Lesson 8 Part 1
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School
University of British Columbia**We aren't endorsed by this school
Course
FNH 313
Subject
Biology
Date
Jan 6, 2025
Pages
4
Uploaded by yoona23
The Good: Beneficial Microorganisms in FoodLesson 8Make them safer•Prevent pathogen growth (fermentation)•Kill pathogens (bacteriophages)Promote good health•Probiotics•Increased vitamins and digestibility (fermentation)Enhance product flavourMicroorganisms added to foods3Microorganisms are added to foods to:Learning objectives4By the end of this lesson, you should be able to:Distinguish between homo and heterofermentationsDescribe the mechanisms and know the microorganisms responsible for the fermentation and flavour development of various food productsDiscuss the characteristics of probioticsState the regulations surrounding probiotics in foodList the advantages and disadvantages of phage biocontrol12435Lesson map5FermentationsWhat are they?Types of fermentationHow are different fermented foods made?•Processes and conditions involved•Microorganisms responsible•Compounds producedProbioticsWhat are they?How are they regulated?BacteriophagesReviewApplications Pros and cons
Fermented foods6By definition, fermentation is anaerobic; however, it is also commonly used to describe aerobic processes2 key components of a fermentation system:1) Organism2)Feedstock of organismFeedstock is transformed usually into a more palatable productDefinition: Foods that have been subjected to the action of microorganisms or enzymes so that desirablebiochemical changescause significant modification in the food –Campbell-Platt¾Organisms employed in food fermentations are many and diverse¾Key players are:Lactic acid bacteria (e.g. dairy products)Yeast(e.g. alcoholic beverages and bread)Some mouldsMicroorganisms involved in food fermentation7Starter cultures8Traditionally, foods have been fermented with endogenous microfloraHowever, without knowing which microorganisms are naturally present, product inconsistency, food spoilage, and/or food illness can resultMore commonly, starter cultures are used where specific strains have been isolatedand purified for use in foods Organisms must conform to the criterion of being Generally Recognized as Safe (GRAS)Starter cultures can be purchased in freeze-dried (powder), or frozen formStarting inoculum is usually added at 1% to productsStarter cultures9
Conversion of Feedstock10Since LAB are only weakly proteolytic and lipotypic, they prefer free sugars, amino acids, and FAs as energy sourcesIn order to provide these free molecules, external sources of enzymes sometimes need to be added to foods first before the action of LAB fermentation can take placeExamples:•In beer making barley is germinated prior to yeast being added, to release enzymes to breakdown starch into simple sugars•In soy sauce, Aspergillus oryzegenerates high levels of enzymes (protease, amylase, lipase, cellulase and peptidase) that produce nutrients for yeasts and LAB to use in fermentationTypes of fermentations11Homolactic fermentationLactic acid is major product (70-90%) produced from glucose/hexose fermentation Results in 2x more energy from glucose than heterolactic fermentationIncludes: Pediococcus, Streptococcus, Lactococcus, and some Lactobacillus (Lb. acidophilus, Lb. delbrueckiisubsp. bularicus)Have aldolase and hexose isomerase but lack phosphoketolaseUse Embden-Meyerhof-Parnas (EMP) pathwayUsed for most fermented dairy products: yogurt, buttermilk, sour cream, cottage cheese, and cheddar cheeseTypes of fermentations12Heterolactic fermentation Glucose Ælactic acid + ethanol + CO2 + ATP (+ other compounds)Lack aldolase and hexose isomerase but have phosphoketolaseUse phosphoketolase pathwayProduce flavourand aroma compounds such asacetylaldehydeanddiacetylIncludes: Leuconostocand some Lactobacillusspp.While many of these LAB are naturally present in dairy products, they usually cause defectsUsed inkefir, buttermilk, and sauerkrautfermentationsHetero vs. Homolactic fermentation13Phosphoketolase(breaks pentose in half)Hexose isomerasealdolase
Types of fermentations14Propionic acid fermentation3 Lactate Æ1 acetate + 1 CO2+ 2 propionateE.g. PropionibacteriumandBifidobacteriumUsed in the manufacture of Swiss cheese, which is distinguished by the distinct flavorof propionate and acetate, and holes caused by entrapment of CO2Types of fermentations15Alcoholic fermentationsGlucose Æ2 ethanol + 2 CO2E.g. Saccharomyces cerevisiaeUsed to produce beer, wine, breadand distilled spiritsTypes of fermentation16Acetic acidMain bacteria genus of importance is AcetobacterProduces large quantities of acetic acid from ethanolUsed primarily in vinegar productionFermentation pathways17Homolactic(EMP pathway)Heterolactic(phosphoketolase pathway)AlcoholicAcetic acidPropionic acid