Bursting into a leadership slot in the United States’ growing $80-billion fresh produce industry is the often-overlooked $12.5-billion segment of pre-washed, pre-cut, and actively packaged fruits, vegetables, and ready-to-eat salads.
“Fresh-cut” produce delivers convenience plus a relatively easy way to increase consumer consumption of allegedly “healthy” fruits and vegetables. It has established a new paradigm in the consumption of fruits and vegetables, so much so that most members of new generations may never see or know a head of lettuce or broccoli or cauliflower.
Fresh-cut produce sales have grown from near zero as recently as 1985 to $5 billion at retail and $7.5 billion in foodservice in 2004. Whether at or away from home, salads from fresh produce are rapidly moving toward the center-of-the-plate. With 37% growth in 2003, salads led the National Restaurant Association’s list of menu items ordered most often by diners.
But what is being ordered is not your ordinary garden variety salad. Increasingly, foodservice chefs, cooks, and managers are devising more-elaborate, sophisticated offerings across all levels of retail establishments. In the home, after potatoes, vegetable salads are the most likely side dishes.
With only about $200 million in sales last year, projected sales for fresh-cut fruit will range up to $2 billion by 2008. The relatively high water and sugar content of fresh-cut fruits present chilled shelf life challenges. Liquid loss from fresh-cut fruit (including tomatoes) is generally high and must be controlled to enable convenient use. Experiences from vegetables, however, can be and are being applied to fresh-cut fruits. Except for melons with their high pH, safety and extended refrigerated shelf life are not as great an issue as is the answer to the question, “Does the produce present the target consumer a good experience?”
In the era before minimal processing and packaging, shrink—product loss due to spoilage during distribution—probably ran about 30%. Lettuce, tomatoes, and apples account for 70% of retail sales. Salad mixes today are often blends of green vegetables packaged in kits that combine tomatoes and other precut vegetables; packages of croutons, nuts or dried fruits, and salad dressings; and even cheese and/or meats, prepackaged to protect against the moisture of the produce and prolong the chilled shelf life.
Modified-atmosphere technologies for preservation and packaging of fresh-cut vegetables have pushed shelf life—always chilled, preferably at temperatures near 32°F— to 15–21 days, depending on the produce. Refrigerated shelf life for fresh-cut fruits has already crept up to 10 days or more, again depending on the fruit.
Several fresh-cut produce manufacturers envision opportunities for salads with protein accompaniments, such as meats and cheeses, to find a broader role in prepared foods or in the retail delicatessen departments where consumers perceive salads as entrées or main dish items. An increasing number of food processors are developing and marketing enhanced fresh-cut vegetables as meal side dishes. Fresh-cut vegetable producers will be promoting their fresh-cuts as side dishes by offering partially cooked or cook-chilled dishes with multiple ingredients.
• Foodservice Products. The rapidly expanding foodservice consumes about 60% of fresh-cut vegetable and fruit production, mostly for pre-washed, pre-cut pre-packaged lettuce and other greens, tomatoes, and onions for side and now main course salads. Nearly every major quick-service restaurant now offers fruit-and vegetable-based salads.
• Take-Away Fresh-Cut Produce. Americans reportedly are consuming nearly 20% of their meals in automobiles (or SUVs or pickup trucks). Convenience stores represent yet another opportunity for marketing value-added fresh-cut vegetables and fruits. With many of the 90,000 stores in this sector gravitating toward the “grab-and-go” market, positioning fresh-cut produce as “immediate consumption” items will require new packaging solutions. How can you dine and hold/eat a salad at the same time while “tooling” down the highway at 60 miles/hr—at stop lights only? About 10% of the population buys food, more than half of which is a “meal” purchase, at a convenience store during any two-week period.
Issues with fresh-cut produce for convenience outlets include package sizes and forms. While ambient-temperature shelf-stable beverages, snacks, cookies, crackers, and confections dominate food sales in vending, interest is evolving in hand-held fresh-cut fruits and vegetables, e.g., baby carrots, celery sticks, broccoli florets, and even salads. Whole fruit items like apples and bananas are mostly vended intact and awkward for consumption, but easy-to-handle cut-fruit is on the way.
Fresh-cut produce is generally processed and packaged under some form of modified atmosphere—altered levels of oxygen, carbon dioxide, and water vapor—to prolong quality retention, always under refrigerated conditions since the solution kinetics of gases dictate that the lower the temperature the greater the gas solubility in the produce fluids. The integration of all the variables offers the ability to extend the shelf life by factors of 2–10, depending on the produce and the controls instituted.
While most package materials are typically engineered to erect barriers to gas exchange, i.e., to exclude oxygen, fresh-cut produce prefers a “gate” that can swing either way to minimize the probability of respiratory anaerobiosis that leads to off-flavors.
The objective in modified atmosphere is to reduce the rate of respiration and not try to alter the reactions—a direction that leads to adverse reactions. The “gate” or the rate of gas permeability may swing in to permit the entry of a prescribed limited amount of oxygen-containing air from the exterior environment, while swinging out to provide the escape of excess carbon dioxide, water, heat, and other metabolites such as ethylene.
Each fruit or vegetable has its own optimum rate of respiration. By reducing a product’s respiration rate, the ripening or senescence process can be delayed.
Package structures that can control this gas permeation or transmission rate (through deliberate openings) makes a significant difference in fresh-cut produce shelf life and product quality. Oxygen permeation rates (O2TR) for flexible plastic package structures have been steadily ratcheted up to today’s 300–400 cc/100 in2/day mark while precision-microperforated films and some polymeric blends have permitted even higher gas permeation rates, as much as 1,000cc/100 in2/day. Continued work with polymeric resins and plastic film manufacturing may soon permit O2TR ranges in some films as high as 15,000 cc/100 in2/day, according to some plastic-film experts.
Flexible packaging for fresh-cut produce represents an approximately $300-million market segment for package material converters.
• Anti-Fog Coatings. Anti-fog coatings reduce condensation that can occlude the view of the product so prized by many marketers—the consumer evidently wants to see the product. Increasingly, anti-fog compounds are compounded directly into the master batch before extrusion that film producers use to blow or cast films.
• Easy-Open Features. In the realm of convenience, reclosable, resealable packaging ranks high on consumers’ expectations.
Much development has been focused on peelable lidstocks for semi-rigid plastic trays, critical as more salads move into trays for the cut-fruit category, which is currently tending toward open-top trays, tubs, or other semi-rigid containers. Reliably attaching lidding films with high gas permeability requirements to rigid, gas-impermeable trays can affect sealing properties.
Laser scores are being added to standup flexible pouches, offering easier-opening convenience. With consumers already accustomed to seeing a range of dried fruits in standup flexible pouches, it may not be too great a leap to push further into fresh-cut fruits, salads, or vegetables. Today’s widely used standup flexible pouch structures have too low O2TR and will be modified to accommodate fresh-cut product modified-atmosphere requirements.
To date, reclosable zipper packaging, a mainstay in an increasing proportion of other food product categories, has been largely absent from “bagged” salads. Depending on the type chosen, zippers may add an additional $0.01–0.03 per package, so relatively few producers have found an attractive cost-benefit formula for zippers yet—but wait until next year.
• Shelf Appearance. The “bagged” salad category is, in the view of some marketers, “a wall of sameness” in terms of shelf presence/attractiveness. In cut-fruit, where the premium is on visibility of the product, to date little attention has been paid to packaging distinction. More likely, this uniformity of appearance will not remain; it is too large an opportunity for competitors to exploit an obvious marketing paucity.
• Standup Flexible Pouch. Oddly absent from the fresh-cut produce category, since otherwise it is the fastest-growing concept in flexible packaging over the past 10 years, is the standup flexible pouch. Improvements in laminations, film substrates, and printing made the standup flexible pouch an attractive glossy, sharp-looking package with eye-catching graphics. When reclosable zippers were added to the category during the late 1990s, the now-more-convenient package became even more appealing. Filling speeds have leaped from nearly 40 units/min all the way up to 100 units/min in some multi-lane, horizontal form/fill/seal filling configurations.
• Unit-Portion Sizes. One largely untapped segment is smaller, unit-portion, or single-serve packages, such as snack packs.
Packaging costs may retard the use of more portion or single-serve packaging for fresh-cut produce. When the total systems cost is computed, however, the net is better for the unit-portion size than for bulk, based on less food loss and waste.
• Semi-Rigid Plastic Trays. Although flexible packaging has dominated the fresh-cut salad category, semi-rigid plastic packaging has been a desired packaging form for cut vegetables, where they are often packaged and presented as catering or snack trays or for simply snacking from the refrigerator. Although the costs of semi-rigid plastic trays and packs are more than for most pouches, the presentation can offer a superior view of the product. Especially for increasingly sophisticated, upscale salad blends, semi-rigid formats may play a greater role across the fresh-cut produce spectrum.
Semi-rigid packs have also become the standard for cut-fruit, with most tubs, trays, and cups manufactured from polyester (PET). Cantaloupe, honeydew melon, watermelon, grapes, strawberries, and pineapple have entered distribution channels packaged in clear PET trays. Chiquita’s fresh-cut fruit line is believed to make use of modified-atmosphere packaging (the same as for almost all fresh-cut produce) using microperforated film lidding for breathability. Semi-rigid plastic packages may offer a better platform than flexible for graphics for brand identity, so these formats may play a greater future role across the fresh-cut produce offerings.
Packaging technologists and engineers accustomed to working with packaging films and membranes that control gas exchange will also be able to tailor or restrict levels of moisture, purge, ethylene, microbiological growth, and odor with increasing precision. Controlling the rate of O2 ingress and CO2 egress is the linchpin of fresh-cut produce packaging. While the O2TR of many unsupported pristine materials (not combined or laminated with other films) may not reach high levels, most sophisticated, retail-level packages require a sufficiently wide range of properties—clarity, sealability, printability, anit-fog, stiffness, gas transmission, etc.—that they must be married with other polymers/materials to achieve those performance attributes. Those combinations may add to overall gauges and tend to reduce the final O2TR.
Although oriented polypropylene (OPP) films with very high O2TR might reach as high as 600 cc/100 in2/day, OPP is typically laminated with polyethylene for sealing/closure performance. Even if the polyethylene is from the higher range of around 900 cc/100 in2/day, the combination of the two might yield a final structure with a O2TR of only up to 325 cc/100 in2/day. Films produced from metallocene resins—e.g., polymers such as polyethylene or polypropylene manufactured with single-site catalysts—generate gas permeabilities in the range of 500–1,000 cc/100 in2/day, plus provide a variety of other improved values such as clarity and low-temperature seal initiation.
Additives, including clay or mineral platelets, are being added to resin compounds that give film converters a much wider range of flexibility in tailoring O2TR to up to 10,000 cc/100 in2/day or greater.
• Fresh Hold. One of packaging’s original “active” packaging concepts is Fresh Hold, first developed by chemical company Hercules and today owned by produce grower River Ranch Fresh Foods, Salinas, Calif. In this concept, a comminuted mineral such as calcium carbonate is dispersed through the plastic package film, creating very small micro-pores throughout the structure. These pores, in turn, establish pockets of air which facilitate the transfer of O2 and CO2 through the film. O2TR ranges with Fresh Hold membranes act more like microperforated films, reflected in beta values (ratios of CO2 to O2 passage) of 1:1. In application, Fresh Hold is typically produced as a label which fits over an opening in the lidding stock of a tray.
• Intelimer. One of the more technically elegant solutions is the Intelimer technology from Landec, Palo Alto, Calif. This proprietary polymer system can be designed to sense changes in temperature and/or internal gas atmospheres and then selectively alter the rate of either CO2 release or O2 entry. The goal of most of these exchanges is to allow CO2 to escape at a higher rate than the rate at which O2 is entering the package. Generally a membrane made from the polymer is placed over a hole punched in a plastic pouch or case liner to reduce the cost of the active package component.
The chief asset of an Intelimer membrane is to function like a temperature “switch,” changing its gas exchange functions based on environmental temperatures. For every 10 degrees of temperature change, for example, the respiration rate of produce items can double. Membranes based on this technology increase permeation rates based on those climatic changes, making it a true “active” packaging concept.
• Microperforation. A more direct mechanical way to enhance oxygen transfer is to create tiny perforations or holes (from 50 to 200 microns in diameter) in the film. Microperforations typically permit an O2 and CO2 transfer in a 1:1 ratio.
The technologies for creating microperforations vary, including application of hot or cold needles, electrical sparks, and sophisticated laser technology.
One long-time leader in this area is Amcor Flexibles, whose P-Plus film started with Pulse Spark technology and has moved on to laser technology. Printpack, another leading converter in the fresh-cut produce market, has a license from Amcor allowing it to operate under the P-Plus patented hole size.
• Antimicrobial Packaging. Development of an effective, reliable, and affordable antimicrobial agent for packaging could benefit fresh-cut producers, enhancing product shelf life by reducing the microbiological burden that often contributes to produce deterioration. Unfortunately, most antimicrobial agents today function solely with contact between the agent and the microorganism, and of course, foods infrequently exhibit smooth surfaces for uniform contact—and microorganisms tend to hide in crevices. The better recent antimicrobial solutions center on generating a volatile environment to which microorganisms are exposed.
Used for more than 1,000 years in preparation of a variety of foods such as sushi and sashimi, wasabi (Japanese horseradish) contains allyl isothiocyanate, a chemical that can retard the growth of microorganisms. The volatile can diffuse into the interior of the container to restrict or eliminate microbiological activity, but the odor is pungent—it could possibly be ameliorated by vanillin.
Fresh-cut produce packagers are familiar with Microsphere technology from Bernard Technologies, Chicago, Ill., a controlled-release technology based on the release of chlorine dioxide. As a biocide, it is said to be effective against bacteria, viruses, mold, and yeasts, as well as being a neutralizer of undesirable odors. But there are sometimes adverse secondary effects.
• Moisture Control. Among the better known advanced systems for purge and moisture absorption is Fresh-R-Pax technology from Maxwell Chase Technologies, Atlanta, which can be incorporated into absorbent pads, pouches, and trays. The concept is to absorb excess moisture from fruits and vegetables and thus sequester spoilage organisms, keeping them from contact with the produce and the consumer. The pads use a powder which forms an irreversible gel that traps liquid purge.
And Paper Pak Industries, La Verne, Calif., has its cellulose-based pads engineered to maximize purge absorption and thus control moisture.
Humidipak is a two-way technology concept that adjusts the internal package relative humidity to the environment by either adding or removing moisture to a predetermined level. The technology is based on a gelled saturated salt solution packaged in a pouch film made from DuPont’s Hytrel resin to pass moisture.
• Multiphase Packaging. Perhaps the most novel active packaging concept on the market is based on the idea of creating microscopic “channels” throughout a polymeric item, such as a rigid container or film. The technology is based on entraining an active agent, perhaps a desiccant or oxygen absorber, into the channels to either absorb or emit the desired molecules, such as O2, CO2, ethylene, or moisture. CSP Technologies, Auburn, Ala., is commercializing products based on this polymer blending technique.
CSP’s technology has the potential to deliver a range of functions—maintaining specific relative humidity, absorption of gases and odors, controlled release of aromas, flavors, etc., and fine-tuning film transmission rates—that is staggering.
One application has been to enhance the shelf life of strawberries with CO2 release. A multiphase plastic sheet, in which CO2 release agents are entrained, is placed in cases of strawberry packs. The sheets are activated by moisture in the range of 50–60% RH.
• Aroma Control. Fabri-Kal, Kalamazoo, Mich., a thermoformer of semi-rigid plastic packaging, has a patented approach for incorporating desirable aromas in thermoformed cups, bowls, tubs, and trays. The aromas can be engineered for release by an integer of trigger-time, opening of the container, microwaving, etc.
And the reverse, removal of undesirable aroma—optimally by the venerable activated carbon—has been developed at the University of Georgia with funding by Soldier Systems, Natick, Mass.
As with almost all journeys into relatively new food products and their underlying technologies, we have ventured from acknowledging a major growing food product category into the sciences and their applicable technologies. Fresh-cut, almost unknown 20 years ago, dominates future thinking and implementation, driven by consumer demand, industry research and response, and a fundamental series of technologies from the processing and packaging resources around the world.
Meeting retailer and consumer desire for quality and convenience has led industry professionals to identify the deteriorative vectors and means to control them through integration of environmental alterations. The comprehension of fresh-produce respiration and its control represents technological progress in which bold moves into process control and packaging were married to deliver added-value food products.
And the same forces are poised to drive further into the realms of convenience—to attempt to move fresh-cut far beyond side dishes into main-meal eating experiences. It is not easy, but it is truly food product and packaging development at its classical best.
Portions of this article were based on a white paper, “Fresh-cut Produce Fuels an America on the Go,” prepared by Bill LeMaire of PakIntell, West Chester, Pa., for the International Fresh-cut Produce Association, 1600 Duke St., Suite 440, Alexandria, Va. 22314-3400 ( www.fresh-cuts.org ).
by AARON L. BRODY
President and CEO,
Packaging/Brody, Inc., Duluth, Ga.