Microorganisms in the Food Industry - Research Paper Example

?Microorganisms in the Food Industry Introduction Microorganisms are used extensively by humans in many domains of life. They have also been used in the food industry. Microorganisms are often in the news for causing spoilage of foods but they are in fact, used every day to actually produce several of these foods. They have been exploited both knowingly and unknowingly for several thousand years by people. Some of the microorganisms used include bacteria and yeasts. Nowadays, there is much research done on the complex processes microorganisms undergo in food so as to further understand these processes. Understanding these will possibly lead to much of the food production processes becoming shorter and less time consuming and will lead to less waste being produced. Some examples of foods that are produced using microorganisms include wine, cheese and bread. This paper will attempt to take a look at the microorganisms used in each of these foods and attempt to explain some of the mechanisms they utilise to achieve the result that humans desire. Winemaking Yeast in Wine Wine is a popular beverage where microorganisms play an important part. Wine has been consumed by humans for thousands of years (Okamura et al,1596) and the exact science of the wine making process is still being decoded. The quality of a wine is determined by whether the taste of that wine is original, the finesse, intensity of taste and by the microbiological and physicochemical stability (Dubourdieu, 1986; Noble, 1988; Rapp and Mandery, 1986; Schreier, 1979 of Colagrande, Silva and Fumi, 2) (Refer fig1). The microbiology behind the wine making process was only established less than 2 centuries ago by the work of Louis Pasteur (Bakalinsky and Penner, 1993 from Okamura et al,1596, Colagrande, Silva and Fumi,2). Yeasts are used extensively in wine making. There are approximately 700 species of yeast and sixteen of these species have been used in the process of making wine. These include Brettanomyces, Dekkera, Candida, Cryptococcus, Debaryomyces, Hanseniaspora, Kloeckera, Kluyveromyces, Metschnikowia, Pichia, Rhodotorula, Saccharomyces, Saccharomycodes, Schizosaccharomyces, Torulaspora and Zygosaccharomyces (Pretorius et al, 1999 of Swiegers et al, 142). Saccharomyces cerevisae is one of the most commonly used organisms for producing wine though other such as Pleurotus ostreatus, Flammulina velutipes and Agaricus blazei have recently been exploited (Okamura et al, 1596). A specific variety of grape can be exploited to produce some qualities of wines such as the distinctive smell (Dubourdieu 2000, Lambrechts and Pretorius 2000, Guth and Sies 2002, Swiegers and Pretorius 2005 of Swiegers et al, 142). Some of these distinctive volatile compounds which cause properties of a wine like smell arise from grapes. However, several are due to the action of yeast and bacteria during the production of wine. Taste is also greatly affected by the bacteria and yeast used during wine (Schreier, 1979; Simpson, 1979; Williams et al, 1989; Etievant 1991, Guth, 1998; Boulton et al, 1998; Rapp,1998; Dubourdieu, 2000; Ferreira et al, 2000; Lambrechts and Pretorius, 2000; Ribereau-Gayon et al, 2000a,b; Ortega et al, 2001; Guth and Sies, 2002 of Swiegers et al, 141). Grapes can only support the proliferation of few microorganisms (Henschke, 1997 of Swiegers et al, 142). This has been attributed mainly due to the selective pressure on the microorganisms due to the high content of sugar and the low pH of grape (Swiegers et al, 142). In addition, sulphur dioxide is usually added to the mixture during wine making and this adds even more selectivity to the microorganisms that can grow. Usually, oxidative microorganisms that may be harmful are limited due to the sulphur dioxide (Swiegers et al, 142). Once anaerobic conditions start to predominate during the winemaking process, even more microorganisms find the conditions unfavourable for growth and the production of ethanol further limits the types of microorganisms that grow (Henschke, 1997 from Swiegers et al, 142). It is generally the yeasts that have the most effective fermentative catabolism that is favoured during the winemaking process (Swiegers et al, 142). To elaborate on the point just made on the species of microorganisms that survive at the different stages of winemaking, it is useful to mention some examples. In the early stages of the winemaking process, it is usually yeasts like Kloeckera, Hanseniaspora and Candida that show a lot of growth. In the middle stages, several species of Metschnikowia and Pichia predominate when the ethanol is between 3-4% (Fleet and Heard, 1993 of Swiegers et al, 142). The end stages where there is a high concentration of ethanol present, only alcohol tolerant organisms can survive and this usually includes species like Saccharomyces cerevisiae (Swiegers et al, 142). In addition, there is the possibility that some yeasts that will negatively affect the properties of the wine will survive too, such as Brettanomyces, Kluyveromyces, Schizosaccharomyces, Torulaspora and Zygosaccharomyces (Swiegers et al, 142). S. cerevisiae has often been called wine yeast. It is mainly because it is the most commonly used yeast for the starting alcoholic fermentation. The main use of S. cerevisiae is to act as a catalyst for the conversion of sugars in grapes and to convert them into ethanol, carbon dioxide and some other compounds that may affect the quality of wine (Pretorius, 2000 of Swiegers et al, 142). Secondly, S. cerevisiae is also important in modifying the by products of alcoholic fermentation so that the quality of the wine is enhanced (Swiegers et al, 143). Bacteria in Winemaking While yeast is commonly used winemaking, bacteria are less commonly used. Acetic acid and lactic acid bacteria are the only ones known that can survive in the hostile environment present in both grape juice and wine (Swiegers et al, 158). Only four lactic acid bacteria genera are known to survive in wine Lactobacillus, Leuconostoc, Oenococcus and Pediococcus (Swiegers et al, 158) and Oenococcus oeni is by far the best adapted to winemaking and is used in production of red, white and sparkling wines (Wibowo et al, 1985 ;Henick-Kling, 1993; Henschke, 1993 of Swiegers et al, 159). On the other hand, acetic acid bacteria are not used in the production of wine and actually are considered spoilage organisms for wine due to the production of oxidised products (Swiegers et al, 2005). It has been seen that bacteria, like yeast can alter the quality of the wine and so is an important avenue of research for winemakers (Henick-Kling,1993; Bartowsky et al, 2002b, Matthews et al, 2004 of Swiegers et al, 159). Cheese production using a combination of yeast and bacteria In addition to wine, microorganisms are used in the production of several other foods, one of which is cheese. Over a thousand types of cheese are in production and microorganisms are used in the production of all of these. Depending on the type of cheese, there are usually several different types of bacteria and yeast present which occupy unique niches and make use of the various carbon sources available (Irlinger and Mounier,142). The population densities of the yeasts and bacteria present can often be very high and can reach as high as eight to ten logs of colony forming units (CFU) per gram of cheese when cheese is ready for consumption (Irlinger and Mounier,142). As in wine, the yeast or bacteria chosen for use during the cheese making process is dependent on the properties of cheese desired when production is complete. These include the pigmentation and aroma (Irlinger and Mounier,142). It is usually a starter culture of lactic acid bacteria like Lactococcus lactis and also Streptococcus thermophilus which is used. This can grow very quickly and results in the production of acid in milk (Delbes et al, 2007 of Irlinger and Mounier, 142). In the subsequent first few days of cheese ripening, yeast and moulds like Debaryomyces hansenii, Geotrichum candidum and Penicillium camemberti grow rapidly and use up lactate (Callon et al, 2006 of Irlinger and Mounier,142) (Refer fig.2). De acidification the surface of the cheese results and it is only the microorganisms that are tolerant to acid that survive (Irlinger and Mounier, 142). Examples of this include Arthobacter arilaitensis, Brevibacterium aurantiacum, Brevibacterium linens and Corynebacterium casei (Rademaker et al, 2005; Rea et al, 2007; Belen et al, 2006; Saubasse et al, 2007, Abriouel et al, 2008; Parayre et al, 2007; Licitra et al, 2007 of Irlinger and Mounier,142). There have also been found other types of microorganisms in cheese such as halophiles such as g-Proteobacteria (such as Halomonas), Enterobacteriaceae (such as Hafnia alvei), and halophilic and alkaliphic lactobacillus species. The precise function of such organisms in cheese ripening has yet to be identified (Ishikawa et al, 2007; Mounier et al, n.d of Irlinger and Mounier, 142). There are four pathways that are important in the formation of the flavour of cheese. These include glycolysis and the utilisation of citrate, proteolysis and lipolysis (van Hylckama and Hugenholtz, 2007; Landaud et al,2008 of Irlinger and Mounier, 145). The flavour production is dependent on the degradation of milk by the enzymes of each microorganism. It is also dependant on the metabolic pathways that occur between strains (Irlinger and Mounier, 145). This is the primary reason as to why the species of microorganism chosen is extremely important. The enchantment of some flavours has to primary uses. The first is to make shorter the amount of time taken for ripening and the second one is to improve the quality of cheese (Irlinger and Mounier,145). Use of attenuated bacteria It has been noted that the use of attenuated enzymes increases the bacterial populations in the cheese making process. The acidification process is unaffected by the increase in the numbers of bacteria. These attenuated cultures do not produce lactic acid but promote cheese maturation by the production of active enzymes (Banks, 202). Attenuation of bacterial cultures for cheese making can be carried out by heat treatment, freezing, freeze drying or some other methods (Johnson et al, 1995; Klein and Lortal 1999 of Banks ,202). Some examples of microorganisms that can be used include Lactobacillus Helveticus which has been used in low fat cheeses (Ardo et al. 1989 of Banks, 202). Bread production using yeast in conjunction with bacteria Another food that is produced using microorganisms and is a staple in many parts of the world is bread. As in the production of wine, S.cerevisiae is made use of as is species of Lactic acid bacteria (LAB) like Lactobacillus brevis (Spier et al, 1). The use of both of these in conjunction has been seen to produce even better results (Spier et al, 1). To produce sweet breads, the fermentation process is approximately 24 hours long. There is usually yeast added and interact with species of Lactobacillus to contribute to the dough leavening process. Some examples of species used include Lactobacillus plantarum, L. delbruchii, L. leichmanii, L. brevis, L. casei, L. alimentarius, L. delbrueckii, L. fermentum, Leuconostoc citreum, Lactococcus lactis, L.acidophilus, Weissella confuse (Sugihara, 1977; Barber et al., 1983 and 1987; Lonner and Akesson, 1989; Corsetti et al. 2001, Rehman et al., 2006 of Spier et al, 1). In general, the yeast used uses up the glucose produced by the bacteria and so the yeast and bacteria can work in conjunction with each other. The yeast uses up carbon to produce carbon dioxide while LAB produces a high content of lactic acid. This results in a lower pH and an increase in moisture content of the finished product (Spier et al, 1). The yeast is also unaffected by the antibiotics and acetic acids that are usually produced by the bacteria (Sugihara et al, 1971 from Spier et al,1). In turn, the yeast provides the bacteria with nutrients for growth which act as a supplement to those in flour (Spier et al,1). The system of the yeast and bacteria working in conjunction appears to be one that is self-regulated (Spier et al, 1). It is mainly the bacteria that appear to affect the flavour of the bread Furthermore, LAB contributes mainly to the flavouring compounds of these breads (Rehman et al, 2006; Vuyst and Neysens, 2005; Foschino, 1995 of Spier et al, 1) while the yeast acts as a leavening agent (Spier et al, 1). As previously mentioned using a mixture of yeast and LAB usually results in improved properties of the bread produced. These properties include a better flavour, better texture and longer lasting freshness (Meignan et al, 2001 from Spier et al, 1). Conclusion To conclude, it is obvious that humans use microorganisms in a wide variety of applications and the good industry is no exception. Microorganisms appear to have been used for thousands of years in the food industry and was used unknowingly for much of this time. Now that humans have become aware of the advantage of the use of microorganisms in food, they have begun to exploit it in several ways. Three such examples are in the production of wine, in cheese production and in the making of bread. The most common yeast used in winemaking is S.cerevisiae and it has even been called the wine yeast. There are different microorganisms present at different points in the wine making process but S.cerevisiae is one of the few that survive the harsh conditions provided by wine in terms of the high alcohol concentration present. Very few bacteria have been seen to be useful in the wine making process due to the harsh conditions of wine. In the making of cheese, four main pathways are utilised by microorganisms in its production and flavour and pigmentation are largely dependent on the type of bacteria used. It has been found that the use of attenuated bacterial cultures greatly impacts the flavour of the cheese too. There are several different species of bacteria used depending on the cheese that is being produced. Another main product made with the help of microorganisms is bread. Unlike wine and cheese, bread production is usually enhanced by the use of both yeasts and bacteria, in particular lactic acid bacteria (LAB). The yeast and the bacteria seem to work in conjunction with each other and while the bacteria contribute to flavour, the yeast seems to aid in the leavening process. It can be said that it is likely microorganisms will continue to be used in the food industry in the foreseeable future. While there is often spoilage due to some microorganisms in foods, some organisms are extremely useful for the production of foods. Understanding the complex mechanisms by which they interact with each other will definitely help in being able to control the flavour, textures and overall quality of food. Fig 1. Source: Colagrande, Silva and Fumi, 1994 Fig.2. Source: Irlinger and Mounier, 2009 Works Cited Banks, J.M. The technology of low-fat cheese manufacture. International Journal of Dairy Technology. 57.4. (2004):199- 207. Print. Colagrande, O.;Silva,A.; and Fumi,M.D. Recent Applications of Biotechnology in Wine Production. Biotechnology Progress.10. (1994): 2-18. Print. Irlinger, F. and Mounier,J. Microbial Interactions in cheese: implications for cheese quality and safety. Current Opinion in Biotechnology, 20: (2009).142–148. Print. Okamura, T.; Ogata, T.; Minamimoto,N.; Takeno, T.; Noda, H.; Fukuda, S. and Oshsugi, M. Characteristics of Wine Produced by Mushroom Fermentation. Bioscience, Biotechnology, Biochemistry. 65.7. (2001):1596-1600. Print. Spier, M.R; Rapacci, M; Dutcosky, S.D; and Tedrus,Souza. G.A. Sweet Bread Produced by the Lactic Acid Bacteria L. Brevis and the Yeast S. Cerevisiae," International Journal of Food Engineering. 3.5. (2007): 1-15. Print. Swiegers,J.H,; Bartowsky,E.J.; Henschke,P.A. and Pretorius,IS. Yeast and bacterial modulation of wine aroma and flavour. Australian Journal of Grape and Wine Research. 11. (2005): 139–173. Print. Read More