The use of liquid nitrogen for cooling ensures product quality on a par with carbon dioxide use in at least some food processing applications, according to a recent study available from United Kingdom-based Air Products.

Contrary to widespread perception, according to the report by Dr. Chris Kennedy, carbon dioxide (CO2) does not have qualitative benefits over liquid nitrogen (LIN) in cooling in meat-mixing and -forming applications. This means that processors can choose freely between the two options without worrying about variations in end-product quality.

“Comparison of Chilling Meats by Carbon Dioxide and Nitrogen” looked at the effects of both cooling agents on shelf life, coloration and dehydration. Because of CO2’s ability to protect against spoilage in modified-atmosphere packaging (MAP) applications, many processors also use it to chill meats, intending to achieve a potential increase in shelf life. However, the study showed that CO2desorbs from meat very quickly after chilling and is therefore unlikely to have any meaningful impact on shelf life if it is not also used for subsequent MAP packaging.

The report also revealed that meat placed in LIN or CO2atmospheres could result in oxygen loss from its surface. This causes a reversion of the bright red oxymyoglobin pigment, which consumers often associate with freshness, to myoglobin, which has a deep purplish red color. Although CO2may lighten this color slightly, the study determined that all color changes were reversed when the meat was exposed to a normal atmosphere again.

Looking into dehydration rates, the study showed that LIN could actually offer advantages over CO2. When using similar chilling equipment, liquid nitrogen was found to cause less dehydration than carbon dioxide because surface temperature is reduced more quickly.

“Dr. Kennedy’s study will be welcome news for many meat processors,” commented Emma Guthrie, European marketing manager, food and industrial cryogenics, at Air Products. “His research shows they have the choice between CO2and LIN for their cooling and freezing applications, and [they] don’t need to be concerned about quality variations in the end product. In fact, more manufacturers may now consider the use of LIN because of its other advantages, including rapid and controlled temperature reduction during mixing and processing.”

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