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FOSC202 > Handling and storage quality > Flashcards

Handling and storage quality Flashcards

1
Q

factors affecting quality changes during handling and storage (8)

A

temperature
gaseous atmosphere
plant hormones
physical damage
moisture
micro-organism
light
biochemical reactions

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2
Q

relationship between temp and respiration

A

as one increases so does the other

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3
Q

what is Q10

A

the ratio of the rate of reaction at the given temperature/ rate of reaction at -10C

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4
Q

Q10 of most f and v at temps > 10C

A

2-3

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5
Q

what can lowering the temperature do to f and v (3)

A

-reduce the rate of undesirable physiological changes
-reduce microbial activity
-reduce water loss

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6
Q

physiological disorders associated with temperature extremes (3)

A

high heat injury
chilling injury
freezing injury

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7
Q

result of high heat injury

A

inactivated enzymes
abnormal metabolism
-breakdown of membrane structure and integrity
-disruption of cellular organisation and rapid deterioration
-loss of pigments

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8
Q

what component of the membrane structure causes the breakdown

A

pectin is attacked by polygalacturonase

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9
Q

result of chilling injury (3)

A

loss of fluidity in membrane
imbalance of metabolic reactions
undesirable quality changes

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10
Q

what does the extent of a chilling injury depend on

A

duration of exposure
extreme of temperature

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11
Q

can fruit with chilling injury be eaten?

A

YES, but has changes in its sensory properties

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12
Q

example of chilling injury in capsicum

A

pitting

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13
Q

what is the affect a chilling injury has on ripening

A

it can no longer ripen

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14
Q

some general symptoms of chilling injury (4)

A

surface lesions
internal browning
accelerated internal senescence
loss of growth capacity

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15
Q

what does the freezing temperature of F and V depend on

A

conc of solutes

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16
Q

effect of freezing

A

initiates desiccation and osmotic stress
solvent water loss due to ice crystal formation
physical disruption from ice crystals

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17
Q

Controlling which factor will result in the biggest difference for maintaining quality

A

temperature

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18
Q

4 types of cooling methods

A

cold air (room cooling, forced air/pressure)
cold water
ice
evaporation of water

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19
Q

most common type of cooling

A

room cooling

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20
Q

what does room cooling involve

A

Produce that has been packed into boxes being exposed to cool air in a store room

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21
Q

advantage of room cooling

A

cool and store in the same place (simple)

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22
Q

Disasvantage to room cooling

A

low efficiency
large space required

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23
Q

disadvantage ot room cooling

A

low efficiency
requires large storage area

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24
Q

describe pressure cooling

A

cold air forced through packages

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25
Q

the advantage to pressure cooling

A

faster

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26
Q

describe hydro cooling

A

water is used as a heat transfer medium

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27
Q

advantages to hydro cooling

A

increased surface exposure increases efficiency
allows for cleaning from the environment

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28
Q

purpose of icing

A

pre-cooling or transport

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29
Q

describe vacuum cooling

A

reduced pressure decrease water BP so it evaporates

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30
Q

advantage to vacuum coolig

A

rapid

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31
Q

describe evaporative cooling

A

dry air is blown across wet surface

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32
Q

disadvantage to evaporative cooling

A

requires low RH and quality water

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33
Q

advantage to evaporative cooling

A

low energy cost

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34
Q

how can changing the gaseous atmosphere slow respiration

A

reducing O2
low levels of CO2

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35
Q

normal composition of air

A

21% O2
78% nitrogen
0.034% CO2

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36
Q

what % is O2 generally reduced to

A

<10%

37
Q

what is important to consider when changing the air composition

A

critical levels for different fruits

38
Q

what does a yellow door mean

A

gas composition is being controlled

39
Q

types of technology used to control atmosphere

A

CA-contorlled atmosphere
MA-modified atmosphere

40
Q

what is CA

A

proportion of gases is carefully controlled throughout storage

41
Q

what is MA

A

packaging of f and v is changed then allowed to respire normally

42
Q

what is MA good for

A

short term storage

43
Q

methods to minimize ethylene concentration

A

hypobaric chamber
ventilation

44
Q

when should climateric products be harvested

A

maximum cell enlargement and enough starch to convert to sugar during maturation

45
Q

when should non-climacteric products be harvested

A

when mature

46
Q

what kinds of treatments can be used for eythlene

A

ethylene-action inhibitors:
2, 5 nobornadiene
1-methyl cyclopropane (1-MCP)

47
Q

what will physical damage/stress cause

A

localised bursts in respiration
ethylene formation
accumulation of secondary metabolites

48
Q

what does wounding lead to

A

undesirable colour and flavour changes

49
Q

what causes the wounding changes

A

release of enzymes and substrates from damaged cells
more susceptible to microbial invasion

50
Q

draw wound flow diagram on paper

A

wound ->
respiration
-heat
-ripening->softening
-reduced CHO, organic acids and ascorbic acid-> poor flavour

ethylene-> ripening-> softening

phenolic metabolism
-PPO + O2 + phenolic compounds-> browning
-PAL-> phenolic compounds->browning or lignin -> toughening

wound healing
-suberin
-peridium -> cell division

51
Q

Classes of metabolites formed form physical stress/damage

A

protective
stress
lipid

52
Q

what do protective metabolites do

A

form a waxy or lignified layer to prevent microbial invasion

53
Q

examples of stress metabolites

A

isoflavonoids, diterpenes, polyacetylenes, glycoalkaloids

54
Q

effect of stress metabolites

A

antibiotic
reduced quality
can be toxic
precursor to enzymatic browning

55
Q

how do lipid metabolites form

A

stress causes PUFA breakdown and autolysis of cell membranes

56
Q

which enzymes are involved in lipid metabolism

A

lipoxygenase, peroxidase, lipase, phopholipase

57
Q

what doe enzymatic reactions caue

A

off flavours
-even in frozen of dehydrated produce

58
Q

how are hydroperoxides involved in lipid metabolism

A

formed by lipogenases

59
Q

what do hydroperoxides do

A

cause bleaching of carotenoids and chlorphyll
react with other consituents

60
Q

technologies to prevent physical injury

A

hand harvesting
corrugated fiberboard packing
separated layers/padding

61
Q

what does low humidity cause in f and v

A

water loss

62
Q

how is water lost

A

transpiration
evaporation

63
Q

adverse affects of waterloss

A

wilting
decreased crispness + saleable weight

64
Q

factors that affect water loss

A

surface volume affect
surface coatign
mechanical damage to tissue

65
Q

what can high humidity cause

A

excess water
-microbial growth
-fogging of packaging

66
Q

technologies to control moisture

A

coatings(waxes)
use water vapour to increase RH
water scrubbers in packaging
maintain temp gradient in storage

67
Q

what does microbial invasion cause in f and v

A

stress reposnse

68
Q

what kind of barriers to plants have as microbial invasion barriers

A

physcial and chemcial

69
Q

what can happen to plants barriers during processing

A

comprimised

70
Q

describe two natural chemical and physical barriers plant use to protect against microorganisms

A

skin/fuss
phenolic and benzoic acids

71
Q

what are phytoalexins toxic to

A

microbes

72
Q

how to reduce exposure to micro attack

A

minimise processing
washing
chilling
-fungicide treatments (not in NZ)

73
Q

adverse effects of light on the quality

A

formation of glycoalkaloids
photo-oxidation of chlorophyll

74
Q

what does the formation of glycoalkaloids do to potatoes

A

makes them go green

75
Q

what does the photo-oxidation of chlorophyll cause in broccoli and spinach

A

yellowing

76
Q

positive effect of light on f and v

A

ripening
-i.e tomatoes

77
Q

what does the photo-oxidation of chlorophyll cause in broccoli and spinach

A

yellowing

78
Q

technologies to protect from light exposure

A

dark storage (light excluded packaging)
irradiation

79
Q

positive effects of irradiation

A

inhibition of sprouting
destruction of pests + insects in grains
ripening delay

80
Q

negative effects of irradiation

A

irradiation injury
-blemishes, accelerated yellowing
interferes with wound healing

81
Q

biochemical processes that affect the quality

A

cell wall changes
starch-sugar transformation
pigment metabolism
aroma compounds

82
Q

what changes occur in the cell wall during processing

A

softening
-loss of turgor
-depolymerisation, demethylation, and loss of calcium in cell wall polysaccharides

hardening
-lignin formation

83
Q

describe some starch-sugar transformation

A

synthesis of starch
starch degradation to simple sugars

84
Q

Why do potatoes stored below 5C for too long go brown during frying

A

they have been allowed to ripen for too long and the starch has been converted to simple sugars which causes the Maillard reaction to occur during frying

85
Q

what happens during pigment metabolism

A

anthocyanins are lost due to polyphenol oxidase and peroxidase enzymes

86
Q

what happens to aroma compounds during process/storage

A

biosynthesis and degradation of volatiles

87
Q

technologies to protect from biochemical reactions during processing

A

plant hormones
coatings

88
Q

how do plant hormones protect from biochemical reactions

A

delay senescence
improve quality + shelf life

89
Q

how do coatings protect from biochemical reactions

A

control water loss
slow respiration and ripening
reduce surface injury

FOSC202 (28 decks)

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