MICROSCOPIC STUDY OF MIGRATION OF MICROBES IN FOOD-PACKAGING PAPER AND BOARD

The microbiological barrier properties of food-packaging paperboards, coated with polyethylene, mineral pigment or a biodegradable polymer a nd of high-density paper were examined with confocal laser scanning mi croscopy, The results show that the spatial distribution of microscopi cally observable bacterial cells was uneven inside the paperboard. The concentration in the interface between the polyethylene coating and t he cellulose fibers was 100-200 times higher than inside the cellulose matrix, The bacteria in the interface and the mineral coating layer g rew in response to access to food and moisture, whereas no growth was observed inside the fiber web, not even after extended exposure for up to 90 days, The paper and paperboards studied contained soluble nutri ents (C:N:P 54:9:1 to 309:3:1) and no measurable antimicrobial activit y, The factor limiting growth and migration of bacteria inside the fib er web was most likely limited access to free water, even under condit ions of extensive wetting. The studied paperboards functioned as effic ient barriers against translocation of microbes, The microbes residing between the paperboard and its polymer coating facing food, was the o nly potential site from which microbes could leak into food. This emph asizes the need for high hygienic quality of surface-sizing chemicals, Mineral-coating pigments were a source of microbes and their applicat ion behind the PE coating facing food is contraindicated.