Protective Atmospheres

In packaging of hard cheese, carbon dioxide is used first and foremost. It effectively stops or reduces microbic activity and contributes to retained texture. Carbon dioxide concentrations as low as 20% strongly inhibit the growth of mold fungi. Lactic acid bacteria, a natural constituent of cheese, is affected very little by the surrounding atmosphere.

Soft cheeses are also packaged in atmospheres with increased carbon dioxide and low oxygen levels to inhibit bacterial growth and rancidity.

In packaging of hard cheeses the carbon dioxide level is up to 100%, and for soft cheeses the level is usually restricted to 20–40%. This is done to prevent the package from collapsing under atmospheric pressure as the carbon dioxide dissolves into the contained water.

Value-added cheese, such as grated or sliced cheddar, are also packaged in modified atmospheres. Grated cheese is normally packed in an atmosphere of 70% N₂ and 30% CO₂ . The use of only 30% CO₂ makes it possible to avoid package collapse.

Product	Hard cheeses	Hard cheeses (sliced)	Soft cheeses
MAPAX Gas mixture	80 - 100% CO2 and 0 - 20% N2	80 - 90% CO2 and 10 - 20% N2	20 - 40% CO2 and 60 - 80% N2
Gas volume per Product weight	50-100 ml per 100 g cheese	50-100 ml per 100 g cheese	50-100 ml per 100 g cheese
Typical shelf-life	2-3 weeks in air 4-10 weeks with MAP	2-3 weeks in air 4-10 weeks with MAP	4-14 days in air 1-3 weeks with MAP
Typical material*	OPA/PE-PA/PE PA/PE	OPA/PE-PA/PE PA/PE	OPA/PE-PA/PE
Typical machine	Deep-draw machine Horizontal flow-pack	Deep-draw machine Horizontal flow-pack	Deep-draw machine Horizontal flow-pack
Storage temp.	+40 to +45 oF	+40 to +45 oF	+40 to +45 oF

*PVC is being replaced by APET or PS/EVOH, PVdC is being replaced by EVOH or OPA.

Cultured products, such as cottage cheese and yogurt, have only recently been packaged in modified atmospheres. However, demands for longer shelf life have led to its use. The shelf life of cottage cheese packed in carbon dioxide can be extended by a week.

Cream and dairy products containing cream rapidly turn sour in carbon dioxide atmospheres. This gas is therefore replaced by nitrogen. By keeping out oxygen, nitrogen prevents rancidity and the growth of aerobic bacteria.