Bacterial population dynamics and decay on leaves of different ages of ready‐to‐use broad‐leaved endive

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Abstract
Summary: Mesophilic, fluorescent, and pectolytic bacteria were quantified on leaves of five different age groups (AG) of broad‐leaved endive (Cichorium endivia var. latifolia) before and after ready‐to‐use (RTU) processing and daily over their 7‐day French ‘sell by’ period. At harvest, significant differences in bacterial population sizes expressed as log10 colony‐forming units (cfu) cm−2 were observed among leaves of the different AG resulting in decreasing contamination from outer (‐ older) to inner (‐ younger) leaves of the head. This persisted throughout storage at 6°C for RTU‐processed leaves separated by age implicating leaf physiology as one of its causes. Leaf age also affected types and frequencies of decay occurring during storage. Although the population sizes of mesophilic, fluorescent and pectolytic bacteria were always positively correlated, the sizes of fluorescent and pectolytic populations could not consistently be predicted from mesophilic ones. Thus fluorescent and pectolytic populations should be quantified independently due to their potential role in decay. Atmospheric changes in the packs resulting from vegetable respiration and microbial activity confirmed the limiting effect of high CO2 and low O2 on the development of spoilage without an effect on bacterial populations sizes. the importance of the effect of leaf AG for plant cultivation and industrial production of RTU salads is discussed.