Posts Tagged ‘OAV’

TGRWT #2: Banana and parsley

Tuesday, May 8th, 2007

It’s time for the second round of the They go really well together food blogging event (hereafter referred to as TGRWT #2). Ingredients to pair this time are banana and parsley, which should be an easy match compared to last round with coffee, chocolate and garlic. Deadline is June 1st, so there’s still a couple of weekends left for you to do some experimental cooking. The event and round-up is hosted by Tara over at Should you eat that, so check out her post with instructions on how to participate!

tgrwt-2.jpg

I’ve tried to track down the origin of this pairing. First place I saw it mentioned was by Heston Blumenthal at eGullet, and in an interview with The Independent Heston explains how he discovered it:

He gives an example of this creative process in action. “I was cooking rabbit stew for the kids last summer in France, lifted the lid and threw in chopped parsley and got a smell of banana.” Which prompted him to pair banana with parsley, and banana with tarragon. “It worked really well.”

I have found odour activity values (OAV) for parsley, but not for banana. A search at The good scents company reavels that (Z)-3-hexen-1-yl formate and linalool are present in both banana and parsley. When comparing the OAV data of parsley with a search for banana only at The good scents company oct-1-en-3-one and (Z)-hex-3-enyl acetate were also found. Please post a comment if you have more data on the volatile compounds of this pairing and their OAV values.

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.

    Searching for flavour pairings

    Tuesday, April 17th, 2007

    Google can be of great help when exploring flavour pairings, especially for those of us who don’t have access to the commercial database VCF. The following tip has been mentioned in a comment to a previous blog post, but I thought it could be a good idea to bring it to everyones attention:

    The Good Scents company has en extensive range of aroma components, and the nice thing is that they list natural occurences and uses. The latter I guess, is based on the organoleptic properties of the aroma compounds. Using google, it’s possible to check if two or more foods have anything in common. Just type in the foods of interest and add site:http://www.thegoodscentscompany.com at the end. The triple combination in my last post for instance gives the following search string (click to perform the google search) and the top 5 hits are:

    furfuryl mercaptan * 98-02-2
    benzothiazole * 95-16-9
    isovaleraldehyde * 590-86-3
    bis(2-methyl-3-furyl) disulfide * 28588-75-2
    5-methyl furfural * 620-02-0

    The numbers following the name of the aroma compound are CAS registry numbers and indentify each compound uniquely. They are often more useful than the chemical name when searching the internet and databases.

    Unfortunately there is no way to distinguish whether the foods listed for each aroma compound occur under the “Natural occurences” or “Used in” labels.