The authors, writing in Food Control, argue that identification of LM survival points could be of value in terms of optimising pathogen control as part of a HACCP programme.
The microbiology experts found that sites that showed “systematic presence” of LM were the floor of the factory and objects in close contact with it including the sanitary barrier, shoe soles, equipment brackets, stair treads, and small pools of water.
LM was not detected on food contact surfaces, they continued.
Listeriosis is a food-borne disease-causing bacterium can produce infections in susceptible populations such as immuno-depressed people, infants and pregnant women.
The bacterium, LM, usually enters the food through raw materials, water and workers, say the Spanish team.
And the researchers point out that LM is quite resistant to the deleterious effects of freezing, drying, and heating, despite not forming endospores, and can grow between 0 and 45 °C. It also survives for long periods in refrigerated, frozen and dried foods, they added, and shows a high tolerance to acidic conditions and high salt concentrations.
Foods that are more likely to be contaminated with LM include soft cheeses, dairy products, pâtés, sausages, smoked fish, salads, infant cereals, cakes, cream, butter and, in general, refrigerated ready-to-eat products consumed without cooking or reheating, said the authors.
The aim of their research, explained the authors, was to determine the presence and persistence of LM after using two sanitization protocols in different parts of a dessert-processing factory in order to establish microbiological critical control points.
The pathogen specialists carried out sampling for LM detection on various food contact and non-food surfaces; after and before treatment using two different sanitization protocols. Two types of cleaning and disinfection agents were tested.
Protocol A involved sanitizers being applied daily. Protocol B involved sanitizer being applied once every three weeks, with weekly air disinfection performed at weekends under both cleaning systems.
The places where the sanitizers were applied included the pastry preparation, elaboration and packaging areas, said the researchers. The treatments were applied to areas such as cream dispensers, working tables, conveyors, floors, drains, walls, and doors. The removable parts of the equipment from the production lines were cleaned in the washing room, said the team.
The surfaces in contact with food were rinsed with clean water, and dried with single-use flannels. Surfaces not in contact with food were not dried, they added.
Both sanitizing protocols managed to reduce the LM load but did not to eradicate the microorganism completely, found the authors.
LM was detected in 15.2 per cent of the places sampled before sanitizing, 7 per cent after applying protocol A and 5.9 per cent after employing protocol B.
They note the efficiency of cleaning and disinfection products against LM is strongly influenced by the sort of the food matrix present in the environment.
The Spanish team added that their results indicate that infrastructure changes could be useful for reducing the presence of potential pathogens by reducing water condensation.
They note that the floor, and objects in contact with it, should be considered the reservoir for LM and other potential hazardous micro-organisms that can contaminate foods by bioaerosol formation.
And the authors stress that these areas should be included within good-hygiene practices and HACCP systems for bakers and other food processors.
The results obtained through sanitization protocol B, although not statistically significant, suggest that it might be effective at reducing all indicators of microbial contamination, add the authors. “However, further studies will be needed to increase the frequency or number of samples to prove this,” they added.
Source: Food Control
Published online ahead of print: doi:10.1016/j.foodcont.2011.05.017
Title: Effectiveness of two sanitation procedures for decreasing the microbial contamination levels (including Listeria monocytogenes) on food contact and non-food contact surfaces in a dessert-processing factory
Authors: M. Campdepadrós et al.