Vibratory Sifting Improves Baked Goods ThroughputYONKERS, 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
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.