PACKAGING HOUSE UNIT OPERATIONS

Presorting

Cleaning and Washing Sizing/Grading Waxing

Packaging Materials

Modified Atmosphere/Controlled Atmosphere Packaging Active/Intelligent Packaging

Labeling Laser Etching

Storage and Transportation Cold Chain Management

Packaging Requirements For Fresh-Cut Produce Packaging Requirements For Frozen Fruits Packaging Requirements For Dried Fruits

Packaging Requirements For Thermally Processed Fruit Products

Canned/Retort Pouched/Bottled/Aseptically Packed Packaging of Juices

Packaging Requirements For Fruits and Fruit Products Processed by Newer Technologies

Characteristics of Packaging Materials for Nonthermally Processed Foods

Antimicrobial Edible Films and Coatings for Nonthermally Processed Foods

Packaging for High Pressure Processing Packaging for Irradiated Foods

Packaging for Pulsed Electric Field Processed Food Products

Future Research Needs References

Abstract:This chapter provides an overview of the developments in packaging of fresh and processed fruits right from packaging house unit operations, that is, precooling, presorting, cleaning/washing,

sizing/grading, waxing, type of packaging materials, modified at- mosphere/controlled atmosphere packaging, active/intelligent pack- aging, labeling, storage and transportation, cold chain management, and packaging requirements for fresh cut, frozen fruits, dried, ther- mally and nonthermally processed fruits and fruit products. Pack- aging requirements for fruits and fruit products processed by newer technologies such as high pressure processing (HPP), pulsed electric field, irradiation, and future research needs are also discussed.

INTRODUCTION

Specialized packaging is critical for shelf life, sensory, mi- crobiological, and nutritional qualities of fresh and pro- cessed fruits. Food packaging has many dimensions includ- ing, preservation, convenience, safety, marketing, and pro- motion of products (Stilwell et al. 1991). It reduces food waste and spoilage during storage and marketing. This chap- ter provides an overview of developments in packaging of fresh and processed fruits.

PACKAGING HOUSE UNIT OPERATIONS

The typical packaging house unit operations are as follows:

Precooling

Precooling is the first step in preserving quality of harvested fruits. The field heat of a freshly harvested crop is usually high, and it should be removed as quickly as possible before shipping, processing, or storage. Precooling is generally a separate operation requiring special equipment and/or rooms.

Rapid precooling to the product’s lowest safe temperature is most critical for fruits with inherently high respiration rates.

Handbook of Fruits and Fruit Processing, Second Edition. Edited by Nirmal K. Sinha, Jiwan S. Sidhu, J´ozsef Barta, James S. B. Wu and M. Pilar Cano.

C 2012 John Wiley & Sons, Ltd. Published 2012 by John Wiley & Sons, Ltd.

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The following methods described by Wilson et al. (1995) are the most common:

r Room cooling: Produce is placed in an insulated room equipped with refrigeration units. This method can be used with most commodities, but it is slow compared with other options. Containers should be stacked in a way that cold air can move around and through them.

Used refrigerated truck bodies make excellent small cooling rooms for field situations (Hardenburg et al.

1986).

r Forced-air cooling: Fans are used in conjunction with a cooling room to pull cool air through packages of produce. Although the cooling rate depends on the air temperature and the rate of air flow, this method is usu- ally 75–90% faster than room cooling. Fans should be equipped with a thermostat that automatically shuts off as soon as the desired product temperature is reached (Patchen 1969).

r Hydrocooling: Dipping produce into cold water, or cold water running over produce, is an efficient way to re- move heat and can serve as a means of cleaning at the same time. In addition, hydrocooling reduces water loss and wilting. Use of a disinfectant in the water is recom- mended to reduce microbial pathogens. Hydrocooling may not be appropriate for berries, grapes, cherries, or other soft fruits that do not tolerate wetting. To avoid over-cooling and dehydration of produce, it is recom- mended not to operate forced-air fans after the produce has been cooled to its optimum temperature (Wilson et al. 1995).

Water removes heat about five times faster than air, but it is less energy efficient. Well water, mechanical refrigeration, or a thermal storage immersion hydrocooler system can be used economically to suit various volume requirements. Used stainless-steel bulk farm milk coolers may be an option. If hydrocooling water is recirculated, it should be chlorinated to minimize microbial problems (Talbot et al. 1991).

r Top or liquid icing: Icing is particularly effective on dense products or palletized packages that are difficult to cool with forced air. In top icing, crushed ice is added to the container over the top of the produce by hand or machine. For liquid icing, slurry of water and ice are injected into produce packages through vents without removing the packages from pallets or opening their tops (Howell 1993).

r Vacuum cooling: Produce is enclosed in a chamber in which a vacuum is created. As the vacuum increases, water within the plant evaporates and removes heat from the tissues. To reduce water loss, water is sometimes sprayed on the produce prior to placing it in the cham- ber. This process is called hydrovac cooling. The pri- mary drawback to this method is the cost of the vacuum chamber system (Sasseville 1988).

Presorting

The presorting process eliminates cull, overripe, misshapen, and otherwise defective fruits and separates product by color, maturity, and degree of ripeness (e.g., tomato and muskmel- ons). Electronic color sorters are used in some tomato sorting operations.

Cleaning and Washing

Cleaning and washing is an important process for removing surface dirt and organisms and contaminants (Fig. 17.1). The wash water must have permitted level of chlorine and other substances. The recirculating and stagnant water must not be used for the washing of organic produce (use only running water).

Sanitation and water disinfection: Preventive food safety programs, sanitation of equipment and food contact sur- faces, and water disinfection should be integrated into ev- ery facet of postharvest handling of fruits.Escherichia coli, Salmonella,Shigella,Listeria, Cryptosporidium,Hepatitis, and Cyclospora are the major disease-causing organisms that have been associated with fresh fruits and vegetables.

Water used in washing of organic produce should not contain any prohibited substances in dissolved form. Even inciden- tal contamination from a prohibited material would keep the product from being certified as organic. Organic growers, shippers, and processors may use chlorine (or other natural food grade disinfectants) within specified limits. As a gen- eral practice, field soil on product, bins, and pallets should be kept to a minimum by prewashing, before loading the pro- duce in it. Prewashing also removes plant exudates released from harvest cuts or wounds, which can react rapidly with oxidizers such as hypochlorite and ozone, and so requires higher rates of the chemical to maintain the target 4 to 10 ppm downstream activity. For both organic and conventional operations, liquid sodium hypochlorite is the most common form used (Boyette et al. 1993).

For optimum anti-microbial activity with a minimal con- centration of applied hypochlorite, the pH of the water must be adjusted between 6.5 and 7.5. At this pH range, most of the chlorine is in the form of hypochlorous acid (HOCl), which delivers the highest rate of microbial kill and minimizes the release of irritating and potentially hazardous chlorine gas (Cl2). Chlorine gas will exceed safe levels if the water is too acidic. Products used for pH adjustment must also be from a natural source such as citric acid, sodium bicarbonate, or vinegar.

Drying: After washing, drying is necessary without caus- ing bruising or damage to outer surfaces (Fig. 17.2). Soft roller material is used to avoid bruising.

Sizing/Grading

After drying, grading is done to produce a uniform prod- uct as per the market requirements. Grading can be done manually as well as mechanically. The grading system must

Figure 17.1.Steam heat treatment. (Source: International Course on Fruits and Vegetables, Volcani, Israel.)

be sterilized before use. Color grading using sortex systems and size grading are the common procedures (Hardin 1995).

After sorting for defects and color differences, produce are segregated into several size categories. Sizing is done manu- ally for many of the produce, including the legumes, soft and hard rind squashes, cucumber, eggplant, chili peppers, okra,

pumpkin, muskmelons, and watermelon. These may be sized by volumetric weights, or diverging roll sizers; sweet peppers are sized commonly by diverging bar sizers; and tomatoes are sized by diameter with belt sizers or by weight. Only after drying and grading, the postharvest treatment such as waxing (food grade only) and packaging can be done.

Figure 17.2.Drying of vegetables. (Source: International Course on Fruits and Vegetables, Volcani, Israel.)

Waxing

Waxing is done to remove surface organisms and save mois- ture loss during the storage and transportation. Food grade waxes are commonly applied to cucumber, eggplant, sweet peppers, cantaloupe, and tomato and occasionally to some summer squashes. The purpose is to replace some of the nat- ural waxes removed in the washing and cleaning operations, to reduce water loss, and to improve appearance. Waxing may be done before or after sizing, and fungicides may be added to the wax. Application of wax and postharvest fungi- cides must be indicated on each shipping container (Hulbert and Bhowmik 1987). Waxing and fungicides are used only in packing house handling of fruit and vegetables. European cucumbers are frequently shrink-wrapped rather than waxed.

Various waxes like carnauba (palm), sisal (sisal waste), ba- nana (shrub), sugarcane (cane), rice bran (bran oil);petroleum waxes: crude petroleum-(A), paraffin (B), microcrystalline waxes; insect waxes: shellac and bee waxes; and synthetic waxes: carboa waxes, polythene, santo waxes are used in the form of emulsions, which are applied either by dipping the fruit in emulsion or spraying or dripping foam or melted wax over the fruits.

Treatments to minimize water/transpiration loss during transportation: Transpiration, or evaporation of water from the plant tissues, is one of the major causes of deterioration in fresh horticultural crops after harvest. Water loss through transpiration not only results in direct quantitative losses (loss of saleable weight) but also causes losses in appearance (wilting, shrivelling), textural quality (softening, flaccidity, limpness, loss of crispness and juiciness), and nutritional quality. Transpiration can be controlled either through the direct application of postharvest treatments to the produce (surface coatings and other moisture barriers) or through ma- nipulation of the environment (maintenance of high relative humidity). Treatments that can be applied to minimize water loss in fruits and vegetables include the following:

r Curing of certain root vegetables, such as garlic, onion, potato, and sweet potato.

r Waxing and the use of other surface coatings on com- modities, such as apple, citrus fruits, nectarine, peach, plum, pomegranate, and tomato.

r Packaging in polymeric films that act as moisture barri- r ers.Careful handling to avoid physical injuries, which in-

crease water loss from produce.

r Spraying of water on to those commodities that tolerate moistening with water, such as leafy vegetables.

Packaging Materials

Bags, crates, hampers, baskets, cartons, bulk bins, and pal- letized containers are convenient containers for handling, transporting, and marketing fresh produce. Although the in- dustry generally agrees that container standardization is one way to reduce cost, the trend in recent years has moved toward

a wider range of package sizes to accommodate the diverse needs of wholesalers, consumers, food service buyers, and processing operations. Packing and packaging materials con- tribute a significant cost to the produce industry; therefore, it is important that packers, shippers, buyers, and consumers have a clear understanding of the wide range of packag- ing options available (Peleg 1985). A package performs the functions of containment, protection, and identification of the produce packed. The container must enclose the produce in convenient units for handling and distribution. The produce should fit well inside the container, with little wasted space.

The package must protect the produce from mechanical dam- age and poor environmental conditions during handling and distribution. To a consumer, a torn, dented, or collapsed pack- age usually indicate an unsafe product.

Air-freighted produce may require special packing, pack- age sizes, and insulation. Marketers who export fresh pro- duce should consult with freight companies about any spe- cial packaging requirements. In addition, the United States Department of Agriculture (USDA) and various state export agencies may be able to provide specific packaging informa- tion (Ashby et al. 1987).

The package must identify and provide useful informa- tion such as the produce name, brand, size, grade, variety, net weight, count, grower, shipper, and country of origin along with nutritional information, recipes, and other useful information directed specifically at the consumer. Universal product codes (UPC or bar codes) may be included as a part of the labeling. Although no price information is included, UPCs are used more and more by packers, shippers, buyers, and retailers as a fast and convenient method of inventory control and cost accounting. Efficient use of UPCs requires coordination with everyone who handles the package (Erdei 1993). There are different types of packaging materials used for food packing such as the following:

r Wooden pallets: These form the base on which most fresh produce is delivered to the consumer. Pallets (Fig. 17.3) were first used during World War II as an

Figure 17.3. Well-packed produce over a pallet.

efficient way to move goods. The produce industry uses approximately 190 of the 700 million pallets produced per year in the United States. About 40% of these are single-use pallets. Because many are of a nonstandard size, the pallets are built as inexpensively as possible and discarded after a single use. Efforts have been slowly under way for standardization of pallets from many years. Over the years, the 40-wide×48-long pallet has evolved as the unofficial standard size. Standardiza- tion encourages reuse, which has many benefits. Besides reducing cost by reusing, standard size pallets make ef- ficient use of truck and van space and can accommodate heavier loads and more stress than lighter single-use pallets. In addition, the use of a single pallet size could substantially reduce pallet inventory and warehousing costs along with pallet repair and disposal costs. The adoption of a pallet standard throughout the produce in- dustry would also aid efforts toward standardization of produce containers (Anon 1993).

Depending on the size of produce package, a single pallet may carry from 20 to over 100 individual packages. Because these packages are often loosely stacked to allow for air circulation, or are bulging and difficult to stack evenly, they must be secured (unitized) to prevent shifting during handling and transit. Although widely used, plastic straps and tapes may not have completely satisfactory results. Plastic or paper corner tabs should always be used to prevent the straps from crushing the corners of packages (Paine 1987).

Plastic stretch film is also widely used to secure produce packages. A good film must stretch, retain its elasticity, and cling to the packages. Plastic film may conform easily to various size loads. It helps protect the packages from loss of moisture, makes the pallet more secure against pilferage, and can be applied using partial automation. However, plastic film severely restricts proper ventilation. A common alternative to stretch film is plastic netting, which is much better for stabi- lizing some pallet loads, such as those that require forced-air cooling. Used stretch film and plastic netting may be difficult to properly handle and recycle (Aharoni et al. 1996).

r Pallet bins: Substantial wooden pallet bins of milled lumber or plywood are primarily used to move produce from the field or orchard to the packing house. Depend- ing on the application, capacities may range from 12 to more than 50 bushels. Although the height may vary, the length and width is generally the same as a standard pallet (48×40). More efficient double-wide pallet bins (48×80) are becoming more common in some produce operations (Stokes 1974).

Most pallet bins are locally made; therefore, it is very important that they must be consistent in materials, construc- tion, and especially the size. Pallet bin can add up to bigger problems when several hundred of these are stacked together for cooling, ventilation, or storage. It is also important that

stress points be adequately reinforced. The average life of a hardwood pallet bin that is stored outside is approximately 5 years. When properly protected from the weather, pallets bins may have a useful life of 10 years or more (Hardenberg et al. 1986).

Uniform voluntary standards for wood pallets and other wood containers are administered by the National Wooden Pallet and Container Association, Washington, DC, and the American Society of Agricultural Engineers, St. Joseph, MI, publishes standards for agricultural pallet bins (ASAE S337.1) (Hardenberg et al. 1986).

r Wire-bound and wooden crates: These crates are used extensively for snap beans, sweet corn, and several other commodities that require hydrocooling. Wire-bound crates are sturdy, rigid, and have very high stacking strength that is essentially unaffected by water. Wire- bound crates come in many different sizes with open space to facilitate cooling and ventilation. Although few are reused, wire-bound crates may be dissembled after use and shipped back to the packer (flat). In some areas, used containers may pose a significant disposal prob- lem. Wire-bound crates are not generally acceptable for consumer packaging because of the difficulty in affix- ing suitable labels (Anon 1982). Wire-reinforced wood veneer baskets and hampers of different sizes were once used for a wide variety of crops from strawberries to sweet potatoes. They are durable and may be nested for efficient transport when empty. However, cost, disposal problems, and difficulty in efficient palletization have severely limited their use to mostly local grower markets where they may be reused many times (Anon 1982).

Wooden crates have been almost totally replaced by other types of containers due to a greater concern for tare weight, and advances in material handling have reduced their use to a few specialty items, such as, expensive tropical fruit. The 15-, 20-, and 25-pound wooden lugs still used for bunch grapes and some specialty crops are being gradually replaced with less costly alternatives (Anon 1982).

r Corrugated fiber board: Most of the corrugated fiber- board (Fig. 17.4) is made from three or more layers of paperboard containing wood and synthetic fibers so as to give it the additional strength, sizing (starch), and other materials to give it wet strength and printability. Most of the fiberboard contains some recycled fibers. Tests have shown that cartons of fully recycled pulp have about 75% of the stacking strength of virgin fiber containers.

The use of recycled fibers will inevitably lead to the use of thicker walled containers (Anon 1992).

Corrugated bulk bins used for fresh produce which require high stacking strength, may have double- or even triple-wall construction. The inner layer may be given a special coating to resist moisture. Corrugated fiberboard manufacturers print box certificates on the bottom of containers to certify certain strength characteristics and limitations. There are two types