《食品發(fā)酵工藝》英文課件PPT,食品發(fā)酵工藝,食品,發(fā)酵,工藝,英文,課件,PPT Chapter 6 Fermented Food ProductsProducts from Microorganisms2FoodandfoodrelatedproductsWholecellsproductsCheeseandyogurtFermentedfruitsandvegetablesOrganicacidsAlcoholicbeveragesFlavoringagents:aminoacidsandnucleotides3Non-foodproductsEnzymeVitaminsAntibioticsBiotechdrugsLacticacid-ANaturalProduct It is made by fermentation of different sugars(glucose,sucrose,or lactose)by means of the genera lactobacillus,streptococcus and pediococcus.Organic Acid1.Lactic acid fermentationLactobacillus bulgaricusStreptococcus thermophilusLactobacteriaceae Gram positive,rods or cocci Obligate anaerobes(no respiratory chain)Catalase negative(often aerotolerant)Homolactic fermentation(homofermentation)Glucose degraded via EMP pathway,with lactic acid as the only end product glucose+2 ADP+2 Pi 2 lactic acid+2 ATP Important in dairy industry(yogurt,cheese)homofermentationHeterolactic fermentation(heterofermentation)Glucose degraded via phosphoketolase pathway(PK)In addition to lactic acid,also ethanol and CO2 produced glucose+ADP+Pi lactic acid+ethanol+CO2+ATPphosphoketolasepathway(PK)G xylulose 5-phosphate acetyl phosphate+glyceraldehyde 3-phosphate phosphoketolaseethanolpyruvatelactic acid C C6 6H H1212O O6 6ADP+PiCHADP+PiCH3 3CHOHCOOHCHOHCOOHCHCH3 3CHCH2 2OHOHCOCO2 2+ATP+ATPTypesPath.ProductsEnergyInversion rateHomoEMP2 Lactic acid 2ATPhighHeteroPK1 Lactic acid 1 alcohol1 CO21ATPlow Homofermentation vs.heterofermentationHow to recognize heterofermentation strain in lab?（1）Production of C02 （2）Gram staining Lactic acid production processLactic acid in Food Lactic acid is naturally present in many foodstuffs,such as cheese,yogurt,soy sauce,fermented meat and pickled vegetables,etc.It serves as either a flavoring agent,pH regulator or a preservative.Food TrendsHealthConvenienceValueTaste20What is YogurtA semi-solid casein gel formed by the action of specific lactic acid bacteria on milkFermented milkMicrobes used in Yoghurt InvolvedLactobacillus bulgaricus and/or acidophilus Streptococcus thermophilus They work better together than they doseparately because.AcidproductionrateismuchhigherFormationoftypicalyogurtflavourandtextureIngredients and FunctionLactose is partial converted to lactic acid,which makes digestion easier for lactose-intolerant people.Containing higher amino acid than milk.Lactic acid causes the milk proteins(casein)to coagulate into a semisolid curd and also restricts spoilage bacteria.Freshly prepared yogurt contains 10,000,000,000(109)bactria per gram.Main Families of Lactic BacteriaFig 1:Lactobacilli(Small Intestine)Fig 2:Bifidobacteria(Large Intestine)Small IntestineLarge IntestineYogurt ProductionMilk SelectionCooling to 42-45Dry Matter StandardizationHomogenizationHeat TreatmentInoculationDeaerationSterilizationDenaturingproteinYogurt variations1.Setyogurt：pouring the inoculated milk into pots and fermenting it,normally consumed by use of a spoon or sold into customers containers.2.Stirredyogurt:fermented in bulk,stirred and then dispensed into pots.Two types of yogurtInoculationFlavoringFill Retail ContainerFermentFermentCool/StoreBreakStir/CoolFillSet yogurt Stirred yogurt Cone Bottom ProcessorBasic Cheese-making Steps1.Collect/deliver milk2.Pasteurize milk 3.Add starter culture4.Add rennet and CaCl25.Cut the curd and Heat 6.Separate curd from whey7.Salt the curd(dry salt)8.Package and ripen cheese Rennin,an acid protease from calves stomach,that partially hydrolyses the milk protein(casein)and leads to coagulation in the presence of Ca2+to form“curds.”The liquid portion of the milk at this time is called“whey.”Pasteurization SeparatethecurdfromthewheySaltingPackage,CoatCheeseandRipening Q:Whats the difference between yogurt making and cheese making?Citric acid is a weak organic acid found in citrus fruits(lemon).It is a good,natural preservative and is also used to add an acidic(sour)taste to foods and soft drinks.Citric acid Aspergillus nigerWell-known production organism of citric acid and other organic acids.Also a well-known over-producer of enzymes,in particular starch-degrading enzymes and plant cell-wall degrading enzymes.PhosphofructokinaseQ:Citrateisoneofthebest-knowninhibitorsofglycolysis,whyA.niger couldoverproducecitratebyanactiveglycolyticpathway?1.Biochemistry of citric acid formation EMP acetyl-CoA Gulcosepyruvate HMP oxaloaceticacid decarboxylationCO2fixationcondensationcitricacid 2.Metabolic regulation of citric acid production by A.niger（1 1）Phosphofructokinase(PFK)inhibited by a high internal concentration of ATP（2 2）-keto-glutarate dehydrogenaseinhibited by glucose and ammonium(NHNH4 4+)Three excess and three limiting Excessive concentrationsGlucose Ammonium(NHNH4 4+)Dissolved oxygen -An alternative respiratory pathway without the formation of ATP -Sudden interruptions in aeration cause anirreversible impairment of citric acid productionPhosphate limitationMn2+deficiency Results in a high intracellular ammonium concentrationLow pH Citrate degrading enzyme(e.g.aconitase or isocitrate dehydrogenases)within the TCA cycle are pH sensitive Suboptimal concentrationsFermentation conditions SolidcultureorliquidcultureRawmaterials:sweetpotatostarch With Chinese characteristicsPurificationofCitricAcid 1.Brothpre-treatment：heat2.Filtration3.NeutralizeCaCO3+CitricAcidCO2+CalciumCitrate4.AcidifyingCalciumCitrateH2SO4CitricAcidCaSO45.ConcentrationReact citric acid with calcium carbonateFilter precipitateReactprecipitatewithsulfuricacidFilter precipitatePurifiedCitricAcidPrecipitationandFiltration.FurtherPurification CrystallizationandDryingCitricacidmonohydrate Requires repeated crystallization until water content is approx.7.5-8.8%Citricacidanhydrous Prepare by dehydrating the monohydrate citric acid product at a temperature above 36.6C Review Questions1.Tellthedifferencebetween homolacticfermentationandheterolacticfermentation,yogurtandcheese.2.Statetheprinciplesofthethreeexcessandthreelimitingofcitricacidproduction.3.Howtoobtaincitricacidfromfermentationbroth?