Involvement of pseudomonads in deterioration or ‘ready‐to‐use’ salads

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 readyto-use (RTU) processing and daily over their 7-day French 'sell by' period. At harvest. significant differences in bacterial population sizes expressed as log,, colony-forming units (cfu) cm-' 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 CO, and low 0, 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.

Section: Discussioncontrasting

confidence: 52%

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

Jacques¹,

Morris²

1995

“…For broad-leaved endive, the focus of the present study, pectolytic strains of Pseudomonas fluorexens are likely to be responsible for decay in RTU packages (Nguyen-the & Prunier, 1989), although other miscellaneous Gram (-) pectolytic bacteria have been reported to induce decay of packaged endive under experimental conditions (Jacques & Morris, 1993).…”

Section: E Morris DI T Lucottementioning

confidence: 92%

“…To understand the epidemiology of microbial decay of RTU salads, attempts have been made to correlate bacterial population size on fresh plant material before packaging and subsequent decay in storage of sachets (Bolin et al, 1977;Nguyen-the & Prunier, 1989). However, these studies provide information only about the average contamination of a plant and do not indicate leaf-to-leaf variability in microbial contamination.…”

Section: E Morris DI T Lucottementioning

confidence: 99%

“…RTU salads may discolour or decay during storage, posing important losses particularly in countries where the recommended date of limit of consumption is about 1 week after packaging. The physiology of the cut salad tissue as well as its microbial load may influence deterioration during storage (Bolin et af., 1977;Kader, 1986;Nguyen-the & Prunier, 1989), although the relative importance of these factors Authors' address: INRA, Station de Pathologic Vegetale, B.P. 94, 84143 Montfavct cedcx, France.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Dynamics and variability of bacterial population density on leaves of field‐grown endive destined for ready‐to‐use processing

Morris¹,

Lucotte²

1993

To quantify the variability and dynamics of bacterial populations on field-grown broad-leaved endive (Ckhnrium endivia cv. Samy) destined for ready-to-use processing, plants were sown at three dates in 1990 for cultivation during the autumn season in southern France. Densities of populations of total, fluorescent pseudomonad and pectolytic bacteria were determined for entire seedlings in the greenhouse and for outer and inner leaves of plants in the field throughout the season until harvest. On seedlings from the greenhouse, bacteria were always detected but fluorescent and pectolytic bacteria were only sporadically detected and generally composed less than 0.1% of the total population. In the field there were significant differences in total, fluorescent and pectolytic bacterial populations on outer and inner leaves, among different plants of the same age, and among inner leaves sampled at the three different dates of harvest. The variability observed suggests that it is reasonable to pursue development of cultural or industrial sorting methods to reduce the microbial load of endive destined for ready-to-use processing.

“…These changes are, for instance, on mixed salads, both soft rots caused by pectinolytic pseudomonads (Nguyen-The & Prunier, 1989) and discolorations caused by the oxidation of phenolic compounds (Goupy, 1989).…”

Section: Introductionmentioning

confidence: 98%

Effects of controlled atmospheres on microbial spoilage, electrolyte leakage and sugar content of fresh ‘ready‐to‐use’ grated carrots

Carlin¹,

Nguyen-Thé²,

Chambroy³

et al. 1990

Self Cite

The effects of controlled atmospheres (C02 concentrations ranging from 0.03 to 40% and 0 2 concentrations ranging from 21 to lob, measured in pack) were studied on fresh 'ready-to-use' grated carrots, stored at 10°C. High C02 or low 0 2 conditions favour the growth of lactic acid bacteria (LAB) on grated carrots, but not in a sterile carrot medium, and induce an increased potassium ion leakage. A 25% COz and 2% O2 atmosphere improves retention of sugars. Grated carrots were inoculated by a strain of Leuconostoc mesenteroides, which caused increased potassium ion leakage and exudation only under an atmosphere containing 40% C02 and 10% 0 2 .The origin of the spoilage of 'ready-to-use' grated carrots is discussed.