Planning is an important part of grocery shopping for many consumers, with some wanting produce that's ready to eat right away or others choosing something they can save for later. However, these purchases don't always go as expected.

It was this need that prompted two Mexican developers to create a smartphone app 'Fru Tap', which allows consumers to know just how ripe their fruit is before buying it.

Mexican researcher professor Bernardo Reyes Guerra, from the Monterrey Institute of Technology and Higher Education's (ITESM) Puebla campus, teamed up with electronic engineer Alberto Hugo Deloya Vélez to work on the app, using algorithms based on a glucose meter for diabetics.

"We are doing research to determine people's glucose. The amount of diabetics, at least in Mexico, is very high, and the only way to measure glucose is to prick the finger to take a drop of blood, and do a chemical analysis with an apparatus," Reyes told www.freshfruitportal.com.

"These devices and lancets have a relatively low cost if one looks at them one by one, but if a diabetic has to do it four or five times daily, this starts to become very significant economically."

Building on their work to make a non-invasive app so that diabetics could avoid this tedious task, Reyes and Deloya got started on the 'madurómetro' - translated as 'ripemeter' in English - for fruit.

"We have been doing this investigation for a bit more than two years, and we believe we are very close to getting a non-invasive glucometer. However, in the process one needs resources, and we thought about a simpler collateral product, which is precisely to measure the ripeness of fruit," Reyes said.

As the ripeness of fruit is tightly related to the amount of glucose it contains, the researchers claim it has been much easier to measure glucose levels in fruit than humans.

"We thought this would be an interesting problem because many people end up buying fruit that takes too much time to ripen, or it is so ripe that they have to eat two kilos of papayas practically on the day they buy them.

"We found it interesting to develop this 'ripemeter' that determines the amount of time the fruit has to be ready to eat, thinking that the habits of many people are to buy fruit or food for the whole week, and that maybe they would want to have a kiwifruit or a papaya for eating Monday, another for Wednesday and another perhaps for Friday.

The app works on smartphones that have cameras with a flash function. According to Reyes, the flash illuminates the fruit directly, and analyzes the amount of red, green and blue light detected on the skin.

"So, we simply determine the combinations in the palate of colors in the reflection, and we relate it to the ripeness of the fruit to give the person an indication whether the fruit is ready to eat today, or to eat in 24, 48 or 72 hours.

"We checked, did tests, and effectively we could determine the amount of glucose in a fruit without any problems

He highlighted the app only worked with fruits that had soft skin, such as papayas, kiwifruit, peaches, melons and greenskin avocados. Meanwhile it did not work with fruits with harder skins like coconuts, pineapples or Hass avocados.

"We are trying to see the possibility of an option for hard skins," he said.

He said modifications and updates would be made throughout the year for the app, which will be available on Android systems for MXN10 (US$0.76). He added it would be ready within a couple of weeks for iOS systems.

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