A combination of high oxygen atmosphere and equilibrium modified atmosphere packaging to improve the keeping quality of red fruits.

When high-barrier material is used to package fresh whole fruit in high oxygen atmospheres, shelf life is limited due to the accumulation of its produced CO2 and its creation of an anaerobic atmosphere. In this study, the effect of the combination of High Oxygen Atmosphere and Equilibrium Modified Atmosphere Packaging was tested on the shelf life of two non-climacteric red fruits, particularly strawberries and raspberries, at 7 degrees C. Herefor, the following packaging systems are compared: the conventional method of packaging in a macroperforated high-barrier film (air conditions) (1), Equilibrium Modified Atmosphere (EMA, i.e. 3-5% O2 and 5-10% CO2-balance N2) (2) and two novel modified atmospheres: High Oxygen Atmosphere (HOA, i.e. > 70% O2-balance N2) in a high-barrier film (3) and HOA in a EMA film with an adjusted film permeability (4). The shelf life of the fruits was determined by evaluating the evolution of the internal oxygen, carbon dioxide and ethylene concentrations in the packages, the microbial and sensorial quality during the storage, the loss of weight due to transpiration and respiration of the fruit and the loss of marketable fruit due to visual decay or to Botrytis growth. The High Oxygen Atmosphere in the EMA film re-established after five days to an equilibrium of 3% O2 and 5% CO2. The High Oxygen Atmosphere in the high-barrier film remained high during the first five days of storage, but decreased then rapidly to anaerobic conditions, resulting in off-flavours and odours. To avoid an accumulation of ethylene inside the high-barrier package, an ethylene adsorbing monolayer was added. Shelf life of strawberries and raspberries, packed in air conditions, was limited by growth of moulds and yeasts, rather than by sensorial unacceptance. On the other hand, sensorial properties limited the shelf life of the fruits packed under modified atmosphere. Especially High Oxygen Atmosphere improved the microbial quality, due to the inhibiting effect on yeasts and moulds. However, when oxygen was depleted and carbon dioxide had accumulated, sensorial quality (odour, taste andfirmness) was deteriorated. As this is not the case with high O2 in an EMA film, the latter can be assumed as a promising configuration for respiring fresh produce, combining the beneficial effect of high O2 and EMAP.