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food preservation Flashcards

1
Q

what portion of food produced for human consumption is lost or wasted

A

1/3

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2
Q

what % of the landfills in the us are filled with food?

A

20%

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3
Q

what are the most perishable foods?

A

foods that are high in protein or water

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4
Q

what is more detectable food spoilage or food contaimination & why?

A

food spoilage due to decreased quality of appearence, texure & taste.

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5
Q

what type of changes lead to food spoilage

A
  • biological (yeast, bacteria & mold)
  • chemical (enzymes that are naturally occuring)
  • physical (Water loss and separation)
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6
Q

how is yeast used in food

A

it is used to ferment sugars such as in bread and alcohol.

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7
Q

effect of bacteria & mold in foods

A

molds are visible but bacterias aren’t
bacterias can ferment CHO into CO2 & alcohol
they can also produce toxins

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8
Q

methods to prevent biological spoilage by destruction or growth inhibition

A

boiling,
refrigeration,
drying,
curing (high sugar/ salt)

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9
Q

how do enzymes cause food to spoil?

A 
they catalyze reactions
-proteases will trigger proteins
-lipases: TG--> FA + glycerol
-carbohydrase: CHO --> glucose
others
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10
Q

what are nonenzymatic types of spoil spoilarges

A

-oxidation of fats
-maillard rxn
may occur in long storage of non fat daity (non enzymatic browning)
bioavailibilty of protein may decrease since AA are not released during digestion

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11
Q

what does separation involve?

A
  • drip loss
  • emulsion breakdown
  • syneresis (gel)
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12
Q

how is high temperature used to preserve food?

A

destroy microorganisms & enzymes

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13
Q

how is low temperature used to preserve food?

A

control growth of microorganisms

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14
Q

what happens moisture is removed from a food?

A

it controls microbial growth

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15
Q

how does adding chemical preservatives control microbial growth

A

inhibits it

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16
Q

why is ionizing radiation used to control microbial growth

A

it destroys microorganisms and controls enzyme activity

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17
Q

what is the use of drying foods? give examples?

A

removed water hence inhibits microorganisms growth.

ex: pandanus, seeweed and fish

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18
Q

how is drying used in commercial settings?

A

-conventional uses heat in a drying room,
-vacuum uses low pressure
-osmotic uses strong syrup
freeze drying allows for ice crystals to vaporize

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19
Q

what is the use of curing foods? give examples?

A

preservation using salt and drying
sugar, spices and nitrates may be added
products may also be smoked for additional flavour

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20
Q

fermentation in preserving foods?

A

microorganisms converr CHO to co2 and alcohol thus preserving food and changing the flavor, color and texture

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21
Q

what is kimchi and where is it from

A

cabbage

korea

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22
Q

what is natto & where is it from

A

fermented soy beans

japan

23
Q

what is netetou & where is it from

A

fermented seeds

west africa

24
Q

what is hakarl and where is it from?

A

fermented shark

from iceland

25
what is pickling?
preservation through acidification. | may add spices and herbs
26
what is edible coating used for?
it is used to preserve fruits, vegetables, cheese, nuts etc.
27
how does edible coating function to preserve foods?
- increases shelf life since it acts as a barrier to moisture 02 & CO2 - improves handling= less dammage and breaking - improves appearence: glossy and better color - can serve as a vehicle for added ingredients: flavors, antioxidants & antimicrobials
28
what is canning used for?
to preserve fruits, vegetables and meats
29
what are the steps needed for canning?
1- food is packed in a sterile and sealed | 2- containers are heated to destroy microorganisms and enzymes
30
what is the boiling water method best for
good for foods with low pH
31
pressure canning is best for
-foods with high pH boiling at higher temperatures under pressure -to destroy clostridium botulinum
32
what to do when canning high acid food?
- fruits and tomatoes - heat resistance of the microbes is decreased du to the low pH - surviving organisms do not grow in acidic environment
33
canning low acidic food?
-vegetables, meat, fish poultry & milk -requires high Temps to destroy all spore forming organisms requires a pressure canner to allow temperature to be above boiling point
34
how is boiling used as a heat preservation method
- simplest method | boil for 10 minutes
35
pasteurization as a heat preservation method?
- liquids are heated ito a certain T for a certain time period 71 C for 15 seconds or 138 for 2 seconds
36
ohmic heatingas a heat preservation method
-electrical current is passed through the food generting heat that destroys microorganisms used in liquid eggs and fruit juices
37
what is cold preservation
refrigeration and freezing
38
how does refrigeration preserve foods?
- it slows down biological, chemical and physical reactions that shorten foods shelf life - high h20 foods should be refrigerated - perishable foods should be refrigerated asap
39
how does freezing preserve foods?
- needs to be at -18C or lower = least dammagin to flavor - h20 becomes unavailible to microorganisms - slows down chemical and physical reactions
40
what are some issues related to freezing foods?
- reactions continue since 02 is present hence shorter life than canned foods - recrystaliztion - cells may rupture - fluids are lost - over time may cause freezer burn - dispersion medium is lost
41
what happens in rapidly frozen foods?
ice crystals are small and numerous. they are mostly multicellular and give superior food quality
42
what happens in slowly frozen foods?
ice crystals are larger and fewer in numbers. the form in the extracellular spaces. once thawed, juices may be lost
43
what causes freezer burn?
the dehydration on the surface of the forzen foods resulting in white/greyish patches inadequate packing will cause water to evaporate of recrystallize on the surface of the food
44
what will oxidation during freezing result in?
-results in undesirable browning -when vegetables are blanched enzymes are destroyed which causes them to brown fat may be oxidized
45
Ascorbic acid may also undergo oxidation during freezing.
-may be inhibited by blanching of vegetables however some losses do occur in the blanching process -losses are increased through long periods of frozen storage
46
how do colloidal stubstances change during frozen storage?
- retrogradation of starch and syneresis - cellulose thoughens - emulsion breaks - nutrient values are barely altered - vitmin C & B may be lost up to 4% by drip.
47
off odors may be caused during freezing
-caused by the accumulation of volatile carbonyl compounds in unblanched or under blanched frozen vegetables
48
why is it important to blanch veggies before freezing them?
- destroys enzymes responsible for the development of off flavours - control undesirable charges in texture & colour - inhibits conversion of bright green chlorophyll to olive green pheophytin - but destroys some vitamin C and folate
49
what is irradiation?
it is a form of cold pasterizatuon which treats food with ionizing radiation. - it reduces microbial load on spices and dehydrated seasoning. - it controls insects in wheat flour & whole wheat flour - increases shelf life by preventing spouting or germination
50
what foods are approved to be treated with irradiation?
potatoes. onions, wheat, whole and ground spices & fresh/frozen ground beef.
51
what type of rays are used in irradiation?
gamma x rays electrons
52
whats is aseptic packing?
sterile, packed and sealed in a steilized container under sterilized conditions. can sit at room temps. ex: juice boxes, puddings, baby food
53
Modified atmosphere packing
composition of surrounding air is changed (decrease of 02 and increase of CO2) used in fruits and veggies, meat and poultry and baked goods.

Food fundamentals 2 (10 decks)

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