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Probiotics in fermented sausages
Meat Science 80 (2008) 75–78
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Meat Science journal homepage: www.elsevier.com/locate/meatsci
Review
Probiotics in fermented sausages Luc De Vuyst, Gwen Falony, Frédéric Leroy * Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Department of Applied Biological Sciences and Engineering, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
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Article history: Received 3 March 2008 Received in revised form 29 May 2008 Accepted 30 May 2008
Keywords: Probiotics Fermented sausage Lactic acid bacteria
a b s t r a c t Probiotic foods receive market interest as health-promoting, functional foods. They have been introduced in a wide range of food industries. However, commercial application of probiotic microorganisms in fermented sausages is not common yet. There are both advantages and disadvantages connected to fermented meat matrices. They are adequate for the carriage of probiotic bacteria since they are usually not or only mildly heated and may promote the survival of probiotic bacteria in the gastrointestinal tract. In contrast, bacterial viability may be reduced due to the high content in curing salt and the low water activity and pH. Therefore, results are expected to be strain-dependent. Up till now, several approaches have been followed but most results are too preliminary to be able to evaluate the effect of probiotic fermented meats on human health. Candidate probiotic strains have been obtained through screening for technological requirements among bacteria that are naturally present in the meat or that originate from meat starter cultures. Alternatively, existing probiotic bacteria have been applied in meat products. Finally, the evaluation of the end-products needs to deal with both health effects and technological characteristics, for instance through human intervention studies and taste panels, respectively. Ó 2008 Elsevier Ltd. All rights reserved.
Contents 1. 2. 3. 4. 5.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Probiotic microorganisms and health benefits . . . . . . . . . . . . . . . . . . . . . . . . . Fermented meat as a carrier for probiotic bacteria . . . . . . . . . . . . . . . . . . . . . Evaluation of healthiness and overall quality of probiotic fermented meats . Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1. Introduction Probiotic foods are a group of health-promoting, so-called functional foods, with large commercial interest and growing market shares (Arvanitoyannis & van Houwelingen-Koukaliaroglou, 2005; Parvez, Malik, Ah Kang, & Kim, 2006; Senok, Ismaeel, & Botta, 2005). In general, their health benefits are based on the presence of selected viable strains of lactic acid bacteria (LAB), that, when taken up in adequate amounts, confer a health benefit on the host (FAO/WHO, 2001). They are administered mostly through the consumption of fermented milks or yoghurts (FAO/WHO, 2001; Makras, Avonts, & De Vuyst, 2004). In addition to their common use in the dairy industry, probiotic LAB strains may be used in other food products, including fermented meats (Hammes & Her* Corresponding author. Tel.: +32 2 6293245; fax: +32 2 6292720. E-mail address: fl[email protected] (F. Leroy). 0309-1740/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2008.05.038
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tel, 1998; Incze, 1998; Jiménez-Colmenero, Carballo, & Cofrades, 2001; Kröckel, 2006; Leroy, Verluyten, & De Vuyst, 2006; Työppönen, Petäjä, & Mattila-Sandholm, 2003). Although the concept is not new, only few manufacturers consider the use of fermented sausages as carriers for probiotic LAB (Arihara, 2006). Since meat products are seldom perceived as ‘‘healthy foods”, due to the perceived image of meat and its controversial nutrient profiling clause with respect to the presence of nitrite, salt, and fat, their marketing potential may be compromised (Lücke, 2000). In addition, the more artisan orientation of sausage manufacturers as compared to the dairy industry, the larger variety of products, and a number of uncertainties concerning technological, microbiological, and regulatory aspects seem to be problematic (Kröckel, 2006; Ross, Desmond, Fitzgerald, & Stanton, 2005). If any health claims are to be taken seriously, the application of probiotic LAB must in all cases be based on a careful selection procedure. This requires enhanced scientific research efforts dealing with the use of probiotics in
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fermented meats, taking into account that probiotics are and remain food constituents that are in no case to be considered as drugs or therapeutic agents. Much attention has been paid to the contribution of probiotic strains as meat starter cultures to improve food safety and little to the introduction of beneficial health effects (Leroy et al., 2006). This paper gives an overview of the limited amount of research activities that have previously explored the potential of probiotic LAB strains in fermented meats. 2. Probiotic microorganisms and health benefits Up to now, mainly bacteria belonging to the genera Lactobacillus and Bifidobacterium have been used or considered for use as probiotics, besides other bacteria (mostly belonging to the group of LAB) and some yeasts (Table 1). Historical data indicate that lactobacilli and bifidobacteria are safe for human use (Reid, 2005). Although minor side effects of the use of probiotics have been reported, infections with probiotic bacteria rarely occur and invariably only in diseased or immunocompromised patients (Gueimonde, Frias, & Ouwehand, 2006; Marteau, 2002; Reid, 2005; Vankerckhoven et al., 2008). Throughout the years, several selection criteria for probiotics have been formulated (Table 2). It should, however, be stressed that probiotic strain characteristics such as survival of the passage through the upper gastrointestinal tract, thus resisting the action of gastric juice, bile salts, and digestive enzymes, are not enough to call a certain microbial strain probiotic. According to the WHO/FAO definition, the main criterion for a probiotic strain should be the fact that it confers a health benefit on the host (FAO/WHO, 2001). This benefit can only be demonstrated through well-designed, randomized, double blind, placebo-controlled, multi-centre human trials, of which the results are published in peerreviewed international scientific journals (Guarner & Schaafsma, 1998; Makras et al., 2004; Mercenier, Pavan, & Pot, 2003; Salminen Table 1 Examples of microbial strains that are commercially used as probiotics [partly based on data from Collins and Gibson (1999), Makras et al. (2004) and Senok et al. (2005)] Microbial strain Lactobacilli Lactobacillus casei Imunitass (DN-114 001) Lactobacillus casei Shirota (YIT 9029) Lactobacillus johnsonii La1 (NCC 533) Lactobacillus plantarum 299v Lactobacillus rhamnosus GG (ATCC 53103) Bifidobacteria Bifidobacterium animalis subsp. lactis Bb12 Bifidobacterium animalis subsp. lactis Bifidus Actiregularis (DN 173-010) Bifidobacterium breve Yakult Bifidobacterium longum BB 536 Mixtures of lactic acid bacteria VSL#3 (mixture of eight strains) Other bacteria Escherichia coli Nissle 1917 Yeasts Saccharomyces boulardii
Brand name
Target application
Actimel
Immune response
Yakult
Gut health, digestive system, natural defense Gut health, natural defense
LC1 ProViva Gefilus, Vifit, . . .
Digestive system Gastro-intestinal health, immune response
Various brand names Activia
Gut microbiota, immune system
Bifiene Various brand names (yoghurt, powder)
Digestive system/gut microbiota Gut microbiota, immune system
VSL#3 (powder)
Biotherapeutic agent (irritable bowel syndrome, bowel diseases)
Mutaflor (suspension)
Biotherapeutic agent (gut microbiota, bowel diseases)
Enterol (pills)
Biotherapeutic agent (diarrhea, Clostridium difficile)
Gut transit
Table 2 Selection criteria for probiotics [partly based on data from Makras et al. (2004)] – Survival of the passage of the upper gastrointestinal tract (resistance to gastric acid, bile salts, and proteolytic enzymes; activity during transit from stomach to colon) – Interaction with the resident microbiota (ability to transiently adhere to the intestinal epithelium and colonize the colon; no significant effect on the dominant microbiota; effect on the numbers and diversity of the endogenous Lactobacillus and Bifidobacterium species) – Beneficial effect on the function of the host (probiotic-host interactions; prevention of the risk of disease) – Resistance towards technological processing (e.g., effects of food matrix, food ingredients, and mechanical and heat treatments) and storage (e.g., refrigeration and duration) – High safety profile and excellent tolerance (no risk group II LAB species, no Dlactic acid)
et al., 1998). Furthermore, it should be stressed that health effects are strain-dependent, and extrapolation of existing data from closely related microorganisms is not sufficient and even not acceptable to identify a strain as probiotic (Falony & De Vuyst, 2007; Makras et al., 2004; Reid, 2005). Precise identification and characterization of the probiotic strain used at genus, species, and even strain level, using internationally accepted state-of-the-art methodologies, is the required first step in every process of development of probiotic food products (Reid, 2005). Other steps include the investigation of physiological characteristics and technological requirements, the unravelling of underlying mechanisms of action, and the demonstration of human benefits (Dunne et al., 2001; Maldonado Galdeano, de Moreno de LeBlanc, Vinderola, Bibas Bonet, & Perdigón, 2007; Rastall et al., 2005; Santosa, Farnworth, & Jones, 2006; Saxelin, Tynkkynen, Mattila-Sandholm, & de Vos, 2005; Servin & Coconnier, 2003). For instance, in vitro pathogen inhibition studies might help to elucidate the mechanisms behind a probiotic anti-pathogen effect, but in vitro inhibition of pathogens by a probiotic by no means guarantees its functionality in the complex human gut ecosystem. A wide variety of beneficial health effects have been attributed to probiotics and shown to be strain-dependent (Table 3). Some of the well-established claimed effects include the shortening of intestinal transit time and the relief of lactose maldigestion. Proof of claims related to antibiotic-associated and travellers’ diarrhoea and related to immune response is sometimes controversial. Claims related to cancer prevention or the effect on blood cholesterol levels, however, need further scientific backup to achieve consensus (Gill & Guarner, 2004). Probiotics can influence human health on three levels, in a strain-specific manner: (i) by interacting with other microorganisms present on the site of action (competition for nutrients, production of antimicrobial agents, competitive exclusion), (ii) by strengthening mucosal barriers, and/or (iii) by affecting the immune system of the host (O’Hara & Shanahan, 2007). 3. Fermented meat as a carrier for probiotic bacteria Dry fermented meat products are usually not or only mildly heated, which is adequate for the carriage of probiotic bacteria (Ammor & Mayo, 2007; Arihara, 2006). In addition, there is reason to believe that the sausage matrix protects the survival of probiotic lactobacilli through the gastrointestinal tract (Klingberg & Budde, 2006). However, the potential negative impact of the meat environment on cell viability must be taken into account, in particular with respect to its high content in curing salt and its low pH and water activity due to acidification and drying. In general, cell viability in a fermented meat environment will most likely be strain-dependent. Therefore, the choice of appropriate microorganisms to be applied as probiotic strains in a fermented meat matrix
L.D. Vuyst et al. / Meat Science 80 (2008) 75–78 Table 3 Health-promoting effects of probiotics [partly based on data from FAO/WHO (2001), Mercenier et al. (2003), Naidu et al. (1999) and Parvez et al. (2006); Sanders (1998); Sanders and Huis in’t Veld (1999)] – Improved food digestion (e.g. proteins, dietary polysaccharides) – Reduction of lactose maldigestion – Supply and bioavailability of nutrients and growth factors (e.g. vitamins, minerals) – Maintenance and balancing of the colon microbiota – Reduction of (the risk of) intestinal disturbances (gastrointestinal infections, constipation) – Reduction of the risk and duration of diarrhoea (rotavirus, acute infectious, antibiotic-associated, Clostridium difficile-associated, travellers’ diarrhoea) – Inhibition of undesirable and pathogenic bacteria (orogastrointestinal infections caused by Streptococcus mutans, Helicobacter pylori, E. coli, Salmonella Typhimurium, Clostridium difficile; urinary tract infections; respiratory tract infections) – Modulation/stimulation of the immune system (cell-mediated and antibodymediated effects) – Reduction of the risk of atopic diseases and allergies (asthma, hay fever, food allergy, eczema, dermatitis) – Beneficial effects on functional bowel disorders (irritable bowel syndrome) – Beneficial effects on inflammatory bowel diseases (pouchitis, ulcerative colitis, Crohn’s disease) – Anti-carcinogenic activities – Lowering of blood serum cholesterol levels
will be important. One obvious possibility is the use of bacteria that are commonly associated with the meat environment and that possess the appropriate physiological requirements and healthpromoting properties. Such bacteria can be obtained by screening natural sausage isolates (Klingberg, Axelsson, Naterstad, Elsser, & Budde, 2005; Papamanoli, Tzanetakis, Litopoulou-Tzanetaki, & Kotzekidou, 2003; Pennacchia et al., 2004; Pennacchia, Vaughan, & Villani, 2006; Rebucci et al., 2007; Villani et al., 2005) or existing commercial meat starter cultures (Erkkilä & Petäjä, 2000) for probiotic properties. Several candidate strains have thus been obtained. As an example, the commercial meat starter strains Lactobacillus sakei Lb3 and Pediococcus acidilactici PA-2 may be of interest because of their survival capacities under simulated gastrointestinal conditions (Erkkilä & Petäjä, 2000). Likewise, isolates of Lactobacillus casei/paracasei from sausages fermented with L. casei, L. paracasei, L. rhamnosus, and L. sakei were screened for relevant properties (Rebucci et al., 2007). The latter properties included viability in artificial gastric juice and intestinal fluid, in vitro adhesion to human intestinal cell lines, organic acid production, and pathogen inactivation. In addition, several L. plantarum sausage isolates were found to have appreciable adhesion rates towards Caco-2 cell lines and were considered as better adhesive bacteria than Lactobacillus brevis and L. paracasei-group sausage isolates (Pennacchia et al., 2006). However, the demonstration of such properties does not necessarily lead to the consolidation of health-promoting properties, in particular because human studies are generally missing (see below). Alternatively, the performance of strains with documented health-promoting properties may be investigated in a fermented meat environment. Since such strains are usually human intestinal isolates, they should be able to compete with the natural meat microbiota in an environment which is not their natural habitat. They need thus to be able to survive the fermentation and drying process as well as refrigeration and storage conditions, and, preferably, be able to grow to numbers that enable the display of health-promoting effects. In this way, several lactobacilli of human intestinal origin have been shown to survive the sausage manufacturing process and can be detected in high numbers in the end-product (Arihara et al., 1998; Erkkilä et al., 2001a, Erkkilä, Suihko, Eerola, Petäjä, & Mattila-Sandholm, 2001b; Muthukumarasamy & Holley, 2006, 2007; Pidcock, Heard, & Henriksson, 2002; Sameshima et al., 1998). Unfortunately, most research concerning this strategy focuses on the survival of the
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added species in the meat matrix and its influence on the technological and sensory characteristics of the final product and not on health effects as such. Also, focus was on pathogen inactivation, as probiotic strains with additional food safety assets could confer added value to healthy fermented meat products. For instance, Lactobacillus reuteri ATCC 55730 and Bifidobacterium longum ATCC 15708 increased inactivation of Escherichia coli O157:H7 during sausage manufacturing (Muthukumarasamy & Holley, 2007). Lactobacillus rhamnosus FERM P-15120 and L. paracasei subsp. paracasei FERM P-15121 inhibited growth and enterotoxin production of Staphylococcus aureus to the same extent as a commercial L. sakei starter culture (Sameshima et al., 1998). In contrast, L. acidophilus FERM P-15119 could not satisfactorily decrease Staph. aureus numbers, indicating the importance of careful strain selection with respect to both health-promoting and food safety properties. 4. Evaluation of healthiness and overall quality of probiotic fermented meats In contrast to the successes obtained in the dairy industry, human studies using probiotic fermented meats are very scarce up to now. Such human studies are, however, crucial in the validation process required for the confirmation of the eventual functionality of probiotic fermented sausages. As a rare example, the effect of the daily consumption of 50 g of probiotic sausage containing L. paracasei LTH 2579 on immunity and blood serum lipids was investigated in healthy volunteers during several weeks (Jahreis et al., 2002). Results were only moderately successful. Modulation of various aspects of host immunity was observed, but there was no significant influence on the serum concentration of different cholesterol fractions and triacylglycerides. In faecal samples, a statistically significant increase in the numbers of L. paracasei LTH 2579 was observed for some but not all volunteers. Besides contributing to human health, probiotic fermented meats need to be of sufficient commercial value. Therefore, a primary requirement remains – as for any fermented meat – the sensory and technological aspects of the end-product. Negative side effects on the overall quality of the obtained fermented meats can not be tolerated and evaluation of such effects is primordial. For instance, it has been shown in Northern European sausage that the (potential) probiotic strains L. rhamnosus GG, L. rhamnosus LC705, L. rhamnosus E-97800, and L. plantarum E-98098 do not negatively affect the technological or sensory properties of the end-product, with a (minor) exception for L. rhamnosus LC-705 (Erkkilä et al., 2001a, 2001b). When applying the intestinal isolates L. paracasei L26 and Bifidobacterium lactis B94 in conjunction with a traditional meat starter culture, no negative impact on the sensory properties of the product was noticed (Pidcock et al., 2002). Also, the use of alginate-microencapsulation of L. reuteri ATCC 55730 did not result in differences concerning sensory quality (Muthukumarasamy & Holley, 2006). 5. Conclusions Full assessment of the probiotic effects of fermented sausages on human health is not possible yet. Although probiotic meat products are being marketed since 1998 by German and Japanese producers (Arihara, 2006), controversy about their usefulness remains, due to the preliminary nature of most scientific results obtained. Therefore, more research is needed to justify the launch of new probiotics and of probiotic fermented sausages, in particular with respect to human studies. Importantly, this research should rigorously follow the guidelines formulated by the FAO/WHO (2002), including detailed identification of the strain and an approved beneficial health effect of the food product. Only such an approach will
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Contents lists available at ScienceDirect
Meat Science journal homepage: www.elsevier.com/locate/meatsci
Review
Probiotics in fermented sausages Luc De Vuyst, Gwen Falony, Frédéric Leroy * Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Department of Applied Biological Sciences and Engineering, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
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Article history: Received 3 March 2008 Received in revised form 29 May 2008 Accepted 30 May 2008
Keywords: Probiotics Fermented sausage Lactic acid bacteria
a b s t r a c t Probiotic foods receive market interest as health-promoting, functional foods. They have been introduced in a wide range of food industries. However, commercial application of probiotic microorganisms in fermented sausages is not common yet. There are both advantages and disadvantages connected to fermented meat matrices. They are adequate for the carriage of probiotic bacteria since they are usually not or only mildly heated and may promote the survival of probiotic bacteria in the gastrointestinal tract. In contrast, bacterial viability may be reduced due to the high content in curing salt and the low water activity and pH. Therefore, results are expected to be strain-dependent. Up till now, several approaches have been followed but most results are too preliminary to be able to evaluate the effect of probiotic fermented meats on human health. Candidate probiotic strains have been obtained through screening for technological requirements among bacteria that are naturally present in the meat or that originate from meat starter cultures. Alternatively, existing probiotic bacteria have been applied in meat products. Finally, the evaluation of the end-products needs to deal with both health effects and technological characteristics, for instance through human intervention studies and taste panels, respectively. Ó 2008 Elsevier Ltd. All rights reserved.
Contents 1. 2. 3. 4. 5.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Probiotic microorganisms and health benefits . . . . . . . . . . . . . . . . . . . . . . . . . Fermented meat as a carrier for probiotic bacteria . . . . . . . . . . . . . . . . . . . . . Evaluation of healthiness and overall quality of probiotic fermented meats . Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1. Introduction Probiotic foods are a group of health-promoting, so-called functional foods, with large commercial interest and growing market shares (Arvanitoyannis & van Houwelingen-Koukaliaroglou, 2005; Parvez, Malik, Ah Kang, & Kim, 2006; Senok, Ismaeel, & Botta, 2005). In general, their health benefits are based on the presence of selected viable strains of lactic acid bacteria (LAB), that, when taken up in adequate amounts, confer a health benefit on the host (FAO/WHO, 2001). They are administered mostly through the consumption of fermented milks or yoghurts (FAO/WHO, 2001; Makras, Avonts, & De Vuyst, 2004). In addition to their common use in the dairy industry, probiotic LAB strains may be used in other food products, including fermented meats (Hammes & Her* Corresponding author. Tel.: +32 2 6293245; fax: +32 2 6292720. E-mail address: fl[email protected] (F. Leroy). 0309-1740/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2008.05.038
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tel, 1998; Incze, 1998; Jiménez-Colmenero, Carballo, & Cofrades, 2001; Kröckel, 2006; Leroy, Verluyten, & De Vuyst, 2006; Työppönen, Petäjä, & Mattila-Sandholm, 2003). Although the concept is not new, only few manufacturers consider the use of fermented sausages as carriers for probiotic LAB (Arihara, 2006). Since meat products are seldom perceived as ‘‘healthy foods”, due to the perceived image of meat and its controversial nutrient profiling clause with respect to the presence of nitrite, salt, and fat, their marketing potential may be compromised (Lücke, 2000). In addition, the more artisan orientation of sausage manufacturers as compared to the dairy industry, the larger variety of products, and a number of uncertainties concerning technological, microbiological, and regulatory aspects seem to be problematic (Kröckel, 2006; Ross, Desmond, Fitzgerald, & Stanton, 2005). If any health claims are to be taken seriously, the application of probiotic LAB must in all cases be based on a careful selection procedure. This requires enhanced scientific research efforts dealing with the use of probiotics in
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fermented meats, taking into account that probiotics are and remain food constituents that are in no case to be considered as drugs or therapeutic agents. Much attention has been paid to the contribution of probiotic strains as meat starter cultures to improve food safety and little to the introduction of beneficial health effects (Leroy et al., 2006). This paper gives an overview of the limited amount of research activities that have previously explored the potential of probiotic LAB strains in fermented meats. 2. Probiotic microorganisms and health benefits Up to now, mainly bacteria belonging to the genera Lactobacillus and Bifidobacterium have been used or considered for use as probiotics, besides other bacteria (mostly belonging to the group of LAB) and some yeasts (Table 1). Historical data indicate that lactobacilli and bifidobacteria are safe for human use (Reid, 2005). Although minor side effects of the use of probiotics have been reported, infections with probiotic bacteria rarely occur and invariably only in diseased or immunocompromised patients (Gueimonde, Frias, & Ouwehand, 2006; Marteau, 2002; Reid, 2005; Vankerckhoven et al., 2008). Throughout the years, several selection criteria for probiotics have been formulated (Table 2). It should, however, be stressed that probiotic strain characteristics such as survival of the passage through the upper gastrointestinal tract, thus resisting the action of gastric juice, bile salts, and digestive enzymes, are not enough to call a certain microbial strain probiotic. According to the WHO/FAO definition, the main criterion for a probiotic strain should be the fact that it confers a health benefit on the host (FAO/WHO, 2001). This benefit can only be demonstrated through well-designed, randomized, double blind, placebo-controlled, multi-centre human trials, of which the results are published in peerreviewed international scientific journals (Guarner & Schaafsma, 1998; Makras et al., 2004; Mercenier, Pavan, & Pot, 2003; Salminen Table 1 Examples of microbial strains that are commercially used as probiotics [partly based on data from Collins and Gibson (1999), Makras et al. (2004) and Senok et al. (2005)] Microbial strain Lactobacilli Lactobacillus casei Imunitass (DN-114 001) Lactobacillus casei Shirota (YIT 9029) Lactobacillus johnsonii La1 (NCC 533) Lactobacillus plantarum 299v Lactobacillus rhamnosus GG (ATCC 53103) Bifidobacteria Bifidobacterium animalis subsp. lactis Bb12 Bifidobacterium animalis subsp. lactis Bifidus Actiregularis (DN 173-010) Bifidobacterium breve Yakult Bifidobacterium longum BB 536 Mixtures of lactic acid bacteria VSL#3 (mixture of eight strains) Other bacteria Escherichia coli Nissle 1917 Yeasts Saccharomyces boulardii
Brand name
Target application
Actimel
Immune response
Yakult
Gut health, digestive system, natural defense Gut health, natural defense
LC1 ProViva Gefilus, Vifit, . . .
Digestive system Gastro-intestinal health, immune response
Various brand names Activia
Gut microbiota, immune system
Bifiene Various brand names (yoghurt, powder)
Digestive system/gut microbiota Gut microbiota, immune system
VSL#3 (powder)
Biotherapeutic agent (irritable bowel syndrome, bowel diseases)
Mutaflor (suspension)
Biotherapeutic agent (gut microbiota, bowel diseases)
Enterol (pills)
Biotherapeutic agent (diarrhea, Clostridium difficile)
Gut transit
Table 2 Selection criteria for probiotics [partly based on data from Makras et al. (2004)] – Survival of the passage of the upper gastrointestinal tract (resistance to gastric acid, bile salts, and proteolytic enzymes; activity during transit from stomach to colon) – Interaction with the resident microbiota (ability to transiently adhere to the intestinal epithelium and colonize the colon; no significant effect on the dominant microbiota; effect on the numbers and diversity of the endogenous Lactobacillus and Bifidobacterium species) – Beneficial effect on the function of the host (probiotic-host interactions; prevention of the risk of disease) – Resistance towards technological processing (e.g., effects of food matrix, food ingredients, and mechanical and heat treatments) and storage (e.g., refrigeration and duration) – High safety profile and excellent tolerance (no risk group II LAB species, no Dlactic acid)
et al., 1998). Furthermore, it should be stressed that health effects are strain-dependent, and extrapolation of existing data from closely related microorganisms is not sufficient and even not acceptable to identify a strain as probiotic (Falony & De Vuyst, 2007; Makras et al., 2004; Reid, 2005). Precise identification and characterization of the probiotic strain used at genus, species, and even strain level, using internationally accepted state-of-the-art methodologies, is the required first step in every process of development of probiotic food products (Reid, 2005). Other steps include the investigation of physiological characteristics and technological requirements, the unravelling of underlying mechanisms of action, and the demonstration of human benefits (Dunne et al., 2001; Maldonado Galdeano, de Moreno de LeBlanc, Vinderola, Bibas Bonet, & Perdigón, 2007; Rastall et al., 2005; Santosa, Farnworth, & Jones, 2006; Saxelin, Tynkkynen, Mattila-Sandholm, & de Vos, 2005; Servin & Coconnier, 2003). For instance, in vitro pathogen inhibition studies might help to elucidate the mechanisms behind a probiotic anti-pathogen effect, but in vitro inhibition of pathogens by a probiotic by no means guarantees its functionality in the complex human gut ecosystem. A wide variety of beneficial health effects have been attributed to probiotics and shown to be strain-dependent (Table 3). Some of the well-established claimed effects include the shortening of intestinal transit time and the relief of lactose maldigestion. Proof of claims related to antibiotic-associated and travellers’ diarrhoea and related to immune response is sometimes controversial. Claims related to cancer prevention or the effect on blood cholesterol levels, however, need further scientific backup to achieve consensus (Gill & Guarner, 2004). Probiotics can influence human health on three levels, in a strain-specific manner: (i) by interacting with other microorganisms present on the site of action (competition for nutrients, production of antimicrobial agents, competitive exclusion), (ii) by strengthening mucosal barriers, and/or (iii) by affecting the immune system of the host (O’Hara & Shanahan, 2007). 3. Fermented meat as a carrier for probiotic bacteria Dry fermented meat products are usually not or only mildly heated, which is adequate for the carriage of probiotic bacteria (Ammor & Mayo, 2007; Arihara, 2006). In addition, there is reason to believe that the sausage matrix protects the survival of probiotic lactobacilli through the gastrointestinal tract (Klingberg & Budde, 2006). However, the potential negative impact of the meat environment on cell viability must be taken into account, in particular with respect to its high content in curing salt and its low pH and water activity due to acidification and drying. In general, cell viability in a fermented meat environment will most likely be strain-dependent. Therefore, the choice of appropriate microorganisms to be applied as probiotic strains in a fermented meat matrix
L.D. Vuyst et al. / Meat Science 80 (2008) 75–78 Table 3 Health-promoting effects of probiotics [partly based on data from FAO/WHO (2001), Mercenier et al. (2003), Naidu et al. (1999) and Parvez et al. (2006); Sanders (1998); Sanders and Huis in’t Veld (1999)] – Improved food digestion (e.g. proteins, dietary polysaccharides) – Reduction of lactose maldigestion – Supply and bioavailability of nutrients and growth factors (e.g. vitamins, minerals) – Maintenance and balancing of the colon microbiota – Reduction of (the risk of) intestinal disturbances (gastrointestinal infections, constipation) – Reduction of the risk and duration of diarrhoea (rotavirus, acute infectious, antibiotic-associated, Clostridium difficile-associated, travellers’ diarrhoea) – Inhibition of undesirable and pathogenic bacteria (orogastrointestinal infections caused by Streptococcus mutans, Helicobacter pylori, E. coli, Salmonella Typhimurium, Clostridium difficile; urinary tract infections; respiratory tract infections) – Modulation/stimulation of the immune system (cell-mediated and antibodymediated effects) – Reduction of the risk of atopic diseases and allergies (asthma, hay fever, food allergy, eczema, dermatitis) – Beneficial effects on functional bowel disorders (irritable bowel syndrome) – Beneficial effects on inflammatory bowel diseases (pouchitis, ulcerative colitis, Crohn’s disease) – Anti-carcinogenic activities – Lowering of blood serum cholesterol levels
will be important. One obvious possibility is the use of bacteria that are commonly associated with the meat environment and that possess the appropriate physiological requirements and healthpromoting properties. Such bacteria can be obtained by screening natural sausage isolates (Klingberg, Axelsson, Naterstad, Elsser, & Budde, 2005; Papamanoli, Tzanetakis, Litopoulou-Tzanetaki, & Kotzekidou, 2003; Pennacchia et al., 2004; Pennacchia, Vaughan, & Villani, 2006; Rebucci et al., 2007; Villani et al., 2005) or existing commercial meat starter cultures (Erkkilä & Petäjä, 2000) for probiotic properties. Several candidate strains have thus been obtained. As an example, the commercial meat starter strains Lactobacillus sakei Lb3 and Pediococcus acidilactici PA-2 may be of interest because of their survival capacities under simulated gastrointestinal conditions (Erkkilä & Petäjä, 2000). Likewise, isolates of Lactobacillus casei/paracasei from sausages fermented with L. casei, L. paracasei, L. rhamnosus, and L. sakei were screened for relevant properties (Rebucci et al., 2007). The latter properties included viability in artificial gastric juice and intestinal fluid, in vitro adhesion to human intestinal cell lines, organic acid production, and pathogen inactivation. In addition, several L. plantarum sausage isolates were found to have appreciable adhesion rates towards Caco-2 cell lines and were considered as better adhesive bacteria than Lactobacillus brevis and L. paracasei-group sausage isolates (Pennacchia et al., 2006). However, the demonstration of such properties does not necessarily lead to the consolidation of health-promoting properties, in particular because human studies are generally missing (see below). Alternatively, the performance of strains with documented health-promoting properties may be investigated in a fermented meat environment. Since such strains are usually human intestinal isolates, they should be able to compete with the natural meat microbiota in an environment which is not their natural habitat. They need thus to be able to survive the fermentation and drying process as well as refrigeration and storage conditions, and, preferably, be able to grow to numbers that enable the display of health-promoting effects. In this way, several lactobacilli of human intestinal origin have been shown to survive the sausage manufacturing process and can be detected in high numbers in the end-product (Arihara et al., 1998; Erkkilä et al., 2001a, Erkkilä, Suihko, Eerola, Petäjä, & Mattila-Sandholm, 2001b; Muthukumarasamy & Holley, 2006, 2007; Pidcock, Heard, & Henriksson, 2002; Sameshima et al., 1998). Unfortunately, most research concerning this strategy focuses on the survival of the
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added species in the meat matrix and its influence on the technological and sensory characteristics of the final product and not on health effects as such. Also, focus was on pathogen inactivation, as probiotic strains with additional food safety assets could confer added value to healthy fermented meat products. For instance, Lactobacillus reuteri ATCC 55730 and Bifidobacterium longum ATCC 15708 increased inactivation of Escherichia coli O157:H7 during sausage manufacturing (Muthukumarasamy & Holley, 2007). Lactobacillus rhamnosus FERM P-15120 and L. paracasei subsp. paracasei FERM P-15121 inhibited growth and enterotoxin production of Staphylococcus aureus to the same extent as a commercial L. sakei starter culture (Sameshima et al., 1998). In contrast, L. acidophilus FERM P-15119 could not satisfactorily decrease Staph. aureus numbers, indicating the importance of careful strain selection with respect to both health-promoting and food safety properties. 4. Evaluation of healthiness and overall quality of probiotic fermented meats In contrast to the successes obtained in the dairy industry, human studies using probiotic fermented meats are very scarce up to now. Such human studies are, however, crucial in the validation process required for the confirmation of the eventual functionality of probiotic fermented sausages. As a rare example, the effect of the daily consumption of 50 g of probiotic sausage containing L. paracasei LTH 2579 on immunity and blood serum lipids was investigated in healthy volunteers during several weeks (Jahreis et al., 2002). Results were only moderately successful. Modulation of various aspects of host immunity was observed, but there was no significant influence on the serum concentration of different cholesterol fractions and triacylglycerides. In faecal samples, a statistically significant increase in the numbers of L. paracasei LTH 2579 was observed for some but not all volunteers. Besides contributing to human health, probiotic fermented meats need to be of sufficient commercial value. Therefore, a primary requirement remains – as for any fermented meat – the sensory and technological aspects of the end-product. Negative side effects on the overall quality of the obtained fermented meats can not be tolerated and evaluation of such effects is primordial. For instance, it has been shown in Northern European sausage that the (potential) probiotic strains L. rhamnosus GG, L. rhamnosus LC705, L. rhamnosus E-97800, and L. plantarum E-98098 do not negatively affect the technological or sensory properties of the end-product, with a (minor) exception for L. rhamnosus LC-705 (Erkkilä et al., 2001a, 2001b). When applying the intestinal isolates L. paracasei L26 and Bifidobacterium lactis B94 in conjunction with a traditional meat starter culture, no negative impact on the sensory properties of the product was noticed (Pidcock et al., 2002). Also, the use of alginate-microencapsulation of L. reuteri ATCC 55730 did not result in differences concerning sensory quality (Muthukumarasamy & Holley, 2006). 5. Conclusions Full assessment of the probiotic effects of fermented sausages on human health is not possible yet. Although probiotic meat products are being marketed since 1998 by German and Japanese producers (Arihara, 2006), controversy about their usefulness remains, due to the preliminary nature of most scientific results obtained. Therefore, more research is needed to justify the launch of new probiotics and of probiotic fermented sausages, in particular with respect to human studies. Importantly, this research should rigorously follow the guidelines formulated by the FAO/WHO (2002), including detailed identification of the strain and an approved beneficial health effect of the food product. Only such an approach will
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