Flavor pairing is a controversial* topic which I’ve blogged about many times in the past. In my last post I suggested that predicted aroma similarity may be a more precise term, and below is an attempt to illustrate predicted aroma similarity (of type 2d according to this classification) by using a color analogy. Let me explain a little first: The letters describe different foods and colors are used to illustrate the sum of the key odorants. The normal situation is that foods A and K (which are perceived as different because they are far apart in the alphabet) also have different colors meaning that they share few or no key odorants. A and B however are close in the alphabet and have similar colors, hence they share key odorants. In some cases foods that we think are very different (A and Z) may turn out to share several key odorants (i.e. have similar colors). The “flavor pairing hypothesis” is a way of finding the “Z” based on predict aroma similarity. I think one reason why we cannot always find the “Z” is that our sense of smell is not very analytical (compared to a gas chromatograph). One thing which I hope becomes clearer with the color analogy is that for a successful pairing one will need contrasting elements as well. This was also a general experience from the TGRWT experiments. I’m very curious whether this communicates well or just makes things even more confusing, so feel free to leave a comment below!

Let us assume that the two foods A and K with no key odorants in common taste marvelous together. Many (or possibly even most?) food pairings are of this kind.

Two similar foods A and C share a number of key odorants. This is no big surprise and most people will say that A and C are quite similar.

Aroma similarity prediction (the “flavor pairing hypothesis”) is a tool to identify Z which (surprisingly) turns out to be quite similar to A because they share key odorants. As mentioned above, finding Z is what is difficult.

Let us imagine a dish where A is a prominent ingredient. It’s combined with classic or empirical pairings (indicated with the different colors – the color tones are chose to match each other).

Based on aroma similarity prediction one can then introduce Z which (surprisingly) is similar to A because of overlapping key odorants.

One can even imagine the case where A is replaced by Z. If the process is repeated a dish can slowly morph into a new dish by exchanging one ingredient at a time.

*Controversial: See for instance the latest issue of Gastronomica where Maurits de Klepper criticizes flavor pairing under the title “Food Pairing Theory – A European Food Fad”. It’s an interesting piece and I recommend that you buy access to read it. But I should quickly add that there are a couple of things that I disagree with. What I’ve previously formulated as a flavor pairing hypothesis is turned into a theory, and I also disagree with the formulation that “the more aromatic compounds two foods have in common, the better they taste together”. In my previous blog post on the topic I have reformulated my viewpoint as follows: For foods with a predicted aroma similarity based on the analysis of it’s volatiles there is a good chance that they can be used together in a dish. It’s also a pity that de Klepper doesn’t cover the topic of key odorants (or odor activity values) properly, but mixes up the different categories (2a, 2b, 2c and 2d) of aroma similarity prediction that I’ve outlined previously. Despite this de Klepper summarizes the experiences from TGRWT very well when he says that flavor pairing “is not a guaranteed recipe for success – balancing flavors is what does the trick”. I couldn’t agree more.

The very first blog post on Khymos appeared on August 27th, 2006. That’s 5 years ago today – and to celebrate this the following post will be about Khymos and blogging. It’s going to be quite introvert, but hopefully you’ll appreciate the look behind the scenes! I 2006 had no clue that I would still be going on for so long. Five words that sum up the 5 years of blogging are: fun, readers, research, experiments and photography. Let me explain:

FUN: Blogging has been great fun, and I would never have continued for so long if I hadn’t enjoyed it. I’ve had a couple of long breaks, and my posting frequency varies, but that’s because of a rule I’ve put up for my blogging: No deadlines! This is to make sure the blog is driven by ethusiasm. My philosophy is that if I enjoy writing, I hope you will enjoy reading!

READERS: First and foremost blogging is fun because of you! Without readers, I wouldn’t have kept on blogging. All the feedback, comments, discussions and emails are very much appreciated, not to mention all the interesting questions and observations you send me. My only regret here is that there are questions I received months (and even more than a year ago) which I haven’t answered yet… Easy questions are often answered as quickly as possible, whereas the more difficult ones may take a little longer. But if you haven’t heard back from me in let’s say 1-2 weeks – please send a new email!

RESEARCH: Another reason it has been great fun is the opportunity it gives me to research subjects and do experiments in a more structured way. I actually learn a lot about food and chemistry while blogging. Once I’ve blogged about a topic it’s very easy to include it in presentations/lectures I give on molecular gastronomy and popular food science.

EXPERIMENTS: I really enjoy researching a subject, especially when I manage to figure out of something. In fact, few things are more rewarding than solving a problem or gaining new insight. But the great thing about chemistry is that you can do experiments as well. And with food chemistry you’re even allowed to taste!

PHOTOGRAPHY: When popularising science, and chemistry in particular, I find that illustrations and pictures are essential. As it happens I also enjoy taking pictures, so the blog lets me do a lot of things that I enjoy at the same time!

How I got started
When I first became interested in the connection between food and chemistry in the late 90′s, I searched the Internet without finding much information. I did however find some very interesting books in the faculty library, including Harold McGee’s “On Food and Cooking – The Science and Lore of the Kitchen”. Having found books about the subject, I soon started to give popular science presentations. In 2004 I was invited to attend the “International Workshop on Molecular Gastronomy” in Erice, Sicily. This was a great experience and I enjoyed meeting many of the scientists, writers and chefs involved with molcular gastronomy. When I first put up a webpage in 2002 the main purpose was to maintain a more or less comprehensive listing of books and websites with relevance to molecular gastronomy. I published it mainly as a bibliography related to my popular science lectures. After I left the University of Oslo, the page was moved to it’s present location at khymos.org. Needless to say, I’m no longer able to keep track of all the interesting things happening related to science enabled cooking, given the increasing popularity as well as the many chefs, restaurants, books, websites and interviews appearing. Therefore I’m very thankful when readers contact me about things they think I should blog about.

What do I blog about?
My blog posts mostly fall into one of the following categories:

• Announcements and recommendations of books, blogs, events, new websites etc. It’s often difficult to draw a line here, but my guiding principle here is that if I find it interesting, I hope you will as well. And of course, feel free to share news, tips and announcements with me using the contact form.
• Feature posts on a researched topic which almost always involve some cooking and experimentation, often requiring a litterature search as well. These are time consuming posts to write, but also very rewarding for myself. I wish I had more time for these!
• Travel reports such as those from EuroFoodChem, The Flemish Primitives and the MG seminars in Copenhagen allow me to practice as a journalist.
• The food blogging event They Go Really Well Together (TGRWT) allowed me as well as all the participants to explore food pairings based on shared impact odorants.
• The occasional interview satisfies my thirst for learning more from knowledgeable people I admire. I should do more interviews!
• Book reviews is something I’ve only just begun doing. Time consuming, but also rewarding.

A category which I haven’t dug properly into yet is recipes for conventional food accompanied by scientific explanations. This has been pioneered by Hervé This in Révélations gastronomiques (available in German but not in English), and I love the format that answers all the whys right there in the middle of the recipe. I hope I will find time for such blog posts in the future!

The current blog
After a complete makeover of the blog in January 2009 I decided to move the static content from the old Khymos site to the blog. Some changes have been made, so for those of you who regularily read Khymos feed through an RSS reader or a news aggregator, I suggest that you visit the website to check out what the complete site looks like now.

Since the facelift in January 2009 there are a couple of notable changes to help you navigate around the site. These include a tag cloud, a list of popular posts and a list of the last comments (all shown in the picture below). There is also a search field providing a full text search of the entire contents of Khymos. One of the technical advantages of a blog over a conventional website is of course the RSS funtion which allows posts to be aggregated and served to readers in their favorite RSS reader. If you’re not familiar with this, try pressing the large orange icon in the upper right corner and see what happens! Most web browser today include a basic RSS reader. For those who prefer email there is also a possibility to subscribe to blog posts via email.

If you only read the RSS you miss a number of features available on the webiste.

Most popular posts and pages
The most viewed posts and pages from April 2008 – August 2011 are (total number of views in this time period):

Top 15 blog posts
Towards the perfect soft boiled egg (90,185)
Perfect steak with DIY “sous vide” cooking (43,986)
First experiments with sodium alginate (34,698)
A mathematician cooks sous vide (19,156)
Edible cocktails with gelatin (18,304)
A pinch of salt for your coffee, Sir? (15,299)
Hydrocolloid recipe collection (13,184)
Speeding up the Maillard reaction (12,233)
No-knead bread (9,227)
TGRWT #10: Pizza with blue cheese and pineapple (8,994)
TGIF: Fed up with foam? (8,805)
TGIF: Periodic tables of food (8,180)
Glutamic acid in tomatoes and parmesan (7,696)
Ice cubes and air bubbles (7,477)
Coffee espuma with garlic and chocolate (TGRWT #1) (7,336)

Top 10 pages
Recipe collection (120,066)
TGRWT (25,916)
Flavor pairing (20,389)
Molecular gastronomy (15,949)
Suppliers (13,476)
About Khymos (13,041)
Articles (12,080)
People (7,862)
Videos (7,084)
Reference & technique (6,010)

Blog posts I enjoyed writing
Looking at the list above suggests that my philosophy about you enjoying reading what I enjoy writing doesn’t always hold true. Some of the posts that I really enjoyed researching and writing do not show up on the lists above. Here’s my secret insiders guide to the best hidden posts of Khymos that do not show up in the lists above:

The series on Ten tips for practical molecular gastronomy
The serices on Wonders of extraction: water, oil, ethanol, espresso, pressure
Nocino walnut liqueur part I and part II
The follow up posts on egg yolks: Perfect egg yolks, Perfect egg yolks part 2
Norwegian egg coffee
DIY mineral water (including an Excel spreadsheet)
Soda fountain science explained
Interview with Chris Young (co-author of Modernist Cuisine!)

Some statistics
So far I’ve written 270 blog posts, including the one you are reading now. The blog posts are grouped in 24 categories and have been tagged with 1033 different tags. Comments are moderated, the major reason for this being spam. The Akismet spam killer has so far caught ~445,000 spam comments since I turned it on. Compare that with the 2207 comments that have been approved and I think you see why comment moderation is necessary (although a side effect is that legitimate comments are being held back for approval, thereby delaying the discussion in the comment threads).

A grand total of 2.9 terabytes have been served during these 5 years according to the logs of the company hosting Khymos. This amount of traffic is the result from 8.5 million visits resulting in 78 million hits, requesting 61 million files and 30 million pages in total. But one can only wonder what kind of traffic numbers all the spam comments generate… More numbers from the logs can be found in the table below.

Webmetrics is tricky, and simply counting hits or views may not tell the whole truth. One company which specialises in web metrics is Quantcast. Their monthly visitor count for Khymos is shown below:

More detailed data is available directly on Quantcast’s page about Khymos.

The number of RSS subscribers in Google Reader has been growing steadily and a couple of weeks ago it was around 3500. But then something happened – I don’t know what – and the number is now approaching 40000. The strange thing however is that this increase in subscribers is not reflected in the other statistics, so it’s hard to really tell whether it’s a realistic number or not.

Blogging software
I can still remember how I started reading about different blogging platforms available in 2006. I ended up chosing WordPress which at that time had reached v.2. Today I’m so happy that I chose WordPress! I’m amazed by the development team and what they have achieved, and at this point I should really forward a big thank you to the team behind WordPress. During these five years the software has really matured and it’s a great tool for any blogger – hereby highly recommended (and did I mention that it’s free?).

More about photography
Some of the very first pictures on the blog were shot with a Canon Powershot A400, a simple point & shoot camera that left a lot to be desired in handling. With enough light however the camera takes decent pictures, and the 3MP sensor serves as a good reminder that when having pictures printed in the typical 10 x 13/15 cm size you really don’t need more pixels. In 2007 it was time to upgrade to a Ricoh GX100 – I got this camera after long considerations, and what appealed to me was the combination of a real wide angle zoom (equivalent to 24-70 mm) and full manual controls. The downside is perhaps that the camera is a bit slow, and the low light capabilities are also limited. And then in 2010 I finally stepped up and got myself a DSLR. I considered both D90 and D700 from Nikon, as well as the 7D and 5D mark II from Canon, but in the end I landed at Nikon D300s. The controls and handling are excellent, and the camera is fast – it actually takes the picture when you press the button, not a second or so later as is the case with many P&S cameras. In combination with the my prime lenses Nikkor 35 mm 1:2 and 20 mm 1:2.8 (which I bougt used) I’m well off in most low light situations. Both have excellent close ranges, and with the narrow depth of field they are excellent companions for food photography. And if needed I could always use the macro function on GX100 if needed.

As mentioned in my previous post about the flavor pairing presentation given by Wender Bredie as part of the Copenhagen seminar on molecular gastronomy I’m really happy that the topic has been brought into the scientific community. At the same time is has also become very clear to me that the term flavor pairing needs some clarification. First of all I have come to realize that the the term flavor pairing is slightly misleadning, and I wonder if aroma similarity perhaps is a more precise term. As I see it, today the term flavor pairing is used in a range of different ways:

1. Empirically based pairings. These are the good combinations of ingredients (or even food and wine) that more or less all cooking relies on. An excellent source for such flavor pairings is The Flavor Bible. If one can talk about any chemical principles at all it would be related to balancing the basic tastes and using contrasting elements. But the pleasantness of the empirical based pairings are probably also often subject to the exposure effect – you get used to something and eventually start liking it.
2. Predicted aroma similarity. This is the broad category that I’ve previously referred to as flavor pairing. It can be further subdivided into the following categories:
   1. Predicted aroma similarity based on overlap of one or a few volatiles
   2. Predicted aroma similarity based on the number of overlapping volatiles
   3. Predicted aroma similarity based on overlap between one or more of the high concentration volatiles
   4. Predicted aroma similarity based on overlap between high impact odorants (volatiles to compare are first selected based on OAV, AEDA, CHARM, FD …)
   5. Predicted aroma similarity based on similar neurological responses (as judged by fMRI or any other technique)

The reason I propose aroma similarity for category 2 is to avoid confusion with category 1. Also, such a term does not suggest that only combining the two will yield heavenly combinations. To a chef, it may even be the opposite, as foods or ingredients selected based on aroma similarity may be too similar if used by themselves. The predictive power in category 2 increases from 2a, 2b and 2c (where it is zero or very close to zero) to 2d and 2e (where predictions make sense). Personally I have always thought that what I previously referred to as flavor pairings should at least be of category 2d based on this, but I realize that I probably havent expressed this clear enough before. Another obvious reason to clearify the terms is of course that some of the discussion that arises around flavor pairing stems from different understandings and definitions of what flavor pairing is.

From what I’ve heard the flavor pairing examples Heston Blumenthal has come up with (or at least some of them) belong to category 2d/2e thanks to proprietary research that was made available to him. But since the background data has not been published (and probably never will be) it is difficult to evaluate this further. I also seem to remember that Heston has talked about flavor pairings of category 2a, 2b and/or 2c based on data from the VCF database (I think it was in one of the RSC videos). I do not know in which category the example from François Benzi (indole in jasmine and pork liver) belongs, but since indole was mentioned specifically it maybe category 2a unless indole is in fact present in high concentrations or even is a high impact odorant.

In the food blogging event They Go Really Well Together (TGRWT) I have tried to argue that flavor pairing at least should be based on category 2d types of pairings. But due to the very limited amount of data available it has not been possible to asses whether the pairings published by Heston actually do have an overlap of the impact odorants. From what I’ve heard the foodpairing website (old .be site, new .com site) put together by Bernard Lahousse and Lieven De Couvreur does incorporate threshold values and thereby is based on the impact/activity of the odors and hence falls into category 2d, but regrettably very little has been published about the underlying methodology used to create the website.

Let me also add that although I firmly believe that it makes sense to talk about activity or impact of odorants, I have previously addressed some of the limitations with odor activity values, and I quote myself:

It’s only fair enough to add that the concept of odor activity values has it’s limitations. Some are related to matrix effects, because thresholds are not necessarily recorded in a matrix mimicking the food product. Possible synergies between flavour compounds are disregarded (examples are known where sub-threshold concentrations are detected in the presence of other volatile compounds). Also, the underlying assumption that the odor intensity increases linearily is not quite correct. The typical intensity vs. concentration curve is more ‘S’ shaped with an expansive, linear and compressive region as shown below. At low concentrations (expansive region) synergism (also known as hyperadditivity or mutual enhancement) is observed. At high concentrations (compressive region) antagonism (or subadditivity or mutual suppresion) is observed. This means that a high OAV overestimates and a low OAV underestimates the impact of the individual compounds.

The fact that Wender Bredie in his studies found absolutely no correlation between the hedonic score of the food pairings and the overlap of volatile flavors could at first be a little disappointing. But I believe the only conclusion that can be drawn using data from VCF (which has information about volatiles and some concentration data) is that type 2b/2c predictions are very weak. I strongly believe that one should take into account some kind of metric to filter out the odors that do not contribute to the overall aroma of the food.

For fun I checked Wender’s list of “the good, the bad and the ugly” using The Flavor Bible (a good source of category 1 flavor pairings) and the foodpairing website (presumably category 2c and/or 2d predictions). This is what I found:

It is interesting that The Flavor Bible (being purely empirical) actually mentions three of the “good” pairings. That it also mentions one of the “ugly” pairings is a good reminder that binary mixtures are not actually food and this real life is more complex. And it is also peculiar that all the garlic combinations were perceived as “ugly”. In a moussaka for instance one would combine cinnamon and garlic (with many other spices and herbs of course), and it is indeed quite delicious. Moving on to the predictions from foodpairing.be it is not so easy to draw any conclusions, but it is interesting that the four predicted aroma similarity pairs fall into the whole range of hedonic categories (i.e. ugly, bad and good). These could be interesting cases in a follow up study at lower concentrations as Wender mentioned in his presentation.

Based on the distinction between the different types of flavor pairing suggested above the flavor pairing hypothesis may be reformulated as follows: For foods with a predicted aroma similarity based on the analysis of it’s volatiles there is a good chance that they can be used together in a dish. Needless to say, the prediction should be of type 2d or 2e. Experience from the TGRWT rounds further suggests that some experimentation may be needed to find the right balance between the two and that contrasting elements are very important, otherwise the combination may turn out quite bland.

So to conclude:  What I’m after from a gastronomical perspective is a tool to pair foods and suggest extra ingredients based on aroma similarity. This first and foremost becomes interesting if the combinations are novel or have a surprise element. Because of the aroma similarity the complexity of the combination will presumably be less than anticipated. Thinking about the Wundt curve (which I learnt about in Michael Bom Frøst’s presentation in Copenhagen – more on that in a separate post) which suggests that pleasantness first increases and then decreases with increasing complexity, a less than anticipated complexity combined with novelty/surprise could perhaps be what we are looking for when we try to create new and delicious food.

A topic that I was particularily excited to hear about at the molecular gastronomy seminar in Copenhagen was flavor pairing. Since Heston Blumenthal presented his white chocolate and caviar combination based on amines in 2002 and Francois Benzi of Firmenich the pork liver-jasmine combination based on indole the idea has been further elaborated by Bernard Lahousse and Lieven De Couvreur who launched the foodpairing website and by me in the TGRWT food blogging event. Despite the interest and fascination it is fair to say the flavor pairing is still controversial – see for instance the discussion with in particular Jorge Ruiz. What is clearly lacking in the field is a more stringent scientific approach (as well as someone with time, interest, a sensory panel and the money to finance the activities…). It was therefore great to hear that sensory science professor Wender Bredie together with PhD student Ditte Hartvig actually set out to test the flavor pairing hypothesis formulated as: if major volatiles are shared between two foods it may very well be that they go well together. To achieve this they used a sensory panel to assess the odor of food pairs mixed and unmixed. Bredie proposed that a hyper addition of odor intensities would perhaps be the holy grail of flavor pairing – that is if the intensity of the mixed odors would be more than the sum of the unmixed intensities. Or even better: if there would be a hyper additive effect on pleasantness. 

A finding in their initial study with 8 pure volatiles smelled alone and in pairs was that the total odor intensity only increased when combining up to 2-3 components. This is in accordance with Fechner’s law which states that it takes a larger difference in physical stimuli to give the same rise difference in perceived intensity. The pleasentness of the individual components decreased when mixed. In a further study they prepared 53 binary mixtures from 19 food odors. The recorded responses were: intensity, pleasantness, complexity, “harmonic” and novelty. They found no real hyper additive effects for intensity – in 91% of the cases the mixture was perceived to be more intense than one compound perceived alone, but less intense than the other (= compromise region of hypo-addition). But turning to pleasantness there were a couple of interesting findings which were presented as the good, the bad and the ugly combinations, based on the pleasantness score from the sensory panel:

The good
lemon peel + butter
cinnamon + apple
ginger + apple
cinnamon + peanut butter
malt + peanut butter
cacao + malt
lemon peel + strawberry

The bad
ginger + blue cheese
caviar + apple
basil + caviar
vanilla + blue cheese
anis seed + basil
basil + green tea
anis seed + caviar

The ugly
cinnamon + blue cheese
anis seed + garlic
cacao + garlic
cinnamon + garlic
malt + blue cheese
caviar + blue cheese
malt + caviar

To test the flavor pairing hypothesis they then took the pairings and analyzed the overlap of volatiles using data from the VCF database. They found absolutely no correlation between the hedonic score of the food pairings and the overlap of volatile flavors! But knowing that many (if not most) of the volatiles compounds found in foods do not contribute to the aroma this is not very surprising. A further interesting test was to evaluate pleasantness as a function of complexity, but the conclusion in short was that one cannot use complexity to predict hedonic response.

Wender concluded that flavor pairing should be the subject of further and more elaborate studies, for instance at lower concentrations (in the so-called hyper additive region where the intensity increases exponentially with increasing concentration). Another approach could be to study sensory (dis)similarity rather than chemical similarity. One could also explore the arousal potential in pairs of dissimilar but liked flavours. He also suggested that one should keep on searching for additive hedonic responses. And he finished his presentation with the following quote:

“Flavour pairing is like painting in the dark… you do not really know what you are creating, but at daylight you may discover that you have moved art beyond imagination”.

I’m really happy that the topic has been brought into the scientific community – and I’m very much looking forward to see the results published. At the same time is has also become very clear to me that the term flavor pairing needs some clarification. I’ll discuss that in a separate post.

Wheat beers such as hefeweizen, weissbier and wit are all light beers made from a mix of malted barley and wheat. In southern Germany the typical hefeweizen is fermented with a non-flocculating yeast, and it is not filtered before bottling. This gives the beer a yeasty, bread like flavor accompanied by aromas reminiscent of banan, cloves (we’ve encountered that combo before), coriander and citrus. I’ve just begun to read up on brewing and my first batch of a partial mash hefeweizen is bubling along. As I pitched the liquid hefeweizen yeast into the wort I decided to keep a tiny amount for baking. If hefeweizen beer is reminiscent of bread, why not use the yeast for making bread? In particular I was curious whether some of the aroma top notes characterizing hefeweizen beer would stand out in bread made using the same yeast.

The specific yeast I used was obtained as a liquid suspension from White labs. Their hefeweizen yeast strain (catalogue number WLP300) is identical to Weihenstephan 68. And in case you didn’t know – Weihenstephan is the world’s oldest brewery. Wine yeast is the same as beer yeast (or ale yeast to be more precise) and baker’s yeast – and they are all known under the latin name Saccharomyces cerevisiae (which literally translates to something like a “beer producing sugar munching fungi”). Why bother if they are all the same yeast you may ask. It’s a good question, but despite the common name they are different isolates with very different properties. They certainly have a lot in common: in the presence of air they consume sugars to grow, and in a closed environment without access to air the consumed sugars are instead converted to alcohol and carbon dioxide. But besides this main reaction there are hosts of other enzymes present that produce higher alcohols, aldehyes, acids, esters – all of them volatiles compounds that contribute significantly to flavor. And this is typically where the isolates of S. cerevisia differ. There’s a mind boggling array of beer yeasts available. Take a look at the yeast catalogues of White labs, Wyeast or Fermentis to get an idea of the many yeast strains that are available (note that the lists includes both ale yeasts S. cerevisia which are top fermenting and lager yeasts S. carlsbergensis which are bottom fermenting, meaning that the yeast sinks to the bottom when the job is done). And if this doesn’t impress you – consider the fact that there are thousands of S. cerevisia isolates available from culture collections around the world (ATCC and CBS are among the largest – do a search for S. cerevisiae at ATCC and it tells you to narrow your search because there are more than 5000 hits!).

Apart from the specific strain used the fermentation conditions will also greatly influence the volatile profile: temperature, time, pH, micro and macro nutrients present, and the sugars available all have their say. A general advice for artisan breads is to use only a small amount of yeast (2-3 g) to start with and give the dough plenty of time to develop and rise. This gives a richer flavor compared to using 50 g of fresh yeast to obtain a rapid rise. Since I only started with about a 1/4 teaspoon of yeast slurry I first had to let the yeast grow and multiply. Since S. cerevisiae needs oxygen to grow I added 50 g of water to the yeast slurry and then used a hand mixer to whip in air for a minute or so before adding 50 g of flour. I left the pre-ferment (aka poolish or biga) on the benchtop and the next day there was plenty of bubbling activity. I added more water, whipped in more air with a hand mixer and once again added as much flour as water. This yielded an active starter and all was set for baking.

Hefeweizen bread

Pre-ferment (evening before baking day):
65 g starter (100% hydration)
110 g water
110 g all purpose wheat flour

Baking day:
285 g starter (100%) from day before
466 g water
250 g emmer
485 g all purpose wheat flour
12 g salt

Total dough weight: 1498 g
Hydration: 69%

Add water to starter and incorporate air with a hand mixer to give the yeast a good start. Mix in the flour, cover and leave at room temperature. Next day, mix all ingredients and leave to rise (this may take 1-3 hours). Divide in two, fold over repeatedly and shape into boules. Leave to rise. Preheat oven to 250 °C. Use a baking stone, and generate some steam in the oven during the first 10 min (see picture below). After 10 min, turn down to 220 °C and bake until crust has a nice golden crust.

My current steam setup: I use ice cubes since this prevents a sudden gush of steam towards my hands. The stones serve as a heat reservoir ensuring that the ice cubes melt and evaporate within a couple of minutes. To cope with the heat shock I use a plate of stainless steel to hold the stones. After 10 min I open the oven door to vent out steam and remove the plate with the stones to allow an even heating (no reflection!) of the baking stone from below.

So how did it taste? The bread tasted excellent, but to be honest – I couldn’t detect any aroma that I can’t get using conventional baker’s yeast. The reason for this is probably that other flavors (i.e. from the flour, the baking process etc.) dominate. Another factor is that bread is only fermented for a couple of hours compared to several days for beer. This simply doesn’t give enough time for significant concentrations of the volatile compounds to develop. Lastly, the baking process will drive off the most volatile compounds. Nevertheless, I would still encourage you to try this! I didn’t get the result I hoped for (I was a little optimistic), but it’s a fun experiment to do, especially if you have some yeast left over from beer brewing anyway.

I am by no means the first to try this. But it seems that results are mixed. Some complain about slow rising doughs. But there are also many misconceptions around. One is that some yeasts produce more alcohol whereas other yeasts produce more gas. As long as we’re talking about anaerobic fermentation of sugar to ethanol and carbon dioxide this is plain wrong as ethanol and carbon dioxide are produced in a 1:1 ratio. There is also some confusion with regards to the naming (i.e. beer yeast, ale yeast, brewer’s yeast, baker’s yeast etc. – when all in fact are the same yeast).

Since the bread came out just like bread made with conventional baker’s yeast it’s fair to turn the question around: Do the different beer yeasts really make a difference? I did a quick search in the scientific littereature and found a couple of papers that study the effect of yeast strains on the formation of volatile compounds in beer and wine:

Yeast Influence on Volatile Composition of Wines
Ester Concentration Differences in Wine Fermented by Various Species and Strains of Yeasts
Synthesis of volatile phenols by Saccharomyces cerevisiae in wines
Function of yeast species and strains in wine flavour
Expression Levels of the Yeast Alcohol Acetyltransferase Genes ATF1, Lg-ATF1, and ATF2 Control the Formation of a Broad Range of Volatile Esters

I haven’t had the opportunity to dig really into this, but from the abstracts it definitely seems to be the case that the selection of yeast strains also play a vital role in the resulting aroma profile of the beer.

Oh yeah, one more thing: For this particular bread I used emmer from a local mill, Holli Mølle, specializing in ancient cereals. Emmer (aka farro) doesn’t form as much gluten as conventional wheat (I tried making a 100% emmer no-knead bread which tasted nice but was a fiasco shape wise…), but it does lend a light greyish/brown color to the crumb and also gives the bread a richer flavor. But the use of emmer is of course not a pre-requisite if you want to bake with beer yeast

Looks good and tastes good!

A little more than a week ago Dave Arnold posted a great, new technique: pressure infusion using a conventional iSi whipper! Just think of it – the whipper has been around for decades, and years a go Ferran Adrià pioneered it’s use for espumas. Several have suggested it’s use for carbonation of fruit. But no one had thought of utilizing the whipper for infusions – until August 11th when Dave Arnold of Cooking issues posted the results of his experiments in “Infusion Profusion: Game-Changing Fast ‘N Cheap Technique”. The first blogger to pick up the technique and post about it on August 12th was Linda of playing with fire and water who termed it a revolutionary technique. A couple of days later, on August 17th Aki and Alex of Ideas in food posted a combined pressurized infusion of basil and marination of mozzarella. And then on August 20th James of Jim Seven describes his results comparing conventional cold brewed coffee to cold pressure brewed coffee. It’s really fascinating how fast the idea spread, and it illustrates the benefits of an open and sharing approach to food innovations.

The science behind this is quite simple: in the pressurized canister nitrous oxide (N₂O) dissolves and penetrates the food. When the pressures is suddently released (and it is important to release pressure as fast as possible) the sudden pressure drop causes the dissolved gas to nucleate and form bubbles which expand and disrupt cells, thereby releasing flavor compounds. The physical phenomenon is known as cavitation.

A single N₂O charger contains 8 g of gas corresponding to 0.1818 moles or a volume of 4.1 L at 25 °C and 1 atm pressure. The volume of the chargers is 0.01 L which gives an impressive initial pressure in the chargers of 445 atm! With an approximate volume of 0.7 L the pressure in an empty whipper charged with a single charge would be nearly 6 atm. When liquids are added the volume decreases, but the effect on the head pressure will depend on the type of liquid added. The solubility of N₂O in water is 0.15 g/100 mL at 15 °C, meaning that with 100 mL of water, the head pressure would be roughly 10% higher than in an empty canister (that is, if the solubility is independent of pressure – I’m not quite sure about this). However, since N₂O is a rather non-polar molecule the solubility in ethanol or even oils is much greater than in water, with a resulting lower head pressure. But since flavor delivery is mediated by the dissolved gas suddenly nucleating and bursting cell structures, infusions using ethanol or oil will actually be more effective than those with water because more gas can be dissolved in these solvents (besides the fact that ethanol and oil are better solvents for flavors than water).

Thinking about how I could utilize the pressure infusion technique I came to think about the problems I ran into with hay like off flavors in the parsley and banana flavored marshmallows I made for TGRWT #2. The off flavors can be traced back to 3-methyl-2,4-nonanedione which likely stems from oxidation of unsaturated fatty acids or polyenes. Crushing parsley inevitably leads to oxidation (possibly also enhanced by mixing intra and extra cellular comounds/enzymes), but with pressure infusion – practically in the absence of air – seems to be much gentler than crushing according to Dave’s initial report (as judged by color). So I did a quick experiment with this, infusing a couple of sprigs in 2 dL of water for about 2 minutes. This was by no means enough, and the water had only a faint aroma of parsley (vodka would of course have been much better for the flavor extraction). But it was a clean parsley aroma, and the water was perfectly clear.

Based on the fact that aroma of foods is so important for the way we perceive them, a hypothesis can be put forward: if the major volatile molecules of to foods are the same, they might taste (and smell) nice when eaten together. The concept was first appreciated by Firmenich scientist François Benzi. At one the first International workshops on molecular gastronomy in Erice, he got the idea that jasmin and pork liver which both contain indole could possibly work well together. And they did!

Photo credits: Jasmine flowers by Kpjas. Pig by The Pug Father.

Experimenting with salty ingredients and chocolate, Heston Blumenthal discovered that caviar and white chocolate are a perfect match. François Benzi found that caviar and white chocolate had several amines in common. Since then, Heston Blumenthal has searched a commercial database with information on the contents of more than 7000 volatile molecules in several hundred different foods. Based on this, he has come up with a number of unusual combinations (from egullet.org and other sources). Some of the combinations are also from Herve This. The links are to Heston Blumenthal’s own recipes.

• White chocolate and caviar (trimethylamine)
• Strawberry and coriander
• Strawberry, celery leaves and mint
• Mango and pine extract
• Green peppercorn jelly and beetroot
• Snails and Beetroot (the flavor molecule that contributes to the earthiness in each of these is the same. It also exists in spinach and baby corn)
• Chocolate and pink peppercorn
• Carrot and violet (ionone is the main pairing molecule here)
• Carrot and coriander seeds
• Mango and violet
• Mango and pine
• Pineapple, blue cheese and white wine (methyl hexanoate)
• Caraway and lavender are surprisingly interchangeable
• Cauliflower (caramelized) and cocoa
• Liver and Jasmine (indole)
• Cooked cheese (like Parmesan and Gruyere) and honey (with a slightly chestnut character)
• Banana and parsley
• Banana and cloves
• Harissa (chili paste) and dried apricot
• Chocolate and smoked eel (and possibly other smoked flavours as well?)
• Chocolate and meat (pyrazines)
• Coffee, cooked meat, popcorn, canned tuna, slightly roasted white sesam seeds and yeast extracts (2-furfurylthiol and 2-methyl-3-furanethiol)
  Garlic, coffe and chocolate. Garlic and chocolate don’t have much in common, but both have something in common with coffe (original blogpost, cooking challenge: TGRWT #1).
• Salmon and licorice
• Oyster and passion fruit (methyl hexanoate)
• Oyster and kiwi (methyl hexanoate)
• Pineapple and hop (methyl hexanoate)

Pairings that possibly/probably have a molecular basis:

• Chocolate and caraway (or: sauerkraut, aquavit etc.)
• Chocolate and sage
• Chocolate and tobacco
• Chocolate, peanut and merlot vinegar
• Chocolate and red wine
• Mint and mustard
• Parsnip, pear and vanilla
• Minced meat and caramel
• Orange and butternut squash
• Apple and lavender
• Onions, cinnamon, olives and caramel
• Cocoa and mushrooms
• Stilton and rhubarb
• Chantarelle and apricot
• Hazelnut and nutmeg
• Honey/caramel and truffles
• Sweet white wine and pea shoots
• Cranberries and pistachio
• Semolina pudding and red curry
• Parmesan mousse
• Olives, dried figs and brie
• Onion, garlic and coffee
• Chestnuts and praline
• Tomato and strawberry
• Aspargus and violet
• Potato, coffee and capers

The flavour pairing principle can also be used for substitutions:

• Basil (containing linalool, estagol and eugenol) can be substituted by a combination of coriander (linalool), estragol (tarragon, chervil or star anise) and cloves (eugenol)
• Try to use coffee in stead of stock for gravies
• Strawberries and tomatoes appear to be interchangeable

To explore flavour pairings like the ones I’ve described on this page, I have initiated a monthly food blogging event, They go really well together (TGRWT), and a summary with links to previous announcements and round-ups has been posted. You also check out my blogposts tagged TGRWT and/or posted in the flavor pairing category.

Databases which can be of interest for investigation of further flavour pairings:

• Volatile Compounds in Food
• Flavornet
• The good scents company – an elegant way to search for volatile compounds shared by two foods is to type the following in a google search box: “pineapple cheese site:http://www.thegoodscentscompany.com”.
• The website foodpairing.be has beautiful graphs depicting both flavor pairing and flavor substitution – highly recommended!

Caramelized cauliflower and cocoa taste excellent when eaten together. It is fascinating how well the aroma of the two go together, and if I smell roasted cauliflower now, the smell actually reminds me of cocoa! Here’s how to make it:

Caramelized cauliflower and chocolate jelly
cauliflower
olive oil
salt
cocoa powder
water
sugar
agar

Cut cauliflower in 1 cm slices. Spread them on aluminum foil. Sprinkle with olive oil and salt. Bake in oven at 200 °C for approx. 30 min (turning the slices after 15 min). For the jelly, bring 1 dL of water to the boiling point. Add 1 ts of agar-agar, 1 ts of sugar and 1 TS of cocoa powder. Mix well, pour into a suitably sized container and leave to set. Cut jelly into pieces and serve together with caramelized cauliflower.

Other examples I have tasted include white chocolate/caviar, strawberry/coriander leafs, pineapple/blue cheese and banana/parsley (see picture below). They all go surprisingly well together, and I guess the challenge for the cooks is to find a suitable way of presenting these dishes. You can read about other bloggers attempts at this in the many TGRWT posts.

White chocolate/caviar (top left), strawberry/coriander leafs (or seeds), pineapple/blue cheese and banana/parsley

In my everday cooking sage is really underutilized. The only dish I can think of with sage that I’ve prepared during the last couple of years is potato gnocchi. So this was indeed the most likely candidate for experimentation in this month’s TGRWT #21. Potato gnocchi are one of those dishes that I suddenly feel a craving for, and I make it every now and then. When I get things right the gnocchi have a very light texture which fits nice with the melted butter and cheese. This time I decided to incorporate the peanuts into the gnocchi and apart from that stick to the original recipe.

While cooking I tried to chew some peanuts with a sage leaf, and this was a quite remarkable experience. The roasted peanut flavors blended into the sage, and the sensation was stronger than what is usually the case from the previous TGRWT rounds. When tasting sage by itself it will actually remind me of peanuts and vice versa. The last time I had a similar strong sensation was when combining roasted cauliflower with a cocoa agar gel.


I used a mini-food processor to grind the peanutes to a coarse powder.

Gnocchi with peanuts and sage
1 kg mealy/floury potatoes
100 g roasted peanuts
50 g butter
1 egg
250-300 g flour
1 t salt

For serving:
melted butter
chopped sage
grated parmesan
black pepper

Grind peanuts to coarse powder. Boil (or bake) potatoes (preferably unpeeled) until soft. Drain. While the potatoes are still hot, peel them and mash them. Add peanuts, butter, salt, egg and about half of the flour. Mix. Slowly add more flour until you get a soft and slightly sticky dough. Use as little flour as possible, but remember that with less flour the gnocchi are more prone to fall apoart (the added egg helps bind the gnocchi together by the way). Make a roll, approximately 2.5 cm in diameter and cut 1.5 cm pieces. Press against the back of a fork for the characteristic pattern, and place the gnocchi on a towel sprinkled with flour or semolina. Bring a large pot of salted water to a slow boil (is the salt really necessary here?) and cook the gnocchi for 2-3 minutes, or until they float to the surface. Remove from the water and drain. Serve with melted butter, chopped sage and plenty of grated parmesan and ground black pepper.

Gnocchi ready to be cooked. Use too much flour in the dough and you get boiled lumps of flour. Use too little flour and your gnocchi will fall apart.

Verdict: The amount of peanuts used gave a noticeable, yet mild nutty flavor which actually fitted the gnocchi quite nice (for future gnocchi attempts I can imagine even trying other nuts as well, such as hazelnuts or walnuts). The sage works very well as an aromatic and fresh component together with the more “heavy” flavors of potato, butter and parmesan. And frankly, I must say that the gnocchi were a success! I’ll make a note in the cook book that adding 100 g of peanuts works nice so I won’t forget the next time I make potato gnocchi.

A quick search over at The good scents company reveals that the butyraldehyde occurs naturally in both sage and roasted peanuts. But as I’ve pointed out several times previously – as long as we don’t know the impact odorants it’s impossible to tell whether this is the compound that ties sage and roasted peanuts together or not. If you’ve done litterature searches for impact odorants of roasted peanuts and sage, please tell me about it in the comments

It’s been a couple of months since the last round of “They go really well together” where food bloggers around the world explore food pairings based on similarities in their aroma profiles. The similarity is not based on the concentrations of the aroma components, but rather the odor impact of the components to the overall aroma (and in case you wondered: impact does vary with concentration, but it varies even more with the detection threshold). In other words, what this food pairing does is to point at two foods (which often may seem quite different) and say that these actually have something in common. And because of that it could be worthwhile to try and use them together when cooking. The 21st round of TGRWT is hosted by Greg over at Humbling attemts at creativity, and the foods to pair are sage and roasted peanuts. Head over to his announcement post for more details on how to participate. The deadline is June 1, so there is plenty of time for some creative cooking the next couple of weeks! If you’re not yet familiar with TGRWT you may want to have a look at some of the previous TGRWT rounds.

I prefer my coffee black, and politely decline when offered milk and sugar. However, if offered salt I would probably smile and say “Yes, please!” Salt???! It turns out that adding salt to coffee is not as weird as it may sound at first. There is a tradition for adding a pinch of salt to coffee in Northern Scandinavia, Sibir, Turkey and Hungary. And when available, such as in coastal areas where fresh water from rivers mixes with the salt sea, one would simply use brackish water when preparing coffee. This water typically has a salt content of 0.5-3%, which is lower than the average 3.5% in seawater. This results in a more intense taste and more foaming. And if living far from the sea, the Swedish food blogger Lisa Förare Winbladh let me know that in Northern Sweden one would deliberately add salt if using melt water from glaciers for making coffee. But tradition aside, is there a scientific explanation of this widespread tradition of preparing coffee with addition of salt?

The first thing that comes to mind is that salt reduces bitterness. And to be more precise it is the sodium ion (Na⁺) that interferes with the transduction mechanism of bitter taste. But interestingly the mechanism behind this is not fully understood! One of my very first blog posts was about tonic water and how one by adding salt can suppress the bitter taste and make tonic water more or less sweet. It’s a fascinating experiment that you should try at home. Expect to use about 1,5-2 g salt for a glass with roughly 1,5 dL (150 g) of tonic water. It’s a good idea to start with a little salt and taste it as you go.

Try adding a little salt to tonic water – the effect is quite surprising: The characteristic bitterness from the added quinine disappears!

Bitterness is an important flavor in coffee, but under less-than-optimal extraction conditions it can be too dominant. Generally bitter tasting compounds are less water soluble than other coffee flavors, hence the bitter compounds are extracted towards the end of the brewing. High temperatures (close to boiling) and long extraction times also favor bitterness. In that respect the coffee percolator is known to produce rather bitter, over-extracted coffee due to near boiling temperatures, and such coffee would most likely benefit from a little salt! And before the percolator came the ground coffee was just put into the boiling water and then left to settle. I can really imagine how brackish water could actually benefit

But the salt need not be reserved for over-extracted coffee. I’ve tried using salt both in a drip coffee maker and in the filter basked when pulling an espresso. The tests were very un-scientific, but the tiny amount of salt does dampen bitterness and change the coffee taste (but the coffee does not have a salty taste). Since I lack cupping experience, I certainly lack the language to describe how salt influences the taste, so I leave it up to you to try it out! And maybe some baristas with cupping experience can fill me out on this and do some tests?

In stead of just using plain salt with coffee, cured ham would signal rafinesse if served in central Europe, whereas in Northern Sweden there is a tradition for serving dried meat with coffee. The Swedish author Mikael Niemi describes this in his novel Popular music from Vittula:

“… and then the pièce de résistance among all the sweetmeats: a hard, brown lump of dried reindeer meat. Salty slices were cut and placed in the coffee, chunks of coffee-cheese stirred in, and white sugar lumps were held between the lips. And then, fingers trembling, we all poured the coffee mixture into our saucers, and slurped our way to heaven.”

With cured ham, apart from the salt-coffee interaction, one also has the combination of meat and coffee. From previous flavor pairing rounds TGRWT #1 and #5 (chocolate/coffee and coffee/meat respectively) we have seen that coffee and meat in some ways approach each other and are actually a good combination. A secret tip BTW is to add a little coffee to your beef stocks for extra depth and richness – this works because coffee shares many impact flavors with browned meats due to the Maillard reaction.

Now I’m curious – are you aware of coffee-salt combinations in your own country? Please tell me about it! And if you try a pinch of salt in your coffee – how did it taste?

Update: Read about my tests of coffee with salt at Tim Wendelboe’s coffe shop

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Some articles that discuss the role of sodium ions (Na⁺) in suppression of bitter receptors:

Breslin, P. A. S; Beauchamp, G.K. “Suppression of Bitterness by Sodium: Variation Among Bitter Taste Stimuli” Chemical Senses 1995, 20, 609-623.

Breslin, P. A. S; Beauchamp, G.K. “Salt enhances flavour by suppressing bitterness” Nature 1997 (387), 563.

Bresling, P. A. S “Interactions among salty, sour and bitter compounds” Trends in Food Science & Technology 1996 (7), 390. (free download)

Keast, R. S. J.; Breslin, P. A. S. “An overview of binary taste–taste interactions” Food Quality and Preference 2003, 14(2), 111.

In addition to suppression of bitterness, salt can enhance sweetness at low concentrations and umami flavors at higher concentrations (more about this in part 5 of “Practical tips for molecular gastronomy”).