Vibratory Sifting Improves Baked Goods Throughput

Technical Article Series
Vibratory Sifting Improves Baked
Goods Throughput
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Vibratory Sifting Improves Baked Goods
Throughput
YONKERS, NY Installing a new circular vibratory screener enabled Greyston
Bakery to meet rising demand for small brownie chunks used in single-service
cups of ice cream.
Greyston is a brownie baker for producers of premium ice cream. Its brownies
are used in several recipes in relatively large, 1 in. x 1 in. (25.4 mm x 25.4
mm) squares that look and taste like real brownies.
When one of its customers began making smaller, single-serve cups, it
switched to filling heads with smaller orifices, which required a reduction in
brownie size to 0.25 in. x 0.25 in. (6.35 mm x 6.35 mm) for the new product.
Greyston's production strategy was to bake its brownies just as it always had,
then cut them into smaller pieces and sift the output at the end of the line to
remove any oversized chunks that might block the filling head. Greyston
accomplished this goal cost-effectively by replacing a screener built in-house
with a commercial circular vibratory screener at the end of its production line.
Baking brownies on an industrial scale
Greyston Bakery has an unusual history for a commercial bakery. It was
founded in 1982 as the for-profit arm of the Greyston Foundation, which uses
the bakery's earnings to fund community development initiatives. The
company's Website proudly proclaims: "We don't hire people to bake
brownies. We bake brownies to hire people."
Greyston Bakery has been baking brownies for blending with ice cream since
1988. Since then, it has grown into one of the industry's top suppliers,
producing more than 20,000 lb (18,144 kg) of ice cream mix-ins daily.
Manufacturing brownies commercially involves the same steps as making them
at home, but on a larger scale and at much faster speeds, said Lisa Saltzman,
Director of Operations. "Our 23,000 sq ft (2,135 sq m) facility is in an urban
location where storage is at a premium, so we keep only minimal inventories.
Every step of the production process needs to keep up the pace. We ship
them as fast as we cook them," added plant engineer Vincent Lombardo.
After mixing, baking, cooling and sizing brownies, pieces intended for
single-serve cups move to the vibratory screener, where chunks larger than
0.25 in. x 0.25 in. (6.4 mm x 6.4 mm) are removed. Greyston's first vibratory
screener was a tray-in-a-tray box screener driven by two rotary air vibrators
built in-house by Lombardo. It was unable to keep up with the flow of
production.
"It was not robust enough to handle 20 hours per day of production," Lombardo
said. "We considered going with either a rotary or a vibratory screener. We
eventually decided on the circular vibratory screener because of its low
maintenance requirements, screen longevity, capacity and price."
Separating bite-sized brownies
Particles larger than 0.25 x 0.25 in. (6.35
mm x 6.35 mm) square discharge through
upper spout, on-size particles through
lower spout.
Lombardo specified a 24 in. (610 mm) diameter Vibroscreen® circular vibratory
screener from Kason Corporation. The gravity-fed, food-grade unit is driven by
a single low-horsepower (kilowatt), 230-volt 3-phase, imbalanced-weight,
gyratory motor mounted in an enclosed cage directly beneath the screening
chamber. Due to height limitations, the Vibroscreen screener is limited to one
screen deck, yet it meets throughput requirements while offering reserve
capacity.
When the brownies enter the screener, multi-plane inertial vibration of the
nylon screen causes the 0.25 in. (6.4 mm) square pieces to fall through its
apertures. Larger chunks are transported across the screen surface along
controlled pathways into the discharge spout, which ejects them onto a
conveyor that takes them for regrinding.
"We opted for only one screen, since we're more concerned with removing
oversized pieces than removing any fines that were not removed by the
tumbler," Lombardo said. "If we needed to, we could drop the 0.25 in. (6.4
mm) square pieces onto a 10 mesh screen and remove any fines that fell
through." Instead, the 0.25 in. (6.4 mm) square pieces drop onto a pan and
exit past a vertical metal detector. If it senses any slivers of metal in the
brownies, the batch is discharged automatically through a cylinder-activated
chute and discarded.
While blinding is not an issue, the screener requires daily cleaning. "We run
production for 20 hours, then shut down for four hours to clean the whole
system," Lombardo noted. "The sifter takes about 15 minutes to clean. We
remove the screen with a single disconnect clamp. The motor and connector
box are watertight, so we can rinse down the interior and exterior with a hose,
apply a foaming cleanser, and then rinse it down again. After we sanitize, we
take swabs to make sure there are no coliform bacteria or residual soap," he
explained.
The new circular vibratory screener has proven reliable and enables Greyston
to sift the brownies as fast as it can make them. "It has no problem keeping
up, and we have room to ramp up volume without going to an additional deck
or a larger unit," said Lombardo.
On-size brownie particles discharging from
lower spout fall onto a pan before passing
through a metal detector.
At left are screened brownie pieces <=0.25 x
0.25 in. (<=6.35 mm x 6.35 mm) that go into
single-service cups of ice cream. At right,
material fed to the screener includes
oversize chunks.