Handling and storage quality Flashcards by Kate Edens

factors affecting quality changes during handling and storage (8)

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

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relationship between temp and respiration

as one increases so does the other

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what is Q10

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

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Q10 of most f and v at temps > 10C

2-3

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

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

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physiological disorders associated with temperature extremes (3)

high heat injury
chilling injury
freezing injury

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result of high heat injury

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

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what component of the membrane structure causes the breakdown

pectin is attacked by polygalacturonase

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result of chilling injury (3)

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

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what does the extent of a chilling injury depend on

duration of exposure
extreme of temperature

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can fruit with chilling injury be eaten?

YES, but has changes in its sensory properties

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example of chilling injury in capsicum

pitting

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what is the affect a chilling injury has on ripening

it can no longer ripen

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some general symptoms of chilling injury (4)

surface lesions
internal browning
accelerated internal senescence
loss of growth capacity

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what does the freezing temperature of F and V depend on

conc of solutes

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effect of freezing

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

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

temperature

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4 types of cooling methods

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

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most common type of cooling

room cooling

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what does room cooling involve

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

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advantage of room cooling

cool and store in the same place (simple)

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Disasvantage to room cooling

low efficiency
large space required

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disadvantage ot room cooling

low efficiency
requires large storage area

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describe pressure cooling

cold air forced through packages

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the advantage to pressure cooling

faster

describe hydro cooling

water is used as a heat transfer medium

advantages to hydro cooling

increased surface exposure increases efficiency allows for cleaning from the environment

purpose of icing

pre-cooling or transport

describe vacuum cooling

reduced pressure decrease water BP so it evaporates

advantage to vacuum coolig

rapid

describe evaporative cooling

dry air is blown across wet surface

disadvantage to evaporative cooling

requires low RH and quality water

advantage to evaporative cooling

low energy cost

how can changing the gaseous atmosphere slow respiration

reducing O2 low levels of CO2

normal composition of air

21% O2 78% nitrogen 0.034% CO2

what % is O2 generally reduced to

<10%

what is important to consider when changing the air composition

critical levels for different fruits

what does a yellow door mean

gas composition is being controlled

types of technology used to control atmosphere

CA-contorlled atmosphere MA-modified atmosphere

what is CA

proportion of gases is carefully controlled throughout storage

what is MA

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

what is MA good for

short term storage

methods to minimize ethylene concentration

hypobaric chamber ventilation

when should climateric products be harvested

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

when should non-climacteric products be harvested

when mature

what kinds of treatments can be used for eythlene

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

what will physical damage/stress cause

localised bursts in respiration ethylene formation accumulation of secondary metabolites

what does wounding lead to

undesirable colour and flavour changes

what causes the wounding changes

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

draw wound flow diagram on paper

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

Classes of metabolites formed form physical stress/damage

protective stress lipid

what do protective metabolites do

form a waxy or lignified layer to prevent microbial invasion

examples of stress metabolites

isoflavonoids, diterpenes, polyacetylenes, glycoalkaloids

effect of stress metabolites

antibiotic reduced quality can be toxic precursor to enzymatic browning

how do lipid metabolites form

stress causes PUFA breakdown and autolysis of cell membranes

which enzymes are involved in lipid metabolism

lipoxygenase, peroxidase, lipase, phopholipase

what doe enzymatic reactions caue

off flavours -even in frozen of dehydrated produce

how are hydroperoxides involved in lipid metabolism

formed by lipogenases

what do hydroperoxides do

cause bleaching of carotenoids and chlorphyll react with other consituents

technologies to prevent physical injury

hand harvesting corrugated fiberboard packing separated layers/padding

what does low humidity cause in f and v

water loss

how is water lost

transpiration evaporation

adverse affects of waterloss

wilting decreased crispness + saleable weight

factors that affect water loss

surface volume affect surface coatign mechanical damage to tissue

what can high humidity cause

excess water -microbial growth -fogging of packaging

technologies to control moisture

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

what does microbial invasion cause in f and v

stress reposnse

what kind of barriers to plants have as microbial invasion barriers

physcial and chemcial

what can happen to plants barriers during processing

comprimised

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

skin/fuss phenolic and benzoic acids

what are phytoalexins toxic to

microbes

how to reduce exposure to micro attack

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

adverse effects of light on the quality

formation of glycoalkaloids photo-oxidation of chlorophyll

what does the formation of glycoalkaloids do to potatoes

makes them go green

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

yellowing

positive effect of light on f and v

ripening -i.e tomatoes

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

yellowing

technologies to protect from light exposure

dark storage (light excluded packaging) irradiation

positive effects of irradiation

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

negative effects of irradiation

irradiation injury -blemishes, accelerated yellowing interferes with wound healing

biochemical processes that affect the quality

cell wall changes starch-sugar transformation pigment metabolism aroma compounds

what changes occur in the cell wall during processing

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

describe some starch-sugar transformation

synthesis of starch starch degradation to simple sugars

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

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

what happens during pigment metabolism

anthocyanins are lost due to polyphenol oxidase and peroxidase enzymes

what happens to aroma compounds during process/storage

biosynthesis and degradation of volatiles

technologies to protect from biochemical reactions during processing

plant hormones coatings

how do plant hormones protect from biochemical reactions

delay senescence improve quality + shelf life

how do coatings protect from biochemical reactions

control water loss slow respiration and ripening reduce surface injury