Posts Tagged ‘adaption’

Ten tips for practical molecular gastronomy, part 6

Sunday, July 1st, 2007

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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):

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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.

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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.

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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.

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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

Saturday, January 27th, 2007

In a recent survey 72% of chefs say they may want to experiment with molecular gastronomy in 2007. That’s an impressive number and considering the attention molecular gastronomy gets in media I bet many home cooks would want to experiment in the kitchen as well. Here’s a list of things to consider if you want to make a scientific approach towards cooking:

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

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.

3. Get a basic understanding of heat transfer, heat capacity and heat conductance. “Heat” in this context des not imply high temperature since it also applies to the understanding of freezing/thawing.

4. Learn how to control the texture of food. Some key points: temperature induced changes (freezing, heating), emulsifiers, thickeners, gelling agents, moisture content, pressure/vacuum, osmosis.

5. Learn how to control taste and flavor. Some key points: flavor pairings, spice synergies/antagonies, influence of temperature (Maillard reaction, caramelization, temperature stability, volatility), taste enhancers, taste suppresants, solubility of flavour compounds in fat/water, extraction.

6. Remember that prolonged exposure to a flavor causes desenzitation, meaning that your brain thinks the food smells less even though it’s still present in the same amount. Therefore, let different flavours enhance each other. Similarly, variation in taste, texture, temperature and color can open up new dimensions in a dish. This is referred to as “increased sensing by contrast amplification”.

7. Be critial to recipes and question authority – they do not necessarily represent “the truth”. Nevertheless, you can certainly learn a lot from the experts.

8. 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 test, or even better a triangle test to evaluate the outcome of your experiments.

9. Keep a written record of what you do! It would be a pity if you couldn’t recreate that perfect concoction you made last week, simply because you forgot how you did it.

10. Have fun!

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Heat causes many changes in food, but few appreciate how important it is to know at what temperature they are cooking and at what temperature the desired change occurs.

These tips for molecular gastronomy relate to the technical and scientific aspects of food preparation and eating, and I plan to elaborate on each of the points in separate blog posts. However, according to Hervé This’ definition of molecular gastronomy, one should also investigate the social and artistic components of cooking. A good example of this is the “Five Aspects Meal Model” developed at Grythyttan in Sweden (Gustafsson, I.B. et al. Journal of Food Service, 2006, 84.). Although intended for a restaurant setting, the general idea can also be applied for home cooking.

The meal takes place in a room (room), where the consumer meets waiters and other consumers (meeting), and where dishes and drinks (products) are served. Backstage there are several rules, laws and economic and management resources (management control system) that are needed to make the meal possible and make the experience an entirety as a meal (entirety – expressing an atmosphere).

Or to put it differently: 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.

One last thing: once you’re finished in the kitchen with your culinary alchemy, your gastro physics, your cutting edge science cuisine, your molecular cooking, your hypermodern emotional cooking, your science food or whatever fancy name you attach to it – remember the social and artistic components when you serve the food. Just so people won’t refer to you as a techno chef, a mad scientist or a modern day Willy Wonka. After all, molecular gastronomy is about the science of deliciousness, not technical wizardry.

Questions and topics for future blog posts are welcome at webmaster [a] khymos.org (substitute @ for [a]) or as a comment below.