Suitability of FTIR to distinguish pure cultures of problematic mould species from closely related species in the meat industry.

AIMS: The aim of the study was to apply Fourier Transform Infrared spectroscopy (FTIR) as a rapid screening method for moulds in a specific food production environment (cured meat) and to evaluate whether the method was sufficiently accurate to distinguish Penicillium species that constitute a hazard for the food quality and safety (Penicillium solitum and Penicillium nordicum) from closely related species. METHODS AND RESULTS: FTIR was applied to classify the indigenous mycobiota of two production sites for dried and cured meat products in Norway. Results showed that FTIR was suitable to analyse large amounts of data. While correct classification rates varied depending on the species, overall results indicated that FTIR was able to distinguish the undesired mould species P. solitum and P. nordicum from other species and may hence present an option for rapid screening of large numbers of samples to identify changes in mould composition on site. CONCLUSIONS: FTIR presents a potential method for detecting changes in levels of undesired fungi in meat-processing environments. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study that applies FTIR to a specific food production environment and it increases the knowledge on both possibilities and limitations of the method in classification of fungi.

Microbial background flora in small-scale cheese production facilities does not inhibit growth and surface attachment of Listeria monocytogenes.

The background microbiota of 5 Norwegian small-scale cheese production sites was examined and the effect of the isolated strains on the growth and survival of Listeria monocytogenes was investigated. Samples were taken from the air, food contact surfaces (storage surfaces, cheese molds, and brine) and noncontact surfaces (floor, drains, and doors) and all isolates were identified by sequencing and morphology (mold). A total of 1,314 isolates were identified and found to belong to 55 bacterial genera, 1 species of yeast, and 6 species of mold. Lactococcus spp. (all of which were Lactococcus lactis), Staphylococcus spp., Microbacterium spp., and Psychrobacter sp. were isolated from all 5 sites and Rhodococcus spp. and Chryseobacterium spp. from 4 sites. Thirty-two genera were only found in 1 out of 5 facilities each. Great variations were observed in the microbial background flora both between the 5 producers, and also within the various production sites. The greatest diversity of bacteria was found in drains and on rubber seals of doors. The flora on cheese storage shelves and in salt brines was less varied. A total of 62 bacterial isolates and 1 yeast isolate were tested for antilisterial activity in an overlay assay and a spot-on-lawn assay, but none showed significant inhibitory effects. Listeria monocytogenes was also co-cultured on ceramic tiles with bacteria dominating in the cheese production plants: Lactococcus lactis, Pseudomonas putida, Staphylococcus equorum, Rhodococcus spp., or Psychrobacter spp. None of the tested isolates altered the survival of L. monocytogenes on ceramic tiles. The conclusion of the study was that no common background flora exists in cheese production environments. None of the tested isolates inhibited the growth of L. monocytogenes. Hence, this study does not support the hypothesis that the natural background flora in cheese production environments inhibits the growth or survival of L. monocytogenes.

Characterization of the bacterial spoilage flora in marinated pork products.

AIMS: To investigate the microbiota in marinated, vacuum-packed pork and to characterize isolated bacteria with regard to their spoilage potential. METHODS AND RESULTS: Laboratory marinated pork meat and commercial products from three Norwegian producers were examined. Lactic acid bacteria dominated in all products at the expiration date. The flora in marinated products was similar only for products from the same plant. Strains of Lactobacillus algidus, Lactobacillus sakei, Lactobacillus curvatus, Carnobacterium divergens, Carnobacterium maltaromaticum, Leuconostoc mesenteroides, Leuconostoc carnosum and Leuconostoc sp. were isolated and tested for their spoilage potential. Samples inoculated with Lact. algidus or Leuc. mesenteroides were rated as most unpleasant by randomly selected people. A sensory panel scored samples with Lact. algidus highest for sour and intense odour. Lactobacillus algidus was found in products from two out of three production plants. Culture-independent DNA isolation confirmed that cultivation on Blood agar at 20 degrees C yielded a representative picture of the total flora in marinated flintsteak. CONCLUSIONS: Lactobacillus algidus may be an important, but underestimated, spoilage organism that needs to be focused on more when spoilage of vacuum-packed meat is considered. SIGNIFICANCE AND IMPACT OF THE STUDY: Routine microbial testing may have to be revised in order to detect spoilage LAB that are unable to grow under currently used conditions.