PLPA 010 Midterm Study Guide

Ripening from the Inside Out

The starter bacteria culture serves as the ripening agent

No additional microbes are added to the green cheese

(ex: cheddar, parmesan, swiss cheese)

How are holes/eyes in the swiss cheese formed?

1. Lactose → (starter culture) → Lactic acid → (Propionibacter shermanii - bacterum) → Co2 (create various sizes of pockets)

- P. Shermanii does not function in warmed/pasteurized milk: no holes will form when warm milk is used

2. Hay Fleck theory: hay flecks fall into cheese buckets + holes are formed

Ripening from the Inside Out (by a fungus)

Lactose (warm milk) → (starter culture) → Lactic Acid

- blue cheese: a fungus is added to the cheese at the beginning of the cheese making process, after the cheese is ready for ripening, holes are poked in the curd to introduce air to encourage the fungus to grow

Ripening from the Outside In

- Washed rind cheese with brine solution w ripening microbes

- Produce (protein) Enzymes that penetrate into the curd

- Break down fats + others further: making them creamy/semi-liquid with unique flavors

Ex: Brie, Comembert, Limburger, Epoisses

What is Ripe?

Lactose to lactic acid, fats to fatty acids, proteins to amino acids and ammonia

- Broken down products blend together to give the ripened cheese its flavors, smell and texture

Aromatic Keytones of Cheese

- produced, flavor compounds

- Metabolized fat (blue mold)

- The smell and taste of Penicillium spp (blue mold)

- Milk (from all kinds of animals): Unique fatty acids → give us different flavors

Cheese: Time

Increased ripening time = increased hardness

Shorter ripening time = increase softness

Cheese: Temperature

(low; 40 to 55 F)

Temp low: microbes do not go out of control- slow and steady microbial growth

- High Heat provides energy (moves the microbes), accelerates production of undesirable chemical by-products

Cheese: Relative humility in the environment

80% for hard cheeses

95% for soft cheeses

Need High Moisture to prevent cheese from drying out

Cheese: pH

Acidic

Low pH = high acidity

high pH = low acidity or high alkalinity

Neutral: 7, Less = acidic

Starter bacteria reduces the pH in the curd to pH 5

Cheese: Oxygen/Air

Ripening microbes such as P. rogueforti are aerobic

Don't need oxygen

Lactic acid bacteria in the starter culture are anaerobic

pH of Milk

Milk: pH 5 = milk is slightly acidic

Low ph is needed for rennet to curdle milk

Implications of reduced pH

Starter bacteria and ripening microbes must survive the drop in pH in order to grow and perform optimally (pH 5)

Undesirable/spoilage microbes that cannot survive or grow in pH 5 will be inhibited

- Good spoilage

Controlled Rot

Food preservation

Microbes in Cheese: Conidiophore

reproductive structures of the fungus

Microbes in Cheese: Conidiospores

projecting off of the stalk of the Conidiophore

Microbes in Cheese: Rest of fungal body

filaments- Hypha(e) or Mycellum

Cocoid

spherical shape

Bacteria Shaped

Singl: Rod shaped- sporeformer

- Chains of rod shaped: Strepobactillius

Bacteria together

(2) Diplococcaus

(4) Tetrad

(bunch) Staphylococcus

(chain) Streptococcus

Flagella + Pili

movement and attachment

Cell Wall

made up of peptidoglycan (polymer- repeated units of sugar and proteins)

- Structure and rigidity

Glycocalyx

Added extra protection

Cytoplasm

full of fluid- contains cellar organelles

Ribosomes

protein factories

Nucleoid

genetic material (DNA)

Plasmids

DNA outside the nucleoid- conferring additional functions (ex: resistance to antibiotics)

Stomata (plants)

Tiny openings for gaseous exchange and water evaporation

Pathogenic E. coli

infects humans do not infect plants; but it can contaminate plant surface Bacteria

Genomics

study of all the genes in the genetic makeup/genome of an organism (what the genes do within the organism)

Viruses

- Infectious agent

- Genetic material (DNA or RNA)

- Protein coat

- Require a living host cell to multiply

Viruses in Cheese Making

They don't directly involved in cheese making, but can affect it by infecting the bacteria/fungi involved in the process

Bacteria v. Viruses

- Bacteria can be infected by viruses

- Bacteria can reproduce without being a living cell

- Bacteria are bigger than viruses

- Viruses infect bacteria but not vise versa

- Viruses that infect bacteria are called bacteriophages or bacteria-eaters

Small --> Big Cells

Atom → Proteins → Viruses → Bacteria → Eukaryotic (Animal, plant, fungal) cells

Eukaryotic cells

Animal, plant and fungal cells

Prokaryotic cells (Bacteria Cells)

- do not have a cell nucleus; genetic material is in the cytoplasm

- Nucleoid: devoid of nucleus

Sources of Contamination

- Natural bacteria in the ducts of the cows

- Confines of fridge, environment of it

Controlled decomposition

Activities of the ripening microbe also contribute to desirable flavors

Random Decomposition

The decomposition occurring in spoiled milk is a random process that results in a disproportionate amount and composition of broken down products or by-products

Psychrophalic microbes (psychophiles)

- can live in the cold arctic and also in the cold environment at your fridge

- Certain psychrophilic Lactobacilli and Streptococcus spp. can grow in milk causing it to turn sour

Alcaligenes spp

produces sticky threads in spoiled milk

Serratia spp.

Causes red milk

Wild yeast

yellow, orange, pink milk (molds)

Pasturization Holding Method

63.8* (145F) for 30mins (gold standard)

Flash Pasteurization Method

71* (161F) for 15 seconds

Ultra Pasteurization Method

82.2 (180F) for 2 seconds

Mycobacterium tuberculosis

pathogenic microbe

Pasteurization does get rid of all the microbe

Endospores of pathogenic bacteria can survive for a long time observed with the genetics Clostridium and Bacillus (soil)

- cause botulism (endospores) are heat resistant, dormant survival forms of the organism

Toxin Batulin

Neurologic disorder- Paralysis → death

Examples of microbes that cause food poisoning

Cholera (Vibrio Cholera)

Pathogenic Escherichia coli - E.Coli food poisoning

Botulin/Botox (Neurotoxin treatment)

- Interrupting the communication between the nerve endings and muscles

- Walls off chemical Acidicolic that causes wrinkles so they are not released so there is no contact = no wrinkles form

Autoclaving

- Moist heat and high pressure and temperature

- 121C / 250F at 1 atmosphere 20-30 mins

- Boiling water or steam penetrates materials easily

Radiation

- sterilizes without affecting the taste of food/beverages)

- UV radiation: found in sunlight; alters/mutilates genetic makeup of microbes; lethal alterations/mutations lead to death of microbes

Gamma Radiation

- aka. ionizing radiation also causes mutation in the genetic material of microbes

- Strips electrons from atoms- end up with ions (aka. Free radicals)

- Cause mutations in genetic material + kill microbes

Infra Rad Radiation

- Sterilizes through heat production (Microwaves_

- Heat are carefully calibrated by adjusting the intensity - amount + duration

- End: little to no affect/changes in flavor

Filtration (filter-sterilization)

Filtration devices to trap microbes in liquid solution

- Can't sterilize solids, No heat required

- microbes that are longer than the pore-size at the filter are prevented from passing through

Drying

Aka. Dessication

- Removal of water/moisture by heat, air, or salt prevents chemical reactions required for microbial activity

- Does not guarantee the elimination of all microbes

- Ex: Salting in Cheese making

- Endospores: dormant without water, but reactivates with water

History of Wine

- Zagros mountains of Iran

- Wine jars found in Godin Tepe (3500 - 3000 BCE)

Jars contained:

- Calcium tartarate (calcium salt of tartaric acid)

- Resin from Terebinth (turpentine) tree turns into turpentine on distillation; undistilled, it inhibits bacteria; masks the offensive flavor of spoiled wine

Microorganism

A small living organism

Cannot see with your naked eye but can be seen with the aid of a microscope

Exception:

Mushrooms: giant microbes

scientific name vs species vs genus

A scientific name: Homo Sapiens

Species: Sapiens

Genus: Homo

Relationship between temperature and firmness of cheese

Low temp: soft

Med: semi-soft

Hot: hard

Why warm milk

Used as a means of pasteurization → no other bacteria (esp spoilage bacteria - undesirable) comes in

Starter Bacteria process

Lactose (milk sugar) → (bacteria - energy) → Lactic acid (Streptococcus sp. + Lactobactilli sp.)

Rennet

Under a low pH, rennet helps curdle the milk protein (a.k.a casein); the enzymes, rennin, in the rennet is responsible for the curdling gives cheese a tangy taste

Milk protein (Cassein) → Rennin → Curds

Importance of Salting

- dehydration, drawing water out

- Intensifying the original flavor

- Desire to remove whey/water/moisture: Removes spoilage - unwanted bad, spoilage microbes

- Slows down activity of starter bacteria

Green Cheese

- Immature, unripeded cheese/fresh cheese/green cheese

- Can eat + are sold

Ex: cottage cheese, ricotta, queso blanco (fresco)

Ripen/Aged Cheese

Special mold or bacterium or fungi

Limburger

Brevibacterium linens (a bacterium)

Brie

Penicillium candidum (a mold)

Camembert

P. camemberti (a mold)

Roquefort (blue cheese)

P. roqueforti (a mold)

Éppoisses

B. linens

- hailed the "king of cheese" by the 19th century French Gourmand Jean Anthelme Brillat-Savarin

Wine: Phrygian Grog (King Midias (Funeral Banquet))

alcholoic beverage- mixture of grape wine, barley beer, and mead (made from honey)

Wine: Homer's time (700 BCE)

- Different grades of wine for citizens of different status

- wine for free people

- wine for slaves

- Uncontaminated portable water, very rare: Prefer wine over water

- Bread + wine dip

Wine: Plato-"the Laws"

- metaphysics and social psychology

- Age for drinking (+18)

- Don't be drunk

- +40 can enjoy wine

Dionysus

god of grape harvest and wine

Vines → Italy about 200 BCE

Oenotria (that land of the grape)

Concord grape

Vitis labrusca- 'foxy' wine

Plague #1

Microbes that caused Powdery mildew

Plague #2

Phylloxera (an insect)

Plague #3

Microbes that caused Downy mildew

European wine grapes

Vitis vinifera- 99.9% of world's wine production

Video: Main death of Civil War soldiers (+delivering mothers)

Infection, wounded + allowed microbes into the body

Video: Fleming's discovery

Mold: penicillin chrysogenum - antibiotic

Video: Mystery Microbe

Sar 11 - Ocean microbe, eats organic carbon