Homepage of Paw Dalgaard  (Revised 7 November 2007)

pad@difres.dk, phone office +45-45252566, phone laboratory +45-45254913.

Employment and background:  

Started at the Danish Institute for Fisheries Research in 1990. Since 1996 senior research scientist in microbiology and quality assurance. Trained as food scientist supplemented with a French M.Sc. in fermentation technology (DEA from Institut National Polytechnique de Lorraine) and a Ph.D. in food preservation (Royal Veterinary and Agricultural University, Copenhagen). Visiting scientist, studying predictive microbiology at University of Tasmania, Australia, in 1992 and in 1998 studied Photobacterium phosphoreum at Scripps Institution of Oceanography, University of California, San Diego, USA.  

Notes from lectures and presentations (download of pdf files)

Hand-out material prepared for conference presentations and lectures at the Technical University of Denmark (DTU, Lyngby) and at Faculty of Life Science, University of Copenhagen (LIFE-KU):

bullet

'Mikrobiologisk kvalitet af fisk og fiskeprodukter' (30 November 2007, course 270009 'Fødevaremikrobiologi', KU-LIFE)
bullet

'Microbial safety and quality of aquatic muscle food' (4-7 November 2007, Atlantic Fisheries Technology Conference, Portland, Maine, USA)
bullet

'Fiskens mikroflora og mikrobielle fordærv'  (10 October 2007, course 300007, lecture given 2002-2007)
bullet

'Fiskebåren sygdom - produkter og agens'  (10 October 2007, course 300007, lecture given 2002-2007)
bullet

"Mikrobiologisk kvalitet af fisk og fiskeprodukter" (14 May 2007, course 150520 'Fødevarekvalitet og sikkerhed: Modul 2 - Kvalitet af råvarer')
bullet

'Packaging of seafood - effect on quality and safety' (9 May 2007, course 270023, lecture given 1999-2007)
bullet

'Fish and shelfish - prediction of shelf-life and safety' (22-23 March 2007, European Fish and Seafood Conference 2007, London, UK)
bullet

'Prædiktiv mikrobiologi' (12 December 2006, course 'Fødevaremikrobiologi' 270009, lecture given 2002-2006)
bullet

'Fisks mikrobiologi' (1 December 2006, course 'Fødevaremikrobiologi' 270009, lecture given 2006)
bullet

'Holdbarhed og opbevaring af fisk og fiskeprodukter' (30 Juni 2006, Kursus i fugtig luft, indeklima og fødevareopbevaring, 29-30. juni, Sandbjerg, Sønderborg)
bullet

'Listeria monocytogenes: Predicting the growth boundary in seafood - a key to comply with new EU regulation'.  Invited presentation at 'New developments to manage microbial seafood safety', 3rd open SEAFOODplus conference, 30-31 May Tromsø, Norway.
bullet 'Koldrøget laks: Forudsigelse af holdbarhed og sikkerhed' (21 April 2006, Kæden fra opdræt af laks til produkt - kvalitet, sundhed og udbytte, Nordisk konference på DTU i Lyngby)
bullet

'Modificeret atmosfære pakning af fiskeprodukter - forudsigelse af holdbarhed og sikkerhed' (19 January 2006,  Workshop on Food with short shelf life, Øresund Food Network)
bullet

'Photobacterium phosphoreum: Bioluminescence and importance for seafood safety and quality' (Invited paper presented at IAFP 2005 within the symposium 'Oceans and human health: Trends and practical tools for seafood safety'. Baltimore, USA, 14-17 August)

bullet

'Fiskens mikroflora og mikrobielle fordærv'  (17 June 2005, course 27501, lecture given 1995-2005)

bullet

'Predictive microbiology (Lecture notes)' and 'Exercise 1' (16 March 2005, course 27751/076018, lecture given 2003-2005)

bullet

'Letkonserverede fiskeprodukter' (19 January  2005, course 27502, lecture given 2000-2005)

bullet

'Prædiktiv mikrobiologi 2' (19 January  2005, course 27502, lecture given 2001-2005)

bullet

'Predictive microbiology - concept, models and software' (27 April 2004, FELFO workshop)

 

Research:

My research at DIFRES is within the area of 'Seafood spoilage and predictive microbiology'. An important part of this research involves development of techniques which allow microbial spoilage and shelf-life of seafood to be the:                       

bulletdetermined by objective indices of quality
bulletpredicted by mathematical models and
bulletextended by targeted inhibition of specific spoilage organisms.

The specific spoilage organisms (SSO) concept is a key component in this research. A multidisciplinary approach is used to identify SSO and to describe the effect of intrinsic and extrinsic parameters on the growth and metabolism of these microorganisms in seafood. The overall objective is to understand the microbial ecology of seafood and to use this understanding for the development of techniques required in quality assurance. Current research focuses on spoilage and safety of modified atmosphere packed seafood, predictive microbiology and Photobacterium phosphoreum (including bioluminescence).

Dalgaard, P. 2006. Microbiology of marine muscle foods. In: Handbook of Food Science, Technology, and Engineering. Chapter 53. Hui, Y. H. (ed.) CRC Press, Boca Raton, FL, USA, pp 53-1 - 53-20.  

Dalgaard, P. 2003. Spoilage of Seafood. In: Encyclopedia of Food Sciences and Nutrition. Caballero, B., Trugo, L., Finglas, P. (Eds.). Elsevier Science Ltd./Academic Press, London, UK. pp. 2462-2471.

Dalgaard, P. 2000. Fresh and lightly preserved seafood. In: Shelf life Evaluation of Foods. 2nd edition. Man, C.M.D. and Jones, A.A. (Eds.) Aspen Publishing Inc. Maryland, USA. pp. 110-139.

P. phosphoreum can produce visible light in seafood. Shown below is a fillet of herring and cooked shrimps inoculated with P. phosphoreum and stored aerobically at 5°C. The products were photographed with and without artificial light.   
Light from electric lamp Bioluminescence produced by the bacteria

Spoilage and safety of modified atmosphere packed seafood:

Spoilage and safety of fresh modified atmosphere packed (MAP) seafood, vacuum packed cold-smoked salmon and cooked and brined MAP shrimps  has been studied. P. phosphoreum was identified as the specific spoilage organism (SSO) limiting the shelf-life of several fresh MAP seafoods as well as batches of vacuum packed cold-smoked salmon. In seafood,  P. phosphoreum produces trimethyleamine (TMA) from trimethyleamine-N-oxide (TMAO) and various biogenic amines from free amino acids. As a result of this metabolic activity the concentration of TMA can be used as a single compound quality index in fresh MAP cod and a multiple compound quality index for vacuum packed cold-smoked salmon has been developed relying on the formation of biogenic amines. In cooked and brined MAP shrimps Carnobacterium spp. seems of importance to spoilage.

Dalgaard, P., H.L. Madsen, N. Samieian, J. Emborg 2006. Biogenic amine formation and microbial spoilage in chilled garfish (Belone belone belone) – effect of modified atmosphere packaging and previous frozen storage. J. Appl. Microbiol. 101, 80-95.

Laursen, B. G., J.J. Leisner and P. Dalgaard 2006. Carnobacterium species: Effect of metabolic activity and interaction with Brochothrix thermosphacta on sensory characteristics of modified atmosphere packed shrimps. J. Agri. Food Chem. 54, 3604-3611 (available on-line).

Mejlholm, O., Bøknæs, N. and Dalgaard, P. (2005) Shelf-life and safety aspects of chilled cooked and peeled shrimps (Pandalus borealis) in modified atmosphere packaging  J. Appl. Microbiol. 99, 66-76.

Dalgaard, P., Vancanneyt, M., Euras Vilalta, N., Swings, J., Fruekilde, P. and Leisner, J.J. 2003. Identification of lactic acid bacteria from spoilage associations of cooked and brined shrimps stored under modified atmospheres at temperatures between 0°C and 25°C. J. Appl. Microbiol. 94, 80-89. 

Emborg, J., B.G. Laursen, T. Rathjen, T. and P. Dalgaard 2002. Microbial spoilage and formation of biogenic amines in fresh and thawed modified atmosphere packed salmon (Salmo salar) at 2 °C. J. Appl. Microbiol.  92, 790-799.

Dalgaard, P. and L.V. Jørgensen 2000. Cooked and brined shrimps packed in a modified atmosphere have shelf life > 7 months at 0 °C, but spoil in 4-6 days at 25 °C. Int. J. Food Sci. Technol. 35, 431-442.

Jørgensen, L.V., Dalgaard, P. and Huss, H.H. 2000. Multiple compound quality index for cold-smoked salmon (Salmo salar) developed by multivariate regression of biogenic amines and pH. J. Agri. Food Chem. 48, 2448-2453.

Jørgensen, L.V., Huss, H.H., Dalgaard, P. 2000. The effect of biogenic amine production by single microbiological cultures and metabiosis on cold-smoked salmon. J. Appl. Microbiol. 89, 920-934.

Dalgaard, P., Munoz, L.G. and Mejlholm, O.1998. Specific inhibition of Photobacterium phosphoreum extends shelf life of modified atmosphere packed cod fillets. J. Food Prot. 61, 1191-1194.

Dalgaard, P., Mejlholm, O., Christiansen, T.J. and H.H. Huss 1997. Importance of Photobacterium phosphoreum in relation to spoilage of MAP fish products. Lett. Appl. Microbiol. 24, 373-378.

The bioluminescence of P. phosphoreum is stimulated by salt as shown below for two pieces of Atlantic salmon without added NaCl (left) and with ~2% added NaCl (right). The same two pieces of salmon were photographed with and without artificial light.     
Light from electric lamp Bioluminescence produced by the bacteria

Predictive microbiology:

Predictive microbiology and particularly prediction of shelf-life and growth of Listeria monocytogenes have been important parts of my research. With Listeria monocytogenes a model including the effect of smoke components and the inhibitory effect of simultaneous growth of lactic acid bacteria was recently developed. Expanding microbial growth models to include the formation of important metaboites such as TMA and biogenic amines is currently being studied. In products where no SSO have been identified, simple relative rates of spoilage (RRS) models allow shelf-life to be predicted at different temperatures. RRS-models have been developed for fresh seafood from tropical waters and for different lightly preserved products. The Seafood Spoilage and Safety Predictor (SSSP) software was developed to facilitate the use of different models to predict growth of Listeria monocytogenes and shelf-life at constant and fluctuating storage temperatures i.e. for time-temperature integration. This software is available free of charge from the SSSP homepage (http://www.dfu.min.dk/micro/sssp/).

Mejlholm, O. and Dalgaard, P. (2007). Modeling and predicting the growth boundary of Listeria monocytogenes in lightly preserved seafood. Journal of Food Protection. February 2007.

Giménez, B. and Dalgaard, P. 2004. Modelling and predicting the simultaneous growth of Listeria monocytogenes and spoilage microorganisms in cold-smoked salmon. Journal of Applied Microbiology. 96, 96-109.  

Ross, T. and Dalgaard, P 2004. Secondary models. In: Modeling Miocrobial Responses in Foods, McKellar, R.C. and Lu, X (eds.), CRC Press, Boca Raton, USA, pp. 63-150.

Dalgaard, P. 2002 . Modelling and predicting the shelf-life of seafood. In: Safety and quality issues in fish processing (Chapter 12). Bremner, H.A. (ed). Woodhead Publishing Ltd. pp.191-219.

Dalgaard, P., P. Buch, and S. Silberg 2002. Seafood Spoilage Predictor – development and distribution of a product specific application software. Int. J. Food Microbiol. 73, 343-349.

Dalgaard, P., Mejlholm, O. and H.H. Huss 1997. Application of an iterative approach for development of a microbial model predicting the shelf-life of packed fish. Int. J. Food Microbiol. 38, 169-179.

Both luminous and non-luminous strains of Photobacterium phosphoreum are found in seafood. Of the four P. phosphoreum cultures below, no light is produced by the culture to the left, whereas the other three cultures glow with very different intensities.   
Light from electric lamp Bioluminescence produced by the bacteria

Photobacterium phosphoreum:

P. phosphoreum is studied to understand and control spoilage in fresh MAP fish including cod, plaice, garfish, salmon and tuna. A specific and sensitive detection method and mathematical models including the effect of temperatures and CO2 levels have been developed to predict shelf-life of products. In addition, mild preservation by targeted inhibition of this SSO was shown to extend product shelf-life considerably. Furthermore, the occurrence and identification of luminous and non-luminous variants of P. phosphoreum have been evaluated. Of particular interest is TMAO reduction, production of histamine and biogenic amines, routes of contamination in seafood processing and new methods for identification and detection.

Emborg, J. and P. Dalgaard (2006) Formation of histamine and biogenic amines in cold-smoked tuna – an investigation of psychrotolerant bacteria from samples implicated in cases of histamine fish poisoning. J. Food Prot. 69, 897-906.

Emborg, J., Laursen, B.G. and Dalgaard, P  (2005). Significant histamine formation in tuna (Thunnus albacares) at 2°C - effect of vacuum and modified atmosphere packaging on psychrotolerant bacteria. Int. J. Food Microbiol. 101, 263-279.

Flodgaard, L.R., Dalgaard, P., Andersen, J.B., Nielsen, K.F., Givskov, M., and L. Gram (2005), Non-bioluminescent strains of Photobacterium phosphoreum produce the cell-to-cell communication signal 3-hydroxy-octanoyl homoserine lactone. Appl. Environ. Microbiol. 71, 2113.2120.

Mejlholm, O. and P. Dalgaard 2002. Antimicrobial effect of essential oils on the seafood spoilage microorganism Photobacterium phosphoreum in liquid media and in fish products. Lett. Appl. Microbiol. 34, 27-31.

Dalgaard, P., Bartlett, D.H. and Haygood, M.G. 1999. Photobacterium phoisphoreum – identification and detection of luminous and non-luminous isolates from seafood and natural marine habitats. In: Food microbiology and food safety into the next millennium, Tuijtelaars et   al. (eds), Proceedings of FoodMicro 1999, Veldhoven, The Netherlansds, pp 160-1164.

Guldager, H.S.; Bøknæs, N.; Østerberg, C., Nielsen, J. and Dalgaard, P. 1998. Thawed cod fillets spoil less rapidly than unfrozen fillets when stored under modified atmosphere at 2oC. J. Food Protect., 61, 1129-1136.

Dalgaard, P., Manfio, G.P. and M. Goodfellow 1997. Classification of Photobacteria associated with spoilage of fish products by numerical taxonomy and pyrolysis mass spectrometry. Zbl. Bakt. 285, 157-168.

Dalgaard, P., O. Mejlholm and H.H. Huss 1996. Conductance method for quantitative determination of Photobacterium phosphoreum in fish products. J. Appl. Bacteriol. 81 57-64.