Yogurt

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Yogurt

• Robert Roberts, Ph.D.
• Associate Professor of Food Science
• 121B Borland Laboratory
• University Park, PA 16802
• 814-863-2959
• rfr3_at_psu.edu

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Outline

• Brief History of yogurt
• Definition of yogurt
• Composition of yogurt
• Function of ingredients
• The bacteria
• Yogurt manufacture
• Probiotics
• Resources for the home

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History of Yogurt

• Possible origin in the Middle East, Turkey or
  Iran (10,000 BC)
• Praised for its healthful benefits (500 BC)
• Milk of eternal life
• 1900 Dr. Ilya Metchnikoff isolated bacillus
  cultures for making yogurt
• 1925 First modern yogurt plant
• 1970s increasing popularity in U.S.

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What is Yogurt

• A semi-solid casein gel formed by the action of
  specific lactic acid bacteria on a mix composed
  of milk solids non-fat, milk fat, sugar and
  stabilizer, which means

Fermented milk
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Definition of Yogurt 21 CFR 131.200

• Culturing cream, milk or skim milk with
  Lactobacillus bulgaricus and Streptococcus
  thermophilus
• 3.25 milkfat, 8.25 MSNF
• TA ? 0.9 lactic acid
• May be heat-treated after culturing to destroy
  viable organisms and extend shelf-life

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Yogurt Composition
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Composition of Typical Commercial Yogurts
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Nonfat Yogurt Vanilla
Cultured Pasteurized Grade A Nonfat MilkModified
Corn StarchFructoseContains Less Than 1 of
AspartameKosher GelatinCitric AcidNatural
FlavorPotassium Sorbate (To Maintain
Freshness)Annatto Extract (For Color)Caramel
ColorVitamin A PalmitateVitamin D3 Contains
Active Yogurt Cultures IncludingL. acidophilus
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99 Fat Free French Vanilla
Cultured Pasteurized grade A Low fat
MilkSugarModified Corn StarchWhey Protein
ConcentrateKosher GelatinTri-calcium
PhosphateCitric AcidNatural FlavorColored with
Tumeric and Annatto Extract Active Yogurt
Cultures Including L. acidophilus
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Low fat Yogurt Vanilla
Cultured Grade A Low fat MilkSugarNatural
FlavorPectin Contains Active Yogurt Cultures
IncludingL. acidophilus
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Whole Milk Plain
Cultured Pasteurized Organic Whole
MilkPectin Made with Multiple OrganismsS.
thermophilus, L. bulgaricus, L. acidophilus,
Bifidus, L. casei, and L. reuteri Live Active
Cultures
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Ingredients and Function

• Dairy Ingredients
• Milks, Creams, Milk Powder, Condensed Milk
• Whey Protein Concentrate
• Sweeteners
• Sucrose, Fructose, Aspartame
• Stabilizers
• Gelatin, Modified Food Starch, Pectin, Whey
  Protein Concentrate
• Functional Ingredients
• Tri-calcium Phosphate, Citric Acid, Potassium
  Sorbate

• Source of protein, lactose, and minerals
• Sweet taste
• Control Water and texture
• Buffering
• Mold inhibition

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Comparison of Various Fat Levels
Yoplait comes in a 160g container. The number is
parenthesis was calculated for sake of comparison
to the other (227g) containers.
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Yogurt Manufacture
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General Categories

• 1. Firm yogurt (set-style) firm gel in a pack,
  normally consumed by use of a spoon
• 2. Stirred yogurt gel has been broken, cooled
  and packed after coagulation
• 3. Drinkable yogurt like stirred, but product
  has been homogenized and brought into a liquid
  form before filling

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Yogurt Production
Milk Selection
Pasteurization
Dry Matter Standardization
Heat Treatment
Inoculation
Homogenization
Deaeration
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Yogurt Production
Inoculation
Flavoring
Ferment
Fill Retail Container
Break
Ferment
Stir/Cool
Cool/Store
Fill
Homogenize
Fill
Set
Stirred
Drinkable
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Fermentation Culture

• Streptococcus thermophilus and Lactobacillus
  delbrueckii ssp. bulgaricus (ST and LB)
• thermophilic (42C, 107F)

Figure taken from Dairy Processing Handbook, Alfa
Laval
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(No Transcript)
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Cone Bottom Processor
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Probiotic Aspects of Yogurt
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gt103 CFU/g
gt103-5 CFU/g
gt1012 CFU/g
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Adult Faecal Microbiota
Finegold et al 1983
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Influence of Intestinal Microorganisms

• Beneficial
• Pathogen inhibition
• Immune stimulation
• Vitamin synthesis
• Digestive aids
• Prevent diaper rash

• Detrimental
• Constipation
• Diarrhea
• Infections
• Flatulence
• Liver damage
• Arthritis

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Gut Ecosystem Equilibrium
Diet
Host Physiology
Microbes
External Stresses (environmental, emotional, etc)
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Probiotic

• A single or mixed culture of live microorganisms
  which beneficially affects the host by improving
  the indigenous microflora
• (Havenaar and Huis int Veld, 1992)

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Prebiotic

• A non-digestible food (food component) that
  beneficially affects the host by selectively
  stimulating the growth and/or activity of one or
  a limited number of bacteria in the colon
• (Gibson and Roberfroid, 1995)

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Synbiotic

• Combining the effects of probiotic and prebiotics
  to produce health enhancing functional foods
  (food ingredients)
• (Gibson and Roberfroid, 1995)

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Physiological Benefits of Probiotic Cultures

• Improved lactose digestion
• Reduced infantile/adult diarrhea
• Immune system stimulation
• Reduction in bacterial enzymes
• Competitive exclusion of pathogens
• Reduction in serum cholesterol
• Anti-tumor activity
• Folic acid and B-vitamin synthesis
• Enhance mineral bioavailability

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Probiotic Strains

• Lactobacillus
• L. casei
• L. paracasei ssp. casei
• L. rhamnosus GG
• L. acidophilus (various)
• L. reuteri
• L. plantarum
• L. Fermentum

• Bifidobacterium
• B. lactis (various)
• B. longum BB536
• Enterococcus faceium
• Streptococcus thermophilus

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Probiotic Strains
Bifidobacterium
Lactobacillus
Patricia Conway, Sydney, 2000
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Modes of Function

• Direct Effects
• Nutrient competition
• Site competition
• Growth inhibition
• Adhesion inhibition

• Indirect Effects
• Establish indigenous microorganisms
• Restore indigenous microorganisms
• Immune stimulation
• Peristalsis stimulation

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Issues with Probiotics

• Species variability
• Viability in the product
• Contradictory results
• Non-conclusive reports

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Resources for Making Yogurt at Home

• http//muextension.missouri.edu/xplor/hesguide/foo
  dnut/gh1183.htm
• by University of Missouri Extension
• http//ianrwww.unl.edu/pubs/Dairy/g449.htm
• by University of Nebraska Extension

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