Microbial and sensory quality of fresh processed lettuce salad under high O2 atmosphere throughout the distribution chain

High O-2 atmospheres (higher than 70 kPa O-2) have been recently suggested as an innovation to modified atmosphere packaging (MAP) for fresh processed vegetables to maintain sensory quality and safety. Visual appearance, colour, taste, off-odour, crispness, and microbial growth were monitored in a variety of lettuce salads, packed initially in 95% O-2, combined with the use of a barrier film for packaging. Mixed vegetable salads packed under conventional MAP (3 kPa 02 and 5 kPa CO2) were used as controls. Since temperature changes along the cool chain must be taken into account when quality loss and shelf life of fresh processed vegetables are evaluated, actual documented conditions (i.e. abusive temperatures of 7 and 12degreesC) in the retail sale display were applied. Four days after processing the microbial recommended limit of 10(8) CFU/g for psychrotrophic bacteria was exceeded when product was held at 12degreesC. However, when temperature within retail sale cabinets was 7degreesC, this limit was exceeded almost 6 days after processing. At 7degreesC no significant difference on total bacterial count between high O-2 and conventional atmospheres was observed and a slight difference in sensory quality was found. As expected, the best quality occurred when the lowest temperature was used, although no significant difference was found between high O-2 atmosphere and conventional MAP.