at 0.05 probability level. A more extensive table can be found here.

It seems that this would be the ultimate way to determine whether or not there is a difference between pepsi and coke. It’s more than 50 years since the first experiments were conducted. The theory is simple, but in the real world things aren’t always that simple. Read the entertaining story about Fizzy logic.

balancing-forks-3.jpg

There are several examples of experimental cooking out on the net, and I thought I’d share some of them with you as this might illustrate my ideas on the subject.

Many cooks have strong opinions about how garlic should be treated. Should it be minced, crushed or microplaned? And does this really influence the taste and aroma? Or does it only affect the degree of extraction and hence the intensity of the flavor? Dominic of Skillet Doux had a excellent post on this subject in 2006, Deconstructing garlic. The task was formulated as follows:

The subject of this experiment is the effect that various methods of breaking down garlic have on its flavor when used to prepare a dish. The hypothesis is that not only does mincing garlic create a different flavor than crushing it, but also that mincing is the preferred method for pasta sauces. Furthermore, the experiment is intended to determine if microplaning garlic achieves a character different from mincing or crushing.

In his conclusion, Dominic writes ” I was surprised to discover that the difference between the minced and crushed garlic sauces was even more significant than I had previously thought”. Check out his post to find out which kind of garlic treatment he prefers for his pasta sauces. As a side comment it can be mentioned that a group of researchers in 2007 studied the effect of cooking on garlics ability to inhibit aggregation of blood platelets. They found that crushing could reduce the loss of activity upon heating. But unfortunately they didn’t report anything about the flavor.

Other food bloggers have also adopted experimental cooking with emphasis on systematic and thorough testing. Examples include Chad’s experiments with gellan, konjac and iota/kappa carrageenans, Michael Chu’s parallell cooking of bacon and his eggplant test and Papin’s comparison of orange juices – to mention but a few! And I shouldn’t forget Dylan Stiles either whom I mentioned in part 5 of this series:

A challenge with aroma molecules is that they should remain intact during storage and not be released until cooking (or even better, until consumption). A example would be to install a Liebieg condenser over your pot. Dylan Stiles has explored this in his column Bench Monkey by placing a bag of ice on top of the lid. He claims that his roommates preferred the curry which has been cooked under “reflux conditions”. The study was performed in a double blind manner (which I will come back to in part 8 of this series).

An extreme example of the application of the scientific method to cooking appeared in the news last spring when the recipe for the ultimate bacon buttie was revealed by scientists from Leeds University. Commissioned by Danish Bacon, the study evaluated more than 700 variations of a bacon buttie. They even came up with a “formula” for the perfect bacon buttie and quantified the required crispiness and crunchiness. The news story was picked up by many news agencies, so although it wasn’t necessarily ground breaking science, at least it was clever marketing.

*

Check out my previous blogpost for an overview of the 10 tips for practical molecular gastronomy series. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry, presentation/photography) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

Ten tips for practical molecular gastronomy, part 7

Monday, August 27th, 2007

book-pile-450px.jpg
Click here for full size image

7. Question authorities and learn from the experts

A thick, nicely bound cook book with marvelous pictures and a professional layout signals quality and authority. But unfortunately the nice wrapping is no guarantee that the contents is scientifically sound. I would guess that the searing/sealing myth and adding salt to water used to boil vegetables are among the most ubiquitious of the myths. The challenge for everyone is to question the procedures and explanations given in cook books and those that are inherited from your parents and grand parents. Most of them are fine, but some are not. In fact Hervé This has collected more than 20.000 so called “precisions” from French culinary books that he wants to test.

My seventh tip for pursuing molecular gastronomy in your very own kitchen is to question the cook book authorities, but also to learn from the experts in the field. The site Khymos originally started out as a listing of books and web pages that could be useful for anyone interested in molecular gastronomy and popular food science. When giving presentations it was more convenient for me to refer to a webpage than to have people taking notes of all the references. My own collection of books is constantly growing as you can see from the picture (I justed crossed the 100 cm mark), and I am more than happy to share with you my favorite books. Most of what I know about food chemistry and molecular gastronomy is from these books.

book-pile-meter.jpg

Molecular gastronomy should of course never become a theoretical practice only, so remember that “the proof is in the pudding”, as Nicholas Kurti, one of the pioneers of molecular gastronomy often said. Let taste guide your cooking and learn how to conduct simple blind tastings (more on that in part 8). If possible, do an experiment: if there are two or more procedures, follow them and compare the end result.

Despite the many books and articles that have appeared on food chemistry and molecular gastronomy there are still many questions that remain unanswered. Scientifically, molecular gastronomy is tremendously complex. The science of deliciousness lies in the cross section of analytical, biological, inorganic, organic, physical, polymer and surface chemistry. But even though describing and understanding what happes is difficult, everyone is able to judge the end result! This is quite intriguing and because of this it is possible to become an excellent cook – even if you don’t understand the chemistry behind in every detail. This makes me confident that there will always be an “art” and a “love” component in cooking, as Hervé This puts it in his definition of molecular gastronomy.

*

Check out my previous blogpost for an overview of the 10 tips for practical molecular gastronomy series. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry, presentation/photography) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

Ten tips for practical molecular gastronomy, part 6

Sunday, July 1st, 2007

cherry-1.jpg

6. Learn how our senses work

Prolonged exposure to a flavor causes adaption and habituation, meaning that your brain thinks the food smells less even though it’s still present in the same amount. Back in 1953 Lloyd M. Beidler isolated nerves from the tongue of rats to study these phenomena. The nerves were situated in a flow-chamber through which aquous solutions with salty, sweet, acidic and bitter compounds could be flushed. The electric signal produced by the nerve was then recorded and fed to an amplifier and a plotter. Very simplified, the perceived intensity of the stimulus looked something like this (the curve is not to scale in any dimension and it’s my own qualitative interpretation of the data presented in the article):

physiochemical-response-curve.png

After a short initial latency period a transient is followed by a slower prolonged decrement. There is even some nerve activity after the stimulus has been removed. What is interesting from a molecular gastronomy perspective is that the initial burst of taste quickly fades away – some call it fatigue or adaption. If the same stimulus is applied repeatedly, the maximum intensity of the initial taste burst decreases for each time it is applied. This is known as habituation and is illustrated in the figure below. As the time between stimulation of the receptor increases, the receptor recovers from the habituation and the intensity of the second stimulus increases to match the intensity of the first.

habituation-recovery.png

Adaption and habituation are also observed with odor. If you have used eau de cologne or perfume you might have noticed that you can smell it very well once applied, but after some minutes or hours you hardly notice it unless you sniff intentionally for it. The same applies for food.

Variation is the spice of life, and variation helps our senses to overcome adaption and habituation. More technically this has been referred to as “increased sensing by contrast amplification” which I think is a good way putting it. An illustrative example is Heston Blumenthal’s potato purée with small pieces of lime jelly (made with agar agar which is heat stable once it has set). The idea was that to avoid the adaption to the flavour and texture of the potatoe purée, small pieces of lime jelly would help “reset” the taste buds and thereby lead to an increased overall perception of the purée. I’m personally very fond of the variation provided by multiple component dishes. A curry sauce for instance is normally not served alone but alongside many other dishes: rice, dal, chicken/meat/fish, chutney, raita, nan, chapati, pakora, lime juice, salt etc. The different components contrast each other and help bring out the most of the meal.

Contrasts also help us smell better. When we sniff there is an abrupt change in the amount of air passing through our nose. More molecules pass the receptors and the sudden change in their concentration makes it easier to sense them. It has been shown that sniffing in fact gives an optimal odor perception.

face.jpg

Our senses are not unrelated, and there are many interesting articles illustrating this. For instance, adding color to make white wine darker or even red influences the perception of the wine aroma. Along the same lines, consider crystal pepsi which wasn’t a great success after all, probably due to the lack of color. With juice and soups it has been demonstrated that odors smelled through the mouth are perceived differently than those smelled through the nose. Similarily colors can either enhance of suppress the intensity of odors depending on whether they are smelled through the nose or through the mouth.

There are a number of odor-taste interactions. For example, through repeated pairing with sugar, odors become “sweeter”. We become better at detecting sugar solutions if strawberry aroma is added to them, but worse if ham aroma is added. And you shouldn’t be to surprised that both perceived and imagined odors influence taste (that’s right – think of strawberries, and sucrose will taste sweeter!). Heston Blumenthal uses this in the savory ice creams he makes. We associate the cold and rich mouthfeel of ice cream with something sweet, and this influences our perception of the flavour, making it sweeter. In general, the “sweeter” an odor is perceived, the more it enhances tasted sweetness and the more it suppresses sourness. Preliminary experiments suggest that even pure tastants have a smell.

A thing to consider when eating is that our body position influences olfactory sensitivity. And don’t forget that your emotional state also has an effect on the olfactory perception. Emotionally labile people are more sensitive to certain smells and less sensitive to others.

The examples of how our senses are not independant has some practical implications for cooking and eating:

Presentation is paramount, and it is worthwile to consider the art of food presentation. There is a lot to learn from food photography blogs and food blogs with good photos: still life with…, matt bites, 101 cookbooks, la tartine gourmande too mention but a few. Also check out the pictures submitted to the monthly food photography blogging event does my blog look good in this (google DMBLGiT to find out which blog hosts this month’s event).

Taste, smell, texture, mouth feel, temperature and appearance will all contribute to the overall experience when eating and drinking. But also the room, the atmosphere and the people present have an influence. I have previously mentioned the five aspects meal model which has been developed for restaurant settings and takes all of this into account.

Many of the ideas found in this blog post can be expressed in appetizers. With small, well prepared amuses bouche there is variation with every bite, creating excitement and anticipation.

And remember that average food eaten in the company of good friends while you’re sitting on a terrace with the sun setting in the ocean will taste superior to excellent food served on plastic plates and eaten alone in a room with mess all over the place.

Update: I submitted the picture of the cherries in the heading to the monthly “Does my blog look good in this” (or DMBLGIT for short) photo competition for food blogs – and guess what – the picture was the winner of the August 2007 round. This is a great honour, because there are so many good photographers out there with food blogs. Click to view the complete gallery of the August 2007 round.

*

Check out my previous blogpost for an overview of the 10 tips for practical molecular gastronomy series. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry, presentation/photography) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

Practical molecular gastronomy, part 5

Tuesday, May 1st, 2007

5. Learn how to control taste and flavor.

apple-pear.jpg

When invited over to friends for dinner, even before eating, you judge the food by it’s aroma, handing out compliments such as “It really smells nice”! Thankfully, nature is on the cook’s side, because when we prepare food and heat it, volatile aroma compounds are released which trigger very sensitive receptors in our noses. It is generally said that 80% of “taste” is perceived by our nose (what we refer to as aroma), whereas only 20% is perceived by our tongue. How important smell is becomes clear if you catch a cold – suddenly all food tastes the same. Too illustrate the importance of smell, prepare equally sized pieces of apple and pear. Close your eyes, hold your nose and let a friend give you the pieces without telling which is which. Notice how difficult it is to tell them apart. In fact, with a good nose clip you wouldn’t even be able to tell the difference between an apple and an onion! Then, with a piece of either in your mouth, let go of your nose. Within a second you can tell whether it’s apple or pear!

Taste
Our tongue has approximately 10.000 taste buds and they are replaced every 1 to 3 weeks. Their sensitivity increases roughly in the following order: sweet < salt < sour < bitter. In addition to the four basic tastes there is umami, the savory, fifth taste. This taste is produced by monosodium glutamate (MSG), disodium 5’-inosine monophosphate (IMP) and disodium 5’-guanosine monophosphate (GMP). Pure MSG doesn’t taste of much, but can enhance the taste of other foods. There are also some claims of a sixth taste.

A number of taste synergies/enhancements exist. I’ve also included three examples of how flavours can influence taste:

  • MSG, IMP and GMP enhance each other
  • IMP and GMP enhance sweetness
  • MSG, IMP and GMP generally enhance saltiness and vice versa
  • Salt enhances MSG, so foods with a natural high level of MSG (tomatoes) taste more if a pinch of salt is added
  • Salt and acid at low/medium concentrations enhance each other
  • Salt at low concentrations enhances sweet taste
  • Black pepper reduces sweet taste
  • Vanilla enhances sweet taste
  • Cinnamon enhances sweet taste
  • The only general, over-all trend which can be found is that binary tastes enhance each other at low concentrations and suppress each other at higher concentrations (but there are several exceptions!). Do check out “An overview of binary taste–taste interactions” (DOI:10.1016/S0950-3293(02)00110-6) if you’re interested in more details on binary taste interactions. I’ve tried to visualize taste enhancements (green) and suppresions (red) in the following figure using arrows to indicate the direction. For example, salt suppresses sweetnes at high concentrations.

    binary-taste-interactions.jpg

    In addition to taste, our tongue also percieves texture, temperature and astringency. An interesting thing about the temperature receptors is that they can be triggered not only by temperature, but also by certain foods. The cold receptor is triggered by mint, spearmint, menthol and camphor. There is even a patented compound, monomenthyl succinate, that triggers the cold receptor, but without the taste of menthol. It’s marketed under the name Physcool by the flavour company Mane.

    Substances such as ethanol and capsaicin trigger the trigeminal nerve, causing a burning sensation. Capsaicin also triggers the high temperature receptors of the tongue, hence the term “hot food” which can refer both to spicy food and food which is very warm. For a general article about taste, check out “Taste Perception: Cracking the Code” (DOI:10.1371/journal.pbio.0020064, free download).

    Flavour
    Our nose has about 5-10 million receptors capable of detecting volatile compounds. There are about 1000 different smell receptors and they allow us to distinguish more than 10.000 different smells – perhaps as many as 100.000! In order for us to smell something, the molecule needs to enter our nose at a concentration sufficient for us to detect. Aroma compounds are typically small, non-polar molecules. The fact that they are small means they will have low boiling points – they are volatile and spread rapidly throughout a room. They are often referred to as essential oils and are very soluble in fat, oil and alcohol. These aroma compounds generally not soluble in water, but there are also water soluble aroma compounds; just think of a well prepared stock – no fat but lots of taste and aroma!

    A challenge with aroma molecules is that they should remain intact during storage and not be released until cooking (or even better, until consumption). A example would be to install a Liebieg condenser over your pot. Dylan Stiles has explored this in his column Bench Monkey by placing a bag of ice on top of the lid. He claims that his roommates prefereed the curry which has been cooked under “reflux conditions”. The study was performed in a double blind manner (which I will come back to in part 8 of this series).

    Because aroma compounds are volatile, spices should be obtained whole and stored in tight containers away from light. If possible, fresh herbs should be used. The flavour of herbs and spices can be extracted by chopping or grinding to increase the surface area. To speed up grinding in a mortar you can add a pinch of salt or sugar.

    grinding-saffron.jpg

    Heat can help extract flavour (just think of how we brew tea or coffee), but will also evaporate volatile compounds, so a general advice would be to add spices at the start and herbs towards the end of the cooking time. Some herbs can even be sprinkeled over the food just before serving. In Southeast Asia (and especially India) it is quite common heat spices in a dry pan or in oil. This matures flavours and allows reactions to occur (possibly Maillard reactions). Coarse spices should be added earlier than finely ground spices.

    In addition to adding flavour using spices, herbs and other foods, we can also use heat to create new flavours. When sugar is heated, caramel is formed. And if a reducing sugar is heated in the presence of an amino acid, they react and form a host of new flavour compounds in what is known as the Maillard reaction. Caramelisation and the Maillard reaction are known as non-enzymatic browning. Enzymatic browning on the other hand is detrimental to many fruits (such as apples and bananas), but there are a few exceptions. Enzymatic browning is essential in the production of tea (black, green, oolong), coffe, cocoa and vanilla, although this is rarely attempted in kitchen.

    Another source of flavour is fermentation. It refers to a process were sugar is converted to alcohol and carbon dioxide by the action of a yeast. In the process a number of flavour compounds are formed as well which is why this is of great interest also from a molecular gastronomy viewpoint. Some examples of fermented products include wine, beer, cider and bread. Fermentation also refers to the process where some bacteria produce lactic acid. Some examples of foods resulting from lactic acid fermentation are yoghurt, kimchi and pickled cucumbers.

    Flavour pairing
    Cookbooks and recipes throughout the world are the result of billions of experiments. As a result, some very good combinations of herbs and spices have been discovered. Some of these mixtures have even been given names of their own and it is fascinating how easily one can forget that curry for instance is a mixture of spices. Wikipedia has a wonderful overview of herb and spice mixtures from all over the world. I must admit I only new a fraction of these:

    Adjika | Advieh | Berbere | Bouquet garni | Buknu | Cajun King | Chaat masala | Chaunk | Chermoula | Chili powder | Curry powder | Djahe | Fines herbes | Five-spice powder | Garam masala | Garlic salt | Harissa | Herbes de Provence | Khmeli suneli | Lawry’s and Adolph’s | Masala | Masuman | Mixed spice | Niter kibbeh | Old Bay Seasoning | Panch phoron | Quatre épices | Ras el hanout | Recado rojo | Shake ‘N’ Bake | Sharena sol | Shichimi | Spice mix | Tajín | Tandoori masala | Tony Chachere’s | Za’atar

    A book which I’ve found to be very useful when combining flavours is “Culinary artistry” by Andrew Dornenburg and Karen Page. It is the most comprehensive book about flavour pairing that I’m aware of, and I would say it is indispensible for someone who likes to cook without a cookbook. It has lists of basic flavors contributed by various foods. For example a sweet taste is contributed by foods such as bananas, beets, carrots, coriander, corn, dates, figs, fruits, grapes, onions, poppy seeds, sesame and vanilla (plus sugars and syrups of course). It has lists of “flavor pals”, a term attributed to Jean-Georges Vongerichten. For example, the flavour pals of ginger are allspice, chiles, chives, cinnamon, cloves ,coriander, cumin, curry, fennel, garlic, mace, nutmeg, black pepper and saffron. By far the most extensive part of the book are listings of food matchings. An illustrative example is pork which combines well with (classic/widely used combinations in bold):

    apples, apricots, bay leaves, black beans, beer, brandy, cabbage, Calvados, dried sour cherries, clams, Cognac, coriander, cream, cumin, fennel, fruit, garlic, ginger, hoisin sauce, honey, juniper berries, lemon, lime, marsala, molasses, mustard, onions, orange, parsley, black pepper, pineapple, Chinese plum sauce, plums, prunes, quinces, rosemary, sage, sauerkraut, soy sauce, star anise, tarragon, thyme, vinegar, walnuts, whiskey, white wine

    Despite the abundance of combinations, I dare say that little is understood about the science behind these flavour pairings. Why do these combinations of herbs and spices go particularily well together? Is it all about getting used to the combinations, so that we learn to like them? What influence does the complexity of the flavour play? These are easy questions that probably have rather complex answers.

    Very recently a different approach to flavour pairing has emerged. If two foods share one or more key odorants, chances are that they will go well together. The first step towards finding new pairings would be to identify key odorants. More info on key odorants can be found in the article “Evaluation of the Key Odorants of Foods by Dilution Experiments, Aroma Models and Omission” (DOI: 10.1093/chemse/26.5.533, free download). I’ve initiated the food blogging event “They go really well together” (TGRWT) to explore new flavour pairings and develop new recipes. There are also several blogposts with interesting comments on about flavour pairing.

    *

    Check out my previous blogpost for an overview of the tips for practical molecular gastronomy. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

    Practical molecular gastronomy, part 4

    Saturday, March 17th, 2007


    (Photo by vintage_patrisha at flickr.com)

    4. Learn how to control the texture of food

    Taste and flavour normally get more attention when food is discussed, but the texture of food is equally important and our tongue is very sensitive, not only to taste and temperature, but also to the texture of food. The texture of food determines it’s mouthfeel and it is related to many physical properties of the food. Wikipedia lists the following aspects of mouthfeel (click to see the full description of each aspect) which can be useful when analyzing food:

    Adhesiveness, Bounce/Springiness, Chewiness, Coarseness, Cohesiveness, Denseness, Dryness, Fracturability, Graininess, Gumminess, Hardness, Heaviness, Moisture absorption, Moisture release, Mouthcoating, Roughness, Slipperiness, Smoothness, Uniformity, Uniformity of chew, Uniformity of bite, Viscosity, Wetness

    I will barely scratch the surface of how texture can be controlled by highlighting a couple of topics and point you to further resources. Hopefully it will spark your interest and give some new ideas for you to play with in the kitchen. Those interested in a comprehensive review of food texture are referred to the CRC handbooks on food texture (volume 1: semi-solid foods, volume 2: solid foods).

    What determines the texture of food?
    Put very simple, it’s the relative amounts of air, liquid and solids that determines the texture of food. This is complicated by the fact that liquids have different viscosities. Furthermore the air, liquid and solid ratio is not necessarily constant. A liquid can solidify or evaporate, solids can melt or dissolve, and air bubbles can escape during cooking or storage. An elegant but quite abstract way of describing the complicated mixtures of air, liquids and solids found in food, is to use the CDS formalism (CDS = complex disperse systems), introduced by Hervé This.


    (Photo by Subspace at flickr.com)

    How can texture be controlled and changed?
    Texture can be controlled by temperature, pH, air/liquid/solid ratio, osmosis, hydrocolloids and emulsifiers – to mention a few. Here’s some examples:

  • Heating induces a change in the structure of proteins referred to as coagulation or denaturation. Typical examples are the boiling of eggs and the cooking of meat. When proteins denature they contract and become firmer. There are several helpful tables relating the doneness of different meats to temperature.
  • At around 70 °C (160 °F) collagen, the connective tissue in meat, turns into gelatin. As a result the meat becomes more tender, which is desireable in stews and other slow cooked meats.
  • Heat causes air/gas to expand and water to evaporate to give a foamy/airy texture. For example, experiments have shown that it is mainly the evaporation of water that causes a soufflé to rise.
  • Heat will cause certain hydrocolloids to solidify (for exaple methyl cellulose) whereas it will cause others to melt (such as gelatin).
  • Brining meat can greatly improve it’s texture and juicyness. This is done by immersing the meat in a 3-6% salt solution from anyhere between a few hours to two days before cooking.
  • Frozen water in the form of tiny ice crystals are important for the smooth texture of sorbets and ice cream. Ice cream that has been partly melted and frozen again will grow larger ice crystals that impart a coarser texture to the ice cream.
  • Acidic solutions (low pH) can cause proteins to denature. This allows fish to be cooked without the use of any heat. An example is the use of lime juice in ceviche.
  • Emulsifiers, thickeners and gelling agents have almost become synonymous with molecular gastronomy for many. They can greatly alter the texture of foods and typically only a very small amount is required. Where gelatin was the only gelling agent videly available to cooks in Europe and America only a decade ago, this has changed with the advent of many internet suppliers of speciality ingredients.
  • Cooking under vacuum can create new and exciting textures. First of all it’s a way of removing excess water without having to raise the temperature all the way up to 100 °C. When the water is removed, this will create pockets of air in the food, and when the pressure is released, the liquid surrounding the food that is prepared will rush in and fill these pockets. There is a commercially available vacuum cooker, but a DIY version can be made from a pressure cooker and a vacuum pump.

  • (Photo by Trinity at flickr.com)

  • Green leaf vegetables such as lettuce loose water upon storage. As the pressure inside the cells drops, the leaf becomes softer. By immersing the leaves in cold water for 15-30 min, thanks to osmosis, water will enter into the cells again. As the pressure increases, the leaves become crisper.
  • Air bubbles can greatly modify textures, and foams really are ubiquitious (which becomes obvious if you read the book “Universal foam – from cappuccino to the cosmos”). Ferran Adria’s espumas have become very popular, as has his recent invention, the Espesso. Air bubbles are also very important for the texture of ice cream, in fact ice cream is nearly 50% air (just consider the fact that ice cream is sold by volume, not by weight!).
  • A very recent addition to the modern kitchen pantry is the enzyme transglutaminase. The enzyme acts like a meat glue and Chadzilla has nice blog post on his transglutaminase experiments.
  • There are also enzymatic counterparts of transglutaminase available: proteolytic enzymes also known as proteases. You can find them in pineapple (bromelain/bromelin), papaya (papain), figs (ficin) and kiwi (actinidin) – and they are capable of degrading proteins and muscle tissue. Despite this, they have only found limited use in marinades, as their action can be difficult to control (as Nicholas Kurti experienced, look for the “But the crackling is superb” link).
  • When mixing flour and water, glutenin and gliadin react to form gluten which gives bread it’s elasticity and plasticity. Addition of 1-2% salt to bread tightens the gluten network and increases the volume of the finished loaf. Similarly, addition of 1% oil to the dough (after the first kneading) can further increase the volume. Larger amounts of fat added before kneading will interfere with the formation of long gluten strands, hence the name shortening.
  • The no-knead bread that recently hoovered around in the blogosphere challenges the conventional wisdom that bread needs kneading to get a good texture.
  • Once bread is baked, the staling process starts. Staling does not necessarily involve loss of water from the bread and is caused by crystallisation (or retrogradation) of starch. In this process water molecules are trapped. The process proceeds fastest at 14 °C, but is halted below -5 °C. This is the reason why bread should be stored at room temperature. The staling process can be slowed down by addition of an emulsifier such as lecithin which is abundant in egg yolk.
  • A way of turning high fat foods and oils into powders is by the use of tapioca maltodextrin. Hungry in Hogtown has shown how Nutella can be turned into a powder.
  • *

    Check out my previous blogpost for an overview of the tips for practical molecular gastronomy. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

    Practical molecular gastronomy, part 3

    Monday, February 26th, 2007

    Get a basic understanding of heat transfer, heat capacity and heat conductance.

    Since a lot of cooking involves temperature manipulations, it’s a good idea to get a basic understandning of how heat is transferred and how well it is stored in different materials. “Heat” in this context does not imply high temperature since it also applies to the understanding of freezing/thawing.

    ceramic-stove-top.jpg
    Closeup of ceramic stove top

    Heat transfer

    Conduction: flow of heat through an object or between two objects in contact. Metals are typically good conducters whereas air is a poor heat conductor.

    Convection: heat transfer occurs because particles are moved from a warm region to a colder one. One can say that convection is a combination of conduction and mixing. For example, convection occurs when heating water since its density varies with temperature – warm water is lighter than cold water and will float. This video illustrates convection currents in water as a crystal of potassium permanganate dissolves (this salt is not edible).

    Radiation: in the kitchen we encounter two types of heat transfer by radiation corresponding to two different parts of the electromagnetic spectrum. The heat we feel from hot burning charcoal, a stove top or the sun are all a result of infrared radiation. The other type is microwave radiation. Heat transfer by radiation does not require a material for the heat to pass through (as a consequence, a blowing wind will not have any significant effect when grilling). Microwaves easily penetrate plastic, glass and wood, but not metal. Infrared radiation is blocked by opaque materials.

    Heat capacity and heat conductance

    Heat capacity: the heat requried to raise the temperature of the material. Water has a very high heat capacity, metals (shown in red) generally a low heat capacity.

    Heat conductance: how well heat flows through the material. Some metals (shown in red in the graph) are excellent heat conductors (silver, copper, aluminum), others less so (iron and stainless steel). All other materials (shown in blue) are generellay poor heat conductors.

    The heat capacity (or to be precise, the specific heat capacity – which means heat capacity per weight unit) and the heat conductance of materials encountered in the kitchen are plotted in the the graph below:

    heat-capacity-conductance.jpg
    (for the technically interested, the plot units are Wm-1K-1 for the heat conductance and Jg-1K-1 for the specific heat capacity)

    For a more extensive treatment of heat transfer, heat capacity and heat conductance (+ more on cooking methods and materials) in a gastronomical setting, I recommend the Gourmet Engineering Lecture Notes for a very interesting course given at Tufts University in Medford, MA, USA. Cooking for Engineers also has a nice post on heat transfer and browning of foods and one on common materials of cookware (with comprehensive comparisons of different materials used).

    Examples related to food preparation and handling

  • Convection ovens utilize fans to circulate hot air allowing reduced cooking times and temperatures. Because of efficient convection, two or more trays can be baked simultaneously.
  • In a steam oven water is introduced to increase the humidity (this can also be done by spraying water into the hot oven). Heat transfer is more efficient due to 1) the higher heat capacity of humid air and 2) the energy released when steam condenses onto the surface (it’s the energy it took to boil the water in the first place). For bread, the condesed water prevents the surface from drying out which facilitates the exapansion of the loaf. Furthermore, the hot surface causes starch to gelatinize and subsequently dry into a delicate crust.
  • Water will cool faster than the same volume of a thickened soup because of less resistance to the convection currents in water. The amount of convection decreases in the following order: water > chicken soup > creamy soup > thick onion soup > porridge. In the latter heat is transferred by conduction only from the interior to the exterior (where heat transfer proceeds mainly by radiation and conduction). This will also affect cooling times, which is of importance with regard to microbial safety (food should be cooled rapidly past the window from 30-60 °C where microorganism thrive).
  • For rapid defrosting, place the frozen food in cold water or on a metal object – this will allow an efficient transport of heat to the frozen food. Defrosting in a microwave is not easy because most of the water molecules are locked in rigid structure and even microwaves cannot make them move (they only melt by conduction of heat from melted neighbouring areas).
  • To freeze icecream or a parfait, use a metal container as this will allow a faster dissipation of the heat in the freezer.
  • When whipping cream, it’s essential to keep the temperature low (otherwise the fat will melt). Use a thick glas bowl and cool it in the freezer before whipping.
  • When cooking meat in a pan or on a grill, notice how the surface browns relatively fast compared to the time it takes for the interioir of the meat to heat up. Heat transfer to the surface by radiation or conduction is very efficient compared to conduction of heat through meat itself. Therefore it’s advisable to fry/grill the meat at high temperature first to get a nice browning, then let the meat rest for 5-10 min to allow for heat conduction to the interioir (cover with aluminum foil to reduce radiative heat loss), followed by a second frying/grilling at lower temperature until desired doneness.
  • In an oven, the heating caused by radiation can be increased by moving food closer to the walls or reduced by wrapping the food with reflective aluminum foil. For example, to caramellize sugar on a creme brulee if you don’t have gas burner, place them as high as possible in the oven, preferably using a grill element. Turkey legs stick out and easily get overdone – wrapping them with aluminum foil reduces heat radiation from the oven walls.
  • For a bain marie, always use a metal bowl as this gives you better temperature control. When making egg based sauces such as hollandaise or bernaise, use a thin metal bowl this allows rapid heating and cooling (if temperature gets to high, the metal bowl allows quick cooling which might save the sauce).
  • A pizza baking stone has a higher heat capacity than a metal plate/sheet – this ensures proper rising and gives a crispy crust.
  • Ever burnt your tongue on a pizza? Tomatoes (mostly water) retain heat far better than the crust (many air bubles, low heat capacity) and cheese topping (cools fast due to radiation from surface).
  • The vacuum in a thermos does not conduct heat by conduction or convection, only by radiation. The latter is minimized (in thermoses of glas) by a silver or aluminmum coating, creating a reflective mirror.
  • From the graph it doesn’t seem like cork is a particularly good insulator. This is because the heat conductance is plotted per weight unit. For a porous material such as cork, the effective heat conductance is much lower than for the same volume of other materials.
  • Lastly, just to illustrate how complex heat transfer and convection sometimes can be, take a look at the Mpemba effect: Believe it or not, under certain conditions, hot water freezes faster than cold water!
  • *

    Check out my previous blogpost for an overview of the tips for practical molecular gastronomy. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

    Ten tips for practial molecular gastronomy, part 2

    Sunday, February 11th, 2007

    2. Know what temperature you’re cooking at.

    A dip probe thermometer with a digital read out is a cheap way to bring science into your kitchen. It should preferably cover the temperatures from -30 to 300 °C (-22 to 570 °F). It’s a good idea to check how accurate it is. This is easily done using a water/ice mixture and boiling water.

    calibrate-zero.jpg

    Fill a glas with crushed icecubes and top of with cold tap water. Leave if for some minutes for the water to cool and stir every now and then. Make sure the tip of the probe does not come in direct contact with ice. A mixture of water and ice is exactly 0 °C (32 °F). If the reading is off by 2 °C (~4 °F) or more I would take the thermometer back to the shop and claim a refund.

    calibrate-ninetynine.jpg

    Similarly, you can use boiling water as a high temperature reference point. Water boils at 100 °C (212 °F) at sea level and standard barometric pressure. The exact boiling point at your location can be calculated.

    When I bought my first thermometer it turned out that the temperature readings were quite erratic so I had to return it. The one I have now however works fine (1 degree off for the boiling water is OK).

    As an addition to a dip probe thermometer, contact-less thermometers with infrared sensors are becomming more affordable. Suppliers include Raytek, Strathwood, Radiant (here, here or here) and Extech Instruments (links to product pages at Amazon).

    *

    Check out my previous blogpost for an overview of the tips for practical molecular gastronomy. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

    Ten tips for practial molecular gastronomy, part 1

    Saturday, February 10th, 2007

    green-apples.jpg

    1. Use good and fresh raw materials of the best quality available.

    No amount of cooking and preparation – be it traditional, modern or molecular – can fully disguise ingredients of poor quality. No one will probably disagree with this and it’s elementary knowledge for every cook, yet I include it because after all molecular gastronomy is also about the raw materials you use. Do not always reach for the cheapest products. Eat better, but less – it won’t cost you more, because you’ll just get less calories for the same price!

    I will also encourage you to support local producers. This will probably make me sound like a slow food practitioner which is fine, because molecular gastronomy is not in any opposition to slow food or traditional cooking, it’s more about understanding the chemical and physical principles underlying all handling and preparation of food. Part of my motivation when writing about molecular gastronomy is actually to bring it a little more down to earth.

    When talking about freshness it’s important to consider how food deteriorates. Assuming that safety and toxicological issues are taken care of, from a molecular gastronomy viewpoint it is interesting to discuss flavor. The most important pathways to flavor deterioration include exposure to air (particularly oxygen), light, moisture, high temperature, bacteria and fungi.

    The flavor of foods stems largely from the presence of volatile organic compounds. Because of the low boiling point, these compounds easily escape from the food. And at higher temperatures evaporation of aroma compounds is even faster. Also, many of the compounds can react with oxygen in air. A typical example is the oxidation of fats which gives a rancid flavor. Generally, fats and oils should be stored in the refridgerator to slow down this oxidation, but it turns out there’s an exception for olive oil.

    To retain as much of the volatile compounds as possible it is advisable to store spices in tight containers kept in a dark and cool place. If you for some reason need to store spices for a long time, put them in the freezer. Since the loss of aroma comounds is proportional to the surface area of the spice, it’s also a good idea to buy whole spices and grind them yourself immediatly prior to use. I would also recommend the use of spice pastes (such as curry pastes for instance) since the oil helps extract aroma compounds. Such pastes should preferably be stored in the fridge.

    whole-spices.jpg

    Like me, you probably have many different spices in your pantry. Some of them have probably been sitting around there for years which is far from optimal. Therefore, as a reminder to myself, I have started to mark each spice with the date of opening (or purchase) using a water proof pen.

    spice-date.jpg

    With fresh fruit and vegetables, finding the right storage conditions can sometimes be difficult, but this pdf from UC Davis provides a quick overview of recommended storage conditions (ie. what should be stored in the fridge and what should be stored on the countertop).

    One last example of the importance of correct storage conditions is the staling of bread. Contrary to popular belief, staling of bread is not caused by evaporation of water from the crumb. This is easily demonstrated when you heat a slice of bread in a toaster or a microwave oven. What happens upon storage is that starch and water crystallize. As a consequence the crumb loses its elasticity and goes stale. The aging process proceeds fastest at 14 °C. Because of this, bread should be stored at room temperature – never in a fridge. When freezing bread, rapid cooling is important because the staling is halted below -5 °C.

    *

    Check out my previous blogpost for an overview of the tips for practical molecular gastronomy. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.