FRESH CUT FLOWER & FRUIT PACKING:
The fresh-cut packaging revolution is most noticeable in bagged salads, where the moisture-controlled plastic bags created a whole new category. However, it’s since moved into many additional sections of the produce department. What do executives need to know about it? And what does the future of fresh-cut packaging look like?
Jacob Shafer, senior communications specialist with Mann Packing, a Salinas, CA-based provider of fresh and ready-to-use fresh-cut vegetables, provides a basic definition: “Fresh-cut packaging allows manufacturers to sustain product quality and provide consumers with a fresh experience without the use of preservatives.” Jeffrey Brandenburg, president of the JSB Group, a Greenfield, MA-based consulting firm specializing in package design/technology and food safety, has a more in-depth explanation for what he refers to as modified atmosphere packaging. “Almost always, you’re packaging something that’s inert,” he says. “It just sits there. With produce, it’s alive and breathing. It breathes in oxygen and gives off carbon dioxide. Once you seal the bag, the atmosphere begins to change; and by definition, you’re in a modified atmosphere package. The trick with modified atmosphere packaging is designing a package around that breathable produce that achieves an optimal modified atmosphere with steady conditions that extend the shelf life.”
According to Brandenburg, a good modified atmosphere package will do three things. “By reducing the oxygen, you put the produce to sleep. You slow down its physiologic properties, and that extends the shelf life. By getting the oxygen down below 3 percent, you reduce enzymatic browning reactions or ‘pinking.’ By increasing the carbon dioxide in the package, you also slow down the growth of spoilage bacteria, as well as yeast and mold.”
“The trend toward fresh-cut packaging is in response to the increase in demand of grab-and-go eating patterns among consumers,” says Jack Tilley, market research manager at Inline Plastics Corp., which designs and manufactures clamshells and two-piece packaging. The company is based in Shelton, CT. “These can be time-stressed parents who want to grab something healthy for themselves or their family, as well as Millennials, who often embrace four to five smaller meals during the day, which translates to more snacking occasions.”
Steamable Packaging
A fresh-cut packaging type that’s been around for a while but is getting more popular is steamable packaging. “As ready-to-eat foods get more popular, consumers are flocking to vegetables that can be steamed in the packaging,” says Shafer. That can include cut vegetables, such as broccoli florets or green beans, or whole foods like microwavable sweet potatoes.
Stores that want to create their own steamable vegetable packets should take care to select the right type of packaging. “You want the container to be able to sustain the heat so it doesn’t melt all over the product,” says Brandenburg.
Anti-Fogging Properties
Fogging occurs when water beads up on the front of the bag. It doesn’t affect the quality of the produce at all. However, “a fogged container reduces the merchandising value of the product because consumers can’t judge the quality of the food contents,” says Tilley.
To create anti-fogging bags, manufacturers typically coat the material with a chemical from the surfactant family. The chemical changes the surface tension of the water. “It’s the same idea as wax on a car,” says Brandenburg. “The chemical makes the water lie flat instead of beading so you can still see through it.”
Micro Perforated Bags
Mann's Fresh Cut BroccoliBesides using bags with an anti-fogging agent, Tilley says a good way to deal with fogging issues is to offer containers with venting to release outgassing from produce outside the container.
Another option for venting is micro perforation. “Micro perforated bags have tiny holes not visible to the eye that allow gases to move in and out,” says Brandenburg. “They’ve been around for a while, but they’re getting much more accurate.”
A newer technology is bags with breathable membranes. “They can adjust their breathability with the temperature,” says Brandenburg. “So if the produce gets warm, the membrane allows more gas to move in and out.”
“The pouch bags make it a lot easier to display products on the shelf. For grapes and cherries, it also helps as a safety issue. You don’t have loose grapes rolling all over the place like you did years ago.”
— Rick Rutte, North State Grocery
Packaging Geometry
Brandenburg calls fresh-cut packaging in the form of stand-up pouches “the most innovative thing that’s come along in a while. It’s not the packaging per se, it’s the new geometry.”
“The pouch bags make it a lot easier to display products on the shelf,” says Rick Rutte, produce director for North State Grocery, which operates stores under the names Holiday Markets and SAVMOR, and is headquartered in Cottonwood, CA. “For grapes and cherries, it also helps as a safety issue. You don’t have loose grapes rolling all over the place like you did years ago.”
The other advantage to the pouch bags is the ability to print brand names and marketing messages on them. “We do really well with Welch’s grapes when we have California grapes in season,” says Rutte. “That Welch’s label is obviously well-known. It gives that sense of freshness and quality. Companies are also able to provide recipes or health information on the back of the bag.”
“The quality of the graphics, the message that’s getting across and the brand management is becoming a big part of produce packaging,” says Brandenburg. “It’s all about differentiating yourself from your competition and having it pop at the retailer so it’s noticeable.” Being able to print on packaging also helps from a regulatory standpoint, he adds. Printable packaging can be used to share details such as country of origin, allergens and food safety information.
Fruit In Fresh-Cut Packaging
Because bagged salads have been such a hit, people tend to think of fresh-cut packaging as a way to manage vegetables. But placing fruit in modified atmosphere packaging is a big part of the market segment.
“You’re going to see more and more different types of produce items in packages, and in different configurations — shredded, chopped, sliced, etc.”
— Jeffrey Brandenburg, JSB Group
“Fruit tends to be the strongest in-house category we do,” says Jeff Fairchild, produce director for New Seasons Market, a 20-store chain headquartered in Portland, OR. “That stands in contrast to most vegetables. We’ve found it’s a good skinny category,” he says. “We haven’t found that the sales continue to ramp up.”
Rutte agrees the fruit category is an important one. North State Grocery has been purchasing fresh-cut packaged fruit for a year now and the program has grown. “I see a lot of people buying it for lunches,” he says.
The store doesn’t add its own marketing materials to the packages, but it does have a marketing program. “If there’s something I want to promote, I’ll have in-store signage in the refrigerator case,” he says. “The signage on the doors draws attention.”
Uniquely Cut Vegetables
Mann's Sweet Potato RibbonsAs gluten-free, Paleo and other diets gain in popularity, many shoppers are looking to substitute vegetables where they used to use carbohydrates. Produce departments can cash in on this trend by selling spiralized vegetables, cauliflower “rice” and similar products in fresh-cut packaging.
“Spiralized vegetables like zucchini and sweet potatoes have done pretty well,” says Fairchild. “Those have a pretty strong pull right now.”
“You’re going to see more and more different types of produce items in packages, and in different configurations — shredded, chopped, sliced, etc.,” says Brandenburg. “There will be more and more blends, even whole meals where you make a mixture of produce, protein and carbohydrates. We’ve seen some of that, but I think you’ll see more of it. That’s something that’s been very common in Europe for a long time.”
Sustainable Packaging
Another area of growing interest is sustainable packaging. “Shoppers are very conscious of it,” says Rutte, especially his organic customers.
Some eco-friendly fresh-cut packaging does exist already. NatureWorks LLC, Minnetonka, MN, manufactures film and sheets for rigid packaging under a product line called Ingeo. “Plants produce sugar in the form of starch,” says Stefano Cavallo, global segment lead for films and cards at NatureWorks. “The starch is fermented using advanced and patented processes and eventually polymerized into Ingeo plastic pellets.” Those pellets are then sold to converters and turned into the materials produce managers see on their shelves.
“Ingeo films use 50 percent less non-renewable energy and results in 75 percent less greenhouse gases to manufacture than films made from non-renewable fossil carbon,” says Cavallo.
The company is also working to develop a film that may be as much as 50 percent thinner than current polypropylene film. “Thinner film contributes to more sustainable packaging through less material sourced,” says Cavallo. “In terms of film used for commodity products, consumers care about freshness, not necessarily what those films are made of,” he adds. “For differentiated high-end organic products, which command higher prices for product and package, the fact that they are packaged using renewably sourced plastic helps generate consumer satisfaction.”
JSB Group’s Brandenburg sees demand for eco-friendly packaging growing. He also sees more interest in using science to deliver packaging that fits with other consumer demands, including products with antimicrobial properties.
No matter what type of bag or box a product is packaged in, the best way to keep its contents fresh is to store correctly. “That affects shelf life more than anything else,” says Brandenburg. Generally, bags and containers should be kept at less than 5 degrees C.
Today's consumers shopping the produce section of the grocery store have high demands of their fruits and vegetables. The items must be fresh and minimally processed, have an extended shelf-life, and look pretty to boot. One way that CPG companies can achieve all of the above for fresh-cut produce is by leveraging modified atmosphere packaging technologies.
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What is modified atmosphere packaging?
Modified atmosphere packaging (MAP) is a collection of packaging modifications that work to create or maintain an atmosphere inside of a package which controls and slows oxidation of fresh food. Oxidation of food results in spoilage, off-textures, offensive odors, and discoloration. Think lettuce turning brown or apples becoming gritty in texture. By preventing oxidation, the useful life of fresh products is greatly extended and their visual presentation is preserved.
Below are some examples of widely-used types of modified atmosphere packaging used in fresh cut packing:
Gas (nitrogen) flush. This component of a packaging system pumps harmless nitrogen gas into the package to displace oxygen right before sealing.
One-way valves. Often used in the coffee industry, these plastic valves allow gases to escape the package without letting anything else in.
Barrier packaging materials. These special packaging films provide decreased permeability to oxygen and/or moisture.
Desiccant packs. Often found inside pill bottles, desiccant packs absorb ambient oxygen or moisture.
For an in-depth explanation of modified atmosphere packaging technologies, see our guide here.
Why is MAP so important for fresh-cut fruits and vegetables?
Fresh-cut fruits and vegetables have a high respiration rate, meaning they spoil and discolor quickly when exposed to oxygen. Because fresh produce is minimally processed and contains few (if any) preservatives, modified atmosphere packaging technologies must take on the role of 'preserver'.
For CPG companies, the extended shelf life created by modified atmosphere packaging means an enhanced product lifespan, wider geographic distribution of their product, and brand exposure to a larger audience. Bottom line: It increases their bottom line.
For consumers, modified atmosphere packaging enables them to maintain a healthy diet in a convenient manner. It's no longer necessary to stop at the grocery store for fresh produce multiple times per week. Now, consumers can stock up in greater quantities knowing that the product will remain fresher longer.
For society at large. extending the shelf life of fresh produce allows for wider access to healthy foods and increased food security. Food waste is also decreased when produce can remain viable for a longer period of time.
What is the history of MAP for fresh produce?
Modified atmosphere packaging for fresh-cut fruits and vegetables was developed in the early twentieth century and is widely used today. Here's a short history of the advancements in this field:
1930s: Ships transporting fruits maintained high concentrations of carbon dioxide in storage rooms to extend shelf-life of products.
1940s – 1950s: Fresh apples and pears were stored in a warehouse with high levels of carbon dioxide to slow respiration. They could be eaten as many as 6 months after harvest.
1950s – 1960s: Whirlpool Corporation developed methods to replace air inside bulk shipping containers of produce with different gases.
1990s: UK supermarkets Tesco and Asda began packaging fresh-cut fruits and vegetables in modified atmospheres. In North America, modified atmosphere packaging really began to take hold when McDonald’s began using MAP to extend shelf-life of their bulk lettuce and produce.
2000s: Rapid growth is seen in demand for fresh, natural produce with extended shelf-life, leading to increased adoption of MAP for fresh-cut produce.
2010s - today: Convenience, healthy lifestyles, and the demand for preservative-free food are major contributors to the continued growth of MAP for fresh-cut fruits and vegetables.
How is MAP used in packaging fresh-cut fruit and vegetables?
Modified atmosphere packaging maintains or decreases ambient oxygen within a package to levels that are conducive to extending shelf life. In general, oxygen levels of 1 - 5% are enough to delay oxidation of fresh produce. At concentrations below 8%, ripening and maturation can be delayed.
The below list describes the approximate storage life of different kinds of produce when using MAP technologies under optimal conditions:
Apples: 2 - 11 months (1 - 2% oxygen levels)
Bananas: 15 days (2 - 5% oxygen levels)
Lettuce: 3 - 4 weeks (1 - 3% oxygen levels)
Onions: 8 months (1 - 2% oxygen levels)
To achieve these low oxygen levels, nitrogen gash flush is often utilized for packaging fresh-cut fruits and vegetables. A nitrogen generator is integrated with a packaging machine and pumps nitrogen gas into each package after filling and right before sealing.
Many produce companies are also seeing the added value of investing in high barrier packaging materials that feature low oxygen transfer rates (OTR). These films have low oxygen permeability which provides a higher level of protection against oxidation.
Fresh-cut-produce-associated foodborne outbreaks are a major public health concern worldwide. Recent foodborne outbreak statistics showed that there is an increasing trend in fresh-cut produce-linked outbreaks mostly associated with Salmonella and Escherichia coli O157:H7 as the causative agents. There are multiple sources of contamination for fresh produce during preharvest and harvest–postharvest stages of production. Both endophytic and epiphytic colonization have been reported for foodborne pathogenic bacteria in fresh produce. The endophytic colonization occurs through natural openings, damaged tissue, and chemotaxis. The mechanisms of attachment for epiphytic colonization mainly include curli, fimbriae, flagella, and biofilm formation. Once attached onto the injured parts of the tissue, pathogenic bacteria can grow to high numbers in fresh fruits and vegetables. The interaction of the bacterial cell with the damaged plant tissue can result in the upregulation of genes involved in attachment, virulence, and resistance to oxidative antimicrobial agents. This represents a major challenge for the fresh-cut industry, as oxidative sanitizers are mainly used for the sanitization of fresh-cut produce, especially leafy greens.
Packaging design for fresh cut fruit and vegetable:
Ready-to-eat, fresh-cut consumer products are one of the few segments within the industry that has shown consistent growth within the last few years. Cutting however, increases senescence rate and the shelf life of the products can be very limited. Modified atmosphere packaging (MAP), combined with a good cold chain can extend the shelf life, but challenges still exist, due to fresh-cut products containing much higher respiration rates due to the cell stress, caused by cutting.
Ready-to-eat, fresh-cut consumer products are one of the few segments within the industry that has shown consistent growth within the last few years. Cutting however, increases senescence rate and the shelf life of the products can be very limited. Modified atmosphere packaging (MAP), combined with a good cold chain can extend the shelf life, but challenges still exist, due to fresh-cut products containing much higher respiration rates due to the cell stress, caused by cutting.
Ready-to-eat, fresh-cut consumer products are one of the few segments within the industry that has shown consistent growth within the last few years. Cutting however, increases senescence rate and the shelf life of the products can be very limited. Modified atmosphere packaging (MAP), combined with a good cold chain can extend the shelf life, but challenges still exist, due to fresh-cut products containing much higher respiration rates due to the cell stress, caused by cutting.
A high respiring product inside a low permeability film means anoxia soon establishes (absence of oxygen) conditions, under which very dangerous pathogens thrive (e.g. lysteria). Towards the end of 1996, we witnessed the largest outbreak ever recorded in the UK. This originated in Wishaw (Lanarkshire), southwest Scotland. Although the source of infection was traced to cold cooked meats, it is an alarm for other food products like fresh cut fruits and vegetables. There was an outbreak of Salmonella Typhimurium in the United States indicating that tomatoes consumed at restaurants are the food responsible for this outbreak (Centres for Disease Control and Prevention, October, 1996).
The MAP technique means that the product is packed in a permeable package and preferably stored at refrigerated temperature. The gas composition inside the package is modified to the optimum level for the packaged product, generally low O2 and high CO2, as shown in Figure 1. This passive/natural modification relies on the interplay between the product respiration rate and the gas exchange rate through the package. Proper MAP design is required to achieve the optimal atmosphere by considering the factors shown in Figure 2. A MAP system, if not designed correctly, may be ineffective or even shorten the storage life of a product. The existing commercial packages deviated from the optimum conditions of MAP (Figure 1). This shortens the shelf life with poor quality product and possibility of infection. Simulation is a valuable tool in this context. The shelf-life and packaging group led by Prof. Fernanda Oliveira at University College Cork, Ireland have developed user-friendly software for packaging design for fresh-cut produce. The group is also actively involved in analysis of respiration rate of fresh-cut produce and Perforation-Mediated MAP (PM-MAP) which is an alternative to conventional MAP.
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.
Packaging
“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.
Fresh-Cut Opportunities
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.
Modified-Atmosphere Packaging
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 Technologies
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.
Technological Progress
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.