UC Davis researchers have found a method for using an electronic nose to detect if fruit has fully ripened, which in the future could reduce costs for farmers harvesting crops, as well as give researchers a more objective tool for measuring fruit flavor and maturity.
The electronic nose, called zNose, uses a technique called gas chromatography to separate and identify the chemical compounds that cause aroma in a blended fruit by vaporizing the compounds. Each compound vaporizes at a different time, which allows the user to detect which compounds are present in the juice.
“We use aroma compounds produced by fruits during the ripening process as markers to distinguish between fruits harvested at different maturity stages.” said Simona Vallone, a postdoctoral researcher in the department of plant sciences at UC Davis.
The researchers tested the zNose’s ability to detect the ripeness of melons in a laboratory setting as well as in the field. They found that the technique was able to differentiate between the different stages of maturity.
“The mixture of the aroma compounds are separated [by gas chromatography] so you can look at the composition of the aroma mixture,” Vallone said. “During the fruit ripening process, qualitative and quantitative changes in the aroma profile occur and we use that information to evaluate if the fruit is ripe or not.”
The biggest difficulty the researchers faced was not in using the device, but in the vast amount of data they collected. They soon found that the software provided with the zNose was not able to efficiently process all the information, so coauthor Nathan Lloyd had to program a new one.
“We’re hoping that [Nathan Lloyd’s software program] is going to help other labs who are interested in using the electronic nose,” said Florence Negre-Zakharov, assistant professor of plant sciences at UC Davis and lead author of the paper. “It avoids a lot of caveats of data analysis that you can fall into if you’re not careful with data interpretation.”
Negre-Zakharov said that the research is important for farmers trying to efficiently harvest their fruits.
“For a tomato, it’s easy to see when it ripens,” said Negre-Zakharov. “For something like a melon, it’s not so easy to see.”
Negre-Zakharov also thinks that the technique for using the zNose will also be helpful for researchers in fruit and vegetable breeding programs.
“The breeders often rely on visual characteristics, some taste their fruit, but they don’t really have an objective measure of the quality of their fruit,” Negre-Zakharov said. “This technology could be used as a more objective assessment of flavor quality.”
The research was funded in part by the US Department of Agriculture (USDA) in a program seeking to increase consumption of fruits and vegetables by improving their quality and safety. The project is a collaboration between UC Davis, the USDA and the University of Florida. Funding was also provided by the seed technology company Harris-Moran, which grew the melons the researchers used for the research.
The zNose was developed by Electronic Sensor Technology, Incorporated from Newbury Park, Calif. Ken Zeiger, a sales and marketing representative from Electronic Sensor Technology, Inc. says that UC Davis is one of several research institutions that are looking at the zNose for food science applications.
“I’ve been working with several people in that area,” Zeiger said. “We’ve been testing everything from melons to onions, and we’re waiting for the results on that. Basically, we have a very sensitive, portable gas chromatograph.”
Ultimately, Negre-Zakharov considers this technology “pretty cumbersome, but feasible compared to the machines we use on a regular basis for our research.”
She and the other researchers hope that the technology will continue to develop, becoming more portable and affordable so that fruit and vegetable quality will improve.
AMY STEWART can be reached at email@example.com.