NDFS 250 quiz 3

• •Bacteria, molds,
• yeasts, viruses, parasites

• •Biotechnology /
• genetically modified organisms

•Food additives

•Pesticide residues

• •Lipid oxidation
• products

• •Irradiation induced
• products

•Nonenzymatic browning products

• •Pyrolysis products
• (e.g., from charred meat)

• •Glass, metal, bone,
• stones, wood, insects and other filth

CDC estimates that each year roughly 1 in 6 Americans get sick

—One-celled microorganism

—Distinguished by shape: round, rod, spiral or filament

—May form spores

—One-celled microorganism

—Oval or spherical shaped 

—May form spores

—Multicellular microorganism

—Filaments give fuzzy or cotton-like appearance

—Strict aerobes (need oxygen)

—May form spores

• —(40 to 70 °C)
• —Optimum growth at 45°C (113°F) and up.

• —(10 to 50 °C)
• —Optimum growth at 20-45°C (68-113°F)

• —(0-30 °C)
• —Can grow at refrigerated temperatures, but optimally grow at higher temperatures

  (some grow slowly even when frozen)

• —(-10 to 20 °C)
• —Grow well at refrigerated temperatures

—Capable of growth below 10°C (50°F)

Do not hold between 40 – 140 °F for more than 2-3 hours

•An illness caused by toxin produced by an organism

•e.g. Staphylococcus sp. toxins

•An illness caused by an organism that grows in G.I. tract

•e.g., Salmonella sp.

—Norovirus

• Salmonella
• Norovirus

Colstidium perringes

Campylobacter spp.

Staph aureus. 

(toxins produced by mold) can be carcinogenic)

—Mycotoxin produced by mold

—Aspergillis flavus

—Aspergillis parasiticus


—Penicillium puberulum


—Found in certain foods

—Peanuts

—Wheat

—Corn

—Causes liver cancer in animals

—20 ppb maximum limit in food

Clean, Seperate, Cook, Chill

•Soy sauce

•Roquefort  (blue) cheese

•Camembert cheese

•Bread 

•Beer 

•Wine 

•Vinegar (and bacteria)

•Yogurt 

•Buttermilk

•Swiss cheese

•Fermented pickles

•Sauerkraut

•Vinegar (and yeast) 

•Microorganisms (bacteria, yeasts and molds)

•Infestation (insects, parasites, rodents)

•Nonenzymatic reactions, e.g., lipid oxidation, Maillard browning

•Enzymatic reactions

•Inappropriate storage temperatures

•Gain or loss of moisture

•Reactions with oxygen or light

•Physical stress or abuse

•Time

•Drying, humectants 

•Thermal processing

•Refrigeration, freezing

•Packaging, processing in sterile conditions (free of microorganisms)

•Vacuum or inert atmosphere packaging

•Antimicrobials, antioxidants

Gamma Rays

•Removal of water from a food using ambient conditions

•Often used as a synonym for dehydration

•Removal of water from a food using controlled conditions of heating, forced air circulation, and relative humidity

•Drying in sun with no specific controls.

•Often done with raisins, prunes, figs, apricots, pears, peaches, grains

•Causes largest loss of nutrients of any drying method

Amount of time it takes to dry is draw out if nutrients are being lost at a given right

Sunlight radiation destroys 

Spraying liquid into a current of dry, heated air.

•Product is frozen then ice is sublimed to water vapor by pulling a vacuum

•Expensive but preserves texture

•The product is made into a slurry and spread on the surface of a drum heated inside by steam; when it dries, the product is scraped off; may also use a vacuum.

•Not as economical as spray drying.

•Dry air is blown cross-current or counter-current at a high velocity around the food; the dry air provides heat and takes away the water.

Hot oil replaces hot air as drying medium.

Product tossed in bed of sucrose crystals which pull water from cells.

Slurry of cereal is passed through heated tube under pressure.  As product exits through a sized opening, sudden pressure release causes water to evaporate. 

Water is vaporized.

HALT

• humidity
• air
• light
• temperature

allows mold growth, accelerates chemical reactions

allows mold growth, destroys fats and pigments

destroys fats, pigments, and some vitamins

accelerates chemical reactions

Clostridium botulinum spores

pH of 4.6, costridium

the French inventor of airtight food preservation. Appert, known as the "father of canning"

Peter Durand was a British merchant who is widely credited with receiving the first patent for the idea of preserving food using tin cans

Anaerobic environment

pH > 4.6

aw > 0.92 

Temperature 3.3 to 97 °C 

• ¢Protein
• and/or carbohydrate medium favors growth

• Low salt content
•    —Growth is prevented in products with 5-10% salt, e.g., salt-cured meats)

•Increased sugar (up to a point)

•Increased lipid concentration

•Increased protein concentration

•0.5 to 3 % NaCl

•Neutral pH (for most microbes)

•Higher microbial load

•Longer heating time

•Higher temperature

•Will decrease heating time

•> 3% NaCl

•Extreme pH

• Time at a given temperature to reduce microbial population of a given
• population (species) by 90%.

•Treatment to destroy all microbes and spores

•Treatment to destroy all pathogenic and spoilage organisms

•May contain some thermophiles

•Treatment to destroy pathogenic organisms

•Example: Milk

•Batch: 145oF(62°C)/30 min.

•HTST: 161oF(72°C)/15 sec.

•UHT: 280°F(138°C)/2 sec.

•Steaming or boiling water immersion for a short period of time

•Inactivates enzymes, usually prior to freezing vegetables

• •Red berries, cherries, plums, pumpkin, rhubarb, winter squash, etc. which have red anthocyanin pigments (which react
• with metal ions)

•Corn, hominy which contain S

•Can made with Sn or Fe

•If no enamel

•S +Sn or Fe       SnS or FeS (black)

•Enamel contains ZnO

•ZnO + S      ZnS (white)

Allows contents to expand

Helps create a partial vacuum (after processing and cooling)

Helps maintain seal; assures the consumer that the product is properly sealed

—Potentially fatal

—Harmless

—Caused by acid in food reacting with metal (iron or tin)

—Hydrogen gas produced

—Large pressure cooker, holding hundreds of cans or other food containers, used to heat process packaged foods

—Removing air from a vessel, especially a pressure cooker or retort.  Ensures the retort contains only steam.

Process is based on pure steam in the retort

If not all steam, process may be inadequate to destroy all pathogens

—Process where food is commercially sterilized, cooled, filled into separately sterilized containers 

—Process where hot food is filled into container, sealed, inverted and held before cooling to sterilize lid.

• —Only used with acid or acidified foods where C.
• botulinum is not a concern, e.g. jams and jellies.

—The seal is complete before process

—Therefore, it is necessary to displace some air so that once the container cools a partial vacuum will develop

—Air is displaced by steam, thus the need for high sealing temperature (~170 F)

—The seal is not complete before the process

—Air is displaced during processing, thus the sealing temperature does not have to be high.

•<15 ºC (Slightly cooler than outside temp.)

•Short term

•Root crops, potatoes, cabbage, celery, apples

•0 to 10 ºC

•Weeks to months

•Most foods 

•< -18 ºC  or 0 ºF

•Months to 2 years

•Most foods

Air-blast, where frigid air at –18 to –57 °C is blown over food

•Indirect contact, with refrigerant flowing through separate passage. Plate freezer at –18 to –46 °C

•Direct immersion of food, e.g., liquid N2 at –196 °C and CO2 at    –79 °C

• •Better sensory quality 
• •Better nutrient
• retention (in some cases)

• •Cost  (requires continual input of energy)
• •Shorter shelf life (compared to canning, drying)

•Slowed, but continues

•Starch to sugar in potatoes

•Staling of bread 

•When stored with certain foods 

•Bananas

• •Formation and growth of ice crystals (texture)
• •Movement of water from cells(freezer burn)
• •Microbial load(no major change)

Faster rate gives best texture

• —-18 °C (0 °F) orbelow
• —Should not fluctuate 

—Dehydrated surface on a frozen food

—Small white patches or larger greyish-white blemishes, that are dry, grainy and tough in texture

—Caused by the sublimation of ice from the surface of the frozen product

—Fluctuations in freezer temperature (automatic defrost) worsens this problem.

•Easy to seal plastic, or tight fitting lids

•Water proof

•Water vapor proof (or resistant)

•Low permeability to other gases

•Durable:  High wet strength, will not become brittle and crack when cold

•Use small containers

•> 1/2 gallon or 5 lbs. not recommended due to slow freezing rate

•Dry products

•Containers may be filled to capacity

•Liquids

•Leave ~10% headspace to allow for expansion during freezing

—Most vegetables blanched prior to freezing

—Improves color, flavor, and texture (largely due to enzyme inactivation)

—Reduces microbial load

—Provides better packing

—Wilts leafy vegetables like spinach

—Preserves nutrients (e.g., destruction of ascorbic acid oxidase preserves Vitamin C)

—Removes objectionable odors and flavors

• 1. boiling water and ice bath
• 2. plunge food into boiling water let cook (cooked yet crisp)
• 3. plunge into ice bath halts cooking
• 4.  keep in bath until cooled