Bag-in-box, liquid product

Bag-in-box is a form of commercial packaging for food and nonfood, liquid and semiliquid products consisting of three main components: (a) a flexible, collapsible, fully sealed bag made from one or more plies of synthetic films; (b) a closure and a tubular spout through which contents are filled and dispensed; and (c) a rigid outer box or container, usually holding one, but sometimes more than one, bag (see Figure 1).

The bag-in-box concept appeared in the United States in the late 1950s. As early as 1957 (1), the package was introduced into the dairy industry in the form of a disposable, single-ply bag for bulk milk. By 1962, it had gained acceptance as a replacement for the returnable 5- gal (19-L) can used in institutional bulk-milk dispensers (2). One of the first nonfood items to be offered in a bag-inbox package was corrosive sulfuric acid used to activate dry-charge batteries.

During this early period, bags were manufactured from tubular stock film by labor-intensive methods. Initially, the physical properties of monolayer films (chiefly lowdensity polyethylene homopolymers) limited the applications, and filling equipment was slow and often imprecise. This situation changed significantly with the introduction in the 1960s of ethylene–vinyl acetate (EVA) copolymer films that provided added sealability and resistance to stress and flex cracking. By 1965, faster, dual-head fillers became available featuring semiautomatic capping capabilities. Developments in automated box forming and closing kept pace. Also, by 1965, proprietary bag-manufacturing equipment capable of making bags from singlewound sheeting sealed on all four sides had been developed (see Sealing, heat). In the mid-1970s, filling machines that automatically loaded filled bags into boxes came on-line. This was followed by totally automatic filling equipment that accepted a continuous feed of bags in strips (3), separated, filled, and capped them, then placed them in outer boxes. Meanwhile, barrier films (4) (see Barrier polymers) with improved handling and storage characteristics were being developed. Multilayer films of polyethylene coextruded with polyvinylidene chloride or PVDC to provide an oxygen barrier had become commercially available as Saranex (Dow Chemical Co.) in the early 1970s (see Vinylidene chloride copolymers). The application of this barrier film permitted packaging of oxygen-sensitive wines and highly acidic foods such as pineapple and tomato products. Beginning in 1979, multiple- ply laminates (5) (see Multilayer flexible packaging) combining foil (aluminum) or metallized polyester substrates were introduced and were also in wide use by 1982 (see Film, polyester). Such laminations are thermally or adhesively bonded and in some instances by hot melt extruding the adhesive layer (see Adhesives; Extrusion coating). The most commonly used barrier film in the United States today is a three-ply laminate consisting of 2-mil (51-mm) EVA/48-gauge (325-mm) metallized polyester/ 2-mil (51-mm) EVA. The barrier properties of metallized polyester are directly proportional to the optical density (OD) of the metal deposit. Multilayer coextruded films combining the barrier properties of ethylene–vinyl alcohol copolymer (EVOH), the strength of nylon, and sealability of linear low-density polyethylene are being successfully used for some bag-in-box applications. It is the sensitivity to moisture by EVOH that is limiting the films’ wider use (see Ethylene-vinyl alcohol; Nylon; Polyethylene, low density).

Fully automatic filling machines with as many as six heads (6) handling up to 40 two-liter (B2 qt) bags per minute are in operation. Films have been refined and specialized to meet tight packaging specifications for such procedures as hot fill at 2001F (93.31C) temperatures. Bags are also presterilized by irradiation for filling with a growing number of aseptically processed products for ambient storage without preservatives (see Aseptic packaging). Outer boxes have become not only stronger, but more attractive and appealing as consumer sales units.

MANUFACTURING PROCESS

In general, large producers of bag-in-box packaging design, develop, and manufacture packages to specifications meeting customer requirements. Containers vary in capacity from small, consumer and institutional sizes 1 qt to 5 gal (or 2–20 L), to large, process and transportation packs of 52–312 gal (or 200–1200 L).

A corrugated board box for enclosing a flexible, collapsible bag with a closed spout is described (1997). The box may be used to deliver soft drink syrups, milk, water contained in plastic pouch (7). The next invention (8) relates to post-mix dispensers of the type using peristaltic pump located below a bag-in-box package of concentrate (1997). Novel use of oxygen-scavenging compositions in packaging material that comprise a gas and vapor barrierforming layer or coating is introduced (1998) and disclosed (9). Applications could be for carton, bag-in-box, thermoformed trays or cups, over-wraps, shrink-wraps, closure liners, and cans. More recently (2000), an improved bagin- box packaging system for storing, transporting, and dispensing liquid products such as chemicals, soft drink syrup, fruit juices, and food condiments is patented (10). It allows for more complete drainage of the liquids. An improved bag-in-box packaging has a shell surrounding the carton (11) that can be separated to form a stand for the carton (2004) is presented. It facilitates dispensing of the beverage from the bag by allowing glasses and cups to be placed on the table under the tap, eliminating the need to use two hands to fill the glass. A multipurpose foursided sealed bag with a bag-in-box container system for viscous or powdery (particulate) products as vegetable oils, syrups, salad dressings, peanut butter, or soy sauce is described (12). The method of producing and using the bag are also included (2004). A bridge and adapter system for filling a bag-in-box packaging with liquids, solids, and semisolid products is claimed to provide a quick connection between the supply line and the dispensing part of the packaging (13). The bridge can be made of food grade stainless steel, plastic, or aluminum (2004). A collapsible flexible liner for a bag-in-box container system or flexible intermediate bulk container (FIBC) is detailed (14). The liner is designed to prevent unwanted collapsing of the liner during filling or draining (2005). It is also suitable for shipping various products including powder detergent. A new bag-in-box beverage container and dispenser is patented (15, 16), which incorporates (a) an outer shell preferably fabricated from corrugated paperboard material and (b) an inner liquid-containing bag fabricated from a suitable material (2006). A recessed handle is also provided. Finally, a bag-in-box for containing and dispensing liquids (e.g., beverages) is described (2006). The interior surface of the bottom of the box preferably slopes downwards toward the spout of the bag and/or has terraces, curves, corrugations, fan-like ridges, or beams to help feed the liquid toward the spout (17). The invention may also be used to advantage in other liquid dispensing applications.

Bag

The principal considerations in choosing a film laminate or coextruded for the bag construction are strength and flexibility, with low permeability and heat resistance added critical factors in an increasing number of applications. In the case of laminates, the bond between the layers of dissimilar materials must be maintained at a high level. Minimum requirements of over 1.1 lbf (500 gf) per inch (2.54 cm) (i.e., B193 N/m) is not uncommon. Films, laminates, and coextruded have to be resistant and must also, of course, be compatible with the product from which they are in direct contact with.

Once the appropriate film compositions have been determined for a specific application, the typical manufacturing procedure is as follows: Referring to Figure 2, two or three pairs of rolls of single-wound sheeting (A) are unwound on a machine where the webs advance intermittently, holes are punched (B), and spouts are sealed (C) into one of the duplex or triplex film sheets at predetermined points depending on finished size, and the bags are formed by sealing the two films together along the sides (D) and then at the ends (E). Therefore, the bags for liquids are of a ‘‘flat’’ nature, not gusseted. Because precise time and temperature must be maintained to generate the seal between the thin films, the uneven thickness resulting from wrinkles or folds must be avoided because the resulting ‘‘darts’’ will not be fully sealed. A removable closure is applied to the spout (F), and after passing by the draw rolls (G) the bags are either cut apart as the final operation or are perforated (H) for subsequent machine separation at time of filling.

Bag Size

The box size must be measured first, and then the exact sizing of the inner bag can be determined with respect to capacity or desired volume. The bag must occupy virtually all of the interior space of the box without unfilled corners or potentially damaging excess headspace resulting from an oversize box. The relationship between the effective surface area in contact with atmospheric air from the bagin- box and the volume capacity is important, as well as, the residual air bubble inside. Referring to Table 1, one can demonstrate by doing some rapid calculations that a better shelf life for larger bag-in-box capacity is anticipated for similar bag structure. Furthermore, variability of the bubble diameter or its out-of-control specification per type of volume capacity is a good visual tool for quality control (QC) procedures and automatic filling machine adjustment.

Spout and closure

The spout is the filling port of the bag. Together with the closure, they are designed to mate with filling heads and must be able to withstand the mechanical shock of the closure being removed and replaced during the filling operation without damage to the spout or closure. Spouts are generally molded of polyethylene with a thin flexible flange to which the bag film is sealed. The spout has handling rings for holding the spout during the filling sequence, and the closure likewise has rings for the same purpose. Figure 3 shows the filling head in the fill position.

The closure (A) has been removed and lifted up and away at an angle permitting the filling nozzle (B) to come downward and enter the spout (C) that is being held firmly in position. Because the design of bag-in-box packages provides for the contents always to be in contact with the spout, the spout-closure fit must be leakproof. When high oxygen-barrier property is essential, the spout and closure appear as the weakest area of the global bag + spout/closure structure, even though the valve is now of high barrier material. The oxygen ingress remains important unless the tightness or snugness of the spout/ closure is ensured. This is a mechanical fit with tight specifications. Their behavior with respect to temperature changes is not to be forgotten. Some commercial products are available, but the list is not exhaustive: Presstap, Malpass, Vitop, Flextap, Viniplus, to name a few. The reader is recommended to peruse references 19 and 20 for complementary information. Also of importance is some application of nitrogen gas (N2) or the liquid- form droplet to flush the headspace of residual air moments prior to final positioning of the valve or spout on the bagin- box neck.

Bag-in-Box (BIB) Capacity, Effective Surface Area, and Equivalence per Unit of Volume Table 1.

There are many designs for spouts and closures, depending on function. In packages destined for consumer use, the closure typically is a simple, one-piece, flexible valve that opens and closes as a lever is activated. Such a combination is shown in Figure 4. Two layers (A, B) of film are sealed to the spout sealing flange (C). Around the tubular wall (D) are one or more spout handling rings (E). The closure also has a handling ring (F) that facilitates its removal by the filler capping head. The closure is retained on the spout by a mating groove and head (G), and the liquid seal is achieved by a pluglike fit (H) between the two components. The one-piece closure is molded from a resilient material and becomes a dispensing valve by flexing the toggle (I), creating an opening to an orifice (J) and providing a path for the contents to exit.

For food-service use, such as in restaurants, the closure may have a dispensing tube attached or be compatible with a quick-connect-disconnect coupler leading to a pump. For other uses, just a cap may need to be removed prior to emptying of contents.

Box

In some dairy applications, the bags are transported in returnable plastic crates. Most typically a wide variety of materials in many forms may be used for the nonreturnable box of bag-in-box packages. For smaller sizes (1–6 gal, or 4–23 L), the outer box is usually made of corrugated board in a conventional cubic configuration. For larger sizes (30–54 gal, or 114–208 L), rigid plastic and metal containers, or even cylindrical drums, may be employed. The required strength must be designed into the box as dictated by the specific application.

Outer boxes may be manufactured with built-in handholds or locked-in-place handles, and some have special wax or plastic coatings for moisture protection. Most boxes are built with punch-out openings for easy access to the spout and closure.

FILLING

Filling bag-in-box packages may be a manual or semi- to fully automatic operation and is adaptable to a wide range of standard industrial processing procedures, including cold, ambient, high-temperature, and aseptic filling. The basic design of a typical filling machine incorporates a flow meter, filling head or heads, an uncap–draw vacuum–fill– recap sequence, and filled bag discharge (see Filling machinery, still liquid). Bags may be manually loaded into the film head or automatically fed in strip form into more sophisticated models. Advanced filling equipment can also be provided with such devices as a cooling tunnel where hot-filled bags are agitated and cooled by jets of chilled water; a specialized valve to allow passage of liquids with large particulates; steam sterilizing and sterile air chambers for aseptic filling; or other modifications as determined by application.

Five-gallon (or 19-L) bags can be filled at speeds that range from four units per minute (1200 gal/h or 76 L/min) to 20 units per minute (6000 gal/h or 380 L/min). Lowspeed filling is done on single-head, worker-attended fillers, whereas high-speed is done on filling on multihead equipment, comparing favorably with line speeds of conventional rigid-container operations. Complete systems including box formers, conveyors, automatic bag loading, and top sealers are available to support the automated large-capacity fillers.

SHIPPING AND STORAGE

Bag-in-box packaging offers significant weight- and spacesaving economies. Before filling, components are shipped flat; after filling, the basic cubic shape of most bag-in-box outer boxes occupies less space and tare weight than cylindrical metal containers of comparable volume. Limitations include (a) restrictions on palletizing and stacking height, where content weight may exceed outer box ratings, especially those constructed of corrugated board, (b) vulnerability of uncoated boxes to humidity and moisture, (c) possibility of flex cracking of the bag structure is plausible, mainly if we have metallized polyester from the effect of internal handling, (d) short as well as long transportation, and (e) age in distribution (national and international levels). Damages by surrounding materials, leaking units, and vibrations as well as shocks (frequency and intensity) must not be forgotten nor neglected.

DISPENSING

Dispensing may be accomplished in one of three basic ways: uncapping and discharging contents; attaching one or more packages to a pumping system; or activating a small volume, user-demand closure often referred to as a dispensing valve.

In single-bag packages, the spout closure is contained within the outer box for protection and withdrawn prior to use through a perforated keyhold opening in the box. During dispensing, the bag collapses from atmospheric pressure as contents are expelled without the need for air to be admitted. When completely empty, bag-in-box package components, except those outer boxes or containers specifically designed for reuse, are fully disposable. Corrugated board and polyethylene are easily incinerated, and metallized and foil inner bags compact readily to go to landfills.

APPLICATIONS

With advancements constantly being made in bag film capabilities, along with filling and dispensing techniques, practically every commercial product is either being considered for or is now available in bag-in-box packages. Major users include the dairy industry with fluid milk, cream, and soft ice cream mixes. Also of interest are fruit juices and concentrates, edible oil, sauce, and jams, from 5- to 1000-L (1.3- to 260-gal ) capacity. Clients are increasing for restaurants, institutions, and fast food markets (21, 22). The wine industry since the 1970s in Australia and South Africa have expended their success of the bagin- box material and packing technologies worldwide (23); and, finally, most important transportation abuse and shelf-life extension are under close scrutiny (19, 24). From 3–4L (3.2 qt to 1 gal), soon some 2-L (2.1 qt) containers will be available for retail; also, institutional size (10–20 L, or 2.6l–5.2 gal) and long preservation storage size (1200 L, or 312 gal), respectively, will be available. Purees and ketchup have modest applications too. Some soft drinks are also prepared from fountain syrup pumped from a bag-in-box arrangement (18), which eliminates the need for recycling and accounting for metal transfer containers.