Are Modified Atmosphere Systems Right For You?

The demand for a year-round supply of high-quality fresh fruits and vegetables poses daily challenges and opportunities to growers, intermediaries and retailers. Even after harvest, fruit and vegetables are metabolically active and respire; every day of post-harvest life poses the risk of rapid deterioration, microbial degradation, loss of freshness, changes in colour and flavour, and ultimately senescence of the produce. Maintaining quality and shelf life is a complex problem.

At Sensitech^® we know that correct handling and good temperature control are essential factors in preserving the post-harvest life of fresh produce. However, there are other factors to think about, and atmospheric composition around the produce during handling and transport can be a crucial element. This is where modified atmosphere systems come in.

Modified atmosphere (MA) and controlled atmosphere (CA) technologies regulate atmospheric composition during storage, staging, and/or transport. Typically, MA/CA environments for fresh produce are characterised by a higher concentration of carbon dioxide (CO₂) and a lower concentration of oxygen than is usually present in the air. Such conditions slow down the respiration of the product, reducing the production of ethylene and the activity of aerobic organisms. As a result, in conjunction with good postharvest practices, MA/CA systems can further extend the shelf life of produce.

When MA/CA systems are used, gas levels play an essential role in maintaining the safety of the produce. Ideal levels of CO₂ and O₂ depend on various aspects such as the species, variety, maturity, ripeness of the product, packaging material, post-harvest handling temperature, and humidity. These systems are designed to adjust the air mixture according to the needs of the product in order to prevent any adverse effects.

So, how do you know if a modified atmosphere system is right for you?

Advantages:

• Maintain quality and extend the shelf life of produce by reducing its respiration, cutting down on waste at the retail end.
• Increase post-harvest life of climacteric fruit (for example, bananas and avocados) and those with a high rate of metabolism (for example, asparagus).
• Inhibit ripening. Low levels of O₂ and/or CO₂ (8% or below for O₂, 1% for CO₂) can inhibit fruit sensitivity to ethylene, which is a plant hormone that encourages ripening and senescence. Elevated CO₂ levels can combat the presence of ethylene, delaying premature ripening and softening.
• Inhibit microbial growth. Elevated CO₂ and low O₂ levels have fungistatic and bacteriostatic effects. For example, high concentrations of CO₂ (15%) hamper the growth of Botrytis cinerea (grey mold) in soft fruit such as strawberries and raspberries.
• Slow the yellowing of green tissues (broccoli, leafy vegetables) by preventing chlorophyll degradation.

Disadvantages:

• Exposure to very low O₂ levels may lead to anaerobic respiration (fermentation) and the accumulation of ethanol and acetaldehyde, resulting in an altered flavor and/or odor.
• Physiological disorders such as blackheart in potatoes, brown stain in lettuce, or brown heart in apples and pears may be caused by exposure to very high CO₂ levels.
• Softening or black blotches on green bananas due to high levels of CO₂ and high-temperature transport.
• May not be the right approach for certain fresh produce. For example, sulphur dioxide (SO₂) treatments and high relative humidity management are more beneficial in extending the postharvest life of grapes than MA/CA systems.
• Can be ineffective in the case of modified atmosphere packaging (MAP) solutions, if the packaging material is torn or damaged.
• Increased cost for equipment, transport, packing materials, and gases needed for the gas mixture.
• Require specialized staff members for operation.

For some fresh produce, the disadvantages and costs of modified atmosphere technologies may outweigh the benefits. In an upcoming post, we’ll explore the MA/CA technologies available today. But whether or not these solutions are right for you, it’s important to consider every angle of produce freshness—and in many cases, atmosphere is key.

Above: Ripening control comparison. Source: container.carrier.com

Above: Controlled atmosphere optimum transport conditions. Source: www.carrier.com (cited from University of California at Davis and the former Davis Fresh Technologies, LLC)

Sensitech combines strong food industry expertise and cold chain best practices with state-of-the-art monitoring technology and analytics to help food producers, shippers and buyers ensure the quality and freshness of their food products worldwide. Contact our Professional Services team to learn more about how our CO₂ studies and how Sensitech ColdStream^® Services can help drive process improvements and improve your bottom line.

Don’t miss part two – Modified and Controlled Atmosphere: Today’s Technologies