Testing Herbs for Flavour, Freshness and Nutritional Value
Answered by: Conrad Richter
Question from: Rebecca Omastiak
Posted on: February 12, 2002

My name is Rebecca Omastiak, and I’m a 6th grader at St. Jerome School in Oconomowoc, WI. I’m writing to you, because my school is having a science fair, and my project is: "What herbs maintain more color, flavor, and freshness over a period of time when stored in natural daylight, cool/moist/damp location, and in a freezer."

I have been monitoring samples of the following herbs: Basil, Parsley, Oregano, Marjoram, Garlic, Rosemary, Chives and Thyme. I placed a sample of each herb in three different locations (daylight, cool/moist/damp, and freezer). The idea is to try and determine which location (condition) is the best way to preserve herbs over a 3-4 month period of time.

I also need to test the herbs in order to determine which herbs (in the three locations) maintained the best aroma, taste, freshness and nutritional value. I plan to have an herb taste test as part of my project (example: create a simple dip with each herb and invite several people to sample the dips and rate each herb). I was wondering if there are any other ways to test an herb for flavor, freshness, and nutritional value. If you know of any other ways to test herbs, please e-mail this information to me.

What a wonderful project! I wish you well with it.

What makes one batch of herbs "fresh" or have more "flavour" than another, is not a simple question to answer. There are numerous compounds in herbs that contribute to flavour, aroma and appearance. Generally, fresh herbs will have more flavour, aroma and a nicer, richer coloured appearance than older, stale herbs that have been stored for too long. But there is no single chemical test that measures "freshness".

Most of the culinary herbs and spices owe their characteristic flavours and aromas to essential oils found in the leaves, seeds, roots or stems. This is certainly true of the herbs you are testing. These oils volatilize into the air easily which is why it is possible for you to smell them. But because the oils volatilize easily, herbs and spices eventually lose their oils so that they no longer have much flavour. In addition, dried herbs and spices can become contaminated with fungi and bacteria which grow through the dried material and can cause the flavour to go off.

The oldest and – many would argue – still the most effective testing is what’s called organoleptic testing. This is just a fancy word for testing by smell, taste and eye. Experienced quality control personnel can, using simple organoleptic methods, very quickly and reliably tell which of two batches is the better one. To try to make the same assessment using chemical methods would be time consuming, expensive and not necessarily any better.

When companies handle large amounts of the same herb or spice they develop quantitative chemical tests based on one or a group of what is called "marker" compounds. These are compounds that are selected to be an indicator of a herb’s quality. Usually the marker coumpounds are not the only ones that contribute to the herb’s overall quality, but measuring them does help to generate an objective number that companies can go by to judge quality.

They may also obtain a chemical profile from one of several popular laboratory chromatographic methods such as HPLC (high performance liquid chromatography). This profile looks like a series of peaks and valleys and it allows an analyst to see the relative amounts of different compounds that are present in a herb. An experience quality control analyst can relate the peaks to the quality of a herb. HPLC and other similar tests are expensive to perform and require specialized knowledge to perform them and to interpret the results; they are not practical to in many situations. Indeed most small companies continue to rely on organoleptic techniques for most herbs.

Organoleptic testing is really the only practical test method you can use for your project. The difficulty, however, is that your testers need to be consistent in their assessments over the three month period that you are monitoring the herbs, and that is difficult or impossible to guarantee with inexperienced testers.

If you eliminate unnecessary variables in your testing methods you can improve the likelihood of getting better results. For example, I would not use the dip method you mentioned; rather I would have the testers test the herbs directly, by tasting samples directly, smelling them and judging colour and overall appearance directly. The process of making the dip and the dip materials themselves can easily confuse the results if they are not precisely and consistently done. And I would try to have the testers do each test (taste, smell and colour) separately so that the results of one test does not unduly influence the results of another.

I assume that you are planning to compare the different storage methods by making the assessments of each concurrently over the three month period. This way at least your testers will stand a better chance of yielding consistent results. The testers senses of smell and taste will vary from day to day, but at least the results on the same day should be reasonably consistent.

And don’t forget to record the names of the testers with their test results, because each tester will have his or her own biases as to what is better and what is worse. If you can subdivide the samples 3-5 times so that each tester has to sample each test herb 3-5 times then you can average the results. If you present the samples to your testers in a randomized sequence so that the tester does not know which test herb he or she is testing, that will improve your results because testers can develop biases for one or another teat herb during the testing period.

Dear Mr. Richter:

Išm sorry that it took me so long to respond back to you! I want to thank you for your help with my science fair project

My project was titled: "What Is The Best Way To Store and Keep Herbs Fresh? Natural Daylight? Cool/Moist/Dark Location? Freezer?"

Your responses and information really made my logbook a lot more impressive and complete. I thought you might like to know how my experiment turned out.

In the beginning of my experiment, my hypothesis stated: "Herbs would stay fresh if you stored the herbs in a cool/moist place, because the herbs would absorb moisture."

Here is what I discovered:

Natural Daylight Location

Herbs lost their scent and their color faded.
Herbs didnšt completely lose their flavor.
Herbs became very brittle and dried out.
Some herbs became flimsy (chives).

Cool/Moist Location

Some of the herbs lost their aroma (Thyme, Chives, Oregano, Parsley) while others still had a faint scent.
Herbs did not look fresh.
Some of the herbs had a little mold growing on them (fresh garlic). Many of the herbs were flimsy, or wilted-looking.
Taste was quite strong.

Freezer Location

Herbs still had quality, looked and smelled fresh over 3 weeks.
Flavor and aroma of the herbs became weaker over time.
Some of the herbs had freezer burn on them.
When herbs thawed, they were soggy (Basil & Parsley),

Taste Test

I conducted a taste test (based on your suggestions). The taste test proved that herbs stored in a Cool/Moist Location had the strongest flavor (8 of 15 people rated a dip with herbs from a Cool/Moist Location best flavor). In the same taste test, 13 of 15 people rated a dip made with fresh herbs best flavor. However, the taste test purpose was to rate the flavor of herbs "stored" over a period of time. The taste test confirmed that fresh is always the very best.

Here are the top four awards for the science fair:

1st place was a seventh grader.
2nd place was another seventh grader.
3rd place was an eighth grader.
4th place was a sixth grader - ME. That means I did better than the rest of the sixth, seventh, and eighth graders!

I do not believe I would have been awarded 4th place, though, without all your help. I hope it will make you very happy, knowing that the information and help you provided really made my project a success. Thank you again!


Congratulations!

And thank you very much for letting me know how you made out with your project. I am pleased that I could be of help, but it was your efforts that made the project a success. You posed a clear, answerable question, set up the experimental design, conducted the experiment, and presented the results and conclusions – all the essentials of good scientific inquiry. It is this kind of inquiry that advances human knowledge, and even the age-old field of herbs can benefit from it, as you have demonstrated.

I would like to offer you a prize: Tom Debaggio’s wonderful book, "Growing Herbs from Seed, Cutting & Root". Please let me know your full mailing address so we can send you your prize.

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