High throughput quality and safety assessment of packaged green produce using two optical oxygen sensor based systems

Two new analytical techniques, the GreenLight™ system for rapid enumeration of total viable counts (TVC) in food homogenates and the Optech™ system for non-destructive sensing of residual O2 in package headspace were applied to examine a total of 206 packages of green produce with the aim to assess their main quality and safety characteristics. Three types of ready-to-eat salads—Iceberg lettuce, Caesar salad & Italian leaf mix salad—packed under different modified atmosphere (5% CO2, 5–60% O2) and stored at 4 °C for up to 10 days were examined by monitoring their TVC and headspace O2, CO2. The new detection methodology was compared with traditional methods showing good correlation with Dansensor gas analyzer for O2 (R2 = 0.9912) and with agar plating ISO4833:2003 method for TVC (R2 = 0.7749). The lowest TVC was achieved in 5% oxygen packed salad while in the other conditions showed no clear improvement. Both systems provide affordable high speed, sample throughput and proved themselves to be useful, convenient and capable of supplying important information about the key physical and biological parameters of individual packs.