This article first appeared in the CHELM-ON-THE-MED website. It is published here with author‘s permission.
Up until now, testing the ripeness of watermelons has hinged on folklore – slapping the side of a watermelon and listening to the resonance for the ‘right’ hollow thump.
Of course in Israel, where no one wants to be a frier or sucker, ‘there is a foolproof method: al HaSakeen (‘on the knifepoint’): The vendor at a roadside stand will cut a small square ‘plug’ out of the watermelon and lift it out ‘on the knifepoint’ to show the customer that the fruit is firm and red. While this takes the guesswork out of the equation, the downside is the ‘wounded’ watermelon (the ripest will spontaneously crack open in the process) must be carefully transported home ‘as is’ in a thin plastic bag* and placed immediately in the frig…
Now, finally, three Technion students – Salach Abed el-Halim (23), Eeman Sarhan (23) and Adam Gara (22) – from the computer science department have developed a smartphone app that grades ripe watermelons on ‘looks’ alone, based on pattern recognition of external texture (shade, stripes, the shade of its round dry patch) taken by smartphone. Turns out such patterns on the skin go more than skin deep…despite claims to the contrary among agricultural engineers. When the input is correlated with weight and circumference,** the app can accurately predict the sweetness and firmness of a watermelon on a one-to-five scale in 40 seconds flat.
* In this case, it’s luckily that Israeli supermarkets don’t bag groceries in paper bags, but rather in small flimsy but durable transparent plastic satchels that due to their shape are called in Hebrew ‘undershirt bags’ (sakiyot goofiyah)
** taken in an ‘evaluation bin’ equipped with sensors