Eating fresh, ripe fruit is a delicious treat that many consumers increasingly demand year-round. However, fruits are highly perishable, and maintaining their optimal freshness from farm to table can be challenging. Proper packaging is critical for preserving fruit quality and extending shelf life during transport, storage, and sale.
Various innovative packaging technologies exist to provide the ideal microenvironment for fruits that mimics how they ripen naturally on a tree or vine. Understanding these packaging techniques and materials can help maximize fruit freshness and minimize food waste.
Controlling Respiration Rates
After being picked from plants, fruits continue the process of respiration which produces energy but also leads to ripening and eventual spoilage. Proper packaging techniques can help regulate and slow down fruit respiration rates to extend shelf life. Sealing fruits in plastic films or polymeric packaging materials restricts airflow and oxygen availability, creating a modified atmosphere with reduced O2 and increased CO2 levels inside the package. This suppresses aerobic respiration, which slows the ripening reactions and associated quality deterioration.
Packages also utilize breathable films or microscopic perforations that allow some passage of gases, preventing harmful anaerobic fermentation while still lowering respiration rates. Careful humidity control is also needed to prevent excess moisture build-up inside packs, which could accelerate fruit decay through elevated microbial growth and enzymatic reactions.
Managing Ethylene
Ethylene is a gaseous plant hormone that promotes ripening and senescence in many fruits. To slow these effects and extend shelf life, packaging strategies aim to moderate ethylene production and action after harvest. Incorporating chemicals into packaging films or inner coatings that absorb and trap ethylene can reduce concentrations around the fruit and slow ripening processes. Separating ethylene-producing fruits like apples from ethylene-sensitive produce like bananas during storage and transport also minimizes exposure.
Allowing proper ventilation through breathable packaging regulates the internal accumulation of ethylene gas. Special ethylene scavenger sachets containing minerals like potassium permanganate, activated carbon, or activated clay can be added to actively absorb and react with ethylene, removing it from the internal package atmosphere. Careful ethylene management through packaging is crucial for decelerating fruit ripening reactions and maintaining optimal post-harvest quality.
Maintaining Humidity
Preserving optimal humidity levels is crucial for maintaining fruit quality and limiting moisture loss that causes shriveling and textural softening. Packaging allows some natural transpiration of water vapor but avoids excessive humidity build-up that promotes decay. Breathable packaging films and perforations balance and control internal moisture levels by allowing ventilation while retaining enough humidity. Small moisture absorption pads can also be added inside the packaging to help regulate humidity.
Individually sealing or wrapping fruits in micro-perforated polymer pouches creates a localized humidity bubble around each piece, slowing water vapor loss through the permeable film. Wax coatings applied directly onto fruit peels also provide an extra barrier to moisture loss, helping retain crispness. However, avoiding condensation of moisture inside the package is critical, as this provides a prime environment for microbial growth and accelerated fruit spoilage. Managing humidity while allowing ventilation is key.
Controlling Temperature
Proper temperature control during post-harvest storage and transport is critical for preserving fruit quality and shelf life. Cooling fruits immediately after picking and maintaining chilled temperatures throughout the supply chain slows the chemical reactions and metabolic activities that lead to spoilage.
Ideal storage temperatures range from 0-10°C depending on the specific fruit variety. Refrigerated cold rooms provide temperature reduction for palletized fruit packs.
Insulated packaging with enclosed gel packs or phase change materials that absorb and release heat also helps maintain chilled conditions around individual fruit packs during transit. The gel packs are refrigerated or frozen before use to provide a cooling effect.
Precise temperature monitoring and management prevents exposure to damaging high temperatures which accelerate ripening and senescence. Keeping fruits consistently chilled while avoiding freezing damage ensures maximum freshness retention en route to consumers.
Modified Atmosphere Packaging
Modified atmosphere packaging (MAP) seals fruits in high-barrier flexible pouches or containers that contain an optimized gaseous environment tailored to the specific produce. Reduced oxygen (O2) levels and increased carbon dioxide (CO2) concentrations inside the pack lower the fruit's respiration rate, ethylene production, enzymatic activity, and senescence.
The exact optimal gas proportions differ between fruit varieties. Packages are flushed with an initial premix of gases and may incorporate sachets that absorb ethylene and moisture during storage. Tiny perforations in the packs allow gradual gas diffusion and exchange with the outside environment.
MAP enables precise control over the internal atmosphere surrounding fruits to significantly extend freshness and shelf life after harvest. Properly designed MAP can double or even triple the shelf life of many fruits compared to simple perforated packaging or storage in the air. This enables wider distribution and reduced waste.
Active and Intelligent Packaging
Smart packaging technologies can also help extend fruit quality. Oxygen or ethylene scavenging sachets/films actively absorb gases. Antimicrobial ingredients prevent microbe growth.
Time-temperature indicator labels track cumulative temperature exposure along the supply chain. Sensors can monitor the internal atmosphere and generate alerts if optimal conditions are exceeded. Radiofrequency identification (RFID) tags enable real-time tracking and monitoring.
Edible Coatings and Films
Applying edible protein or polysaccharide-based coatings directly onto the fruit peel protects against mechanical damage, moisture loss, and gas exchange. Beeswax or shellac-based coverings also preserve quality. Antimicrobials are often incorporated to reduce microbe growth.
These thin edible films act as a partial barrier to gases, water vapor, and aromatic compounds. Coatings also maintain surface lubrication to avoid abrasions during postharvest handling.
Cushioning and Immobilization
Cushioning materials molded into trays or dividers immobilize and protect delicate fruits from compression damage during stacking and transport. Foam nets, plastic trays, pulp mold trays, and corrugated dividers are common examples.
Proper immobilization avoids “bruising” which accelerates enzymatic spoilage reactions. Cushioning also reduces abrasion and impact injury.
Sanitation
Packaging materials themselves must be sanitary and free of any contaminants that could transfer to the fruits. Food contact regulations cover packaging production and use. Maintaining the cold chain from packing to retail display cases also restricts microbial growth.
Pre-Pack Treatments
Before packaging, fruits may undergo washing, waxing, fungicide treatment, humidity conditioning, or controlled atmosphere treatments. For example, apples and pears are often held in low-oxygen environments for a period before packing to delay ripening and extend storage capacity.
Packaging Design
Pack shapes, perforations, and openings are designed to allow maximum airflow while retaining fruits. Stacking and ventilation geometry avoids compression and excessive humidity build-up. Packaging is also designed to display fruits attractively at retail. Tray colors, size ratios, viewing windows, and labeling all influence consumer purchase decisions.
Sustainable Materials
Packaging generates substantial waste volume so renewable, compostable, and recyclable materials are increasing. Non-petroleum-based bioplastics from plant starches offer compostable alternatives to conventional polymer films and expanded polystyrene. Reusable plastic containers are also circulating.
Conclusion
Maintaining produce quality post-harvest until consumer purchase is challenging. Packaging technology provides an essential means to deliver fresh, ripe fruits to market by moderating the environment, atmosphere, humidity, and handling stresses encountered. Continued advances in packaging materials, designs, and active sensing will further enhance preservation and reduce waste.
