Posts Tagged ‘eggs’

Two flavour pairing case studies

Saturday, May 5th, 2007

In previous posts and comments I have suggested that flavour pairings based on key odorants could be explored by looking at odor activity values (= ratio of volatile compound to it’s threshold). If two foods share one or more key odorants, chances are that they will go well together. It is also reasonable to assume that the more key odorants are shared, the more similar the flavours will be and the more likely it is that the foods will blend well and match each other.

Having initiated the TGRWT event I figured I should try to see if there was any OAV data available for coffee, chocolate and garlic. I was lucky to find OAVs for coffee (both arabica and robusta beans) and cocoa. To compare coffee and cocoa I sorted the flavour compounds in a descending order based on the OAV, keeping only the 20 first compounds. I turned out that 7 out of 20 key odorants in coffee and cocoa are shared, corresponding to 28/25% and 39% respectively of the total “odor activity” (= sum of OAV of top 20 odorants). Here’s the whole list:

coffee-chocolate-oav.jpg
(I hope the authors stuck to the IUPAC naming conventions as I did not take the time to check if synonyms were present in the compounds lists)

To compare this with a random pairing I search for more OAVs and found data for parmigiano reggiano and mango, so I repeated the excercise. Among the 20 odorants with the highest OAVs respectively for coffee and mango there was no overlap. A neglibile overlap was found between cocoa and mango: one odorant (linalool) was present in both with OAVs corresponding to 0.03% and 0.05% of the “odor activity” respectively. The fact that there is no overlap between coffee or cocoa and mango does not imply that they don’t go well together, only that their key odorants don’t match. Parmigiano reggiano and cocoa however had a lot in common, as seen from the table below. In fact 6 out of 20 key odorants, representing 36% and 89% of the “odor activity” for parmigiano reggiano and cocoa respectively.

parmesan-cocoa-oav.jpg

The degree of overlap between parmesan and cocoa is in fact better than for coffee and chocolate when judging by the percentages (albeit with one less odorant), so this pairing will certainly be included in a future TGRWT event! A quick google search revealed that chef Masaharu Morimoto has come up with a recipe combining cocoa and parmesan:

Chocolate Carbonara with Parmigiano Reggiano Cream

Chocolate Pasta:
1 pound all-purpose flour
4 eggs
½ cup cocoa powder
1 Tablespoon olive oil

Pasta Sauce:
2 cups cream
4 egg yolks
½ cup sugar
½ cup Parmigiano Reggiano

For the Chocolate Pasta:
Sift flour and cocoa powder together and knead in the eggs and olive oil for 15 minutes. Rest for another fifteen minutes then roll and cut in a pasta machine. Heat up a pot of lightly salted water and boil pasta until al dente.

For the Pasta Sauce:
In a medium sauce pot scald the cream. In a separate bowl, whisk together egg yolks, Parmigiano Reggiano, and sugar. Temper this mixture into the hot cream and bring to a light simmer, whisking constantly to prevent curdling.

Unfortunately I couldn’t find any OAVs for garlic, so I haven’t been able to verify the triple pairing forming the basis for TGRWT #1. The claim was that coffee has dimethyl sulfide in common with garlic, and methyl pyrazine in common with chocolate. The table above confirms that coffee and chocolate have several methyl pyrazines in common, but dimethylsulfide is not among the 20 key odorants in coffee. This puzzles me, but there could of course be other volatile compounds that garlic shares with coffee. There should also be quite a difference between raw garlic (not to mention between whole, crushed and possibly even minced) and roasted garlic. If I overlooked something (or perhaps a paper with OAVs for garlic), please drop me an email about this. The OAVs of garlic could easily be calculated if data on volatile compounds in garlic and threshold concentrations are available.

I did a search on coffee, cocoa and garlic on The Good Scents Company website as described previously and found the following compounds either naturally occuring or used for recreating the aroma of coffee, cocoa and garlic:

  • 5-methyl furfural (found naturally in all three, used for coffee and garlic)
  • benzothiazole (found naturally in cocoa, used in all three)
  • 2-furfuryl mercaptan (found naturally in coffee, used in coffee, garlic cocoa)
  • isovaleraldehyde (found naturally in coffee and cocoa, used in all three)
  • ethyl methyl sulfide (found naturally in coffee and cocoa, used in coffee and garlic)
  • bis(2-methyl-3-furyl) disulfide (used in all three)
  • butyraldehyde (found naturally in all three)
  • S-(methyl thio) butyrate (used in all three)
  • isopropyl mercaptan (found naturally in garlic, used in coffee and cocoa)
  • So there are obviously similarities similarities between coffee, chocolate and garlic, but the question is whether these compounds are key odorants or not.

    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. This also means that the odor activity percentages calculated for the pairings above should be take with a pinch of salt. In between these extremes normal additivities are observed.

    intensity-vs-concentration.jpg

    Even though OAVs are not phsychophysical measures of the perceived odor intensity, they compare quite well with models that take different aspects of sensing into accout. The validity of the found OAV can also be tested by a recombination of the flavour compounds to see how good it imitates the original product studied. I can recommend the freely downloadable article “Evaluation of the Key Odorants of Foods by Dilution Experiments, Aroma Models and Omission” (DOI: 10.1093/chemse/26.5.533) for those interested in reading more about the science.

    Despite the drawbacks and limitations I think OAVs can and will be helpful when studying the flavour pairing hypothesis.

    Tips: You can read more about OAVs in books which are (partly) available through Google books.

    Dyeing eggs for the easter holiday

    Thursday, April 5th, 2007

    About.com has a nice guide on how to color eggs, and the list of colors is quite impressive (click for instructions):

    Lavender
    Small Quantity of Purple Grape Juice
    Violet Blossoms plus 2 tsp Lemon Juice

    Violet Blue
    Violet Blossoms
    Small Quantity of Red Onions Skins (boiled)

    Blue
    Canned Blueberries
    Red Cabbage Leaves (boiled)
    Purple Grape Juice

    Green
    Spinach Leaves (boiled)
    Liquid Chlorophyll

    Greenish Yellow
    Yellow Delicious Apple Peels (boiled)

    Yellow
    Orange or Lemon Peels (boiled)
    Carrot Tops (boiled)
    Celery Seed (boiled)
    Ground Cumin (boiled)
    Ground Turmeric (boiled)

    Brown
    Strong Coffee
    Instant Coffee
    Black Walnut Shells (boiled)

    Orange
    Yellow Onion Skins (boiled)

    Pink
    Beets
    Cranberries or Juice
    Raspberries
    Red Grape Juice
    Juice from Pickled Beets

    Red
    Lots of Red Onions Skins (boiled)

    More information about the chemistry behind can be found in the article “Chemistry in the dyeing of eggs” (Journal of Chemical Education, 1987, 291). The article discusses anionic dyes with sulfonate groups. These bond to the cuticle (protein) covering the egg shell forming salt linkages as shown (illustrated using FD&C yellow no. 6):

    egg-colouring.jpg

    By lowering the pH (for example by adding vinegar), more amino groups in the proteins covering the egg shell are protonated and thus available for formation of the salt linkages with the anionic dyes.

    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.

    Chocolate sauerkraut cake

    Sunday, January 14th, 2007

    After giving a presentation about molecular gastronomy I was asked if I had ever heard about a chocolate cake baked with sauerkraut. I admitted that this was new for me, but that I would be very interested in the recipe. Could it be that this is a new flavor/flavour pairing? Remember, the hypothesis is: if the major volatile molecules of two foods are the same, they might taste (and smell) nice when eaten together. Perhaps there’s some one out there with access to a headspace gas chromatographer that could check this out? Or perhaps someone who has access to the Volatile Compounds in Foods database could do a quick search? If you’re unfamilier with such flavor pairings, another nice pairing with chocolate is the one with caramelized cauliflower and chocolate jelly.

    I did get the recipe and it turned out that it was from a cookbook called “Food that really schmecks” by Edna Staebler. The book is a collection of recipes from the Mennonite community in Ontario. Many Mennonites came from Germany, hence the word “schmecks” in the title which is German (zu schmecken = to taste). According to the cookbook, leftover sauerkraut makes the cake moist and delicious – which I can certainly confirm! And the strange things is you can’t really taste the sauerkraut. Here is the recipe (the way I made it):

    Sauerkraut chocolate cake
    170 g butter (ca. 3/4 cup)
    300 g white sugar – less than the 1 1/2 cups in the original recipe
    3 large eggs
    1 teaspoon vanilla (either essence or vanilla flavored sugar)
    2.5 dL water (= 1 cup)
    6 dL flour (= 2 1/2 cup)
    1.3 dL unsweetened cocoa (= 1/2 cup)
    1 teaspoon baking powder
    1 teaspoon soda (sauerkraut is sour, therefore the recipe calls for soda!)
    1/2 teaspoon salt
    330 g drained  sauerkraut (1 1/2 cup) – more than in the original recipe

    Mix butter and sugar. Add eggs, water and dry ingredients. Stir in the sauerkraut and pour batter into greased pan. Bake at 350 F/180 C for 30-50 minutes.

    chocolate-sauerkraut-cake

    The cake was a little too moist in the center when I made it and could have needed a couple more minutes in the oven. Make sure you check if it’s all set by inserting a wooden match or a knitting pin in the center of the cake!

    Interestingly, the cookbook “Food that really schmecks” was recently presented in the blog Cream Puffs in Venice, with the following statement attached: “There is no haute cuisine or molecular gastronomy to be found here”. But chocolate and sauerkraut might turn out to be another flavor pairing based on sound chemical reasoning.

    Update: Read the followup on this post with more about chocolate and caraway (the main spice in sauerkraut)

    TGIF: Molecular gastronomy with a twist

    Friday, November 17th, 2006

    Heston Blumenthal was recently featured in “Private Eye”, a british satire magazine (found via Aidan Brooks). They included the following recipe for boiled eggs:

    heston blumensilly

    A further discussion of boiled eggs from the perspective of molecular gastronomy is found here.

    Perfect eggs?

    Sunday, October 22nd, 2006

    I just came across this fancy egg boiler. It’s designed by Simon Rhymes and bears the name BEM. The egg is cooked in about 6 minutes by the heat from 4 halogen light bulbs with a total output of 500 W.

    bem.jpg

    It sure looks fancy, but I doubt that these eggs can rival the texture of those prepared by the low temperature methods I have described. The reason for this is that the halogen lamps heat up the eggs above the temperature required for the white and the yolk to set. This gives the white a rubbery texture. And even though the BEM has a timer, you still have to figure out (by experimenting?) for how long to cook your eggs…

    I think the best part is the cutting ring with a 125 g mass which is raised and dropped to create a crack around the top of the egg. But there is no need to buy the BEM, because a similar egg cracker can be bought separately here for instance! You place the cup on top of the egg, raise the steel ball and drop it. The energy is transferred to the egg, creating a perfectly circular crack. This is actually very neat!

    clack-egg-punch.jpg