Brazilian scientists have developed an electronic nose that neural network can determine the ripeness of the peach, located on a tree on the concentrations of volatile organic compounds in ambient air. The accuracy of the algorithm was 98 percent. The authors propose to use electronic nose for monitoring the growth of peaches and auto harvest. Article published in the journal IEEE Sensors Journal.
The ripeness of the fruit often is defined with volatile organic compounds, which are responsible for flavor, aroma and color of fruit. The definition of maturity of fruit are largely based on the subjective experience of the manufacturer, which may lead to sub-optimal time of harvest. However, over the last decade in the collection and storage of fruits and vegetables have begun to apply electronic nose — a device to assess ripeness. Electronic nose is an array of chemical sensors composed of metal oxide (e.g. tin oxide). Like the human nose, the electronic nose does not specify the individual compound in each sample, but a mixture of odors, volatile organic compounds, each product has its own (very difficult to find two compounds with the same odor). The development of sensor technologies have greatly improved the accuracy of electronic noses, as scientists began to apply them in many areas of food industry: determination of ethanol in beer, nicotine in tobacco , and quality of Oolong tea. Often, electronic noses are used for monitoring the content of harmful substances in the air.
Although options for determining ripeness of fruit after harvest are many, methods of monitoring the ripeness of fruits collected have not yet developed to a small degree, although theoretically such a possibility exists. For example, peach varieties Eragil using gas chromatography and mass spectrometry, scientists are able to determine the main volatile substances, the content of which depends on the degree of maturity. In the first two stages of fruit growth the main volatile compounds — alcohols (1-hexanol), esters (was hexyl acetate), ketones (acetoin) and aldehydes (hexanal and benzaldehyde). The third stage of maturity is about 71 days growth of the fetus and at this point, the peaches start to secrete terpenoids (alpha and gamma terpinene and linalool) — whereby changes in the texture and color of peach. During the fourth stage, the maturation of the fetus, increased sugar content and reduced acidity due to the formation of lactones (in this stage the fruit becomes soft and bright).
Brazilian scientists led by Sergio Stevan Luis Junior (Luiz Sergio Stevan Jr) from the State University of Ponta Grossa has unveiled a prototype of an electronic nose for field monitoring of the growth of peaches.