Presentation on theme: "Fermented Foods Foods that have been subjected to the action of micro-organisms or enzymes, in order to bring about a desirable change. Numerous food products."— Presentation transcript:
1Fermented FoodsFoods that have been subjected to the action of micro-organisms or enzymes, in order to bring about a desirable change.Numerous food products owe their production and characteristics to the fermentative activities of microorganisms.Fermented foods originated many thousands of years ago when presumably micro-organism contaminated local foods.
2Fermented Foods Help to preserve the food, Micro-organisms cause changes in the foods which:Help to preserve the food,Extend shelf-life considerably over that of the raw materials from which they are made,Improve aroma and flavour characteristics,Increase its vitamin content or its digestibility compared to the raw materials.
3Table 1 History and origins of some fermented foods Approximate yearof introductionRegionMushroomsSoy sauceWineFermented milkCheeseBeerBreadFermented MeatsSourdough breadFish saucePickled vegetablesTea4000 BC3000 BC2000 BC1500 BC1000 BC200 BCChinaChina, Korea, JapanNorth Africa, EuropeMiddle EastNorth Africa, ChinaEgypt, EuropeEuropeSoutheast Asia, North AfricaChina, Europe
4Fermented FoodsThe term “biological ennoblement” has been used to describe the nutritional benefits of fermented foods.Fermented foods comprise about one-third of the world wide consumption of food and % (by weight) of individual diets.
5Table 2 Worldwide production of some fermented foods Quantity (t)BeverageQuantity (hl)CheeseYoghurtMushroomsFish sauceDried stockfish1000 million350 million15 million3 million1.5 millionBeerWine
6Table 3 Individual consumption of some fermented foods: average per person per year AnnualconsumptionFoodCountryBeer (I)Wine (I)Yoghurt (I)Kimchi (kg)Tempeh (kg)Soy sauce (I)Cheese (kg)Miso (kg)GermanyItaly, PortugalArgentinaFinlandNetherlandsKoreaIndonesiaJapanUK130907040252218107
7Table 4 Benefits of fermentation RawmaterialFermentedfoodBenefitPreservationMilk(Most materials)Yoghurt, cheeseEnhancement of safetyVinegarBeerWineSalamiGari, polviho azedoSoy sauceAcid productionAcid and alcohol productionProduction of bacteriocinsRemoval of toxic componentsFruitBarleyGrapesMeatCassavaSoybeanEnhancement of nutritional valueBreadKimchi, sauerkrautNata de cocoBifidus milk, Yakult,Acidophilus yoghurtImproved digestibilityRetention of micronutrientsIncreased fibre contentSynthesis of probiotic compoundsWheatLeafy veges.CoconutMilkImprovement of flavourCoffee beansGrapesCoffeeWine
8CassavaFresh cassava contains cyanhydric acid (HCN) that should be eliminated from any product originating from cassava to render it fit for human consumption. Depending on the production method (particularly traditional methods) gari could contains up to 20 mg / kg of HCN - against 43 mg / kg for fresh peeled cassava.Gari is a fermented, gelled and dehydrated food produced from fresh cassava. It is a popular diet in Nigeria, Benin, Togo, Ghana and in other West Africa's countries. The consumption area even expands to Central Africa: Gabon, Cameroon, Congo Brazzaville and Angola.Polvilho is a fine tapioca/manioc/cassava flour. it can be found at latino markets in california as "sour starch" (polvilho azedo) or "sweet starch" (polvilho doce)
9Nata de Coco A high fiber, zero fat Philippino dessert. A chewy, translucent, jelly-like food product produced by the bacterial fermentation of coconut milk.Commonly sweetened as a candy or dessert, and can accompany many things including pickles, drinks, ice cream, and fruit mixes.Highly regarded for its high dietary fiber, and its zero fat and cholesterol content.It is produced through a series of steps ranging from milk extraction, mixing, fermentation, separating, cleaning, cutting to packaging.
10Lactic Acid Bacteria Major group of Fermentative organisms. This group is comprised of 11 genera of gram-positive bacteria:Carnobacterium, Oenococcus, Enterococcus, Pediococcus, Lactococcus, Streptococcus, Lactobacillus, Vagococcus, Lactosphaera, Weissells and LecconostocRelated to this group are genera such as Aerococcus, Microbacterium, and Propionbacterium.
11Lactic Acid BacteriaWhile this is a loosely defined group with no precise boundaries all members share the property of producing lactic acid from hexoses.As fermenting organisms, they lack functional heme-linked electron transport systems or cytochromes, they do not have a functional Krebs cycle.Energy is obtained by substrate-level phosphorylation while oxidising carbohydrates.
12Lactic Acid BacteriaThe lactic acid bacteria can be divided into two groups based on the end products of glucose metabolism.Those that produce lactic acid as the major or sole product of glucose fermentation are designated homofermentative.Those that produce equal amounts of lactic acid, ethanol and CO2 are termed heterofermentative.The homolactics are able to extract about twice as much energy from a given quantity of glucose as the heterolactics.
13Lactic Acid BacteriaAll members of Pediococcus, Lactococcus, Streptococcus, Vagococcus, along with some lactobacilli are homofermenters.Carnobacterium, Oenococcus, Enterococcus, Lactosphaera, Weissells and Lecconostoc and some Lactobacilli are heterofermentersThe heterolactics are more important than the homolactics in producing flavour and aroma components such as acetylaldehyde and diacetyl.
14Lactic Acid Bacteria - Growth The lactic acid bacteria are mesophiles:they generally grow over a temperature range of about 10 to 40oC,an optimum between 25 and 35oC.Some can grow below 5 and as high as 45 oC.Most can grow in the pH range from 4 to 8. Though some as low as 3.2 and as high as 9.6.
15Starter CulturesTraditionally the fermenting organisms came from the natural microflora or a portion of the previous fermentation.In many cases the natural microflora is either inefficient, uncontrollable, and unpredictable, or is destroyed during preparation of the sample prior to fermentation (eg pasteurisation).A starter culture can provide particular characteristics in a more controlled and predictable fermentation.
16Starter CulturesLactic starters always include bacteria that convert sugars to lactic acid, usually:Lactococcus lactis subsp. lactis,Lactococcus lactis subsp. cremoris orLactococccus lactis subsp. lactis biovar diacetylactis.Where flavour and aroma compounds such as diacetyl are desired the lactic acid starter will include heterofermentative organisms such as:Leuconostoc citrovorum orLeuconostoc dextranicum.
17Starter Cultures flavour, aroma, and alcohol production The primary function of lactic starters is the production of lactic acid from sugarsOther functions of starter cultures may include the following:flavour, aroma, and alcohol productionproteolytic and lipolytic activitiesinhibition of undesirable organisms
18A good starter CULTURE will: Convert most of the sugars to lactic acidIncrease the lactic acid concentration to 0.8 to 1.2 % (Titratable acidity)Drop the pH to between 4.3 to 4.5
19Food scientists frequently use the ability of bacterial cells to grow and form colonies on solid media to:isolate bacteria from foods,to determine what types andhow many bacteria are present.Streak platesA single bacterial colony
20The streak plate technique Bacteria are “streaked”over the surface of an agar plate so as to obtain single colonies.Obtaining single colonies is important as it enables;the size,shape andcolour of the individual colonies to be examined.It can also highlight the presence of contaminating micro-organisms