Team:UNITN-Trento/Project/Vending Machine

Unripe fruit are placed inside several compartments at the back of the machine, the R-Units (ripening units), and exposed to the inhibitor that is produced by the bacterial culture (i.e. MeSA).

Afterwards one fruit at a time is carried to the next chamber and exposed to bacterial ethylene. By the time the treatment is over, the fruit will be ready to be dispensed.

Ethylene is produced by inducing our bacteria with blue light that is activated when the fruit arrives to the ethylene chamber. After an incubation period (dependent on the type of fruit) the fruit goes right behind a tiny window. A coin input unlocks the window and the fruit is released.

The name «R-unit» stands for Ripening Unit: the fundamental mechanism that controls the ripening of our fruit.

The unit consists in a central circular inhibitor-producing culture, from which the inhibitor is transferred to some surrounding chambers, each containing a fruit. Every single fruit moves from a chamber to another thanks to some rotating palettes, resulting in a rotating system in which the fruit is always exposed to MeSA.

Following the course of a single fruit, we can see it passing from chamber to chamber until it reaches the latter one which is not exposed to the inhibitor. Instead, it has a system to get rid of MeSA coming from the previous chamber along with the fruit. This chamber is like an anteroom that allows to extract the gas before the fruit gets to the ethylene chamber. Once the inhibitor is removed, the palette system rotates in order to bring the fruit to the ethylene exposed chamber. The ethylene exposed chamber is a simple open box that is sealed only when the chamber containing ethylene-producing bacteria descends on top of it. As the blue light turns on, the box is filled with ethylene passing through a filter. After the required time, the culture chamber rises back and the fruit is brought behind the exhibition window. The machine is equipped on the inside with a sensor that perceives the level of ethylene: if the concentration is too high, the sensor forces the arrest of ethylene production by turning the blue light off. This is a measure to prevent explosive concentration inside the scaffold.

As far as the cultures are concerned, we thought to base the system on the principles of a continuous culture, thus the vending machine needs a stock nutrient tank and a nutrient waist tank.

Therefore, every R-unit dispenses ripe fruit one at a time, so the end-user gets to choose!!

We also considered a removal system for those fruits at stake that don’t get bought. After a specified time corresponding to when the fruit could become rotten, a trapdoor opens and the fruit is carried on a conveyor belt to the waste bin.