Post midterm 2 Flashcards
Describe fat soluble vitamins
-nonpolar structure.
-DEAK
-require bile from the liver for digestion
-not easily excreted
excess is stored in liver or fatty tissues
-don’t need as frequent doses
describe vit A. Where is it found?
- night vision
- healthy skin and lining of lunds and GI tract
- immune system
- regulation of hormones
- bone reshaping
found in:
- Retinol (active form of vit A). in liver, eggs, butter, milk, cheese
- Precursor for retinol called beta carotene (orange, dark greens)
describe vit D
-can be made by the body with vit D precursors: choleclciferol and ergocalciferol. These are basorbed and turned into vit D by liver and kidneys. The body only converts precursors to vit D as needed
- helps regulate blood Ca levels
- from exposing skin to sunlight. Also in butter, cream, egg yolk, fatty fish
describe vit E
-antioxidant (prevents oxidation by reacting with O2 and other compounds. Prevents damaging red and white blood cells)
sources:
- veg oil
- whole grains
- avocado
- nuts and seeds
Notstable at high temp
describe vit K
- needed for production of proteins for blood clotting
- produced by bacteria in intestines (meets half of vit K needs)
- found in liver and dark leafy greens
describe b vits (in general)
- act as coenzymes in reactions
- found in leafy greens, legumes, pork, whole grains, egg, fish, milk
function of vit b1
thiamin:
- helps nerve and muscle function
- supports nervous system
function of vit b2
riboflavin:
-promotes healthy skin and vision
function of vit b3?
niacin:
-supports skin, nervous system, digestive system
precursor of vit b3?
dietary tryptophan
function of vit b6?
pyridoxine:
- converts tryptophan to niacin (b3)
- RBC formation
- hemoglobin production
function of folate?
coenzyme in new cell formation
function of biotin
helps body make fats and glycogen
describe vit c
- ascorbic acid
- helps production of connective tissue
- protects against infection
- helps absorption of Fe and Ca
- antioxidant
sources:
-citrus, cantaloup, tomato, broccoli
2 categories of minerals and amount needed of each?
major: 100mg or more per day
trace: 100mg or less per day
what are the 3 parts of the whole grain kernel?
bran
endosperm
germ
what part of the grain do refined grains usually consist of?
endosperm
what is the milling process (grains0?
the milling process removes most of the bran and some germ (along with most of the fiber, vitamins, minerals, antioxidants, phytochemicals)
approx 75% phytochemicals (are lost during refining)
describe enrichment of grains
process of restoring nutrients by removing refined grain products during processing
what vitamins are added in enrichment to prevent deficiencies?
niacin, thiamin, riboflavin Fe were added to processed flour in 1930
folic acid added to grain and cereals in 1996
note. grain enrichment doesn’t replace most of the nutrients found in whole grains
what are 3 factors that affect nutrient stability?
- heat: vit A, B1, C, E are not heat stable
- oxygen: vit C, E, B-carotene are damaged by O2
- Water activity level: affects stability of vit A and C
ex of non-nutritive functions of vit/min
calcium as stabilizer in tofu
salt as preservative
how to reduce nutrient losses in food prep?
rise fresh foods rather than soaking
keep fods in large pieces to reduce size of surface area exposed to light, air, water
cut fruits/veg right before cooking
choose steaming over boiling
define food analog
natural or manufactured substances used in place of traditional fod products
they are designed to:
- save money
- change nutritive value of foods
- improve performance of foods
- replace foods restricted for health reasons
example of food analogs
texturized protein made from soybeans that costs less than meat and is lower in fat
artificial sweeteners (for diabetes patients)
pros of food analogs?
- offer low fat/cal options
- keep food prices lower
- more food options for people with food allergies, heart disease, diabetes
cons of food analogs
- believed to be “drawback to current food supply”
- not “natural”
- can tempt people to avoid eating variety of foods
what are the three most common types of food analogs?
sugar, salt, fat substitiutes
decreases problems for obesity, heart disease, diabetes
describe sugar substitues (food analog)
- adds sweetness without adding as many cal as sugar
- nonnutritive sweeteners (aka artificial sweeteners) provide no calories/energy, but nutritive sweeteners do
ex:
-saccharin: high stability. first artificial sweetener. 2000 times sweeter than sugar but bitter aftertaste
- aspartame: 200 times sweeter than sugar. made from aspartic acid and amino acid phenylalanine. common in drinks, puddings, frozen desserts
- polyols: aka “sweet alcohols”. low calorie (nutritive sweetener). found in apples, berries, plums. helps control moisture content, improve texture, reduce browning. in baked goods, ice cream, candy, chocolates
what is a bulking agent?
enhances texture of thickens consistency of food products
ie.
polydextrose: mimics mouth feel of sugar. found in reduced calorie products
what are starch based fat replacers?
- low calorie
- mimics fat mouthfeel
- but can’t create flaky texture in baked goods
- releases flavor all at one instead of gradually
- sugar is often increased in foods with fat replacers to make up for a lack of flavor
- ie. vegetable gums, pectin, polydextrose
what is olestra
- sucrose polyester with 6-8 FA attached at the site of OH groups on a sucrose molecule
- can be solid or liquid depending on the FA used
- looks,feels and performs like fat
- can’t be digested by the body = passes through body undigested along with fat-soluble vitamins = no calories
what is SALATRIM
- fatlike compound
- “short and long chain acid triglyceride molecules”
- doesn’t stand up in frying
- 5kcal/g instead of 9kcal/g (like most fats)
what are examples of salt substitues
potassium cchloride
-benefits heart patients on low-sodium diets but need more potassium
sodium free herbs and spices
what are microorganisms
organisms that can only be visible through a microscope.
they multiply rapidly and transfer easily from one surface to another (cross-contamination). They depend on outside sources of food to grow
what are microorganisms that have a positive use in food?
bacteria (monera kingdom), yeasts (fungi kingdom), molds
what are bacteria?
single-celled organisms that multiply though cell division.
have no nucleus. Filled with cytoplasm
3 micrometers long
what are bacteria classified by?
classified by: shape, cell wall structure, O2 needs
what are 3 shapes bacteria can have?
- bacilli: rod shape
- cocci: spherical shape
- spirilla: spiral shape
what are the 2 types of cell wall structures bacteria can have?
how can it be identified?
type of cell wall is identified by their ability to be stained by a crystal violet dye
- gram-positive cell walls turn blue-violet during staining
- gram-negative cells turn red
bacteria will kill either gram-neg or gram-pos but not both
how is bacteria categorized
categories:
- based on o2 needs
1. aerobic
2. anaerobic
3. facultative: can function in aerobic or anaerobic
explain how aerobic bacteria spoils cabbage
- aerobic bacteria need o2 present for respiration to occur.
- respiration is the transfer or e to release energy where O2 is the final e receptor
- if cabbage is submerged in h20 = low o2 = anaerobic bacteria will multiply
what does bacterial growth rate depend on?
how to they grow?
ph
air
temp
nutrients
the reproduce by increasing cell size. cytoplasm divides in half and cells split into daughter cells. number of cells double each time
how is sauerkraut made? why doesn’t it spoil
made by submerging cabbage in salt water where o2 is unavailable.
anerobes grow and develop flavour and texture of sauerkraut
what is fungus?
- an aerobic, spore-producing plant that lacks chlorophyll
- not always single-celled
- has a nucleus
- breaks down organic matter into nutrients which they absorb
ex: mushrooms, molds, mildew, rust, yeast
what is fungi classified by?
their structure and reproduction methods
what is the basic structure of fungi?
made of filaments or tubes called hyphae
what is hyphae
- elongated cells or chains of cells that absorb nutrients from the environment
- longer chain = intertwining = forms a branched network called mycelium
what is mycelium
- reproduces by creating spores (the reproductive cells of fungi)
- part of the mycelium grows into an energy source to absorb nutrients
- grown in a circular pattern which is created as the hyphae extends outward from a spore
- when mycelium becomes large enough, it can be seen without magnification
what are spores?
- develops in a sac like structure that explodes when full
- resistant to harsh environments
what are molds?
- fungi that form a mycelium structure with a fuzzy appearance
- has a wide range of colors
- can give off an antibiotic that kills bacteria likeley to be growing in the same area
- reproduces through spores
- can produce a visible spore case (basidiocarp) which has a stem, cap and gills (gills contain the spores and is located under the cap). the stem lifts the cap and gills so the wind can disperse the spores.
- ex of basdiocarps: mushrooms
what are yeasts?
fungi with a single-celled structure that produce alcohol and CO2
- forms mycelium structures on soil or plants
- reproduce in animals by budding (forms buds that swell and separate into a duplicate cell or form a chain of ells)
- can form both mycelium and single celled structures. produces a mycelium structure when lands on soil or plants
what are some common characteristics of microorganisms?
- grow rapidly
- good sources of edible protein for animals
- nutritional value in food
- can enter dormant/inactive state as protection from a harsh environment
- can reproduce when the environment supports growth needs
how do manufacturers use microbes that go into a dormant state?
- manufacturers create an ideal environment for microbes to grow
- results in a pure culture (one type of microbe)
- mass produce pure culture
- manufacturers then create an environment that causes microbes to dehydrate
- used in development of foods (ie. cheeses, pickles, beverages)
- starter: pure culture mixed with a food source where microbes come out of the dormant state and they can reproduce to change a food product
describe microbial enzymes
classification?
enzymes produced by microorganisms. the source of most changes in food products
-enzymes excrete digestive enzymes to break down the large molecules for food source
classification:
- based on the organic molecules they use as a food source
1. proteolytic: microorganisms release proteases that change proteins into amino acids. used to clot milk, tenderize meat, remove pulp from cacao beans
2. lipolytic: microorganisms produce enzymes that digest fats and are used to flavor cheese, remove egg yolk, clean up oil spills
2 latin names of microoganism classification
- genus name: indicates a family or organisms that have similar characteristics
- always capitalized - species name:
- identifies the type of microbe within the family
- not capitalized
what are halophilic microbes?
microbes that need high salt concentrations to function.
used in asian dishes
what are the 4 factors that affect microbe growth? describe them
- food supply
- microbes are composed of C, O, N, H.
- they need a food supply that provides all 4. Also need minerals and vitamins (coenzymes)
- most microbes use organic compounds (CHO,lipids,protein) as a main source
- food supply needed depends on the enzyme system the organism can make - water
- some microbes can stay alive without h2o, but none can grow without h2o.
- each microorganism has a range of h2o content it prefers. (measured by water activity)
- water needs depends on temp and pH - pH
- each microbe type has a diff preferred ph range
- fruits have ph less than 4
- most bacteria are killed if ph is below 4.6
- molds can survive pH 1.5 (thus molds are more likely than bacteria to spoil fruits)
- when molds grow on fruit = substances releases = ph rises = more basic = bacteria can start to grow - temperature
- extreme cold doesn’t kill microbes but slows them down or causes them to enter a dormant state
- heating can kill microbes (ie. pasteurization)
describe bacteria, yeast and mold need for water
bacteria need more water than yeast, which need more water than molds for growth
what water activity do bacteria multiply fast in?
what water activity is safe for most food storage?
- 97
safe: 0.70 or lower
how to lower water activity
removing water, adding solutes, freezing (locks water molecules into crystalline structure. limits water access)
what is fermentation? what do changes result from?
when does it occur?
enzymatically controlled change in a food product caused by the action of microorganisms
changes in food products result from
- digestive enzymes released by microorganisms
- release of by-products (ie. co2)
occurs when:
-nutrients broken down by digestive enzymes are absorbed by microorganisms for growth and energy
what is the primary product of a microbial reaction?
energy
in producing energy, microbes also produce byproducts which can change color, texture, flavor, aroma, pH
describe yeast fermentation
used in yeast breads, alcoholic drinks, vinegars
uses: saccharomyces cerevisiae (yeast)
sugar is main source of energy (but too high sugar levels will lower water activity level = microbes cant reproduce = slows yeast growth)
use of yeast in bread making?
- warm liquid activates yeast
- mixing distributes yeast
- kneading dough develops gluten
- proofing allows yeast to produce enzymes that break down sugars = releases alcohol and co2 = gets trapped in pockets throughout the dough = causes gluten to stretch = dough rises
- baking: alcohol produced during proofing evaporates and yeast cells are killed. co2 expands when heated.
can s. cervisiae (yeast) hydrolyze starch?
no
needs added enzymes or amylases to break down starch
what happens if dough is proofed for too long?
- more by-products are produced = too much c02 produced = dough is stretched too far = dough will collapse or develop dry texture
- too much alcohol produced = undesirable texture
yeast fermentation in wine?
what determines quality of wine?
what is added to inhibit unwanted organism growth?
when is the wine making process done?
wine quality depends on what microbes are present
so2 or potassium metabisulfite is added to inhibit unwated organism growth. sulfites also stabilize wine color
yeast feeds on sugars naturally found in the fruit juice = releases alcohol and co2 by products
wine making is complete when bubbling from co2 stops
what determines the sweetness of wine?
difference in fermentation process between sweet and dryer wines?
- degree of fermentation
- sugar content of the fruit
in sweeter wines, the fermentation process is stopped before the yeast breaks down all the sugar (8to9% alcohol)
in dry wines, fermentation lasts until all sugar is broken down (12 to 14% alcohol)
final sweetness and alcohol content can be adjusted by extra sugar or juice
yeast in other alcoholic beverages
beers: fermented barley:
bourbon: corn
sake: fermented rice
rum: sugar cane of molasses
brandy: distilled wine or fermented fruit juice
liquers: brandy base with sugar and flavorings
what are 3 main types of bacterial fermentation?
- lactic acid
- proteolytic
- acetic acid
some foods need 2 separate fermenting agents
describe lactic acid fermentaion
major byproduct of these foods?
what is it used for?
example? what happens if too much salt is added?
major by-product: lactic acid. but may also produce other by-products (ie. acetic acid, formic acid, co2)
used to ferment veg eats, dairy
example: sauerkraut:
- “acid cabbage”
- result of lactic acid fermentaion of cabbage submerged in a vat of brine (brine= mixture of salt and h2o)
- salt controls water activity and pulls water with dissolved sugar and nutrients to the surface (salt helps discourage growth of unwanted bacteria and fungi)
- bacteria utilizes the sugar and releases co2 and lactic acid into the brine. cabbage is shredded to expose more surface area for the bacteria to feed
- if too much salt is added: lactic acid bacteria will be slowed. yeast may begin to grow
describe the bacterial fermentation of pickles?
3 methods?
commercial pickling?
3 basic methods:
- heated in spiced vinegar solution
- refridgerated in an acid brine
- fermentation with lactic acid bacteria (traditional).
commercial pickling:
- washing cucumbers in a Cl solution (removes unwanted yeasts and molds. if not removed, can caused bloating - air pockets in center of pickle))
- placing them in a brine with pure culture of lactobacillus. bacteria feed on cucumber sugars = releases lactic acid into the brine =lowers pH = crisp texture and sour taste
traditional pickling: cucumbers placed in brine. Salt is gradually added until doubled.
bacterial fermentaion in meats?
- used for dry and semi dry sausages
- increases acid which tenderizes meat and adds a tart flavor
- fermenting, smoking, drying prevents spoilage
- sugar provides energy for fermentation and lactic acid production.
- sodium nitrite is added
bacterial fermentation in cheese
- pasteurize milk
- rennin and lactic acid bacteria are added to form curds (curds = clumps of coagulated protein or casein)/ lactic acid lowers the pH = enzymes in rennin will coagulate more
- curds cut in small cubes and heated to help the whey separate from them
- whey is drained
- curds are salted to reduce spoilage and add flavor
cottage cheese: mixed with cream
aged cheese: pressed to squeeze out excess moisture
why are cultured dairy products suggested for people with lactose intolerance?
bacteria use the lactose as their energy supply = low lactose products = easier to digest
what is responsible for characteristic flavor of cheeses?
sharpness of cheese?
flavour: diff bacteria or molds
sharpness: develops as cheese ages. (longer age = firmer, more crumbly, melts into sauce betteR)
by products of mold fermentation?
examples?
by-products produced: antiobiotics, flavor compounds, enzymes
ex:
soy sauce: fermented soybeans and wheat.
-molds produce enzymes which hydrolyze the proteins and carbs
-brine is added which stops the growth of unwanted microbes
-lactic acid bacteria can multiply = pH drops
-yeast is added which ferments the sugars remaining
tempeh: soybean cake of cooked, mashed soybeans pressed into blocks. inoculated with Rhizopus molds. wrapped in banana leaves
describe 2 step fermentation
- lactic acid and other microbes
acetic acid fermentation
- uses 2 or more fermentation steps (ie. lactic acid bacteria and fungi)
cheese: lactic acid bacteria is needed to form. other microorganisms develop flavors and textures
sourdough bread: lactic acid bacteria ferments the product. yeast continues to ferment
- acetic acid fermentation:
- first step is yeast fermentation
- yeast release alcohol as they break down sugars.
- acetic acid fermentation begins
- acetobacter bacteria use the alcohol as energy = releases acetic acid
- vinegar is produced by acetic acid
- turns cacoa beans into chocolate
- candied citron
what are benefits of fermentation?
microorganisms help preserve
- fermented foods have low pH = can be store for longer
- gives wider range of food options
nutritional changed in fermented foods?
depends on:
- microorganisms used (and their energy source). ie. high or low fat cheeses
- other ingredients added. ie pickles have more sodium than cucumbers
- impact of fermentation on bioavailability
what is contamination:
state of being impure or unfit for use due to the introduction of unwholesome or undesirable elements
3 types:
- physical
- chemical
- microbial
describe physical contaminants
nonliving substances that become part of a food mixture (ie. glass, metal filings, insects)
would not spoil food but can cause injury or health hazards if swallowed
can cause other microbes to enter the food (ie. insects can pick up microbes on their feet)
describe chemical contaminants
pesticide residue left on food can enter the food supply
monitored by USDA and CFIA to test if resides pose health hazards
can enter in through water (good solvent = substances can easily pollute water supplies)
2 types of pesticides: insecticides and herbicides
2 main sources of toxins in water supplies: pesticides and industrial waste
what is food spoilage
change in foo that makes it unfit for consumption
consists of microbes and enzymes to cause spoilage
spoilage usually makes the food unpleasant to eat, but does not always mean the food is unsafe
describe foodborne illness
result of pathogens in food:
- pathogens are microorganisms that can cause illness (nausea, stomach cramps, vomiting, diarrhea). can cause food to be unsafe before visible signs of spoilage.
- can cause illness by intoxication or infection
what is a foodborne illness outbreak
when 2 or more people become ill from eating the same food
usually have same symptoms
describe foodborne intoxication:
bacteria that can cause it?
- when microbes give off by-products (toxins) that cause illness
- killing microbe may not be enough to prevent food intoxication
- severity depends on amount of toxins eaten and how susceptible the person is to illness
bacteria that can cause it:
staphylococcus aureus:
-microbe can be killed by pasteurization but toxin is heat-resistant toxin and can still cause damage after microbe is destroyed = important to prevent
-foods likely to be contaminated: red meats and ham
-can include nausea, diarrhea, vomiting and stomach cramps
-prevented by proper hygiene and cleaning and sanitizing (humans is main cause)
clostridium botulinum:
- extremely dangerous anaerobic (gram positive) bacterium
- found in all soil types = found commonly on surface of vegetables
- high risk foods; honey, spinach, canned foods
- can live in fish intestines but don’t multiply there.
- produces toxin (botulin) = passes through intestine wall into blood to nerve cells = prevents nerve impulses from being transmitted = paralysis of muscles
- first symptoms: blurred vision, weakness, red, sore mouth, tongue, throat, diarrhea, constipation
- infants are more susceptible
- prevention: washing veg well
describe foodborne infection
occurs when microbes release digestive enzymes that damage body tissue = cause illness
-causes: bacteria, parasites, viruses. Need large number of organisms to cause illness. (cannot occur if microbes are killed)
escherichia coli:
- gram-neg
- lives in mammal intestines
- contaminates water or food handlers
- 7 strains cause foodborne illness. main type is E.coli O156:H7
causes: diarrhea, nausea, fever, etc. death - due to food contaminated by exposure to raw fecal matter
- prevented by chlorinating water supplies and cooking meat thoroughly and washing hands after the bathroom
listeria monocytogenes:
- gram-positive bacterium
- found in soil, water, animals
- food sources: soft cheese, uncooked meat, unwashed veg, unpasteurized milk
- can multiply at fridge temps = harder to kill
- grows best at low o2 levels and high co2. (10% salt solution and pH9)
- high risk for: pregnant women, newborns, weak immune systems, elderly
salmonella:
- found in eggs (75% of cases), poultry (salmonella can live in poultry without causing birds to be sick), meat, dairy
- prevention: keep hands and work surface clean. thoroughly cooking food.
describe parasitic infections
- caused by parasites (organisms that live in and feed on a host)
- common sources: contaminated water, raw fish, unwashed fruits and veg, swine, cattle, wild animals
trichinella spiralis:
- best known parasite
- roundworm that occurs in hogs and wild game. worms attach to intestine walls = produce new larvae = travels to bloodstream and muscle tissue
- infection is called trichionosis (destroyed when meat is adequately cooked,cured, smoked, fermented
describe viral infections
virus: microscopic disease-causing agent made of genetic material surrounded by a capsid (protein coating)
- don’t multiply in food but can be transmitted in food
- causes the most foodborne illnesses
- virus msut attach to host cell to multiply. genetic material is injected into host cell and into it’s genes. more virus particles are made. host cell ruptures and dies.
- viruses can survive on glass, stainless steel, ground meat, low-moisture food
- transmitted by contact with feces (by not washing hands after the bathroom or sewage contaminated water or fertilizer)
- 3 viruses associated with foodborne illness: rotavirus, norovirus, hep A virus
how do pathogens enter the food supply?
-new strains of bacteria an reproduce very fast.
2 ways microbes can get into food supply:
- pathogens transmitted by animals
- improper handling procedures
- temperature danger zone: 5-57deg c or 41-135deg F (time and temperature abuse = failure to properly cool food). hot foods should be kept hot (vice versa)
- cross contamination
what is HACCP?
7 principles?
hazards analysis and critical control point
food safety system used by food producers
- examines every point in the process where contamination can occur
- reduces food producers risk of liability and prevents outbreak of foodborne illness
7 principles
- conduct hazards analysis
- identify critical control points
- establish critical limits
- establish monitoring procedures
- establish corrective actions
- establish verification procedures
- establish record keeping and documentation procedures
what is the goal of food preservation
to increase shelf life of food
cooking is a form of preserving (denatures enzymes and destroys microorganisms)
4 levels of food preservations
blanching: suspending food in boiling water or steam for a short period
pasteurization: low heat treatment to destroy
microorganisms and stop enzyme activity
-UHT (ultra hight temp): sterilizes milk but doesn’t pasteurize
Commercial sterilization: for canned foods in sealed containers
Sterilization:complete destruction of all microorganisms that cause spoilage(must use wet/moist heat because it’s more deadly to microorganisms than dry heat. limited to liquid foods)
how is heat used in food preservation?
what is aspectic canning?
what are retorts?
- heat is transferred through conduction and convection
- conduction: used when food doesn’t move in the can (ie. tomato paste, beef hash, etc… are more viscous)
- convection: liquid canned foods
- processing time depends on time it takes for the can to reach necessary temperature
aspectic: free of pathogens
- aspectic canning = sterilizing food and placing it in sealed sterilized containers
retorts: large commercial pressure canners with locks and valves to hold the filled cans
- temp is low since foods don’t move (more likely to burn with high heat)
- retorts are agitated (gently shaking) to reduce processing time = saves energy = improveds food quality
what is the “cold point” in food preservation (heat transfer)?
cold point:
- last point in a can or mass of food to reach the desired temperature
- when heating by conduction: centre of can
- when heating by convection: just below centre of the can
what are time versus temperature considerations?
- must balance effects of heat on pathogens against effects of heat on food products
- thermal death curve: shows time to destroy pathogens at specific temperature (lower temp = longer cooking time)
why do food components affect the heat processing method?
- must consider microorganisms, ingredients, particle size, food density
- sugar, starch, proteins, fats interfere with wet heat penetrating food (slows down)
- as density and particle size increase = processing time increases
how does ph affect choice of heat processing?
microbes with high acid (low ph) make you sick
high acid foods can be heat processed but low acid foods must be brought to higher temperatures first
describe dehydration for food preservation?
role of water activity?
oldest method of preservation
- protects food from spoilage
- takes up less space and better convenience
water activity (Aw) role:
- when most free water is removed, molds and bacteria cant grow (reactions that lead to spoilage or stopped)
- compare free water to pure water
- pure water: Aw=1
- microbes stop growing below 0.7Aw (where moisture is less than 20%)
- most dehydrated foods have 1 to 15% moisture content
what are factors that affect quality of dried foods?
- surface area
- higher exposed SA = faster travel of heat to centre of food = water moves out of food faster = foods are cut up smaller - airflow:
- helps move moisture away as it is released from the food
- helps food to dry faster and more evenly - temp and case hardening
- increasing temp = increasing heat energy = faster dehydration = better food quality
- want to avoid potential dry skin forming on outside of food (case hardening). Must determine temp with max evaporation while preventing case hardening - oxidation
- high SA and airflow needed for dehydration increases exposure to oxygen = production of tannic acid from polyphenols reacting with o2 = possible browning in foods high in polyphenols
what are 2 ways to stop enzyme activity in foods to be dehydrated?
- heat treatment
- pasteurization = prepares foods for dehydration
- blanching = stops enzyme activity - sulfiting
- sodium bisulfite: slows enzymatic browning (o2 reacts with sodium bisulfite before reacting with polyphenols in food)
- sodium bisulfite must be dissolved in water first. then used to soak foods
2 disadvantages:
- increased drying time
- consumers can be allergic or sensitive
- sulfuring
- slows enzymatic browning
- sulfur is burned = combines with o2 = forms so2e
- pros: shortens drying time (nosoaking), inhibits mold growth, heat sensitive nutrients arent affected (vit C), food retains more original color and texture because it is not heated
- cons: destroys thiamin
what are the dehydration methods? (commercial)
- tray drying:
- easiest and cheapest
- trays with holes to allow food to dry evenly, hold the food
- for smaller scale operations - belt drying:
- for larger operations
- food is continuously fed into a tunnel dehydrator on moving belts - drum drying
- purees, pastes, mashed foods - spray drying
- fasted dehydration method
5 vacumm drying
-highest quality but costly
- freeze drying
- lypholization of dehydrofreezing
- food temp and atm pressure is powered so that water will sublimate out of food
- used for foods that may lose volatile flavors or be damaged by heat
what are home drying methods??
1 room or sun drying
- oven drying
- home dehydrators
what are pros of concentrates?
cons?
pros:
- more economical to ship (reduced volume and weight)
- extended food shelf life
- simple handling
cons:
- flavor and color changes
- formation of sugar crystals
- can occur in high protein foods = concentrated salts and minerals can cause proteins to denature = concentrate can gel during storage
- risk of foodborne illness
what are methods of concentration?
- open kettle
- open evaporation:
- vacuum evaporation
- filtration
% of moisture in dehydrated, concentrated and intermediate moisture foods?
dehydrated foods have moisture level below 15%
concentrated foods: 80%
intermediate moisture: 20 to 50%
what is food irradiation?
uses?
cold food preservation method. food is exposed to high energy EM waves as it is moved through radiation field by a conveyor belt
uses:
- commonly for products (sterilizing hospital equipment, cosmetic) than food
- to reduce food losses by controlling damage from insects, mold and sprouting
effects of food irradiation?
- chemical changes
- “ionizing radiation”: energy used to irradiate foods. produces ions in substance that it comes in contact with
- increases free radicals (but gives very little health hazard)
- radiolytic products form when EM waves hit the molecule (ie co2, formic acid, glucose)
- can kill salmonellae in poultry without damaging poultry - nutritional changes
- irradiation doesn’t harm nutritional content of most foods except for vit B1 (thiamin)
- can slightly lower b1, but not enough for a vit deficiency
what are forms of energy used to irradiate foods? (4)
units of energy?
- gamma rays
- most common
- cobalt-60 releases high amounts of gamma rays
- cesium-137
2,electron beams
- contains beta particles (produced by electronic machinery)
- has no radioactive source
- more costly
- UV lights
- cannot penetrate food but can kill microbes on surface of food
- used to treat surfaces, air, water in food plants - x-rays
- can penetrate thick foods
basic unit of energy is rad (radiation absorbed dose): amount of ionizing energy absorbed per gram of material
concerns about irradiation?
how does FDA control irradiation?
- risk of genetic damage to humans from radioactivity
- doesnt decrease risk of botulism
- radioactive material
- packaging to not add flavors or toxins
FDA:
- requires separate testing before food is allowed on market
- requires labeling
how is packaging of food preservation regulated?
functions of packaging?
- regulated by FDA
- -packaging is regulated (b/c anything that comes in contact with food can potentially be an additive)
- package can break down and leach into food
- based on type of container
1. primary container: packaging that comes in direct contact with food
2. secondary container: holds primary container (no direct contact with food)
functions:
- act as barrier between food and contaminants
- act as a dispenser
- protects food from moisture, gas, odors, light
- identifies contents
- storage, cooking, serving (ie. microwavable dinners)
types of packaging materials?
types of packaging materials
- based on protection needed
- shipping and storage affects
- chemical contents are considered
- metals:
- most common are steel, tin, aluminum
- steel cons: corrosive = disintegrates =reacts with o2 and acids
- tin = less corodible and stable for longer
- aluminum = lacks strength and rigidity - glass:
- pros: transparency and doesn’t react with food = cant contaminate (inert)
- cons: susceptible to breakage from high heat or pressure - paper:
- pros: low cost, light, recyclable
- must be combined with other substance (wax, plastics, aluminum) to increase strength - plastics:
- 3 types: polymers (one basic unit of organic molecules in one long chain), copolymers (2 or more basic units) , ionomers (ionic instead of covalent bonds) - packaging films:
- cellophane: processed cellulose. one of the first films to be widely used
- wide variance in permeability
- can be an edible film (rice paper)
- holds mixture inside (hotdogs)
- moisture barrier
what is reduced oxygen packaging (ROP)?
types?
function?
- provides atm that has little or no oxygen enclosed with the food
- used for red meat, poultry, seafood, pasta, cheeses, precooked meals, dried foods
Types:
- CAP (controlled atm packaging)
- uses barriers to control and maintain desired gases around food
- “active packaging”: package components may react to the food itself
- “semipermeable barrier”: barrier breathes to control movement of gases in and out (fruits and veg still respire after harvest = gives off co2 = decreases shelf life if sealed off). allows co2 inside package to be replaced with o2 from outside, but water vapour stays inside - MAP (modified atm packaging)
- one time flushing of a food container with a gas before container is sealed
- gas used depends on the needs of the food (ie. chips are sealed with co2 or N2 because O2 in normal air would cause chips to turn rancid) - desiccants: compounds that remove substances harmful to food products from the package.
- can also soak up extra water vapour to prevent microbial growth - enzyme systems
- limited uses
- added to food to react with a substance before flavors and textures can be altered
functions?
- slows ripening
- delay maturation
- reduce microbial spoilage
- slow enzymatic browning
- prevent tissue damage
what are super conductors?
carries electricity with no loss of energy when sufficiently cooled
what is a transgenic organism?
organism whose genes are altered
what are dispersed and continuous phases?
dispersed: particles that are scattered throughout a medium
continuous: the medium that particles are distributed in
suspensions: mixtures with the largest particles in dispersed phase
colloidal dispersion: have larger particles than those in solutions
what are factors that affect solubility of a solute in a solvent?
- temp
- higher = more solubility = decreasing amount of gaseous solute it can hold - particle size
- higher SA = faster dissolving of solute - conc of solution
- unsat solution: can dissolve more
- sat solution: max solute is dissolved
- saturation point: once all water molecules have bonded to a solute (no more H bonds can form). higher saturation = slower rate of dissolving
- supersaturated solution: more dissolved molecules than the saturation point (solution is heated then cooled). forms crystals when cooled - pH
- single charged ions are more soluble than ions with 2 or more charges
- smaller ions are more soluble than larger ions - agitation
- stirring speeds up dissolving rate until saturation point - vapor pressure
- pressure at which gases escape from and dissolve into a liquid at the same rate
- concentration of gas in a liquid is directly related to the pressure of gas over liquid (double pressure = double amount)
- fizz in carbonated drinks is caused by adding gas to liquid under pressure
- how to measure solute concentrations?
2. what happens when solutes are added to water?
- mass percent = mass of solute/mass of solution x 100
- freezing point drops and boiling point rises. (higher mass percent = bigger difference between freezing and boiling points)
what are colloidal dispersions?
types
characteristics
mixtures in which microscopic particles of one substance are evenly distributed in another
3 types:
- emulsions
- foams
- gels
characteristics
- have a continuous phase (medium that holds dispersed small particles)
- dispersed phase (contains bigger particles called colloids)
- colloids are 1000 timex bigger than solutes
- solutes are 1nm
- colloids dont dissolve but can be dispersed
- colloids of the same substance have the same electrical charge (they repel each other)
- most colloids in foods are starches and proteins
what is the tyndall effect?
when light rays pass through a colloidal dispersion, they scatter/bend and become visible (no light bending in solution because solutes are too small)
describe a temporary emulsion?
unstable mixture of polar and nonpolar
if let stand, will separate
need a permanent emulsion to stabilize (need to have a polar and non polar end)
factors that affect emulsion stability?
- temp:
- thermal conductivity: ability to conduct heat energy (water conducts heat energy faster than fat = oil-in-water emulsion will freeze faster than a water-in-oil emulsion - electrical charge
- emulsions are stable bc of the electrical attraction between water and polar end of the emulsifier
- an electric current will destabilize it = separates emulsion
describe foam (colloidal disp).
4 conditions to keep foam stable?
factos that affect stability?
colloidal disp of gas in a liquid. there are unstable and stable foams
to keep foam stable:
- liquid must be viscous to trap air
- stabilizer must be present to stretch a thin film around bubbles
- surface tension of film should be less than that of water
- liquid must have low vapor pressure
stability factors?
- temp
- adding solutes
- acidity (fresher eggs have lower pH = better)
- fat (reduces proteins foaming ability to form a film around air bubbles)
what is a suspension?
mixture of undissolved particles in a liquid
very unstable due to size of dispersed particles
continuous phase must be visous to keep particles from floating or sinking
larger particles = more viscous cont phase must be
