Engineers at the U.S. Department of Agriculture have developed a way of taste-testing and checking the firmness of apples without biting into them -- by blasting them with lasers.
Don't worry. The fruit is fine, and delicious. "By measuring light scattering in the fruit, mathematical models can determine its firmness and sweetness," said Renfu Lu, an assistant professor at Michigan State University and an agricultural engineer at the USDA's Agricultural Research Service Sugar Beet and Bean Research Unit in East Lansing, Michigan. Lu is the lead researcher on a noninvasive apple-inspection project.
Lu's lab is outfitted with a prototype of a fruit-packing warehouse, with a conveyor belt for sorting freshly picked apples. He's added a machine vision station that uses light to probe the fruit without cutting it open.
Currently, USDA inspectors and fruit buyers sample individual apples by cutting them up by hand, biting into them and applying old-fashioned pressure gauges to determine their firmness. Apple juice is also extracted and analyzed for sweetness.
Combining existing hardware -- an imaging spectrograph and a digital camera -- and his own proprietary modeling software, Lu's system allows for inspection without mutilation.
Four lasers are fused into a single beam that hits each apple in rapid fire. Mathematical models and computer algorithms process the light-scattering data from the laser probes, and use the scattering characteristics to determine each apple's firmness, sugar content and acidity.
These proprietary programs relate sugar content to the amount of light absorbed by an apple, and firmness to the amount of light that bounces off it.
Each piece of fruit is analyzed and sorted in less than 0.1 second, and rolls down the conveyor belt into the appropriate bin -- to be sold or rejected. The system will allow fruit packers to sort apples based on customized criteria, according to Lu.
Each apple-producing state has different criteria and requirements for various grades and types of apples, and Lu is tweaking his modeling software to allow fruit packers to customize it based on those requirements. That could help the U.S. apple industry, which is threatened by competition from tree-fruit growers in other countries, particularly China -- which is attempting to export to the United States -- and New Zealand.
Although U.S. apple farmers harvest about 10 billion pounds of apples a year, raking in $2 billion annually, the threat of increased competition has the industry looking to lower costs by as much as 30 percent by 2010. The tree-fruit industry has established a consortium, anchored in Washington state (the largest producer of apples in the country), that has developed a technology road map to battle foreign competitors.
"Ideally, we'd be able to tell if a piece of fruit is good or bad in the snap of a finger," said Jim McFerson, manager of the Washington Tree Fruit Research Commission and one of the leaders of the consortium. And that's the USDA's goal, too.
The USDA's technology transfer office works with scientists to license technologies to companies that can manufacture or cooperatively develop them further.
Although Lu and his team have successfully tested their apple-sorting system over the past two picking seasons, they have a bit more work to do before it reaches the licensing stage. But agricultural engineers are excited about the results so far.
"Grocery stores and other fruit buyers have a long and growing checklist that have to do with the traceability, trackability and characteristics of the fruit," said McFerson. "I've traveled around the world a lot checking out the competition, and there are some clever farmers we have to face. Using this system we hope to speed production and better meet customer needs by sourcing fruit prescriptively."
