EMBARGOED UNTIL: Tuesday 5/21, 10:45 AM MDT
(Poster Session 178, Paper 2020)
University of Helsinki
University of Helsinki, -null-, Finland
Usually shelf life of vacuum-packaged cooked sausages is about four weeks. This is due to the high hygiene employed during manufacture of cooked sausages and the use of nitrites and salt limiting growth of some spoilage bacteria. In association with an unusual spoilage case, very high numbers (microbial cell numbers over 100 million in one gram of sausage) of spoilage lactic acid bacteria were detected in the end of shelf life. These bacteria were identified as common meat spoilage lactic acid bacteria called Leuconostoc using the next generation sequencing techniques. In order to be able to provide food with high quality and to avoid withdrawals, the company had questions where do spoilage bacteria originate and at which stage of the manufacture they enter the product. At the early stages of the manufacture, leuconostocs did not prevail. They were, however, detected at the high-hygiene packaging area, especially on plastic surfaces. In meat raw materials, leuconostocs were detected only at low levels (<5%) whereas in ready sausage emulsion their abundance increased up to 98% of all sequence reads. If levels of lactic acid bacteria reached one million in a gram of sausage, signs of spoilage became visible and leuconostocs dominated the spoilage microbial communities. This information was useful for the manufacturer enabling focusing of cleaning procedures onto relevant areas. In addition, attention was paid to retention time of sausage emulsion before cooking.
This study was conducted by Dr Jenni Hultman and DVM, PhD student Riitta Rahkila, together with Professor Johanna Björkroth, all from Department of Food Hygiene and Environmental Health, University of Helsinki, Finland.
This work is based on nearly 500 000 sequence reads gathered with the 454 pyrosequencing technique, a tool which has not been utilized in food industry contamination studies before. Results from this study show the suitability of the method for contamination studies. Since 1990s Björkroth lab has been performing this kind of studies with cultivation and ribotyping, technique that takes up to one week before receiving the results. With pyrosequencing cultivation of the cells is not required as only total DNA is needed to gain information on all bacteria in a sample in a fast and efficient manner.
Here the meat production plant was sampled twice: first right after the spoilage problem had been detected and second time after thorough cleaning of the production line. Samples were taken from the parts of the factory where raw meat was handled and from the packaging areas with high hygiene practices. From each room air was sampled with Anderson sampler into MRS+A plates. Swabs (approximately 5x5 cm) were taken from production line surfaces into MRS+A plates and for DNA extraction. Altogether 80 samples were taken during the two sampling rounds. To all DNA extracts from swabs the 16S rRNA gene was PCR amplified and 454 sequenced. In addition, meat samples and samples of the sausage material were taken during the two visits. These were also 454 sequenced together with samples from sausages stored at +6°C until the end of shelf life.
The results can be used in manufacturing meat products with smaller carbon footprint as less meat is wasted as spillage and also the food industry benefits from longer shelf life of products. Spillage of meat, high protein food, has also ethical considerations.