carbon dioxide, and just enough oxygen (8% or less) to keep the plant cells functioning normally; and they use bags whose gas permeability matches the respiration rate of the produce (Too little oxygen and fruits and vegetables switch to anaerobic metabolism, which generates alcohol and other odorous molecules characteristic of fermentation, and causes internal tissue damage and browning.) Home and restaurant cooks can approximate such a controlled atmosphere by packing their produce in closed plastic bags with most of the air squeezed out of them The plant cells consume oxygen and create carbon dioxide, so the oxygen levels in the bags slowly decline However, a major disadvantage of a closed plastic bag is that it traps the gas ethylene, a plant hormone that advances ripening in fruits and induces defensive activity and accelerated aging in other tissues This means that bagged fruits may pass from ripe to overripe too quickly, and one damaged lettuce leaf can speed the decline of a whole head Recently, manufacturers have introduced produce containers with inserts that destroy ethylene and extend storage life (the inserts contain permanganate) A very common commercial treatment that slows both water loss and oxygen uptake in whole fruits and fruit-vegetables — apples, oranges, cucumbers, tomatoes — is to coat them at the packing facility with a layer of edible wax or oil A number of different materials are used, including natural beeswax and carnauba, candellila, and rice-bran waxes and vegetable oils, and such petrochemical by-products as paraffin, polyethylene waxes, and mineral oil These treatments are harmless, but they can make produce surfaces unpleasantly waxy or hard Temperature Control: Refrigeration .. .and one damaged lettuce leaf can speed the decline of a whole head Recently, manufacturers have introduced produce containers with inserts that destroy ethylene and extend storage life (the inserts contain... them at the packing facility with a layer of edible wax or oil A number of different materials are used, including natural beeswax and carnauba, candellila, and rice-bran waxes and vegetable oils, and such petrochemical... and extend storage life (the inserts contain permanganate) A very common commercial treatment that slows both water loss and oxygen uptake in whole fruits and fruit-vegetables — apples, oranges, cucumbers, tomatoes — is to coat them at the packing facility with a layer of