3 Organic Acids and Food Preservation fecal matter ans that are accidentally damaged ring removal (Berry and Cutter ne to the ubiquitous nature and increasing presence of the pathogen Listeria m in the slaughterhouse and meat packaging environments,the incidence and behavior of this pathogen in meat products are receiving increasing attention.Contamination of ready-to-eat(RTE)meats with Listeria mono- cytogenes and Salmonella spp.occurs mainly at postprocessing,and it is common practice for these roducts to be consumed without further heat- ing.L. togenes can,th e be hazardous to the umer in both erated and temperature-abused RTE meat (Mba d and Shel 200 An example of foodstuffs where hazardous microbial contaminant are increasingly found,are salad bars,offering freshly cut lettuces.Such salad bars have become increasingly popular,and have introduced new environments that support the growth of foodborne pathogens,including L.monocytogenes.These salad bars are found in restaurants,supermarkets, and con ience stores and L.monocutogenes has been isolated from fresh and minimally sed vege etables.However, washin g and sanitizing eatments should be able to reduce the presence or at l pro liferation ofL storage of vegetable foods(Allende etal,2007. 1.6.3 Laboratory methodologies Bacteria are the only pathogens routinely tested for in food samples whereas viruses and arasites are typically tested in stool spe s infected after food umption he food P s of bacteria and an ch noose among cul tests,gene probes,ma anual immunoassays,and instruments(automated immunoas- says)(Kroll,2001). 1.6.4 Epidemiology food poisoning as well as food spoilage outbreaks are the ultimate cause for ern for any food pro ducer or health authority.It is,hov ever,wort ing a t case meat products,such as roas beef,tu rkey,an ontaining Mexica foods have been implicated in outbreaks of Clostridium perfringens.C perfringens is an important foodborne pathogen that is estimated to cause.in the United states alone.248.000 cases of foodborne illness annually.Spores of C.perfringens are widely distributed in soil and water and often contaminate raw meat and poultry during slaughter operations.Outbreaks occur primarily as a result of consumption of dled after cooking.However,a seriou
12 Organic Acids and Food Preservation fecal matter or via contents from intestinal organs that are accidentally damaged during removal (Berry and Cutter, 2000). Due to the ubiquitous nature and increasing presence of the pathogen Listeria monocytogenes in the slaughterhouse and meat packaging environments, the incidence and behavior of this pathogen in meat products are receiving increasing attention. Contamination of ready-to-eat (RTE) meats with Listeria monocytogenes and Salmonella spp. occurs mainly at postprocessing, and it is common practice for these products to be consumed without further heating. L. monocytogenes can, therefore, be hazardous to the consumer in both refrigerated and temperature-abused RTE meats (Mbandi and Shelef, 2002). An example of foodstuffs where hazardous microbial contaminants are increasingly found, are salad bars, offering freshly cut lettuces. Such salad bars have become increasingly popular, and have introduced new environments that support the growth of foodborne pathogens, including L. monocytogenes. These salad bars are found in restaurants, supermarkets, and convenience stores and L. monocytogenes has been isolated from fresh and minimally processed vegetables. However, washing and sanitizing treatments should be able to reduce the presence or at least prevent proliferation of L. monocytogenes during storage of vegetable foods (Allende et al., 2007). 1.6.3 Laboratory methodologies Bacteria are the only pathogens routinely tested for in food samples, whereas viruses and parasites are typically tested in stool specimens of persons infected after food consumption. The food processor tests for specific types of bacteria and can choose among culture tests, gene probes, manual immunoassays, and instruments (automated immunoassays) (Kroll, 2001). 1.6.4 Epidemiology Food poisoning as well as food spoilage outbreaks are the ultimate cause for concern for any food producer or health authority. It is, however, worth mentioning a few very important cases. Several processed meat products, such as roast beef, turkey, and meat-containing Mexican foods have been implicated in outbreaks of Clostridium perfringens. C. perfringens is an important foodborne pathogen that is estimated to cause, in the United States alone, 248,000 cases of foodborne illness annually. Spores of C. perfringens are widely distributed in soil and water and often contaminate raw meat and poultry during slaughter operations. Outbreaks occur primarily as a result of consumption of foods that are improperly handled after cooking. However, a serious
Chapter one:Introduction 13 problem is that spores present in raw materials that are used in the preparation of meat products can survive the traditional heat process- ing schedules emploved by the meat industry.These heat-activated spores surviving in cooked foodstuffs may then germinate out grow and multiply during subsequent chilling operations,especially if chill rates are not properly followed,if products are not properly refrigerated,or if products have been temperature abused (Juneja and Thippareddi,2004). 1.6.5 A review of emerging organisms 1.6.5.1 Bacteria Since the first recognized outbreak in 1982,Escherichia coli O157:H7 has emerged as a serious,potentially life-threatening,human foodborne pathogen,implicated in causing diarrhea,hemorrhagic colitis,and hemo- lytic uremic syndrome (Jordan,Oxford,and O'Byrne,1999;Cheng,Yu,and Chou,2003).E.coli O157:H7 is a member of the gic E.coli that causes devastating bloody diarrhea in its victims(Audia,Webb,and Foster,2001).It has become clear in recent years that much more attention is necessary to prevent contamination by E.coli O157:H7 in foods,especially low pH foods(Cheng,Yu,and Chou,2003).E.coli O157:H7 is associated with eating contamina d undercooked beef and less frequently with drinking raw milk,unpasteurized apple cider,water,or even person-to-person con- tact(Ryu and Beuchat,1999).The apparent source of these pathogens is the bovine gastrointestinal tract from where the contents can contaminate various processed meat products(Audia,Webb,and Foster,2001).Safety haz rds unpast d fruit a dve etable bever ges have also been noted.E.coli O157:H7 is known to be acid tolerant and has a low infectious dose(10-2000 cfu/g)(Chikthimmah,LaBorde,and Beelman,2003). L.monocytogenes is another major concern to manufacturers world- wide.This is due to the high mortality rate of listeriosis in susceptible populations and due to the pathogen being resistant to a number of food preservation practices.The ability of the organism to grow at refrigeration temperatures,in particular,and the ability to grow on dry surfaces,which would normally inhibit bacterial growth,make it well adapted to food er ents(Ba er and Park,2001).Between 2000 and 2003,there wer at least 111 reported recalls of RTE meat and poultry products suspected of being contaminated with L.monocutogenes (Geornaras et al.2005). Campylobacter gastroenteritis is one of the important diseases that has a serious impact n public health in developing Poultry has initially be en infected by these bacteria and the con sumption of con taminated chicken meat has frequently been implicated as the source of
Chapter one: Introduction 13 problem is that spores present in raw materials that are used in the preparation of meat products can survive the traditional heat processing schedules employed by the meat industry. These heat-activated spores surviving in cooked foodstuffs may then germinate, outgrow, and multiply during subsequent chilling operations, especially if chill rates are not properly followed, if products are not properly refrigerated, or if products have been temperature abused (Juneja and Thippareddi, 2004). 1.6.5 A review of emerging organisms 1.6.5.1 Bacteria Since the first recognized outbreak in 1982, Escherichia coli O157:H7 has emerged as a serious, potentially life-threatening, human foodborne pathogen, implicated in causing diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (Jordan, Oxford, and O’Byrne, 1999; Cheng, Yu, and Chou, 2003). E. coli O157:H7 is a member of the enterohemorrhagic E. coli that causes devastating bloody diarrhea in its victims (Audia, Webb, and Foster, 2001). It has become clear in recent years that much more attention is necessary to prevent contamination by E. coli O157:H7 in foods, especially low pH foods (Cheng, Yu, and Chou, 2003). E. coli O157:H7 is associated with eating contaminated undercooked beef and less frequently with drinking raw milk, unpasteurized apple cider, water, or even person-to-person contact (Ryu and Beuchat, 1999). The apparent source of these pathogens is the bovine gastrointestinal tract from where the contents can contaminate various processed meat products (Audia, Webb, and Foster, 2001). Safety hazards of unpasteurized fruit and vegetable beverages have also been noted. E. coli O157:H7 is known to be acid tolerant and has a low infectious dose (10–2000 cfu/g) (Chikthimmah, LaBorde, and Beelman, 2003). L. monocytogenes is another major concern to manufacturers worldwide. This is due to the high mortality rate of listeriosis in susceptible populations and due to the pathogen being resistant to a number of food preservation practices. The ability of the organism to grow at refrigeration temperatures, in particular, and the ability to grow on dry surfaces, which would normally inhibit bacterial growth, make it well adapted to food environments (Barker and Park, 2001). Between 2000 and 2003, there were at least 111 reported recalls of RTE meat and poultry products suspected of being contaminated with L. monocytogenes (Geornaras et al., 2005). Campylobacter gastroenteritis is one of the important diseases that has a serious impact on public health in developing countries. Poultry has initially been infected by these bacteria and the consumption of contaminated chicken meat has frequently been implicated as the source of
14 Organic Acids and Food Preservation Campylobacter infection.thasbenshown that water is ansmissi ortant route trains that res the lactic acid bacteria LA d been reported to survive disinfection.These organisms then occur as spoilage organisms and can also affect fermentation processes (Sidhu, Langsrud,and Holck,2001).In addition to this,there is increasing evi- dence that LAB can act as opportunistic pathogens(Sims,1964;Adams, 1999:Sidhu,Langsrud,and Holck,2001).Several lactobacilli species have associated with human disea such a septi mia,rhe natic dis es,mening tis lung ab infecti urinary tract i Agu Harty et al,1994;Sidhu,Langsrud,and Holck,2001).Some of the LAE strains known to be implicated in foodborne diseases include Lacfobacillus casei,Lactobacillus plantarum,Lactobacillus rhamnosus,and the Lactobacillus acidophilus group (Sidhu,Langsrud,and Holck,2001). 1.6.5.2F1ugi Yeasts and fungi are a major spoilage threat for many food products that ed at low pH,lo w a or high levels of preservatives (Pipere ucts are species o Eurotium,Aspergillus,and Penicillium(Maren et al.2003).Another impor- tant spoilage fungus is Fusarium,often found in cereal grains where they might produce a number of mycotoxins(Schnurer and Magnusson,2005). Adding to these is Zygosaccharomyces,a genus associated with the more extreme spoilage veasts.These spoilage veasts are osmotolerant.highlv fermentative and e resistant to most vatives(Steels et al. 2000.7 nally attra agent tic acid in the presence of the complex mixtures of sugars present in wine fermentations.It is now known that Z.bailii was the first Zygosaccharomyces gene of resistance to food preservatives that was characterized genetically (Mollapour and Piper,2001).Zygosaccharomyces lentus is another important food spoilage organism able to grow in a wide range of food products, particularly at a low pH as well as foods and drinks containing high levels of s gar.It is likely chilled gnificant than Z.bailii in the spoilage of (Stee 1,19 in the past f w years,interes st ha as been increased in the yeast Yarro lipolytica,due to its numerous biotechnological applications.Although it has often been reported in incidents from food environments,sometimes with serious consequences,this organism is,however,not considered to be among the more dangerous food spoilage veasts.Y.lipolyfica is usu- ally isolated from lipid-rich environments such as mayonnaise and salad dressing,but can be found in dairy products,specifically butter,chee and yogurt.The presence of this organism in e environments could
14 Organic Acids and Food Preservation Campylobacter infection. It has been shown that water is an important route of horizontal transmission on broiler farms (Chaveerach et al., 2002). Bacterial strains that reside under the lactic acid bacteria (LAB) have been reported to survive disinfection. These organisms then occur as spoilage organisms and can also affect fermentation processes (Sidhu, Langsrud, and Holck, 2001). In addition to this, there is increasing evidence that LAB can act as opportunistic pathogens (Sims, 1964; Adams, 1999; Sidhu, Langsrud, and Holck, 2001). Several lactobacilli species have been associated with human diseases such as septicemia, rheumatic diseases, vascular diseases, meningitis, lung abscesses, infective endocarditis, peritonitis, and urinary tract infections (Aguirre and Collins, 1993; Harty et al., 1994; Sidhu, Langsrud, and Holck, 2001). Some of the LAB strains known to be implicated in foodborne diseases include Lactobacillus casei, Lactobacillus plantarum, Lactobacillus rhamnosus, and the Lactobacillus acidophilus group (Sidhu, Langsrud, and Holck, 2001). 1.6.5.2 Fungi Yeasts and fungi are a major spoilage threat for many food products that are preserved at low pH, low aw, or high levels of preservatives (Piper et al., 2001). Of importance in the spoilage of bakery products are species of Eurotium, Aspergillus, and Penicillium (Marén et al., 2003). Another important spoilage fungus is Fusarium, often found in cereal grains where they might produce a number of mycotoxins (Schnürer and Magnusson, 2005). Adding to these is Zygosaccharomyces, a genus associated with the more extreme spoilage yeasts. These spoilage yeasts are osmotolerant, highly fermentative, and extremely resistant to most preservatives (Steels et al., 2000). Zygosaccharomyces bailii originally attracted attention as a spoilage agent of wine, with its high ethanol tolerance and ability to metabolize acetic acid in the presence of the complex mixtures of sugars present in wine fermentations. It is now known that Z. bailii was the first Zygosaccharomyces gene of resistance to food preservatives that was characterized genetically (Mollapour and Piper, 2001). Zygosaccharomyces lentus is another important food spoilage organism able to grow in a wide range of food products, particularly at a low pH as well as foods and drinks containing high levels of sugar. It is likely to be more significant than Z. bailii in the spoilage of chilled products (Steels et al., 1999). In the past few years, interest has been increased in the yeast Yarrowia lipolytica, due to its numerous biotechnological applications. Although it has often been reported in incidents from food environments, sometimes with serious consequences, this organism is, however, not considered to be among the more dangerous food spoilage yeasts. Y. lipolytica is usually isolated from lipid-rich environments such as mayonnaise and salad dressing, but can be found in dairy products, specifically butter, cheese, and yogurt. The presence of this organism in these environments could
Chapter one:Introduction 15 be attributed to their being tolerant or even resistant toward stress envi- ronments,such as the organic acids.Utilization and toxicity depend on their capacity to use (as sole carbon and energy source)most carboxylic acids often used as preservatives in the food industry (Rodrigues and Pais,2000). 1.6.5.3 Viruses Reports on Norovirus outbreaks have increased in the past few years. In 2007 the existence of a new Norovirus strain of genogroup II/4 was confirmed by the CDC Enteric Virus Branch in Atlanta,Georgia.This virus isacid-stable and can pass thre ugh the stor nach unda d There is an obvious problem emerging with regard to Norovirus infections (Leuenberger et al.,2007). 1.6.5.4 Protozoa Protozoa,such as Cyclospora cayetanensis,and also various foodborne trem- atodes have been associated with infections,often with seve re,chronic,or fatal health consequences(Mo s,Motarjemi,an d Kaferstein,2001) References Adams,M.R.1999.Safety of industrial lactic acid bacteria.Journal of Biotechnology 68:171-178 Aguirre,M.and Collins,M.D.1993 Lactic acid bacteria and human clinical infec Allen d, are ,J.E.,and Rodrigu A.2007 oc and their effect on by nd cut lettuce.Food Microbiology 24:759-766. Arroyo,M.,Aldred,D.,and Magan.N.2005.Environmental factors and weak organic acid interactions have differential effects on control of growth and ochratoxin A production by Penicillium verrucosum isolates in bread. Intern tional Journal of Food Microb 0l08y98:223-231. Audia,J.P.,Webb,C.C.,and Foster,J.W.2001.Breaking through the acid barrier An orchestrated re sponse to proton stress by enteric bacteria.International Malo.A and Chan pia,M.S.L s,I.W.2003.Gen ral c etables.In:Handling and Pres ertion of Fruits and Vegetables by Combined Methods for Rural Areas.Rome:Food and Agriculture Organization of the United nations. Barker,C.and Park,S.F.2001.Sensitization of Listeria monocytogenes to low pH, sby ethanol.n
Chapter one: Introduction 15 be attributed to their being tolerant or even resistant toward stress environments, such as the organic acids. Utilization and toxicity depend on their capacity to use (as sole carbon and energy source) most carboxylic acids often used as preservatives in the food industry (Rodrigues and Pais, 2000). 1.6.5.3 Viruses Reports on Norovirus outbreaks have increased in the past few years. In 2007 the existence of a new Norovirus strain of genogroup II/4 was confirmed by the CDC Enteric Virus Branch in Atlanta, Georgia. This virus is acid-stable and can pass through the stomach undamaged. There is an obvious problem emerging with regard to Norovirus infections (Leuenberger et al., 2007). 1.6.5.4 Protozoa Protozoa, such as Cyclospora cayetanensis, and also various foodborne trematodes have been associated with infections, often with severe, chronic, or fatal health consequences (Molins, Motarjemi, and Käferstein, 2001). References Adams, M.R. 1999. Safety of industrial lactic acid bacteria. Journal of Biotechnology 68:171–178. Aguirre, M. and Collins, M.D. 1993. Lactic acid bacteria and human clinical infection. Journal of Applied Microbiology 75:95–107. Allende, A., Martinez, B., Selma, V., Gil, M.I., Suarez, J.E., and Rodriguez, A. 2007. Growth and bacteriocin production by lactic acid bacteria in vegetable broth and their effectiveness at reducing Listeria monocytogenes in vitro and in freshcut lettuce. Food Microbiology 24:759–766. Arroyo, M., Aldred, D., and Magan, N. 2005. Environmental factors and weak organic acid interactions have differential effects on control of growth and ochratoxin A production by Penicillium verrucosum isolates in bread. International Journal of Food Microbiology 98:223–231. Audia, J.P., Webb, C.C., and Foster, J.W. 2001. Breaking through the acid barrier: An orchestrated response to proton stress by enteric bacteria. International Journal of Medical Microbiology 291:97–106. Bailly, M. 2002. Production of organic acids by bipolar electrodialysis: Realizations and perspectives. Desalination 144:157–162. Barbosa-Cánovas, G.V., Fernández-Molina, J.J., Alzamora, S.M., Tapia, M.S., LópezMalo, A., and Chanes, J.W. 2003. General considerations for preservation of fruits and vegetables. In: Handling and Preservation of Fruits and Vegetables by Combined Methods for Rural Areas. Rome: Food and Agriculture Organization of the United Nations. Barker, C. and Park, S.F. 2001. Sensitization of Listeria monocytogenes to low pH, organic acids, and osmotic stress by ethanol. Applied and Environmental Microbiology 67:1594–1600
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