Reliable Method for Selecting Watermelons

[salty9]

I tried Bigmoose' method and got the sweetest watermelon this year. Unfortunately, I had to get a female produce clerk about 35 years old to select it and she knew about the yellow bottom, heavy weight per volume and the healed scratches but didn't know how to interpret the thump and I ended up with watermelon soup.

Off topic, if you like pepper and don't have a peppermill - get one. It is an order of magnitude better than store-bought ground pepper.

[bigmoose]

So after this thread, I took the plunge and picked my own melon yesterday... fail. Wife cut it up and said, 3/4's was ok, but had to throw the other 1/4 away as mush... guess I will go back to my old method of melon selection!

[Harold in CR]

It's one of those "gotta be there to learn it, things" Maybe next time, BM?

[Ykick]

This time of year in NA the odds of over ripe WM start to go up and by September it's practically a given.

I suggest newbies simplify and learn to discern "over ripe" from visual indcations of "ripe" by thumping. All the other levels of "thumping" will be too much to grasp unless you intend to grow and/or have 100's of sucessful selections to rely on.

Hard to describe and maybe check YouTube for video/sound examples but basically you want the visual/physical indications of ripe coupled with a nice tight "ring" when thumped. A dull thud is more likely to be over ripe and resulting mush inside.

My dad used to grow WM's and for the past 30 years I probably go through 2 dozen or more every summer and haven't wasted any money on a dud in decades. My favorite summer fruit!

[Jeremy Harris]

Being the technically inclined lot that we are, couldn't we come up with a means to do this automatically? How about a little gadget with a low frequency contact microphone (or maybe an accelerometer on a contact pad) coupled with a thumper that provides a preset tap to the melon? Some means of capturing and analysing the waveform, using a µcontroller perhaps, would be needed, together with a way to recognise the unique signature of a ripe melon.

Calibration would be needed, maybe by testing a few melons, recording the waveform and then comparing the perfect, ripe, melon with the recordings to try and see what the signature looks like.

[Ykick]

Being the technically inclined lot that we are, couldn't we come up with a means to do this automatically? How about a little gadget with a low frequency contact microphone (or maybe an accelerometer on a contact pad) coupled with a thumper that provides a preset tap to the melon? Some means of capturing and analysing the waveform, using a µcontroller perhaps, would be needed, together with a way to recognise the unique signature of a ripe melon.

Calibration would be needed, maybe by testing a few melons, recording the waveform and then comparing the perfect, ripe, melon with the recordings to try and see what the signature looks like.

Interesting idea and while there's a particular "timbre" and/or "resonance" associated with the ideal "ripe" sound there's the constant variable of Melon size which relates to "pitch" of the sound. Not sure how you can precisely measure and qualify timbre/tone without a known pitch or frequency?

I'm a musician by trade and my ears still work pretty good so it's fairly natural for me to identify the ideal sound even though the pitch changes from Melon to Melon.

[The fingers]

It is similarto what musicians refer to as "tone", not meaning a certain musical note or tone, but the pleasentness of the overall sound produced by high quality instruments and/or electronics; as opposed to lesser quality inferior instruments and/or electronics. For example: an old Hawiaan Koa wood ukulele would usually produce a more pleasing tone to the trained ear than a $19.95 toy store plywood/plastic model.

[Jeremy Harris]

Maybe what's needed is to look at the envelope of the sound, rather than the frequency. If frequency (tone) is related to the size of the melon, then maybe the critical thing to detect isn't the frequency, but the amplitude envelope of the reflected sound, or maybe the time between tapping it and getting a return.

TBH, I know nothing about this, as we don't have a melon season here - any melons we get are imported, I believe.

[fechter]

Excellent idea.

Here's a research paper on it:
Vibrational analysis of seedless watermelons

http://oa.upm.es/6411/1/Diezma_02.pdf

The internal quality of fruit can be non-invasively tested using systems based on vibrational characteristics. In this work, acoustic impulses were used to detect internal hollows in watermelons; the change in the signal revealing the problem. Frequency spectrum variables were analysed for their potential as non-destructive predictors of this defect. The band magnitude variables, obtained from the integral of the spectrum magnitudes between two frequencies, best predicted internal disorders. Experimental modal analysis was used to investigate the vibrational performance of watermelons and to determine the best positions for the impact point and response measurement microphone. A firsttype spherical mode and its resonant frequency was the best indicator of internal quality problems. Finite element modal analysis was performed to establish a watermelon shape/characteristics model and to compare theoretical and experimental results.

It can get even more complex:
http://www.cropj.com/rajabpour_5_7_2011_920_925.pdf

The assessment of watermelon ripeness on the basis of its apparent properties, such as size or skin colour, is very difficult as traditional methods have various problems and limitations. These include lack of uniformity, concentration of excitation energy within narrow bands and need for physical contact between a fruit and the measuring device. In this study a new method making use of Laser Doppler Vibrometry technology (LDV) has been applied to evaluate the ripeness of watermelons, without many of those limitations. At first a watermelon is excited by a shaker as vibration generating device within a range of frequencies. At the same time, the vibrating response of the upper side of the fruit is measured by LDV. The device emits a laser beam on a spot above the sample. The beam reflected from that point is received by the LDV and finally the vibration response of the sample is measured and the signal is sent to the computer. Using a fast fourier transform algorithm and the ratio of input to response signals, the frequency response of the fruit sample was processed and the desired results extracted.

Then they do the Watermelon ripeness destructive test That's got to be the best part. I bet Luke or Methods could help out there.

Hmmm.... I wonder how much a Laser Dopper Vibrometer costs?

[Jeremy Harris]

Might have known that someone else would have had the same idea!

[Harold in CR]

And here I was, just ready to go "Pick" the correct one and enjoy, while y'all were doing all this scientific calculating stuff.

[TylerDurden]

Then they do the Watermelon ripeness destructive test That's got to be the best part.

Enter the sledge-o-matic...

[Hillhater]

. My secret? I wait for a 60 ish year old woman to start picking through the watermelon pile. As she appears about done, I ask her: "Could you pick one for me?" She usually points to one of the last 4 she discarded and says: "That's a pretty good one." I thank her, pick it up, pay for it, go home and enjoy it!

Of course there is a fatal flaw in this method...
If we all did this, eventually all the "Melon experts" would literally die off !..leaving a whole generation of unskilled Melon selectors who had never learned the skills from their elders !

[salty9]

Does the selection criteria presented above apply to melons on the vine? The reason I ask is that I have some baby Sugar Baby melons growing and if any survive our endemic gophers, skunks, opossums, raccoons,deer and bear I want to pick it at its peak of flavor. If the difference between ripe from the vine and store bought is equivalent to that of sweet corn fresh off the stalk it will be worth the effort.

[Harold in CR]

I'm not a fruit scientist. Fruit does not ripen after being picked.

OK, why is nearly all fruit COMMERCIALLY harvested, always picked "green" ?? I'm surrounded by fruit, nearly year round. It always has that "green" tang, just before it gets ripe. Pick fruit early to ship it.

All I can say, is, I can pick the best melons, regardless of species, right at the vine. In the store, you have to settle for the best of the lot.

Last time I was in Florida, I got a couple mush melons, and, my Daughter could not tell the difference. I purposely picked a "Green" one, smell means nothing, and we compared, after getting home. I had gotten the best from the stand, and she saw it.

A person needs to have several to work with, to learn the art.

Ykick said it well, a DULL sound is dead ripe, getting hollow inside. A SOLID sound is green. It's the same as putting different levels of water in identical glasses. Tap each one and you get a different sound-tone- plunk, whatever you want to call it.

All the non-believers can come down and get free lessons.

[John in CR]

Yeah, but watermelons suck down here. Give me a big gulf coast watermelon any time, as long as I can slap them myself, and if it's been rainy I don't even bother.