• Strategies to improve the bacteriocin protection provided by lactic acid bacteria

      O'Shea, Eileen F.; Cotter, Paul D.; Ross, R Paul; Hill, Colin; Department of Agriculture, Food and the Marine; Science Foundation Ireland; 04R and DC; 07/CE/B1368 (Elsevier, 18/01/2013)
      Lactic acid bacteria (LAB) produce a wide variety of antimicrobial peptides (bacteriocins) which contribute to the safety and preservation of fermented foods. This review discusses strategies that have been or could be employed to further enhance the commercial application of bacteriocins and/or bacteriocin-producing LAB for for food use.
    • Streptococcus thermophilus APC151 Strain Is Suitable for the Manufacture of Naturally GABA-Enriched Bioactive Yogurt

      Linares, Daniel M.; O'Callaghan, Tom F.; O'Connor, Paula M.; Ross, R Paul; Stanton, Catherine; Science Foundation Ireland (Frontiers, 23/11/2016)
      Consumer interest in health-promoting food products is a major driving force for the increasing global demand of functional (probiotic) dairy foods. Yogurt is considered the ideal medium for delivery of beneficial functional ingredients. Gamma-amino-butyric acid has potential as a bioactive ingredient in functional foods due to its health-promoting properties as an anti-stress, anti-hypertensive, and anti-diabetic agent. Here, we report the use of a novel Streptococcus thermophilus strain, isolated from the digestive tract of fish, for production of yogurt naturally enriched with 2 mg/ml of gamma-aminobutyric acid (200 mg in a standard yogurt volume of 100 ml), a dose in the same range as that provided by some commercially available gamma-amino-butyric acid supplements. The biotechnological suitability of this strain for industrial production of yogurt was demonstrated by comparison with the reference yogurt inoculated with the commercial CH1 starter (Chr. Hansen) widely used in the dairy industry. Both yogurts showed comparable pH curves [1pH/1t D 0.31􀀀0.33 h􀀀1], viscosity [0.49 Pa-s], water holding capacity [72–73%], and chemical composition [moisture (87– 88%), protein (5.05–5.65%), fat (0.12–0.15%), sugar (4.8–5.8%), and ash (0.74–1.2%)]. Gamma-amino-butyric acid was not detected in the control yogurt. In conclusion, the S. thermophilus APC151 strain reported here provides a natural means for fortification of yogurt with gamma-amino-butyric acid.
    • Structural mechanism and kinetics of in vitro gastric digestion are affected by process-induced changes in bovine milk

      Mulet-Cabero, Ana Isabel; Mackie, Alan R.; Wilde, Peter J.; Fenelon, Mark A.; Brodkorb, Andre; Irish Dairy Levy Research Trust; Teagasc Walsh Fellowship Programme; BBSRC; 2014029; BB/J004545/1 (Elsevier, 2018-03-20)
      Bovine milk is commonly exposed to processing, which can alter the structure, biochemical composition, physico-chemical properties and sensory quality. While many of these changes have been studied extensively, little is known about their effect on digestive behaviour. In this study, heat treatments of pasteurisation at 72 °C for 15 s or Ultra-High-Temperature (UHT) treatment at 140 °C for 3 s and homogenisation at pilot-plant scale were applied to whole milk. The gastric behaviour was investigated using a recently developed semi-dynamic adult in vitro model. The emptied digesta were analysed to assess the nutrient delivery kinetics, changes in microstructure and protein digestion. All samples showed protein aggregation and coagulum formation within the first 15 min of gastric digestion at which time the pH ranged from 5.5 to 6. Homogenised samples creamed regardless of heat treatment, whereas all non-homogenised samples exhibited sedimentation. The consistency of the coagulum of the heated samples was more fragmented compared to those of the non-heated samples. Rheological analysis showed that the higher the temperature of the heat treatment, the softer the obtained coagulum and the higher the protein hydrolysis at the end of digestion. The study also confirmed that gastric emptying of caseins from milk is delayed due to coagulation in the stomach, while β-lactoglobulin was emptied throughout the gastric phase, except for UHT-treated milk. The gastric behaviour also had an impact on the lipid and protein content of the emptied chyme. The homogenised samples seemed to release more nutrients at the end of gastric digestion.
    • Structure and antioxidant activity of Maillard reaction products from α-lactalbumin and β-lactoglobulin with ribose in an aqueous model system

      Jiang, Zhanmei; Brodkorb, Andre; Innovative Research Team of Higher Education of Heilongjiang Province; Program for New Century Excellent Talents in Heilongjiang Province University (Elsevier, 11/02/2012)
      Maillard reaction products (MRPs) were prepared from aqueous model mixtures containing 3% (w/w) ribose and 3% (w/w) of the dairy proteins α-lactalbumin (α-LA) or β-lactoglobulin (β-LG), heated at 95 °C, for up to 5 h. The pH of MRPs decreased significantly during heat treatment of α-LA-Ribose and β-LG-Ribose mixtures from 8.4 to 5.3. The amino group content in MRPs, derived from the α-LA-Ribose and β-LG-Ribose model system, was decreased noticeably during the first hour and did not change thereafter. The loss of free ribose in MRPs was higher for β-LG-Ribose than for α-LA-Ribose. During the Maillard reaction, the concentration of native and non-native α-LA, or β-LG, decreased and the formation of aggregates was observed. Fluorescence intensity of the β-LG-Ribose MRPs reached maximum within 1 h, compared to 2 h for α-LA-Ribose MRPs. Meanwhile, modification of the UV/vis absorption spectra for α-LA and β-LG was mainly due to a condensation reaction with ribose. Dynamic light scattering showed a significant increase in the particle size of the MRPs. Size exclusion chromatography of MRPs revealed the production of both high and low molecular weight material. Electrophoresis of MRPs indicated polymerization of α-LA and β-LG monomers via inter-molecular disulfide bridge, but also via other covelant bonds. MRPs from α-LA-Ribose and β-LG-Ribose exhibited increased antioxidant activities, therefore theses MRPs may be used as natural antioxidants in food products.
    • A study of cryptosporidium parvum in beef

      Duffy, Geraldine; McEvoy, John M.; Moriarty, Elaine M.; Sheridan, James J.; European Union; QLK1 CT 1999 00775 (Teagasc, 2003-07)
      There is increasing concern that foods, particularly those of animal origin, may play a role in the transmission of C ryptosporidium parvum to humans. Studies were undertaken to examine the risk posed by C . parvum in the beef chain.
    • A study on the use of chilling as a critical control point in a beef HACCP plan

      Kinsella, Kathleen; Sheridan, James J.; Rowe, T.; Downey, Gerard; National Development Plan (NDP) (Teagasc, 01/02/2006)
      Investigations were undertaken to establish the critical limits for use of chilling in a Hazard Analysis Critical Control Point (HACCP) system for beef. Information was obtained on the influence of chilling on the survival of bacteria, including the pathogen Salmonella Typhimurium DT104, attached to beef carcass surfaces. In general, a chilling regime could not be identified that gave consistent and meaningful reductions in surface bacterial counts while not seriously compromising the quality of the carcasses in terms of excessive amounts of weight loss. The study concluded that chilling was not a satisfactory process for use as a critical control point (CCP) in beef chilling and could not be recommended to the Irish beef industry for inclusion in a HACCP plan.
    • A study on the use of chilling as a critical control point in a beef HACCP plan.

      Kinsella, Kathleen; Sheridan, James J.; Rowe, T. (Teagasc, 2006-02)
      Investigations were undertaken to establish the critical limits for use of chilling in a Hazard Analysis Critical Control Point (HACCP) system for beef. Information was obtained on the influence of chilling on the survival of bacteria, including the pathogen Salmonella Typhimurium DT104, attached to beef carcass surfaces. In general, a chilling regime could not be identified that gave consistent and meaningful reductions in surface bacterial counts while not seriously compromising the quality of the carcasses in terms of excessive amounts of weight loss. The study concluded that chilling was not a satisfactory process for use as a critical control point (CCP) in beef chilling and could not be recommended to the Irish beef industry for inclusion in a HACCP plan.
    • Subspecies diversity in bacteriocin production by intestinal Lactobacillus salivarius strains

      O'Shea, Eileen F.; O'Connor, Paula M.; Raftis, Emma J.; O'Toole, Paul W.; Stanton, Catherine; Cotter, Paul D.; Ross, R Paul; Hill, Colin; Department of Agriculture, Food and the Marine, Ireland; Science Foundation Ireland; et al. (Landes Bioscience, 2012-10)
      A recent comparative genomic hybridisation study in our laboratory revealed considerable plasticity within the bacteriocin locus of gastrointestinal strains of Lactobacillus salivarius. Most notably these analyses led to the identification of two novel unmodified bacteriocins salivaricin L and salivaricin T produced by the neonatal isolate L. salivarius DPC6488 with immunity, regulatory and export systems analogous to those of abp118, a two-component bacteriocin produced by the well characterized reference strain L. salivarius UCC118. In this addendum we discuss the intraspecific diversity of our seven bacteriocin-producing L. salivarius isolates on a genome-wide level, and more specifically, with respect to their salivaricin loci.
    • Supercritical fluid extraction of veterinary drug residues from meat

      O'Keeffe, Mandy J.; O'Keeffe, Michael; Department of Agriculture, Food and the Marine, Ireland (Teagasc, 1999-10)
      Extraction is a key step in the analysis of food samples for residues of veterinary drugs. Over the last ten years there has been increasing interest in alternatives to the use of organic solvents for sample extraction. The development of supercritical fluid extraction (SFE) for the determination of residues in meat provides alternative methods, which may be automated and which have attractive properties such as avoidance of organic solvents and increased speed of extraction. This project is a jointly-funded United States Department of Agriculture and Department of Agriculture and Food activity with the objective of developing robust SFE procedures suitable for the quantitative recovery of ß-agonists (illegal growth promoters) from animal tissue. Fundamental aspects of SFE in its application to residue analysis are also addressed.
    • Supply Chains Linking Food SMEs in Lagging Rural Regions in Ireland

      Henchion, Maeve; McIntyre, Bridin; Meredith, David; Downey, Gerard; European Commission; QLK5-CT-2000-00841 (Teagasc, 01/04/2005)
      This report reflects the Irish contribution to a 3-year EU-funded research project, SUPPLIERS, which was concerned with the development, innovation, competitiveness and sustainability of food SMEs in lagging rural regions(LRRs) of the EU and Poland. It summarises the results of the research conducted in Ireland, evaluates these findings and makes recommendations to benefit food SMEs located in Ireland’s LRRs. Two regions were selected for study in Ireland. These were the West, comprising counties Galway, Mayo and Roscommon, and the Northwest, comprising counties Donegal, Sligo and Leitrim. Both are classified as Objective 1 regions reflecting their predominantly rural character, economic disadvantage and relative remoteness from urban centres. Three food products were selected for detailed study in each region. Products selected in the West were mushrooms, farmed salmon and speciality foods and, in the Northwest, organic produce, farmed shellfish and prepared consumer foods. This product range encompassed a range of chains from local to international, integrated to fragmented, direct to indirect, providing a basis for comparison and evaluation of different chain structures. This summary report concentrates on the results of four surveys carried out over the course of the study. Producers, intermediaries, commercial customers and support institutions were surveyed.
    • Surface decontamination of meat using thermal processes

      McCann, Máiréad; Sheridan, James J.; Downey, Gerard; European Union (Teagasc, 01/02/2007)
      This study investigated the effectiveness of a novel heat apparatus for decontamination of meat surfaces inoculated with important foodborne pathogens using either steam or dry air.
    • Surface decontamination of meat using thermal processes

      McCann, Máiréad; Sheridan, James J.; Downey, Gerard (Teagasc, 2007-02)
      This study investigated the effectiveness of a novel heat apparatus for decontamination of meat surfaces inoculated with important foodborne pathogens using either steam or dry air.
    • Survival characteristics of monophasic Salmonella Typhimurium 4,[5],12:i:- strains derived from pig feed ingredients and compound feed

      Burns, Ann Marie; Duffy, Geraldine; Walsh, Des; Tiwari, Brijesh; Grant, Jim; Lawlor, Peadar G; Gardiner, Gillian E.; Teagasc Walsh Fellowship Programme; 2011010 (Elsevier, 2015-12-09)
      The presence of Salmonella in animal feed or feed ingredients at the feed mill or on-farm is a cause for concern, as it can be transmitted to food-producing animals and subsequently to humans. The objective of this study was to determine the survival characteristics of five feed ingredient- and feed-derived monophasic Salmonella Typhimurium 4,[5],12:i:- strains. The first part of the study investigated thermal inactivation using an immersed heating coil apparatus. A Weibull model provided a good fit, with low RMSE values (0.04–0.43) and high R2 values (0.93–0.99) obtained. There was considerable inter-strain variation in heat resistance, with D-values ranging from 397.83 to 689 s at 55 °C, 11.35–260.95 s at 60 °C and 1.12 to 6.81 at 65 °C. Likewise, z-values ranged from 2.95 to 5.44 °C. One strain demonstrated a significantly higher thermal tolerance, even though it had been isolated from a meal feed. However, overall the strains investigated do not appear to be that much more heat resistant than Salmonella previously studied. The second part of this study involved assessing the ability of the five Salmonella strains to survive during storage over a 28-day period in pelleted weaner pig feed treated with 0.3% sodium butyrate. While a mean reduction in the Salmonella count of 0.79 log10 CFU was seen in the treated feed during the storage period, a reduction (albeit only 0.49 log10 CFU) was also observed in the control feed. Although there was no overall effect of treatment, sodium butyrate resulted in reductions in Salmonella counts of 0.75 and 0.22 log10 CFU at days 14 and 24 of feed storage, respectively but at the end of the 28-day storage period counts were 0.25 log10 CFU higher in the treated feed. Therefore, the sodium butyrate used appears unsuitable as an agent for feed treatment perhaps due to the protective coating on the particular feed additive used. Overall, the results of this study enhance knowledge about the behaviour and survival characteristics of monophasic S. Typhimurium 4,[5],12:i:- strains in animal feed and may assist the feed industry and pig producers in implementing effective intervention strategies for their control.
    • The survival of added escherichia coli O157:H7 in natural mineral water and its products and the development of a rapid method for enumeration of the heterotrophic bacteria in natural mineral water

      Kerr, Marie; Fitzgerald, Margaret; Sheridan, James J. (Teagasc, 2000-12)
      The consumption of natural mineral water is rapidly growing and outpacing all other beverages on a global scale. In Europe, bottled water already has a bigger market share than carbonated soft drinks. Yet there is only a limited availability of information on the microbiological safety and quality of bottled natural mineral waters sold within the European Community. As natural mineral water does not receive any bacteriocidal treatment prior to bottling, the risk of pathogen contamination is a public health concern. Pathogen contamination may occur as a result of over exploitation of natural mineral water resources i.e. over abstraction by commercial bottling companies may lead to disturbance of the water table causing contaminated surface water to be drawn down into ground water supplies (Green and Green 1994). Such contamination was implicated in an outbreak of cholera associated with the consumption of bottled natural mineral water in Portugal in 1974 (Blake et al. 1977). The transport and dissemination of E. coli and enterococci in a limestone aquifer had been demonstrated by Personné et al. (1998), confirmation that E. coli can survive the transitory period from the surface to underground water supplies, thus raising the question of E. coli O157:H7 with its low infective dose < 10 cells (Willshaw et al. 1994 and Tilden et al. 1996) surviving the transitory period from surface to a natural mineral water aquifer.
    • Symposium review: Genomic investigations of flavor formation by dairy microbiota

      McAuliffe, Olivia; Kilcawley, Kieran N; Stefanovic, Ewelina; Teagasc Walsh Fellowship programme; Dairy Research Ireland; IRCSET; EU Marie Curie Actions Clarin Co-Fund (Elsevier, 2018-10-19)
      Flavor is one of the most important attributes of any fermented dairy product. Dairy consumers are known to be willing to experiment with different flavors; thus, many companies producing fermented dairy products have looked at culture manipulation as a tool for flavor diversification. The development of flavor is a complex process, originating from a combination of microbiological, biochemical, and technological aspects. A key driver of flavor is the enzymatic activities of the deliberately inoculated starter cultures, in addition to the environmental or “nonstarter” microbiota. The contribution of microbial metabolism to flavor development in fermented dairy products has been exploited for thousands of years, but the availability of the whole genome sequences of the bacteria and yeasts involved in the fermentation process and the possibilities now offered by next-generation sequencing and downstream “omics” technologies is stimulating a more knowledge-based approach to the selection of desirable cultures for flavor development. By linking genomic traits to phenotypic outputs, it is now possible to mine the metabolic diversity of starter cultures, analyze the metabolic routes to flavor compound formation, identify those strains with flavor-forming potential, and select them for possible commercial application. This approach also allows for the identification of species and strains not previously considered as potential flavor-formers, the blending of strains with complementary metabolic pathways, and the potential improvement of key technological characteristics in existing strains, strains that are at the core of the dairy industry. An in-depth knowledge of the metabolic pathways of individual strains and their interactions in mixed culture fermentations can allow starter blends to be custom-made to suit industry needs. Applying this knowledge to starter culture research programs is enabling research and development scientists to develop superior starters, expand flavor profiles, and potentially develop new products for future market expansion.
    • Symposium review: Lactococcus lactis from nondairy sources: Their genetic and metabolic diversity and potential applications in cheese

      McAuliffe, Olivia; Teagasc Walsh Fellowship Programme; Dairy Research Ireland; EU Marie Curie Actions Clarin Co-Fund; Irish Research Council for Science, Engineering and Technology; European Union (Elsevier, 2018-02-13)
      The widespread dissemination of species of the lactic acid bacteria (LAB) group in different environments testifies to their extraordinary niche adaptability. Members of the LAB are present on grass and other plant material, in dairy products, on human skin, and in the gastrointestinal and reproductive tracts. The selective pressure imparted by these specific environments is a key driver in the genomic diversity observed between strains of the same species deriving from distinct habitats. Strains that are exploited in the dairy industry for the production of fermented dairy products are often referred to as “domesticated” strains. These strains, which initially may have occupied a nondairy niche, have become specialized for growth in the milk environment. In fact, comparative genome analysis of multiple LAB species and strains has revealed a central trend in LAB evolution: the loss of ancestral genes and metabolic simplification toward adaptation to nutritionally rich environments. In contrast, “environmental” strains, or those from raw milk, plants, and animals, exhibit diverse metabolic capabilities and lifestyle characteristics compared with their domesticated counterparts. Because of the limited number of established dairy strains used in fermented food production today, demand is increasing for novel strains, with concerted efforts to mine the microbiota of natural environments for strains of technological interest. Many studies have concentrated on uncovering the genomic and metabolic potential of these organisms, facilitating comparative genome analysis of strains from diverse environments and providing insight into the natural diversity of the LAB, a group of organisms that is at the core of the dairy industry. The natural biodiversity that exists in these environments may be exploited in dairy fermentations to expand flavor profiles, to produce natural “clean label” ingredients, or to develop safer products.
    • Symposium review: Structure-function relationships in cheese

      Lamichhane, Prabin; Kelly, Alan L.; Sheehan, Jeremiah J.; Dairy Levy Trust; Teagasc Walsh Fellowship Programme; Ornua; RMIS6259 (Elsevier, 2017-10-18)
      The quality and commercial value of cheese are primarily determined by its physico-chemical properties (e.g., melt, stretch, flow, and color), specific sensory attributes (e.g., flavor, texture, and mouthfeel), usage characteristics (e.g., convenience), and nutritional properties (e.g., nutrient profile, bioavailability, and digestibility). Many of these functionalities are determined by cheese structure, requiring an appropriate understanding of the relationships between structure and functionality to design bespoke functionalities. This review provides an overview of a broad range of functional properties of cheese and how they are influenced by the structural organization of cheese components and their interactions, as well as how they are influenced by environmental factors (e.g., pH and temperature).
    • Synergistic Nisin-Polymyxin Combinations for the Control of Pseudomonas Biofilm Formation

      Field, Des; Seisling, Nynke; Cotter, Paul D.; Ross, R Paul; Hill, Colin; Science Foundation Ireland; TIDA14/TIDA/2286; 10/IN.1/B3027; 11/PI/1137; SFI/12/RC/2273 (Frontiers, 26/10/2016)
      The emergence and dissemination of multi-drug resistant pathogens is a global concern. Moreover, even greater levels of resistance are conferred on bacteria when in the form of biofilms (i.e., complex, sessile communities of bacteria embedded in an organic polymer matrix). For decades, antimicrobial peptides have been hailed as a potential solution to the paucity of novel antibiotics, either as natural inhibitors that can be used alone or in formulations with synergistically acting antibiotics. Here, we evaluate the potential of the antimicrobial peptide nisin to increase the efficacy of the antibiotics polymyxin and colistin, with a particular focus on their application to prevent biofilm formation of Pseudomonas aeruginosa. The results reveal that the concentrations of polymyxins that are required to effectively inhibit biofilm formation can be dramatically reduced when combined with nisin, thereby enhancing efficacy, and ultimately, restoring sensitivity. Such combination therapy may yield added benefits by virtue of reducing polymyxin toxicity through the administration of significantly lower levels of polymyxin antibiotics.
    • Synthesis of trypsin-resistant variants of the Listeria-active bacteriocin salivaricin P

      O'Shea, Eileen F.; O'Connor, Paula M.; Cotter, Paul D.; Ross, R Paul; Hill, Colin; Department of Agriculture, Food and the Marine, Ireland; Science Foundation Ireland; Teagasc Walsh Fellowship Programme (American Society for Microbiology, 25/06/2010)
      Two-component Salivaricin P-like bacteriocins have demonstrated potential as antimicrobials capable of controlling infections in the gastrointestinal tract (GIT). The anti-Listeria activity of salivaricin P is optimal when the individual peptides, Sln1 and Sln2, are added in succession in a 1:1 ratio. However, as degradation by digestive proteases may compromise the functionality of these peptides within the GIT we investigated the potential to create salivaricin variants with enhanced resistance to the intestinal protease, trypsin. A total of 11 variants of the salivaricin P components were generated in which conservative modifications at the trypsin-specific cleavage sites were explored in order to protect the peptides from trypsin degradation while maintaining their potent antimicrobial activity. Analysis of these variants revealed that eight were resistant to trypsin digestion while retaining antimicrobial activity. Combining the complementary trypsin resistant variants Sln1-5 and Sln2-3 resulted in a MIC50 of 300 nM against Listeria monocytogenes, a 3.75-fold reduction in activity compared to wild-type salivaricin P. This study demonstrates the potential of engineering bacteriocins variants which are resistant to specific protease action but which retain significant antimicrobial activity.
    • Targeting the Microbiota to Address Diet-Induced Obesity: A Time Dependent Challenge

      Clarke, Siobhan F.; Murphy, Eileen F.; O'Sullivan, Orla; Ross, R Paul; O'Toole, Paul W.; Shanahan, Fergus; Cotter, Paul D.; Science Foundation Ireland; Alimentary Health Ltd (PLOS, 07/06/2013)
      Links between the gut microbiota and host metabolism have provided new perspectives on obesity. We previously showed that the link between the microbiota and fat deposition is age- and time-dependent subject to microbial adaptation to diet over time. We also demonstrated reduced weight gain in diet-induced obese (DIO) mice through manipulation of the gut microbiota with vancomycin or with the bacteriocin-producing probiotic Lactobacillus salivarius UCC118 (Bac+), with metabolic improvement achieved in DIO mice in receipt of vancomycin. However, two phases of weight gain were observed with effects most marked early in the intervention phase. Here, we compare the gut microbial populations at the early relative to the late stages of intervention using a high throughput sequencing-based analysis to understand the temporal relationship between the gut microbiota and obesity. This reveals several differences in microbiota composition over the intervening period. Vancomycin dramatically altered the gut microbiota composition, relative to controls, at the early stages of intervention after which time some recovery was evident. It was also revealed that Bac+ treatment initially resulted in the presence of significantly higher proportions of Peptococcaceae and significantly lower proportions of Rikenellaceae and Porphyromonadaceae relative to the gut microbiota of L. salivarius UCC118 bacteriocin negative (Bac-) administered controls. These differences were no longer evident at the later time. The results highlight the resilience of the gut microbiota and suggest that interventions may need to be monitored and continually adjusted to ensure sustained modification of the gut microbiota.