The Science of Preserving Fresh Produce

Posted by David Anderson on

Fresh is Best

When you think of fruit or vegetables you probably think of the word “fresh.”

Nothing is better than biting into a piece of perfectly ripe fruit or cutting up a garden’s worth of fresh vegetables for a salad. And, nothing is worse than biting into a rotten piece of fruit or chomping down on a forkful of salad expecting that satisfying crunch only to have your palate disappointed by a slimy, limp mélange of spoiled vegetables.

When it comes to produce, everyone wants fresh and ripe. Most people don't live on a farm or have a huge garden. So, most people depend upon grocery stores that sell produce shipped to them from different states or even countries. Because of this, food scientists, packaging engineers, and supply chain experts have progressively found better ways to preserve produce.

The Complexity of Modified Atmosphere Packaging (MAP), Produce, and Aerobic Respiration after Packaging

While you can use Modified Atmosphere Packaging (MAP) for many packaged food items including: meat, poultry, seafood, pasta, dry food, prepared meals, baked goods, and dairy products, its application for produce may be where its effectiveness is at its most complex and shines the brightest.

The reason for this has to do with the fact that produce continues to respire even after it is packaged, whereas the food items listed above do not. The continual respiration of fresh fruits and vegetables adds a layer of complexity to the process of MAP packaging. We will discuss it briefly below.

In their chapter “Modified Atmosphere Packaging” in the book Minimal Processing Technologies in the Food Industries (ed. T. Ohlsson, N. Bengtsson), Sivertsvik, Rosnes, Bergslien, and Stavangar discuss the basics of MAP for respiring foods:

Unlike other chilled perishable foods that are Modified Atmosphere packed, fresh fruit and vegetables continue to respire after harvesting, and consequently any subsequent packaging must take into account this respiratory activity. The products of aerobic respiration are CO2 and water vapour, whereas fermentation products such as ethanol, acetaldehyde and organic acids are produced during anaerobic respiration. The achievable shelf-life of Modified Atmosphere packed produce is inversely proportional to the respiration rate.

Decrease Respiration Rates to Increase Shelf-Life

In short, if you can decrease the respiration rate of produce, you can increase the shelf-life. Respiration’s input is O2 and its product is CO2. So, if you can deplete O2 and/or enrich CO2 levels  through MAP during packaging, then you can extend its shelf-life by inhibiting the spoilage mechanisms common to produce such as: microbial growth, enzymatic browning, and moisture loss.

The depletion of O2 and/or enrichment of CO2 also increases the shelf-life and improves the sensory qualities of the produce. This is done by reducing respiration, delaying ripening, reducing chlorophyll degradation, and alleviating physiological disorders.

While low O2 and high CO2 can benefit produce, they also can pose risks to the packaged produce. Depletion of O2 and enrichment of CO2 are natural consequences of the respiration of produce. This means that if you store produce in a hermetically sealed package you will run the risk of decreasing its O2 levels to the point where you will initiate anaerobic respiration in the produce. If anaerobic respiration begins in the packaged produce, undesirable fermentation reactions can occur leading to deterioration of the product as well as causing product softening and undesirable odors and flavors to manifest themselves in the produce.

The Importance of Performing Gas Analysis on MAP Packaged Produce

Due to the complex nature of MAP for respiring foods, it is imperative that you perform proper gas analysis regularly as part of a comprehensive Quality Control process.

We designed our Bridge Analyzers Model 9001 – CO2/O2 Gas Analyzer to meet the specific needs of produce packagers. Because of that, it is our bestselling Gas Analyzer for our fresh fruit and vegetable customers.

Bridge Analyzers Model 9001 – CO2/O2 Gas Analyzer

  • CO2 process gas fill and MAP Residual O2 measurement.
  • CO2/O2 balance for natural respiration process evaluation.
  • Sealed for Harsh Environments – Industrial NEMA-4 Design.
  • Cordless Operation – Single or Double Shift Internal Battery.
  • Simple and fast – Single button CO2 and O2 in 15 Seconds.
  • Stable, Trouble-free Infrared CO2.
  • Customer Changeable Self-Calibrating E-C O2 sensor.
  • Small (6″x3″x3″), lightweight (2.5 Lbs), and rugged.

Let us know how we can help you improve your MAP gas analysis by contacting us at