1. Gaseous environments

2. Controlled atmosphere (CA) storage
Control temperature, oxygen (~2-5%), CO2 (~8-10%)
Slows respiration rate of fruits; preserves oxygen-labile components (ascorbic acid)
Slows growth of psychrotrophic aerobic spoilage organisms; lactic acid spoilage bacteria and yeasts not so much

3. Modified-Atmosphere Vacuum packaging
Good: reduces O2, lowers Eh
Bad: anaerobic pathogens (Bacillus sp., Clostridium sp.)
Modified-Atmosphere Packaging (MAP)
CO2, O2, N2
Shelf life, appearance

4. Rationale for gas mixes
Oxygen:
High  red meats
Low  inhibit aerobic spoilage organisms; decrease respiration of fruits/vegetables
Carbon dioxide
High  Inhibit aerobic spoilage organisms
Lower  5% reduces senescence in produce (high levels are phytotoxic)
Nitrogen; filler gas
Atm: 21% O2, 0.04% CO2, 78% N2

5. Red meat: high O2, high CO2
Ecology shifts from aerobic psychrotrophic organisms to lactic acid bacteria

6. Why use CO2 sometimes but N2 others?