• Assessment and Control of Foodborne Pathogens in Ireland

      Ross, R Paul; Hill, Colin; Murphy, P.; Jordan, Kieran; Arendt, Elke; van Sinderen, Douwe; Morgan, S.M.; Hickey, Rita M.; Maher, M.J.; Kelly, J.; et al. (Teagasc, 2001-05-01)
      Consumers are increasingly demanding food that is free from pathogens, but with less preservatives and additives. As a response to these conflicting demands, current trends in the food industry include minimal processing, and the investigation of alternative inhibitors for use in foods. Additionally, the manufacture of an increasing range of novel foods, and the inclusion of non-dairy ingredients into dairy products, and vice versa, poses additional dangers with respect to safety. Furthermore, the dramatic increase in incidence of food-borne illness internationally, as a result of contamination with food-borne pathogens such as Listeria monocytogenes, is a cause of considerable consumer concern. Bacteriocins are inhibitory peptides produced by a number of Lactic Acid Bacteria which are capable of killing other bacteria. These natural inhibitors have widespread applications in the preservation of foods, since they can kill a number of pathogenic and spoilage bacteria. The broad spectrum bacteriocin Lacticin 3147 (discovered in a previous project and patented - see DPRC No. 3) is produced by Lactococcus lactis subsp. lactis DPC3147, a food-grade strain, similar to strains used for commercial cheese manufacture. Lacticin 3147 is effective in the inhibition of all Gram positive bacteria tested including the food pathogens Listeria monocytogenes and Staphylococcus aureus and food spoilage bacteria such as Clostridia and Bacillus species. As part of this project the bacteriocin Lacticin 3147 was assessed as a food preservative for improving food safety via inhibition of pathogenic organisms. Thus the project plan followed a "twin-track" approach to assessing and controlling the food safety aspects of Irish food. The first of these was designed to investigate the current safety status of Irish dairy products. The second approach involved an attempt to exploit natural antimicrobial substances, including Lacticin 3147, to protect foods from pathogenic bacteria.
    • Control of Cheese Microflora using Bacteriocins.

      Ross, R Paul; Hill, Colin; O'Keeffe, T.; McAuliffe, Olivia; Ryan, Maire; O'Connor, Paula M.; Freyne, T. (Teagasc, 2001-08-01)
      Bacteriocins are proteins, produced by some bacteria which are capable of inhibiting other bacteria. The overall aim of this project was the development and exploitation of bacteriocins such as Lacticin 3147 (produced by a food-grade microorganism), as biological tools to control the microflora of foods. Lacticin 3147-producing strains were evaluated for their ability to improve the microbial quality of a variety of dairy products and in particular, Cheddar cheese. The manipulation of cheese flora using bacteriocins should offer manufacturers greater control in the consistency and quality of the final product, in addition to improving its safety. In concert with these studies, Lacticin 3147 was studied in detail at the molecular level resulting in its biochemical and genetic analysis. These studies have demonstrated the complexity and uniqueness of this potent antimicrobial.
    • Use of Bacteriocins to Improve Cheese Quality and Safety

      Ross, R Paul; Hill, Colin; Ryan, Maire; Cunniffe, Alan; McAuliffe, Olivia; Murray, Deirdre; O'Keefe, Triona; Rea, Mary (Teagasc, 1998-09-01)
      The objectives of this project were to generate, characterise and exploit a range of novel bacteriocin producing starter cultures to improve both the safety and the quality of fermented dairy foods. The main conclusions were as follows: Lacticin 3147 is a broad spectrum bacteriocin which inhibits a wide range of Gram-positive bacteria including lactobacilli, clostridia and Listeria. The bacteriocin has been purified by chromatographic procedures and has been shown to be composed of two peptides, both of which are required for biological activity. The mechanism of action of lacticin 3147 has been elucidated. The entire plasmid encoding lacticin 3147 has been sequenced and the bacteriocin in distinct from any previously characterised lactococcal bacteriocin. The Food Grade introduction of the bacteriocin genes into cheese starters was carried out. Lacticin 3147 producing starters have been used to control the pathogen Listeria monocytogenes on the surface of mould ripened cheese. Lacticin 3147 producing starters have been used to control the non-starter lactic acid bacteria complement in Cheddar cheese during the ripening process. A novel starter system using a bacteriocin (lactococcin)- producing adjunct has been designed which gives increased cell lysis during Cheddar cheese manufacture while ensuring that efficient acid production is not compromised. In summary these studies have found that naturally occurring antimicrobials such as bacteriocins have a wide range of applications in the food industry for improving both the quality and safety of fermented dairy products.