Beneficial Microbes in Food Processing PDF

Department of Food Science FST 101 – Food Microbiology BENEFICIAL MICROBES IN FOOD PROCESSING ALESSANDRA M. DOMANACO Assistant Professor IV 1  Lesson VIII: Beneficial Microbes in Food Processing 1. Analyze the advantages a...

Department of Food Science FST 101 – Food Microbiology BENEFICIAL MICROBES IN FOOD PROCESSING ALESSANDRA M. DOMANACO Assistant Professor IV 1  Lesson VIII: Beneficial Microbes in Food Processing 1. Analyze the advantages and disadvantages of emerging food preservation technologies and their implications to microbial food safety and food quality. 2. Discuss the use of microbes in food processing. 2  HISTORY Microorganisms have been used to make food for millennia. Cheese, yogurt and bread all rely on fermentation by microorganisms in their production, as do alcoholic drinks, such as wine and beer. It is thought that beer production may have started as early as 7000 BC and cheese consumed as early as 3000 BC. The techniques used to make these products in modern times are more advanced and more carefully controlled, but the principles remain largely the same. Age old applications: 1. Wine/ Beer/ Spirits 2. Cheese and Yoghurt Louis Pasteur: Hypothesised that bacteria spoils wine Suggested that wine be heated to kill bacteria Hence: pasteurization  FERMENTATION Fermentation is the metabolic process in which carbohydrates and related compounds are partially oxidised, with the release of energy, in the absence of any external electron acceptors. in food processing it is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria or a combination thereof, under anaerobic conditions.  Fermentation Pros vs Cons Extended shelf life of food (ex. Can be unpredictable (i.e. bad Cheese) bacteria win the battle) Eases Digestion (ex. Wild rice) New [worse] flavours (ex. New [better] flavours (ex. Mouldy bread tastes terrible) Chocolate) Fermentation technologies are Detoxification and softening complex and sensitive and require careful control LACTIC ACID FERMENTATION vs. ALCOHOLIC FERMENTATION  LACTIC ACID FERMENTATION Lactic acid fermentation is a metabolic process by which glucose or other six-carbon sugars (also disaccharides of six- carbon sugars, e.g. sucrose or lactose) are converted into cellular energy and the metabolite lactate, which is lactic acid in solution. - Occurs under an anaerobic condition (anaerobic fermentation reaction) LACTIC ACID FERMENTATION GLYCOLYSIS Glucose (2) Pyruvate NAD+ NADH (2) Lactate  ALCOHOLIC FERMENTATION Alcoholic fermentation, also referred to as ethanol fermentation, is a biological process by which sugar is converted into alcohol and carbon dioxide. - Occurs under an anaerobic condition (anaerobic fermentation reaction) ALCOHOLIC FERMENTATION GLYCOLYSIS Glucose (2) Pyruvate NAD+ NADH 2 CO2 (2) Ethanol (2) Acetaldehyde  Lactic Acid Fermentation vs Alcoholic Fermentation Lactic Acid Fermentation Alcoholic Fermentation refers to a metabolic refers to a metabolic process by which glucose process by which glucose is converted into the is converted into ethanol metabolite: lactate and and carbon dioxide cellular energy  Produces lactic acid Produces ethanol and molecules from the carbon dioxide from the pyruvate pyruvate molecule Involves lactate Involves pyruvate dehydrogenase and decarboxylase and pyruvate decarboxylase alcohol dehydrogenase Use in the production of Used in the production of yogurt and cheese bread, beer, wine and vinegar  Types of micro-organisms used in food production Bacteria Fungi Yeasts Moulds Algae Green algae 18  Use of micro-organisms in food production Production of fermented food, e.g. Bacteria are used as the starter culture in the production of cheese and yoghurt Mould is used in cheese ripening Yeast is used in making bread and wine Bacteria, mould and yeast are used in making soya sauce Added to enhance nutritional value of food, e.g. Bacteria as probiotics Used as food sources directly, e.g. Black moss is a kind of blue-green algae Chlorella and seaweed are green algae Mycoprotein (i.e. protein from fungi) is the common ingredient in all Quorn products 19  Micro-organisms used for making fermented foods are called “starters” Benefits of food fermentation: 1. Develop flavours, aromas and textures of food, e.g from coffee beans to coffee, from grapes to wine 2. Extend the shelf life of food, e.g. from milk to yoghurt and cheese 3. Improve the nutritional value of the product improved digestibility (e.g. from wheat to bread) synthesis of probiotic compounds (e.g from milk to yoghurt)  Examples of fermented food Ingredients Food Milk Cheese, Yoghurt Meats Sausages (e.g. Salami), Chinese ham Grains Yeast bread, Beer and sake, Chinese rice wine and rice vinegar Plants Szechuan pickled vegetables, Pickled Chinese mustard, Kimchi, Sauerkraut, Oolong tea, red tea, black tea Legumes Fermented bean curd, bean paste, Miso, soya sauce Fruits Wine, vinegar Fish and shell fish Fermented fish, fish sauce, Shrimp paste 21  Functions of bacteria in the production of fermented foods The most important bacteria in food production is the Lactobacillus bacteria species, also known as lactic acid bacteria. Lactic Acid Fermentation It is the process of the conversion of lactose in milk by lactic acid bacteria into lactic acid. LACTIC ACID BACTERIA Lactic Acid Fermentation LACTOSE YOGURT  Functions of yeasts in the production of fermented foods Alcoholic Fermentation Through fermentation, yeasts are used to make bread, alcoholic drinks and vinegar YEASTS CARBON Alcoholic Fermentation + DIOXIDE SUGAR ALCOHOL Saccharomyces cerevisiae is a very important type of yeasts in food industry as a starter for producing fermented foods 23 Functions of molds in the production of fermented foods Moulds are used to produce specific flavours and textures in several food products, e.g. The moulds Aspergillus oryzae and Aspergillus sojae are used in the production of soya sauce and miso The mould Penicillium is used in the production of cheese, e.g. Roquefort , Stilton, Gorgonzola and Danish Blue 24 Examples of fermented foods 26 Cheese Cheese is a cultured milk product which is rich in casein (a milk protein) and milk fat There are many different types of cheeses Cheeses are differentiated according to their flavour texture type of milk salts & seasoning added type of bacteria & mould species used in ripening 27 How is cheese made? Standard cheese processing is as follows: - Cheese is made from the milk of cows, sheep, Milk treatment goats and buffalo - Milk is heated to the required temperature for pasteurisation and then cooled Acidification (addition - Starter culture is added to the cooled milk of starter culture) - The lactic acid bacteria change the lactose in the milk into lactic acid - The lactic acid helps to coagulate the protein in the milk 28 How is cheese made? Coagulation is the conversion of a liquid into solid Coagulation Rennet is added - Rennet is a general term for enzymes used to coagulate milk - Rennet coagulate the milk protein casein into solid curds (coagulated proteins) casein is the main protein in cheese 29 How is cheese made? The curds are cut into smaller pieces to Pressing release the liquid (whey) The cheese is packed and pressed to remove any remaining whey - Whey is a by-product of cheese production Salting Salt is added for flavour and as a preservative 30 How is cheese made? Most cheese undergo further microbial process called Ripening ripening The action of bacteria / moulds and enzymes in the cheese develop the colour, texture and flavour of the final cheese Ripening should take place in a controlled environment - Different cheeses required different temperature and humidity - Ripening may take from weeks to years depending on type of cheese - The longer the ripening period, the stronger the taste developed 31 Examples of cheese ripened by bacteria Lactobacillus bacteria is used in the ripening of Cheddar cheese Cheddar cheese is the most widely eaten cheese in the world Ingredients: Ingredients: Pasteurised cow’s milk, Pasteurised milk, salt, salt, starter culture, cultures, rennet microbial rennet Cheddar cheese 32 Examples of cheese ripened by bacteria Propionic acid bacteria is used in the ripening of Swiss cheese The bacteria convert acetic acid to propionic acid and carbon dioxide The carbon dioxide gives the Swiss cheeses their characteristic “holes” 33 Swiss cheese Examples of cheese ripened by moulds Natural moulds attracted by the wet and protein rich surface form the rind which acts as a barrier against unwanted bacteria and allow the cheeses to mature In blue cheeses such as Stilton, Penicillium Roqueforti grows throughout the cheese Ingredients: Pasteurised cow’s milk, salt, vegetarian rennet, Penicillium Roqueforti, dairy cultures Use of Penicillium Roqueforti (a type of mould) to make Blue Stilton cheese 34 Use of moulds in cheese ripening Penicillium camemberti is assocaited with surface-ripened soft cheeses such as Camembert and Brie Ingredients: Pasteurised milk, salt, lactic acid culture, rennet (microbial), mould culture (Penicillium camemberti) Use of Penicillium camemberti (a type of mould) to make Danish Brie cheese 35 Yoghurt Yoghurt is a cultured milk product The starter culture for traditional yoghurt is a mixture of equal quantities of Lactobacillus and Streptococcus bacteria Ingredients: Fresh milk, modified corn starch, Lactobacillus Bulgaricus & Streptococcus Thermophilus 36 Use of Lactobacillus and Streptococcus bacteria in yoghurt Yoghurt The bacteria helps to lower the pH value of the yoghurt: helping to preserve the yoghurt a low pH can stop the growth of undesirable micro-organisms coagulating milk proteins, giving the yoghurt its texture The preferred pH of yoghurt is around 4.5 Yoghurt must be chilled to slow down the activity of the starter culture prevent the yoghurt from becoming too acid Rennet is not used in the making of yoghurt and the thickening produced is the result of acidification by lactic acid bacteria 37 Yoghurt Most yoghurts contain a significant level of live, active cultures Bacterial cultures, such as bifido-bacteria, maybe added to yoghurt as probiotic cultures Use of live, active bacteria cultures in yoghurts 38 How is yoghurt made? General yoghurt processing steps: Milk treatment Pasteurisation of milk Homogenisation to blend the pasteurised milk and improve yoghurt consistency Milk is cooled to the ideal temperature (40-43ºC) for growing of the starter culture 39 How is yoghurt made? Fermentation Addition of starter culture – A mixture of equal quantities of Lactobacillus and Streptococcus bacteria The lactic acid bacteria change the lactose in the milk into lactic acid – The lactic acid coagulates the milk proteins Acetaldehyde is a metabolic by product of both bacterial species – It gives the plain yoghurt its characteristic flavour 40  How is yoghurt made? The subsequent steps depend on the types of yoghurt products: 41 How is yoghurt made? Set yoghurt The fruit is added at the bottom of the cup and the yoghurt is fermented in the cup Stirred yoghurt (also known as “Swiss” style yoghurt) The yoghurt is fermented in bulk, stirred and then cooled Fruits and/or flavour is then added Drinkable yoghurt Similar to stirred yoghurt The product is homogenised to produce a smooth beverage product 42 Drinkable yoghurt Fermented vegetables General steps for making picked vegetables: 43 Fermented vegetables Examples of pickled vegetables: Asian style, e.g. Western style, e.g. Szechuan pickled vegetables Sauerkraut (pickled cabbage) Pickled Chinese mustard Pickled cucumbers Kimchi (pickled chinese cabbage) Green olives Sauerkraut Olives Szechuan pickled Kimchi 44 vegetables Fermented meat Meat fermentation is a method for extending the shelf-life of an otherwise highly perishable food products Sausage is meat (pork is most commonly used, but beef, mutton and turkey meat are also used) that has been finely chopped or ground and blended with various ingredients, seasonings and spices Curing salts contribute to taste, colour, safety, stability and texture of the product Lactic acid bacteria are usually the starter cultures Sometimes Debaryomyces yeasts and Penicillium moulds are also used 45 Fermented meat Examples of fermented meat: Salami Ham 46  Yeast bread Fresh or dried yeast is used in making yeast bread In the presence of oxygen, yeast produces carbon dioxide gas bubbles and ethanol (alcohol) The gas bubbles expand when heated and push up the dough The alcohol vaporises and escapes from the dough Used to make bread and other fermented doughs such as buns and doughnuts 47 Yeast bread Yeast is a living organism that requires certain conditions for growth: Sugar in the dough is the food for the yeast to grow Warmth helps the yeast to grow if it is too hot, it kills the yeast if it is too cold, it will slow down the rising process Water is used to bind the flour together to form the structure of the bread. It needs to be warm to help the yeast grow 48 Yeast bread Ingredients: Wheat flour Dry yeast Sugar Butter Salt Dry yeast Water Raisins Raisins 49 Use of bread-maker to make yeast bread at home  Beer and Wine Beer and wine are alcoholic drinks made by fermentation reactions that use yeasts to convert sugar into ethanol – Ethanol is the type of alcohol found in wine and beer 50 Functions of yeasts in beer production Barley is the principal grain used in the production of beer Main steps in producing beer Malting and Brewing Barley contains enzymes to convert starch to simple sugars (malt) which is needed for fermentation Soaking barley in water for germination germination of barley activates the starch-breaking enzymes Variety of barley determines the colour, texture and flavour of beer Hops are added to give flavours, aromas, and bitterness in the beer Hops also act as preservative 51  Functions of yeasts in beer production Main steps in producing beer Fermentation by yeasts Types of beer Lagers lighter in colour produced with yeasts that form clumps at the bottom of fermentation tank and prefer cooler conditions Ales stronger, darker in colour produced with yeasts that form clumps at the top of the fermentation tank at warmer temperature 52 Key points in wine production Wines are made from fermented juice of fruits (usually grapes), grains and vegetables The sugar in fruit juices and starch in grains/ vegetables contribute to yeast fermentation The yeast strain used in wine production determines the flavours found in wine 53 Key points in wine production The word “wine” usually refers to wine made from grapes White wines can be made from white, green, red/black grapes Red wines are made from red/ black grapes red wines are produced from dark-coloured grapes that are fermented together with their skins (which contain most of the colour pigments) sulfites are usually added to red wines to maintain their red colour Chinese wine, whiskey and sake are made from grains Vegetables can also be used such as potatoes (for vodka), sweet potatoes (for Korean Shochu), cassava (for tequila) and sugar cane (for rum) 54 Key points in wine production Contains sulphites Contains sulphites Sulphite are usually added to red wines to maintain their colour red 55 Micro-organisms added to foods to enhance nutritional value 56 Bacteria is used as probiotics to enhance the nutritional value of food What is probiotics? Probiotics are live microbial food ingredients (i.e. bacteria) that have a beneficial effect on human health Functions of probiotics maintain a healthy digestive system by improving the intestine’s microbial balance strengthen the immune system Yoghurt is one of the most familiar sources of probiotics the most common probiotic bacteria added to yoghurt are Lactobacillus and bifidobacterium 57 Example of foods with probiotics Ingredients: Skim milk, milk solids, live yoghurt cultures (incl. L. Acidophilus) Use of L.Acidophilus (a type of Lactobacillus bacteria) in yoghurt 58 Example of foods with probiotics Ingredients: Water, sugar, skimmed milk powder, glucose, Lactobacillus paracasei, flavouring Use of Lactobacillus bacteria in drinks Use of probiotics (e.g. Lactobacillus and bifidobacterium) in dietary supplements 59 Direct Use of micro-organisms as food sources 60 Use of cyanobacteria as food Cyanobacteria is a type of bacteria that can undergo photosynthesis Also known as blue-green algae Examples: Spirulina Black moss Have a spiral coil shape Structure similar to Spirulina Rich in proteins, essential A Chinese food rich in proteins fatty acids, vitamins and Black when dried minerals Also used as dietary supplement 61  Use of algae as food Nori (Porphyra)/ seaweed Sea grapes It is dried edible sheets of a species of A kind of green algae live in the sea red algae called porphyra Commonly eaten in China and Japan Chlorella It is a fresh water, single-celled green algae that grows in fresh water Rich in proteins, vitamins and minerals Also used as dietary supplement 62 Uses of fungi in the production of Quorn Quorn A man-made vegetarian food product which is made from mycoprotein Quorn is derived from the mould Fusarium venenatum Mycoprotein Mycoprotein (protein from fungi) is the ingredient common to all Quorn products It is made up of tiny, fine fibres called hyphae The hyphae are responsible for giving Quorn products their meat like texture 63 Uses of fungi in the production of Quorn Quorn is a healthy, meat-free source of protein It is a good source of dietary fibre (because of the cell walls of the fungal structure) It is also low in fat, contains no cholesterol and no trans fats Quorn is turned into a variety of products such as burgers, minced quorn, sausages, and ready meals 64 Uses of fungi in the production of Quorn Quorn is not suitable for a vegan diet because during manufacture egg white protein is used and some quorn products contain milk protein What is a vegan diet? Vegan diet contains only plant foods such as cereals, nuts and seeds, pulses (peas, beans and lentils), as well as fruits and vegetables No animal food products are allowed, even if the animal has not been killed to provide the food product Vegans are sometimes called strict vegetarians 65  Fermentation – YouTube Lactic Acid & Alcoholic Fermentation - YouTube