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Fermented Food Macro

Terms in this set (172)

What do fermented products do?
-add variety to diet
-main goal is to improve shelf life
-flavors and aromas
-nutritional value and digestibility increased
What are some fermented foods that have an extended shelf life
-fermented sausage
-cheeses
-sauerkraut
-pickles
What kind of factors affect the type of fermentation?
-both extrinsic and intrinsic factors
Fermented Dairy foods:
-cheeses
-yogurt
-buttermilk
-sour cream
Fermented Meat products:
-salami
-pepperoni
-chorizo
Fermented Cereal:
-breads
-pancakes
-crackers
-pizza
Fermented fruits and veggies:
-pickled fruits
-pickled veggies
-olives
-sauerkraut
Fermented Legumes:
-tofu
-fermented soymilk
-tempe
-soy sauce
Fermented Fish:
-bagoong
-fish sauces
-pickled fish
Fermented beverages:
-beer
-wine
-distilled spirits
-coffee
-cocoa
-tea
Fermented starch crop:
products from:
-potato
-sweet potato
-bananas
Other random fermented foods:
-fermented eggs
-vinegar
Definition of Fermentation:
-metabolic process in which carbs and related compounds are partially oxidized with the release of energy without external electron acceptors
-the final electron acceptors are organic compounds produced from the breakdown of the carbs
-no oxygen required, but microbes can be aerobic or anaerobic
-catabolism of organic compounds with the release of energy in the absence of oxygen
Is oxygen required for fermentation?
no
Biochemistry of Fermentation:
1. catabolism of organic compounds (glucose or other sugars)
2. generates energy from catabolism (ATP-chemical form of energy used by cell)
3. Products are acids, alcohols, and CO2
What kind of microorganisms are used in foods?
-actively growing microbial cells
-non growing microbial cells
-metabolic by-products and cellular components of microorganisms
-bacteria should be recognized as safe and have regulatory approval
-must be approved by a regulatory agency
What is yeast fermentation?
-metabolism of sugar
-yeast gets energy as ATP
-use glucose to form 2 ethanol and 2 CO2
Bread making:
-yeast is used to produce CO2 for air holes and texture
-sugar is used as a fermentable carb, fat is used for texture
-the fermentation allows the CO2 to form pockets (proofing)
-baking it kills most of the yeast
-the 2 important steps are the grinding/milling of grain into flour, and the dough being created
What cereal grains are used to make bread?
-barley, maize, oats, and rye
What is a major crop in the U.S?
bread wheats
What are the major proteins in dough flour?
-glutenin and gliadin
-when combined with water, it forms an elastic gluten complex
-this forms an elastic nonporous net which can trap CO2 as it's produced
Amylases in flour hydrolyze starch make what?
maltose
When did bread making start?
-roman times to mid-19th century
-bread making yeast were recycled from beer industry
-top fermenting yeast were skimmed off of grain-malt wort (not used anymore)
-development of lager beer became popular in Bavaria in 19th century
Beer:
-use hops (flavor and antimicrobial activity), yeast (to produce alcohol and CO2), water, and malt (to provide a fermentable carb) or rice (to prevent off-flavor of most grains)
-wort fermented (S. cervisiae)
-product is aged and CO2 is added, pasteurization
-most bottled beer is heat treated to kill the remaining yeast
-draft beer in kegs is not heat treated and must be refrigerated
Why is malt used in beer and ale?
-because starch in grains are not fermented by yeasts
What does barley do in beer and ale?
-it produces germinates and amylases to breakdown starch
What is wort?
-soluble part made during beer process
-it's heated to inactivate enzymes
What is ale produced from?
-top fermenting yeasts in 5-7 days
What is the pH of ale?
3.8
What is lager produced from?
the bottom fermenting yeasts, S. carlsbergensis in 7-12 days
What is the pH of lager?
4.1-4.2
Table wine:
-produced by fermentation of "must" from red or white grapes
-no additives
-final alcohol percentage is 9-14%
-vineyard wines (sold as a specifically named vineyard brand wine and the flavor develops with 5 ages or more of aging
Yeast fermentation process in winemaking:
-wild yeast
-stems are removed and grapes are crushed
-skins are discarded
-fermented for 10-15 days
-aged (depends on wine type)
Acidic Fermentation acids:
-production of lactate mainly, but also acetate, propionate and other organic acids
Lactic Acid Bacteria:
-12 genera
-all gram positive
-plant matter is the natural habitat
-all produce lactic acid from hexoses
-monosaccharides with 6 carbons, glucose, galactose, fructose, mannose
-do not have functional Krebs Cycle; energy- substrate level phosphorylation while oxidizing carbs
12 Genera of Lactic Acid Bacteria
-Enterococcus
-Lactococcus (most commonly used for dairy products)
-Lactobacillus (most commonly used for dairy products)
-Pediococcus
-Leuconostoc
-Streptococcus
-Oenococcus
-Lactospaera
-Teragenococcus
-Vagococcus
-Carnobacterium
-Weissella
Lactic Starter Cultures:
-mainly 5 genera used because of their ability to metabolize large amounts of lactic acid
-Lactococcus, Leuconostoc, Pediococcus, Streptococcus, and Lactobacillus
What is Lactobacillus mainly used for?
dairy, pickles, beer, probiotic
What is lactococcus used for?
mainly dairy fermentations
What is streptococcus thermophilus used for?
dairy fermentation
What is leuconostoc used for?
-it's found in plants, veggies, silage, milk, dairy
-used for raw and processed meats, sauerkraut, kimchi
What is pediococcus used for
sauerkraut
What is bifidobacterium?
-considered to be beneficial in intestine
-another starter culture
What is propionibacterium?
used to make swiss cheese
-another starter culture
What is brevibacterium?
used to make cheese
-another starter culture
What is acetobacter?
-used to produce acetic acid from alcohol
-another starter culture
What mold is used in several oriental food, like sake, soy sauce, and miso?
Aspergillus oryzae
What mold is used in roquefort and blue cheeses?
Pen roquefortii
What mold is used in Camembert cheese?
camembertii
What is homofermentative bacteria used for?
-only to make lactic acid
-used to make acid (shelf-life)
What is heterofermentative bacteria used for?
-to make lactic acid, CO2, and/or acetic acid
-contribute to flavor
What homofermentative bacteria are used at high temp for yogurt and dairy?
-lactobacillus delbruckii
-lactobacillus helveticus (yogurt, swiss cheese, italian cheese, some bread)
-lactobacillus acidophilus (health benefits)
*37-60 degrees C
What homofermentative bacteria are used at low temp?
-Lactobacillus casei (health benefits, acid production for cheese
-Lactobacillus plantarum (acid in pickles, olives; fermented sausages)
*28-35 degrees C
Heterofermentative bacteria?
-L. brevis (sauerkraut, cabbage
-L. viredescens (spoilage in sausage)
-L. fermentum (spoilage in Swiss cheese, rapid gas production; breaks cheese)
Backslopping:
A method of inserting a small portion of a previous batch of fermented food into the start of new batch of food to be fermented.
Starter Cultures:
-heat treat product to reduce natural flora and take selected cultures and add back
-it's more controlled and more uniform than backslopping
-cultures are isolated and identified and then formulated to produce fermented product
-antibiotics used as growth factors may limit ability to create dairy products
-used today
-increase the speed and consistency of fermentations
Requirements for good starter cultures:
-Activity: relative range of producing desired change in food; want change in shortest amount of time
-Metabolism: want same end products produced each time
-No objectionable characteristics: non-toxic, no undesirable metabolites, no disposal problem
Types of Starter cultures:
-single strain (1 strain of 1 species)
-multiple strains (more than 1 strain of 1 species); usually based on bacteriophage types
-multiple species (more than 1 species; may be more than 1 strain of each); 1 species alone doesn't produce change
What kinds of foods don't use a starter culture, but instead natural bacteria?
-sauerkraut
-olives
-pickles
-chocolate
-some cheeses (raw vs. pasteurized milk)
-sourdough bread
Uses of fermented veggies:
-to preserve them
-to develop characteristic sensory properties to destroy naturally occurring toxins and undesirable components in raw materials
-to improve digestibility
-to enrich products with desired microbial metabolites (lactic acid or AA's)
-create new products and to enhance dietary value
Vegetable Fermentation Steps:
1) Select the vegetable preferably sound, undamaged and at the proper ripeness.
2) Pretreat to include peeling, blanching (to inactivate endogenous enzymes) and/or cook.
3) Place in fermentation vessels and add starter culture
4) Exclude oxygen and ensure anaerobic conditions.
5) Allow to ferment over time W STARTER CULTURE
6) Prepare the product for use or distribution.
Salt in vegetable fermentations
-used for flavor
-it enhances fluid release from the product which relates to crunchiness in pickles
-helps create anaerobic conditions
-has a selective effect on the type of lactic acid bacteria that will cause the fermentation
Meat fermentations:
-used in dry and semi dry sausages
-USDA requirements: contain nitrite, pH < 5.0, MPR of 3.1 to 1
-nitride is used to inhibit C botulium and S. aureus during incubation
-uses sugar and starter culture incubated at 90 degrees F for several hours
Selecting Industrial microorganisms:
-metabolic specials
-high yield of particular metabolite
-genetically altered
-metabolically imbalanced
-poor growth in nature, but good growth under industrial conditions
Requirements of industrial microorganisms:
-availability: in pure culture
-genetics: must be genetically stable
-growth: must be able to grow in large-scale culture
-fast growth and product formation: important; efficient use of expensive equipment, less chance of contamination, eaiser to control
Simple definition of fermentation:
conversion of sugars to acids, alcohol, or CO2 without the use of oxygen
Vegetable fermentations rely on:
indigenous microbiota
In what year was it noticed that important characteristics of some dairy cultures were unstable?
-1930's
What can carry genetic information in circular chromosomal DNA, circular plasmids, and transposons?
starter culture
The action of microorganisms on foods and the changes that occur due to the catalytic effect of their enzymes.
Fermented foods
Microorganisms responsible for most fermentation
Bacteria
_____________ is the most common yeast fermentation
Alcohol fermentation
There are two groups of bacteria in lactic acid fermentation:
- Bacteria that convert CHO to lactic acid only
- Bacteria that convert CHO to lactic acid + acetic acid, EtOH, CO2 etc...
- Very often, the bacteria work in sequence in fermentation
- Products of one bacteria increase, the first colonies of bacteria ____ and another strain takes over
Die
- From German meaning acid cabbage
- Definition: the product of lactic acid fermentation of cabbage containing 2-3% salt and at least 1.5% acid
Sauerkraut
- Fresh cucumbers are packed with acetic and lactic acid solutions
- Spices are added for the desired flavors
- Some are just refrigerated - Clausen half sour type
- Others are pasteurized and don't need refrigeration until the jar is opened
Pickles
(Type of pickle fermentation)
- Cucumbers are placed in a salt solution and allowed to ferment
- The same sequence of bacteria as used with sauerkraut are employed here
- Lactic acid is produced and the pH drops
- More salt is added to stop the fermentation
Natural Fermentation
- Cucumbers are washed and sanitized with a chlorine rinse that acts as an anti-microbial agent.
- Salt brine and acetic acid added to the correct pH for a final fermentation with L. plantarum
- This method takes less time and there are fewer problems with wild organisms, but less flavor development.
Controlled Fermentation
- Problem with pickle fermentation
- Gas collects inside the pickles
- Caused by fermentation by yeasts and other undesirable organisms
Bloating
- Problems with pickle fermentation
- Caused by pectinolytic enzymes form the microorganisms
- These pickles are often used for relish
Softening
- Fermentation makes Olives edible
- They are bitter due to a group of glucosides called _________
- To get rid of the _________, olives are soaked in NaOH (lye) for several days and the bitter compounds are extracted into the lye solution
- The lye solution is discarded and the olives are washed
- Greek Olives do not receive this treatment so they remain somewhat bitter
Oleuropein
(Type of olive)
- Picked before they are ripe
- Treated with lye and washed
- Immersed in a 5-10% salt brine
- Allowed to ferment for several weeks
- A succession of organisms grow and change the Olives
- Finally, they are washed and packed in brine
Green Olives
(Type of olive)
- Olives are allowed to ripen before picking
- Dipped in ferrous gluconate to fix the pigment
- Then treated with lye like the green olives
- Brine is added and packed, no fermentation
- Need to be heat processed to preserve them
- Affects the texture and flavor
Black Olives
- Prepared from the taro plant roots
- Roots are washed, steamed, peeled and ground, or mashed with water to desired consistency
- Fermented in barrels for 1-6 days by natural mixed cultures
- Lactic acid is produced
- People who have tried it say it is not very appetizing - is probably an acquired taste.
- It's sometimes mixed with milk and sugar
Poi - from Hawaii
One of the oldest forms of meat preservation
Dry and Semi Dry Sausages
(Meat fermentation)
- Chopped meat is mixed with spices, salt, sugar, ___________ and a starter culture
- Hold for 24 hours at a low temperature
- Fill into casings
Sodium nitrite
- _____________ at controlled temperature and RH (relative humidity)
- pH decreases from 5.8 to about 5.0-5.3 for dry, and 4.6-5.2 for semi-dry
- The low pH preserves the meat
- Products of the fermentation are also antimicrobial
Air-dry or smoke-dry
Can cause greening of the meat due to the formation of Hydrogen Peroxide.
L. viridescins
Some yeasts and molds can grow in low pH and are salt tolerant. They tend to grow under aerobic conditions and are on the outer surface of the meat. Yeast can produce gasses and molds can product ___________
Mycotoxins
- Problem with fermented meats
- very abundant pathogen, not very competitive and not
generally a problem with raw foods. However, once the pH is lowered and salt is increased, it can become a problem
Staphylococcus aureus
- Some is made from dry fish or fresh fish of a single species (anchovies), some are made from whatever is caught
- Salt is added to fish at a 1:3 ratio
- Fermented in sealed pots or tanks for 6 months
- The fish become liquid
- Fish fluid is filtered
- The 30-33% salt prevents pathogens from growing
Fish sauces
(General process of fermented dairy products)
- Created by the action of ________ on the milk components
- _________ are produced by microorganisms
- Lactose is converted to lactic acid
- Lactic acid lowers pH and promotes coagulation of caseins
Enzymes
(Fermented Dairy Product)
- Cultured
- Pasteurized milk - usually skim
- Lactic acid bacteria is added Streptococcus lactis
- Butter flakes or granules may be added
Buttermilk
(Fermented Dairy Product)
- Similar to buttermilk
- Start with milk or cream (much higher fat%)
- LAB are added- Streptococcus lactis
- Can also acidify directly with lactic acid, lemon juice or vinegar.
Sour milk or cream
(Fermented dairy product)
- Use pasteurized skim or whole milk
- Add a mixed culture
Yogurt
- From Asiatic Russia, also Central Asia, Mongolia, Uzbekestan etc...
- Traditionally made from mare's milk, which has a higher sugar content than cow's milk
- A mixed fermentation by LAB (L. bulgarus) and yeast (Torula, or Mycoderma)
Koumiss or kumis
- From mountainous Russia, Yugoslavia, and Bulgaria
- Dried granules (Kumis is started with a liquid) are added to milk
- Granules contain L. lactis and L. bulgaricus along with other yeasts and other organisms
- The granules are produced during fermentation
- They float to the surface and are removed and are dried to make the next batch
Kefir
- Use pasteurized milk
- Add cultures - Lactobacillus acidophilus
- Reduces lactose content so it is food for people with lactose intolerance can consume it
- Can also buy packets of lactase enzyme - LactAid
Acidophilus milk
- Pasteurized low fat milk has a frozen concentrated culture of L. acidophilus added.
- Kept refrigerated so the culture does not grow
- Tastes like regular milk
- The culture is supposed to get to your large intestine and colonize it
- Thought to metabolize cancer causing components of the diet into less hazardous components
Sweet Acidophilus Milk
Yeast plus acetic acid bacteria = _______
Vinegar
- Vinegars are produced by fermentation of alcohol to acetic acid by __________
- The fermentation is aerobic (requires Oxygen)
Acetic acid bacteria
(Fermentation method)
- Done in very large barrels
- Wine inoculated with fresh vinegar
- Bacteria grows to convert ethanol to acetic acid
- This is a slow process
Open Vat method
Bubble method - Air is bubbled through a vat to increase the rate of conversion.
- Bacteria are grown on a packing material such as beechwood shavings, charcoal, ceramics, corn cobs - almost anything that is insoluble and has high surface area
- An alcohol mixture is passed over the material and the ethanol is converted into acetic acid as it trickles through the matrix
Vinegar generator
Fermented Sauces from _________:
- Most use molds rather than bacteria or yeast for the fermentation
- The molds produce the enzymes that convert substrates to other components that make up the food
- The substrate mixture is inoculated with a starter culture
Soybeans
- Type of soy sauce
- A mixture of soybeans, wheat, rice and water is prepared (exact mixture varies by company)
- Mold is added - Aspergillus oryzae
- Held at 25-30°C for 3 days
- The mold grows along with other bacteria and yeasts
- The other bacteria and yeast produce LACTIC ACID and alcohol.
Koji soy sauce
- Type of soy sauce
- A mixture of (Steamed soybeans, Roasted, crushed wheat)
- Roasted color and flavor (Maillard)
Fermentation:
- The koji is added to the mash
- Held at 30°C for 3 days
- The major effect is hydrolysis of proteins
- A concentrated salt solution is added to stop the fermentation.
- The brined mash is held for 10 weeks to a year or more
- It is filtered, pasteurized and bottled
Mash
- Similar to soy sauce but a different mold - Aspargillus tamari
- Rice is added to the mash
- Fermentation time is shorter
- Has a more mild flavor
Tamari sauce
- Like soy sauce but a paste instead of liquid
- Different cereals are added to the fermentation for different flavors
- Also - hot peppers are sometimes added
Miso
- Soybeans are soaked and skins are removed
- Beans are split and boiled for 20 minutes
- Cooled beans are inoculated with a mold
- The mixture is placed in cylinders or wrapped banana leaves
- Incubated at 30°C for 20-24 hours
- The mold grows and it binds the beans together
- The resulting product is unmolded or unwrapped, sliced and fried in oil
Tempe
- Made from the a citrus fruit
- The fruit is held in a 5-10% brine for 6-7 weeks - then allowed to ferment with airborne yeasts for flavor
- The peels undergo alcoholic fermentation
- Then an acetic acid fermentation occurs
Citron
- Made from the seeds of an evergreen shrub that
grows in the tropics
- The most widely traded commodity after oil
- More than 50% of the world's supply is purchased and roasted by 4 companies: Kraft, Nestle, Smuckers and Sara Lee
Coffee
Variety of coffee
- Grows at higher altitudes
- Central and South America - Jamaican, Java, Columbian
- Kona from Hawaii
- Produces a full-flavored beverage
- Comprise about 70% of the coffee beans harvested
Coffea arabica
Variety of coffee
- Easier to grow (robusta) and grows faster
- Grown mainly in Africa
- Less flavor
- Comprises about 30% of beans harvested
Coffea robusta
- The world's most expensive and small production coffee
- Comes from Sumatra - one of the islands in Indonesia
- On the island, an animal called the luwak (Asian Palm Civet) eats the coffee cherries
- It digests the pulp part and the beans go through the digestive tract in tact
- People collect the beans and wash them
- They are roasted etc.....into coffee
- Only 500 pounds are produced each year
- Costs up to $300.00/lb
Kopi Luwak coffee
- Coffee trees flower and produce coffee "______". Coffee ________ are first picked (often by hand)
- They are red, purple and have a fleshy pulp on the outside
- Two coffee beans are inside each
- You need to remove the pulp to isolate the beans
Cherries
- Method of processing green cherries
- Coffee cherries are soaked in water
- The water contains microorganisms that have enzymes to digest the pulp and expose the two internal beans.
- Beans are then dried
- This method produces higher quality beans
Wet method
- Method of processing green cherries
- Cherries are spread out in the sun to ferment, which digests the pulp
- Beans are collected and then dried further
- After each of these methods you have green coffee
- Green beans are shipped to the US and other countries for further processing
Dry Method
- Roasting coffee beans is done at approximately ___°F in roasting drum
- Browning begins around 300°F, when beans reach 400°F, some CO2 is produced and oils in the bean are driven to the surface of the bean
500°F
- Before the coffee beans are ground into variable sizes for extraction of the flavor
- _____ grinds extract more flavor faster (increased surface area)usually associated with shorter brewing times (like espresso)
- Finer grinding exposes the coffee oils to more air so you get more oxidation and rancid flavors and loss of volatiles
Finer
- Hot water extracts various components
- Caffeine and acids are extracted _________
- Bitter compounds are extracted ________
- Quickly
- Slowly
Brewed coffee is about 95% water
________ water can yield cloudy coffee, and interfere with flavor extraction.
Overly ____ water can cause overextraction and give bitter tastes
- Hard
- Soft
- Pressure method: water is heated to 200°F, then pump-driven through a compact cake of finely ground coffee at 8-9 atmospheres for appx 20 seconds
- Because of pressure brewing, more coffee oils are extracted and emulsified with some of the powdered coffee solids and CO2 and forms a foam "crema" on the surface of the espresso
Espresso
________ in coffee give about 1/3 of the body of brewed coffee, some also comes from oils
CHO
Arabica beans contain more ___ (16%) and twice as much sugar than robusta (10% oils)
Oil
There are nearly ______ flavor chemicals in coffee
1000
Caffeine is ____ water soluble
Very
- Soak the green beans in water and the caffeine is extracted (water is then treated with the solvent ethyl acetate - found naturally in fruit - to extract caffeine, which is then sold to pharmaceutical companies)
- Then beans are re-soaked in same water in order to incorporate flavor compounds lost initially
Decaffeinated Coffee: "naturally decaffeinated"
- Trees grow within 20° north and south of the equator
- They need approximately 2 liters of rainfall and warm temperatures - between 70-90°F
- West Africa produces about 2/3 of the world's harvest
Cacao
- 90% of chocolate in the world comes from one type of tree
- hardy and yield bold-flavored beans
Forastero trees
- Trees that produce more delicately flavored cacao beans
- Less hard plant
- More expensive (5% of world supply)
Criollo trees
- Inner pieces of cacao bean - called ________ are removed from the roasted beans and ground forming "chocolate liquor" which is a brown paste
- It's alcohol free. It is appx 30% cocoa solids and 55% cocoa butter (cream colored fat which gives chocolate much of it's texture)
Cocoa nibs
- Solids are filtered from cocoa butter and recombined with extra cocoa butter this is done to most chocolate products.
- It was invented by Rodolphe Lindt in 1879 in Switzerland - it creates a very smooth chocolate product
Chonching
A process of cooling and reheating chocolate to precise temperatures - which gives a glossy, smooth texture chocolate that snaps when broken
Tempering
- Improper storage and temperature fluctuations - it looks like a light gray or a cloudy look to chocolate
- Fats are melted and recrystallized cocoa butter on the surface
- Can also happen when sugars are recrystallized as a result of high humidity or excess moisture
Chocolate "Bloom"
Astringent and bitter flavors in chocolate come from ______ (6% chocolate liquor by weight) and theobromine - an alkaloid compound
Tannins
- Most popular flavor in the world
- Second most expensive flavor ingredient
- approximatly 100x more expensive than the synthetic (vanillin), which is made from lignin and wood pulp
Vanilla
True vanilla is from the ______ family, native to Central and South America - two species are used for flavoring
Orchid
__________ vanilla is 80% of world production
Bourbon vanilla
Flavors are concentrated in the fibrous __________ ______ of vanilla pod (requires soaking in alcohol or oil) and the sticky resin that surrounds the seeds in the pod
Interior wall
Extracts are made by chopping beans and soaking them in ______________ - vanillin is alcohol soluble
Alcohol and water
- Half vanilla in North America goes into ________ production
- Much of the other 50% goes into soft drinks and chocolate
Ice cream
- Pods are dipped in boiling water to damage cell walls - causing phenolics and enzymes to mix and release vanilla flavors - other enzymes cause pod to brown - which makes them very dark
- Pods are sun-dried for 10-20 days - moisture is evaporated - Maillard Browning occurs
- Pods are then aged - Bourbon 30 days, Mexican 3-4 months
- It takes between 3-5 pounds of green beans to produce 1 pound of fermented beans
Vanilla bean fermentation
fermented foods
products and reactions impart unique qualities to foods

quality control for unwanted microorganisms

protect flavor and freshness

harbor probiotics
cheese and dairy products
begin with a milk product and some sort of starter culture.

lactic acid fermentation done by lactic acid bacteria

ripening r aging - various other microorganisms
other fermented foods
pickles, olives, sauerkraut -- lactic acid bacteria

bread -- yeast

chocolate -- cacao seeds are fermented by bacteria and yeasts

soy sauce, miso -- fungi and bacteria
fungi also used in
cheese
major bacteria involved
lactic acid bacteria - major product of lactose fermentation

- gram positive, non-spore forming cocci or bacilli

fermentative pathways
-homolactic
-heterolactic
homolactic
lactic acid is sole fermentative product
- milk lactose -> glucose -> pyruvic acid -> lactic acid

may lactobacillus and streptococcus spp.

yogurt, many cheeses and sour cream
heterolactic
lactic acid and other products
- milk lactose -> glucose -> pyruvic acids -> lactic acid, +/- acetic acid, ethanol and co2
- leuconostoc, propionibacterium and some lactobacillus spp.
- kefir, sauerkraut, pickles, wine, and some cheeses
yogurt is made how?
- start with milk
- homogenization and pasteurization
- cooling to 40-45 degrees C add starter culture (mesophilic with
- mixing with the starter
- fermentation
- cooling again
- Yogurt!
yogurt cultures
lactobacillus bulgarius
streptococcus thermophilus
lactic acid lowers pH to
4.4-4.2 - unfavorable for many bacteria
cheese production
starts the same as yogurt production but with various streptococcus, leuconostoc, or lactobacillus spp.
Enhances the curd formation and helps prevent growth of undesirable microorganisms
rennin
protease that is added to coagulate proteins in milk
liquid whey
must be removed which contains lactose and albumin proteins
further processing, salting, drying
moisture content deciphers the hardness of the cheese
additional microorganisms can be added for
ripening/ aging
- brevibacterium, propionibacterium
- molds: penicillium
swiss cheese
made with propionic acid which ferments and then makes carbon dioxide -- causing the holes in the cheese - also due to hay dust in dirty cheese
propionic acid
gives swiss cheese its nutty/sweet flavor
food safety
focuses on spoilage microorganisms, microbial pathogens, and the toxins that they produce that can contaminate food
food production
microorganisms are essential to the production of certain foods
imparts desirable aspects of food such as flavor and texture
fermentation
breaking down sugars to impart acids, gases, and other products
glucose makes pyruvate, pyruvate makes
fermentation products
saphrophytic bacteria and fungi
involved in biodegredation with spoilage
yeasts on foods
can bring our spoilage through fermentation
staphylococcus aureus
staph food poisoning
- vomiting
- nausea
within a few hours of consumption
clostridium botulinum
bacterium that produces an exotoxin. obligate anaerobe. Ingesting a preformed toxin
fusarium spp
common soil fungi that can infect barley, wheat, corn, it produces a myotoxin that affects rapidly dividing cells like those in skin and the GI tract
food infection
viable microorganisms are ingested in the food product
lactic acid bacteria prefer
acidic environments
universal beer agar
contains beer and tomato juice solids that allow growth for many microorganisms such as lactobacillus, pediococcus, and acetobacter
YPD yeast peptone agar and SAB sabouraud dextrose agar
saccharomyces cerevisiae can be grown on these

SAB is selective for certain fungi due to its pH (5.6) and high glucose concentration

YPD is not selective, it permits growth of more types with pH of 6.5. Peptone provides carbon, nitrogen, vitamins and minerals, and yeast extract supplies B vitamins to stimulate bacterial/fungi growth.
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