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Food fundamentals 2 > food preservation > Flashcards

food preservation Flashcards

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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
Q

what is pickling?

A

preservation through acidification.

may add spices and herbs

26
Q

what is edible coating used for?

A

it is used to preserve fruits, vegetables, cheese, nuts etc.

27
Q

how does edible coating function to preserve foods?

A
  • 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
Q

what is canning used for?

A

to preserve fruits, vegetables and meats

29
Q

what are the steps needed for canning?

A

1- food is packed in a sterile and sealed

2- containers are heated to destroy microorganisms and enzymes

30
Q

what is the boiling water method best for

A

good for foods with low pH

31
Q

pressure canning is best for

A

-foods with high pH
boiling at higher temperatures under pressure
-to destroy clostridium botulinum

32
Q

what to do when canning high acid food?

A
  • fruits and tomatoes
  • heat resistance of the microbes is decreased du to the low pH
  • surviving organisms do not grow in acidic environment
33
Q

canning low acidic food?

A

-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
Q

how is boiling used as a heat preservation method

A
  • simplest method

boil for 10 minutes

35
Q

pasteurization as a heat preservation method?

A
  • liquids are heated ito a certain T for a certain time period
    71 C for 15 seconds or 138 for 2 seconds
36
Q

ohmic heatingas a heat preservation method

A

-electrical current is passed through the food generting heat that destroys microorganisms
used in liquid eggs and fruit juices

37
Q

what is cold preservation

A

refrigeration and freezing

38
Q

how does refrigeration preserve foods?

A
  • 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
Q

how does freezing preserve foods?

A
  • needs to be at -18C or lower = least dammagin to flavor
  • h20 becomes unavailible to microorganisms
  • slows down chemical and physical reactions
40
Q

what are some issues related to freezing foods?

A
  • 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
Q

what happens in rapidly frozen foods?

A

ice crystals are small and numerous. they are mostly multicellular and give superior food quality

42
Q

what happens in slowly frozen foods?

A

ice crystals are larger and fewer in numbers. the form in the extracellular spaces.
once thawed, juices may be lost

43
Q

what causes freezer burn?

A

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
Q

what will oxidation during freezing result in?

A

-results in undesirable browning
-when vegetables are blanched enzymes are destroyed which causes them to brown
fat may be oxidized

45
Q

Ascorbic acid may also undergo oxidation during freezing.

A

-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
Q

how do colloidal stubstances change during frozen storage?

A
  • 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
Q

off odors may be caused during freezing

A

-caused by the accumulation of volatile carbonyl compounds in unblanched or under blanched frozen vegetables

48
Q

why is it important to blanch veggies before freezing them?

A
  • 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
Q

what is irradiation?

A

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
Q

what foods are approved to be treated with irradiation?

A

potatoes. onions, wheat, whole and ground spices & fresh/frozen ground beef.

51
Q

what type of rays are used in irradiation?

A

gamma
x rays
electrons

52
Q

whats is aseptic packing?

A

sterile, packed and sealed in a steilized container under sterilized conditions. can sit at room temps.
ex: juice boxes, puddings, baby food

53
Q

Modified atmosphere packing

A

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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