FS 101: Test 3

SEPTEMBER 30th - Fermentation

History
- 9000 BCE
  - rice fermentation in China
- 5000 BCE
  - beer and wine production in egypt and mesopotamia
- 500 BCE
  - vegetable fermentation in China
Science
- metabolic pathways
  - aerobic vs. anaerobic
    - need an anaerobic environment for fermentation
    - preserves food by creating environment unsuitable for spoilage and for maintaining microbes
  - glycolysis
    - initial breakdown of glucose into pyruvate, followed by fermentation equaling ATP and by products
- stages
  - lag phase: introduction of fermentation conditions
  - initial growth phase: rapid growth and consumption
  - stationary/stabilization phase: by-products accumulate, inhibiting any further growth
  - decline phase: deterioration overtime
- key microorganisms
  - lactic acid bacteria
    - converts sugars into lactic acid
    - benefits
      - extends shelf life by lowing pH
      - development of tangly flavors and aromas
  - yeasts
    - converts sugars into alcohol and CO2
    - benefits
      - alcohol is a natural preservative
      - develops unique flavor
  - molds
    - production of soy products and certain cheeses
    - benefits
      - develops savory umami flavors and buttery notes
benefits
- textural
  - creaminess (yogurt)
  - crispness (pickles)
  - aeration (bread)
- nutritional
  - breaks down antinutrients
  - increases avaliability of nutritional factors
  - probiotic contents (lactobacillus and bifidobacterium)
  - gut health support
  - microbiome diversity
potential risks
- excessive salt intake
- contamination risks
products
- dairy
  - yogurt
    - pasteurized milk + LAB cultures + fermentation at 42-45 C → coagulation of proteins → cooling and packaging
  - cheese
    - pasteurized milk + rennet + LAB → curdling → draining of whey → aging
    - flavors
      - aging = flavors, texture, and nutritional properties
      - many varieties = milk type, fermentation time and cultures
- vegetables
  - sauerkraut
    - cabbage + salt → anaerobic conditions → LAB sugar to Lactic Acid
    - benefits
      - shelf life, gut health, high in vitamin C
  - kimchi
    - cabbage + radish + garlic + spices + salt → LAB sugar to Lactic Acid
    - benefits
      - spicy, tangy flavor
      - nutritional benefits
- Grains
  - bread
    - yeast ferments sugars in dough → CO2 → rising
    - characteristics
      - light airy texture
      - enhanced flavor
      - aromatic quality: alcohol and organic acids = bread flavor
    - sourdough
      - wild yeast and LAB, long fermentation time leading to tangy flavor
    - commercial
      - bakers yeast and LAB, short fermentation time leading to less complex flavor
- beer
  - malted grains + yeasts + fermentation → conversion sugar to alcohol + CO2 → filter and processing
  - alcohol content: time of fermentation
  - flavor
    - ingredients change flavor
      - hops, citrus, etc.

OCTOBER 4th - Food deterioration

food deterioration: the process in which food undergoes changes that make it unsuitable for concumption
- causes
  - microbial activity
  - enzymatic reactions: natural enzymes in food, cause spoilage ex: brown apples
  - chemical reactions: oxidation and hydrolysis
  - physical changes: moisture loss, texture degradation
  - environmental factors: temperature, humidity, light exposure
- food borne microorganisms
  - bacteria
    - salmonella, E.Coli, etc.
    - grow rapidly under favorable conditions
    - undercooked meat, unpasteuized dairy, contaminated vegetables

OCTOBER 9th - Food borne Illnesses

Food borne illnesses
- types
  - salmonella
    - raw poultry, eggs, dairy, contaminated vegetables
    - causes diarrhea, fever, gastroenteritis
    - prevented by proper hygiene among animals, raw meat, and washing vegetables
  - E.coli (Escherichia coli)
    - undercooked beef, unpasteurized milk
    - causes stomach cramps, bloody diarrhea, vomiting
  - Listeria monocytogenes
    - ready-to-eat meat, unpasteurized dairy, smoked seafood
    - causes diarrhea, nausea, etc.
  - norovirus
    - water, shellfish
    - nausea, diarrhea, stomach pain
- prevention
  - proper cooking
  - temperature control
    - cold below 40 F
    - hot above 140 F
  - avoid cross contamination
    - raw meats away from veggies, etc.
  - safe storage
    - temperature, immediate after process
  - use of preservatives
    - sorbates, vinegars, etc.
- outbreaks
  - find sources
  - trace to common point of contamination
  - confirm with lab testing
Food borne microorganism
- molds
  - grown on food surfaces, visible colonies
    - apsergillus, penicillium
      - some have mycotoxins harmful when ingested.
        some beneficial ex cheese
  - viruses
    - norovirus, hepatitius A
    - cannot grow on food but are transmitted through contaminated food or water
    - require living host to reproduce and operate
factors effecting microbial growth
- intrinsic:
  - water activity
  - pH
  - nutrient content
  - redox potential: oxygen availability
- extrinsic
  - temperature
  - humidity
  - gaseous environment

OCTOBER 11th - Dehydration

definition
- removing moisture from food to extend shelf life
importance
- reduces AW, prevents spoilage, storage efficiency, preserved food quality
applications
- fruits
- vegetables
- coffee
- dairy
- meat
scientific principles
- evaporation: removal of moisture from food surface
- diffusion: moisture migrates from inside to the surface
- equilibrium moisture constant: point where food no longer looses moisture in drying process
- mass transfer: inside → surface → air
- heat transfer: process of exchanging thermal energy between different systems or objects due to change in temperature
  - conduction: heat through surface, without moving material itself
  - convection: heat through gas/liquid, through circulation “convection currents”
  - radiation: heat through electromagnetic waves, doesn’t require medium
challenges
- uniformity
- energy consumption
- quality retention, different flavor, color, texture
- loss of nutrients
- varying rehydration quality
methods
- sun drying
  - oldest
  - low cost
  - unreliable, potentially unclean
- air drying
  - faster
  - loss of heat sensitive compounds
- tray drying
  - industrial, small scale
  - batch method
  - easier to control airflow
  - leads to case hardening
- spray drying
  - liquid sprayed into chamber with hot air
  - rapid, good for heat-sensitive products
  - energy consumption, expensive
- freeze drying
  - sublimation via vacuum of frozen products
  - expensive
- drum drying
  - slurry or puree applied as thin layer onto revolving drums
- fluidized bed drying
  - food suspended and dried by hot air
- microwave drying
  - uses electromagnetic waves to dry
  - fast, and retains nutrients
- infrared drying
  - fast, uniform
  - causes case hardening

OCTOBER 14th - Thermal Processing

definition: using heat to treat or prepare food, beverages, or other substances
importance
- extension shelf life
- destruction of microorganisms
- improved safety
- improved quality
- convenience
history
- 19th mid - pasteurization
- late 19th - microbiology + technology increases, and commercial canning industry increases
- mid 20th - sterilization and pressure cooking
- late 20th - microwave and sous vide
- early 21st - continued sustainability advancements
principles
- higher temperature → shorter processing time
  - want temperature and time balance that targets specific microbe at coldest part of product
factors
- temperature = higher → microbe destruction
- time = processing time at time → efficacy
- pH = extreme pH inhibits growth
- moisture = high AW → increased growth
- food composition = effects heat penetration and distribution
- microbial characteristics = varying microorganisms have heat resistance
- packaging = vacuum or modified atmospheric packaging effects microorganism
- agitation = stirring, uniformity
- equipment = uniformity, safety
basic numbers
- d-value = time to decrease population of microbes by 90% at a certain temperature
  - measures sensitivity to heat
- z-value = temperature change needed to alter d by factor of 10
  - measures sensitivity to change in temperature
- f-value = cumulative lethality
  - equivalent time at a reference temperature that achieves same microbial destruction as actual process progresses at a variable temperature
pasteurization
- mild heat treatment to kill pathogens without affecting food quality
- milk, juice, eggs, etc.
- HTST: high temp, short time
- LTLT: low temp, long time
- targeted microbes
  - coxiella burnetii
  - salmonella enteritidis
  - e.coli
sterilization
- severe heat treatment to kill all life forms
- commercial sterilization: free of microbes able to reproduce under typical storage
- methods
  - in container sterilization: sealed and heated to achieve commercial sterility
  - UHT: heating at +135 C before packaging
processes
- retorts
- pressure cookers
- aseptic processing
- blanching: short heat treatment used to inactivate enzymes and prepare food for further processing
- dehydration
- baking/cooking
- frying: submerging foods in hot oil, quick to preserve
effects on food
- texture
  - softening → break down cell walls
  - gelling
- nutrient retention
  - can degrade nutrition
- color
  - browning → when controlled, can enhance appearance
  - fading → pigment degradation in fruit and vegetables
challenges
- overprocessing
  - excessive heat → quality, nutrition, flavor degradation
- under processing
  - insufficient heat → food safety risks
- heat distribution
  - uneven heat distribution can cause over and under processing
  - equipment design + probes can regulate and fix
- energy consumption
  - sustainability, costs, etc.