3.07.16 - 3.11.16
3.07.16 - 3.11.16 Micr 407
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This 0 page Class Notes was uploaded by Molly Gersbach on Sunday March 20, 2016. The Class Notes belongs to Micr 407 at Clemson University taught by Xiuping Jiang in Spring 2016. Since its upload, it has received 20 views. For similar materials see Food and Dairy Microbiology in Microbiology at Clemson University.
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Date Created: 03/20/16
30716 31116 Dairv Microbioloav contd 1 Dairy Products a Fermented milk products i Butter milk yogurt kefir koumiss acidophilus milk cheeses b Function of starter culture amp metabolites i Called starter cultures because they start the fermentation process ii Biopreserve the product due to a fermentation iii Enhance the perceived sensory properties of the product iv Improve the rheological properties ie viscosity and firmness V Contribute dieteticfunctional properties to food 1 Anticancer boost immune system etc c Microbial species used by dairy industry i Traditional starter cultures genus 1 Gram positive non spore formers microaerophilic utilize sugars some are nutritionally fastidious require growth factors that they can t synthesize by themselves 2 Lactococcus a Lactococcus lactis subsp lactics or cremoris amp L lactis subsp lactis biovar diactylactis b Homofermentative LAB c Some strains produce exopolysaccharide EPS material andor bacteriocins 3 Leuconostoc a Leuconostoc mesenteroides subsp cremoris or dextranicum and Lou oeros b Related phenotypically to heterofermentative Lactobacilli 4 Pediococcus a Pediococcus acidilactici Ped Pentosaceus b Cells divide alternatively in two perpendicular directions to form tetrads unique shape 5 Streptococcus a Streptococcus thermophiles only species used good for yogurt production b Predominantly used in combo With other starter cultures for cheese yogurt amp bio fermented milk products c Tolerant to high temps pH 96 salt 65 bile salt 40 d Ferment sugars to produce lactic acid 6 Lactobacillus a Rodshaped nonmotile nonspore forming tolerant to acetic acid b 3 groups i Group A obligately homofermentative lactobacilli ii Group B facultative heterofermentative lactobacilli iii Group C obligately heterofermentative lactobacilli c Food spoilage mo better if you do modified atmosphere packaging d Can find in many environmentswidely distributed soil vegetables etc ii Microbial species incorporated into dairy starter cultures 1 Added into milk products in addition to starter cultures 2 Secondary have additional function appearance or dietetic purposes 3 Propionibacterium Brevibacterium Bifidobacterium Enterococcus 4 Bifidobacterium a Predominant in the stools of breastfed infants b G nonsporeforming nonmotile amp catalase negative c Strict anaerobes d Optimum growth temp 3741C e Principle probiotic bacteria f Optimum pH is neutral range 5 Molds 6 Yeasts 11 Types of Dairy Fermentation just know the different end products don t have to memorize pathways in the powerpoints a Homofermentative LAB i Produce lactic acid as major product of glucose fermentation ii gt60 b Heterofermentative LAB i Producing equal molar amounts of lactate C02 and ethanol from hexose fermentation III Microbiology of selected fermented foods a Butter milk i Fermented skim milk 1 MESOTHERMIC fermentation ii Solids removed iii Pasterurization at 95C for 5 min 1 This is very severe heat treatment iv Starter cultures Lactococcus lactis subsp lactis or cremoris homofermentative Leuconostoc mesenteroides subsp cremoris heterofermentative V The fermentation end products are composed of lactic acid acetic acid diacetyl and C02 b Yogurt production i Skim low or full fat homogenized milk ii Pasteurized at 85C 30 min or 9095C 510 min iii Starter cultures Lb delbrueckii subsp bulgaricus and S thermophiles iv THERMOPHILIC fermentation V Fermentation at 43C for 6 hr pH 48 09 acidity 1 pH must be very controlled added mo Will not be viable if not controlled vi Cool to 1520C IV Inhibtors of starter cultures a Susceptible to infection by hostsepcific bacteriophages b Changes in the activity of starter cultures due to routine subculturing c Presence of antibiotics or other inhibitory substance V Synergistic interactions of starter cultures a Lb delbrueckii subsp bulgaricus proteolytic activity on casein b S thermophiles peptidase to liberate amino acids from peptides c The growth of Lb bulgaricus is stimulated by C02 amp formic acid produced by S thermophiles VI Kefir a Alcoholic milk beverages b Starter cultures are not welldefined c Yeastlactic fermentation 1 End products lactic acid C02 alcohol free fatty acids diacetyl VII Koumiss a Traditional drink of fermented mare s milk VIII Therapeutical milk products a Fermented milk products containing beneficialprobiotic cultures such as lactobacilli and bifidobacteria b Term probiotics live mo which When administerd in adequate amounts confer a health benefit on the host i Digestion immunity etc c Usually these genera Lactobacilli Bifidobacteria Enterococci i Health effects attributed to consumption of probiotics l Alleviation of lactose intolerance a Betagalactidose can break lactose apart and digest 2 Preventiontreatment of infection a Act against pathogens 3 Reduction of serum cholesterol 4 Chemopreventative effects 5 Modulation of immune system ii Probiotic dairy products 1 Yakult containing Lb casei Shirota 2 Nestle s LCl containing Lb acidophilus strain La 1 iii Probiotic survival in food systems 1 Postacidification in yogurt or fermented milk 2 Oxygen toxicity a Start cultures that use oxygen very well Processing parameters a Glass jar rather than polymercontaining ones 9
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