Don't judge an apple by its cover - shiny red skin and a plump appearance might just be masking a squishy texture or sour taste.
Renfu Lu, an adjunct associate professor at MSU and agricultural engineer with the U.S. Department of Agriculture's Agricultural Research Service, is leading a study to change the way apple quality is evaluated. A team of six scientists have spent three years researching and developing a prototype machine that will allow apple producers and packers to determine fruit sweetness and firmness - all without biting into a single apple.
"When you go to the grocery store, all apples look the same, but they don't always taste the same," Lu said.
Most apple-packing facilities sort fruit based on visual traits, including size, color and bruising. Of the thousands of apples running through an assembly line, only a few are hand-picked for pressure testing to determine texture. These destructive pressure tests require the apple to be peeled, making it unfit for consumption.
"We're trying to find the correlation between the destructive methods and the non-destructive methods," said Ben Bailey, a scientist at the Fruit Postharvest Technology Laboratory in Farrall Hall.
But with new technology, every apple can be tested to guarantee ultimate tastiness. And that's good news for Michigan's $100 million apple industry, the third largest in the country.
Lu has developed a prototype machine that uses a multispectral imaging system to zap apples with four lasers as they file down a conveyor belt. Computers equipped with artificial neural networks are trained to recognize the absorption and reflection patterns created by the near-infrared rays. Depending on how much light is reflected or absorbed, scientists can determine each apple's sugar content and firmness.
Researchers hope to expand the machine's capabilities to detect acidity and structural defects. Eventually, the same laser technology used on apples will be applied to peaches, pears and other fruits.
"One beauty of using light is that it allows us to measure multiple quality traits at one time," Lu said.
The prototype machine can analyze one apple every two seconds. Lu said machines capable of handling 10 apples per second on multiple conveyors might be in packing plants within three years.
Lu said though new multispectral machines might cost big bucks for apple packers, the long-range improvements in quality output would be worth it.
"I have the ability to walk out and get a hard, crunchy apple any time I want," said Bruce Heeren, vice president of Heeren Brothers Inc., a Grand Rapids-based company that produces, packages and markets apples. "The trick is getting them to the consumers hard and crunchy."
Heeren said laser-testing at the packaging level would help prevent poor produce from making it to supermarkets.
"There's no question we would be able to have a better product," he said. "If we could eliminate the softies, that would be great."
Those "softies" could be directed into the plant's applesauce and juice facilities, Heeren added.
Lu said apple analysis would allow shippers like Heeren Brothers Inc. to deliver products that better meet variety standards - whether sweet Red Delicious or tart Granny Smith.
"Flavor and texture ultimately determine customer satisfaction," he said.
