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ESL fillers promote long shelf life

Jack Mans

January 29, 2014

9 Min Read
ESL fillers promote long shelf life

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Two double-membrane sanitary fillers, top, fill two cartons simultaneously with a fill accuracy of ? 1 g. Folded cartons are opened, and the bottoms are sealed on five mandrels, above, mounted on a rotating shaft.

Supervalu Fluid Dairy, Richmond, VA, produces 36 million gallons of fluid products per year in a 100,000-sq-ft facility. It runs a full line of milk products, as well as juices, water and drinks, and it is also a major copacker. In the nutritional arena, it produces fluid milk products containing Acidophilus and extra calcium, as well as lactose-free milk.

In the fall of '98, Supervalu installed an extended-shelf-life (ESL) operation that incorporates two Elopak ESL gabletop fillers and a Tetra Pak VTIS extended-shelf-life processing system that produces milk and other low-acid fluid products with a mind-boggling 60-day shelf life. "For all practical purposes, these are sterile products, and we could put a longer shelf life on the packages, but sixty days meets our needs," says vp and general manager Jan tenPas.

Gabletop fillers are rated at 150 cartons/min The two Elopak ESL dual-lane gabletop fillers are rated at 150 cartons/min each. A Model H90UC is dedicated to half-gallon cartons, while a Model S90UC runs up to four preset carton sizes. (Supervalu is running quarts, pints and half-pints at present.) The S90UC is equipped with dual filler bowls and fill lines so a different product can be run on each lane.

A feature of the S90 is automatic size changes that are initiated at the operator panel, which automatically sets the operating parameters so that a change takes less than two minutes.

A major factor in achieving long shelf life with these machines is their combination of a 2-percent hydrogen peroxide solution and ultraviolet light. This achieves a synergistic reaction that produces reactive radicals both inside and outside microbial cells that kill even spores. The two-lane machines run two cartons at a time, so they need to run only 37.5 cycles/min to produce 150 cartons/min (75 cartons on each lane).

Cartons are supplied by Elopak Canada (acquired by Elopak in January, '00) and carry the Pure-Pak® brand name, which is now owned by Elopak. Developed for ESL products, the cartons are a six-layer construction of polyethylene/board/tie layer/aluminum barrier/tie layer/PE and have an opening in one side of the top where the spout fitment will be placed.

To start the operation, the cartons are fed from magazines that hold 2,000 folded carton blanks each. The machine has four of these magazines, two for each dual-lane. The cartons are removed from the magazines and placed onto mandrels mounted on a rotating arm. There are five mandrels spaced equally around the shaft, and five steps in the process. This is an intermittent operation with each step taking place when the mandrels are stopped. At the first station, cartons are opened and placed on the mandrels. The next station is a "soft-heat" step, where the bottom is heated to about 375 deg F. This is followed by a second heating station, where the bottom is heated to 500 deg F. Next is the folding operation, where the bottom is folded flat. At the final stop, pressure is applied to the bottom, and chilled water circulates through the bottom chamber to cool and set the bottom of the carton. After the final stop, the open-top cartons are stripped from the mandrels and placed upright on the conveyors.

Ultrasonic welding
Most of the cartons run by Supervalu have fitments consisting of preassembled caps and spouts. These are applied to the cartons just after they are placed on the conveyor, before they enter the sterilization chamber. This enables the fitments, which are made from low-density PE, to be sterilized along with the cartons. The fitments travel from an overhead hopper down tracks to the application point, where an anvil inserts them into the openings in the carton tops, after which they are ultrasonically welded to the cartons. Supervalu uses a tamper-evident fitment from Portola Packaging that features an internal molded membrane that the customer must physically remove before product can be poured from the container.

Cartons are then conveyed to the sterilization chamber, where the 2-percent hydrogen peroxide solution is applied as a spray, after which they enter the UV-zone where they are exposed to ultraviolet light. Hot air is then blown into the cartons to remove hydrogen peroxide residues. This sterilization treatment consistently achieves a 4-log kill rate.

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Fitments consisting of preassembled caps, left, and spouts are ultrasonically welded to the cartons. Cartons in the Class 100 HEPA-filtered air sterilization chamber, right, are sterilized by a 2-percent hydrogen peroxide solution followed by UV light and hot air.

Next is top-down filling by two double-membrane fillers in series. Given the double-index design of the machine, each filler nozzle completely fills the carton in one shot. Two diaphragms are mounted on the ends of a filling piston located within a fill cylinder that provides a barrier between the product to be filled, the cylinder/piston area, and outside air. Controlled by servo motors, the reciprocating piston opens and closes upper and lower check valves located in the fill chamber. The piston moves back to open the top check valve and close the bottom check valve to admit product into the fill chamber. Next, the piston reciprocates to close the top check valve and open the bottom check valve to discharge product into the carton.

The two fillers, which are regulated by computer-controlled stepper motors, provide a fill-accuracy of ? 1 g. The units are equipped with built-in leak alarms in case a membrane ruptures.

A servo-motor drive system provides control over the fill volume, while allowing for different product characteristics. All drive components and pumps are located outside of the filling zone to ensure a cleaner operation. To assist with fill control, the unit also incorporates a servo motor to lift the cartons for filling. Cartons are top-sealed by an air-operated membrane sealer, while still inside the Class 100 HEPA filtered-air sterile chamber.

The fillers incorporate automatic CIP systems that clean all internal components, including vents and fill nozzles. The procedure is completely automatic and is monitored by the machine's microprocessors. The fillers are accessed through an operator panel that enables the operator to preprogram production functions and monitor the progress. A fault indicator monitors operations and triggers alarms if a parameter deviates from the set point.

Plastic and corrugated cases
Cartons leave the machine in two lanes, each passing by an ink-jet printer from Videojet Technologies that applies the use-by date to the top of the carton. The cartons are then packed into either reusable plastic dairy cases or corrugated cases. A unique conveyor system featuring parallel belts on each side of a bottom Teflon slide-bar transports the cartons to the case-packing operations, which are in a separate room. The belts grip the sides of the cartons and slide them along the rail. Both case-packing systems and all associated conveyors are supplied by Cannon Equipment Co.

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Parallel belts, above, transport cartons to the case-packing area. Half-gallon cartons are packed, right, into corrugated cases.

Both case packers are similar. Two lanes of cartons enter on opposite sides of the machine, and pushers assemble the required number of cartons on a steel plate in the center of the machine. Jaws descend and grip each carton by the top, after which the steel plate retracts, and the jaws lower the cartons into the case, which is located on the conveyor below. Half-gallons and quarts are packed one layer deep while smaller sizes are packed two to three layers deep. The corrugated system, in addition to a case packer, includes a case erector, a Marsh case printer from Videojet and a Loveshaw top taper.

The plastic cases are conveyed to a Cannon Equipment machine that assembles them into stacks five-cases high. In this process, jaws grip the case on the belt, and raise it so another case can move beneath it. The jaws then lower, grip that case, and lift both cases. This continues until the required number of cases is stacked. The stacks are conveyed into the cooler, and automatically palletized by Cannon equipment. Corrugated cases are conveyed into the cooler and are manually palletized.

More information is available:

Gabletop fillers: Elopak, Inc., 313/486-4600. Circle No. 240.

ESL processing system: Tetra Pak, 800/771-4109. Circle No. 241.

Gabletop cartons: Elopak Canada, Inc., 514/326-0350. Circle No. 242.

Gabletop fitments: Portola Packaging, 408/441-1958. Circle No. 243.

Case packers, stackers, case handling equipment, conveyors: Cannon Equipment, 612/322-6300. Circle No. 244.

Carton, case coders: Videojet Technologies, 800/654-4663. Circle No. 245.

Taper: Loveshaw Corp., 800/572-3434. Circle No. 246.



Sterilizing the product

As part of its ESL project, Supervalu Fluid Dairy installed a VTIS sterilization system from Tetra Pak that produces commercially sterile product. Milk products run through the system have already been pasteurized and homogenized in a traditional high-temperature/short-time (HTST) system and then cooled to 35 deg F for storage. Thus, this milk is getting a double-sterilization treatment.
Key to the VTIS system, which is rated at 3,000 gal/hr, is the Ring Nozzle Steam Injector, which forces high-pressure steam into the milk as it is pumped into the sterilization chamber. The high-pressure steam entering the injector instantaneously (for all practical purposes) heats the milk to 290 deg F. The injector is designed so that the incoming product cools all critical surfaces, so that no hot product can burn onto the unit. The hot milk flows through a sanitary pipe carefully sized to provide the correct 2-sec hold time required for sterility at this temperature, and then enters a vacuum chamber that instantly flash-cools it back to its 190-deg-F entering temperature. Cooling the milk back to its exact entering temperature is a critical step in the process, because it ensures that water from condensed steam is removed to return the milk to its proper solids content.

The flash tank has a full jacket through which is pumped chilled water. Product enters the tank tangentially to swirl around the inside wall of the tank to provide maximum contact with the cold heat-transfer surface. From the flash tank, finished product is pumped through a five-piston Tetra Pak homogenizer, and then back through the plate heat exchanger, where it is cooled to 35 deg F, and then into the selected holding tank. From this point on, no pumping occurs. Product is forced through pipes to the fillers by sterile air pressure on the tank.

About the Author(s)

Jack Mans

Plant Operations Editor

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