[NAFEX] Laser Tastes Fruit Without Taking a Bite (ARS-USDA)

Brungardt, Sam Sam.Brungardt at state.mn.us
Mon May 16 09:48:58 EDT 2005

Laser Tastes Fruit Without Taking a Bite 
Created 05/06/2005 - 08:58 
Each fall for the past 3 years, Renfu Lu has gone into Michigan
orchards, picked fruit off the trees, and tasted hundreds of apples and
peaches-without taking a single bite.  How did he do it?  With a
futuristic technology called imaging spectroscopy, or multispectral
imaging, that uses laser beams to detect the sweetness and firmness of
Michigan has a $100 million farmgate apple industry, the third largest
in the country.  It ranks first in production of tart cherries and fifth
in peach production.  Nationally, the tree fruit industry is worth about
$2 billion a year.
Lu, an agricultural engineer with USDA's Agricultural Research Service,
partners with Michigan State University's (MSU) Agricultural Engineering
Department to address priority needs of the fruit industry in the state
and the nation. 
"Nondestructive technologies for grading and sorting fruit by internal
quality-such as firmness and sugar and acid content-are a top priority,"
says Lu.  "Such technologies would ensure a consistent premium quality
product, increase consumer satisfaction, and enhance the U.S. fruit
industry's competitiveness and profitability."
Currently, thick steel probes are used to test fruit samples by punching
a hole in the fruit, making it unmarketable.  "We have to presume that
by destructively testing a few fruits that way, we'll learn about the
condition of the thousands of other fruits in a particular batch," says
Lu. "But our system tests every single fruit, and it can all be sold."
Lu and colleagues in the ARS Sugarbeet and Bean Research Unit, located
on MSU's East Lansing campus, sample apples with a prototype optical
detector.  The detector fuses four laser beams, each at a different
waveband of light, into one.  Light photons momentarily scatter all the
way to a fruit's core.
An imaging spectrograph, a digital camera, and a computer analyze the
amount of laser light absorbed by the apples, which indicates sweetness.
The amount of light bounced back after interacting with fruit tissue
reflects fruit firmness.  Sweet and sour tastes are a factor for apples,
cherries, peaches, and other fruit-but firmness analysis is often more
important to consumers and technologically more challenging.
Multispectral imaging combines spectroscopy-which analyzes light
wavelengths-with machine vision, which enables a computer to "see."
It's emerged in recent years as a powerful sensing technique for quality
evaluation and safety inspection of food and agricultural products as
well as for precision farming. 
It is also used in a wide range of scientific, military, and industrial
fields, including space exploration and remote sensing of Earth from
space, medical diagnostics, biological research, and military target
detection.  This is the first time it's been tried for remote "tasting"
of fruit for sweetness and firmness.
When commercialized, Lu's optical sensor would be used by the fruit
industry to sort fruit just after it's been picked.   He's built a
larger version fitted into a mini-packing line for lab use.  It's a
prototype for a machine that would be used on fruit-processing lines to
make a second quality check after some time had passed and the fruit had
been handled.
Lu and his team developed and tested the computer model and accompanying
software as well as the prototypes. 
"Our sensor can sort peaches and apples into two or three firmness
grades.  The technology's comparable-or superior-to the accuracy of
other nondestructive mechanical techniques, as reported in the
scientific literature.  But it's relatively easy to implement for rapid
online sorting and has potential for measuring multiple quality
attributes simultaneously," Lu says.
"The sensors work better on peaches than on apples in terms of firmness
measurements," says Lu.  "Apples are challenging because they are more
variable in firmness and have a narrower firmness range from apple to
apple.  But our sugar-content predictions for apples compared well with
actual sugar-content measurements," he says.
His goal is to sign a cooperative research and development agreement
with one or more companies to commercialize the prototypes for use in
fruit quality labs, packinghouses, and orchards.  "We will continue to
improve and refine the system so it can meet online sorting needs," Lu
says.  He is currently working to speed up scanning speed to match that
of commercial apple conveyors: 10 fruits per second.  The ability of a
spectrograph to capture images from four light bands at once makes this
speed possible.
You Can't Judge a Fruit by Its Appearance
Lu is researching other factors that might affect firmness predictions,
such as variety, orchard, geographic location, and season.
His equipment would be merged with existing industry sensors that
nondestructively assess superficial visual traits, including size,
color, and bruising.  "Skin-deep appearance gives us the first
impression about fruit quality, but it's internal qualities-mainly
flavor and texture-that ultimately deliver consumer satisfaction," Lu
says.  "Together those two qualities make up taste.  It's vital that
each fruit variety consistently taste the way it should to develop and
retain loyal customers," Lu says.  "Poor, inconsistent fruit quality has
turned some consumers away to other food products, causing the industry
to lose market share and competitiveness."
Eventually Lu's system will also sense acidity-another aspect of
flavor-and it will measure those qualities simultaneously.  His laser
system would sort out the best-tasting fruit during harvesting and again
during packaging so that, for example, soft or sour red apples would be
redirected for use in the packing plant's applesauce and juice
Lasers are giving Lu the high-quality light beam needed for accurate
firmness prediction.  "This should bring us closer to the day when you
can shop for fresh produce in a grocery store and be sure you'll get
just the amount of crunchiness and sweetness or sourness you expect,
justifying your first impression based on the fruit's attractive
appearance," says Lu.
-By Don Comis, Agricultural Research Service Information Staff.
>From ARS [1]

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