MODIFIED ATMOSPHERES IN FILM PACKAGES DELAY SENESCENCE AND DECAY OF FRESH HERBS

The effect of modified atmospheres (MA) produced inside film packages, on the keeping quality of yellowing-susceptible fresh herbs, was examined. The experiments were conducted under simulated conditions of air transport from Israel to Europe, as well as with an actual shipment, during which temperature fluctuations were between 4 and 15°C. Under these conditions, bulk packaging in perforated polyethylene (P.PE)-lined cartons reduced water loss markedly, but were not effective in retarding yellowing and decay of watercress, chives, chervil, sorrel, coriander, dill or parsley. Packaging of these herbs in non-perforated PE (NP.PE)-lined cartons resulted in a remarkable retardation of both yellowing and decay. The beneficial effect of the MA produced in the NP.PE liner, in delaying senescence, could be improved further by a combination with vacuum precooling. The best results for watercress, chives, chervil and sorrel, which are the most yellowing-susceptible herbs, were obtained by packaging them in sealed PE (S.PE)-lined cartons. However, sealed film packaging is applicable only if the temperature during transit and storage is well controlled.

Retardation of yellowing and decay in our experiments was attributed mainly to the accumulation of respiratory CO₂ within the package, rather than to the depletion of oxygen. Thus, chlorophyll degradation of the herbs was delayed effectively when 5% CO₂ in air was applied in a flow-through system. Addition of 10 ppm ethylene to this flow system negated the CO₂ effect partially or completely, depending on the herb species. This implies that the senescence-retarding effect of elevated CO₂ concentrations in green herbs can be attributed mainly to the ability of CO₂ to antagonize ethylene action.