Fruits & Vegetables: Quality & Shelf Stability

Question 1

EXTRINSIC

Answer 1

Temperature
Relative humidity
Gases
Packaging materials

Question 2

INTRINSIC

Answer 2

Respiration rate
Transpiration
Ethylene production

Question 3

Temperature affects

Answer 3

Physiological responses
Starch-sugar balance
Shelf stability

Question 4

van’t Hoff rule

Answer 4

An increase of temp by 10 °C increases respiration
rate by 2-3 folds

Question 5

Temperature effects on physiological responses-A low temp causes reduction in the

Answer 5

respiration rate of fruits, hence slows the metabolic process

Question 6

Temp > 86 °F (30 °C)

Answer 6

the enzymes activity in fruits and veggies reduces

Question 7

Temp ≥ 95 °F (35 °C)

Answer 7

Many enzymes still active, but
at this temp the metabolism of fruits is abnormal
(disruption of cellular organization, rapid
deterioration of produce)

Question 8

Some produces are susceptible to chilling injury, thus
cooling < 50 °F (10 °C)

Answer 8

may not be a good option for
storage stability of produces

Question 9

Normal ripening process:

Answer 9

10-30 degree celcius

Question 10

Low temps may lead to

Answer 10

metabolic abnormalities
causing localized cell collapse

Question 11

Temperature eeefects on starch sugar balance

Answer 11

Generally, starch-sugar balance is at equilibrium
Some sugars degrade during respiration:

Question 12

For some produces like potato and sweet potato:

Answer 12

At ambient temp: tend towards accumulation
of starch
Below critical temp: tend towards
accumulation of sugar
potato (≤ (10 °C))
sweet potato (≤ (15 °C))

Question 13

Temperature eeefect on shelf stability

Answer 13

Susceptibility of certain crops toward injury when stored at
temp <55 to 60 F

Question 14

during chilling injury, The cell structure of produces degrades

Answer 14

and metabolites such as amino acids, sugars, minerals are released: provides substrates for
microbial growth esp fungi

Question 15

Freezing Injury

Answer 15

Occurs due to susceptibility of plant tissues to temp below freezing points, 25-30 °F (-4 to -1 °C)

Question 16

What will happen during freezing injury

Answer 16

1. Crystal puncture cell membranes : turgor loss
2. Crystal breaks up the cell wall structures :
   tissue breakdown, release of degenerative enzymes

Question 17

Rapid cooling (pre-cooling) is important to increase the producesʼ shelf
life:

Answer 17

reduces respiration rate
reduces sensitivity to ethylene
reduces water loss
inhibits/slow down microbial growth

Question 18

Among main factors for the selection of the pre-cooling techniques;

Answer 18

The physiological properties of the produce (the nature of the
produce)
The desired shelf life of the produce
Package design
Room design

Question 19

Room Cooling

Answer 19

Simple, inexpensive method
Less efiicient

Question 20

Forced-Air Cooling

Answer 20

An efficient method compared to room cooling
Using fans in addition to cool air
The use of forced air fans hsould be stopped oncethe priduce has reached its opt temp

Question 21

Vacuum Cooling

Answer 21

Highly dependent on the surface to
volume ratio

Question 22

Hydrocooling

Answer 22

Faster heat removal (15X than air), not
energy efficient
Not suitable for produce that cannot
tolerate wetting

Question 23

Direct contact with ice

Answer 23

Efficietn for produces of high respiration rates
suitable for produces that are not chilling sensitive

Question 24

Relative Humidity

Answer 24

High humidity (90-95%) is recommended to
retain fruits/vegetables freshness

Question 25

However, high humidity may

Answer 25

y promote microbial growth In the case that dew point (moist a

Question 26

In the case that dew point (moist air) is cooled, a temp is reached.

Answer 26

At this temp, the vapor pressure of water reaches its maximum: fog, condensation

Question 27

Fog causes the package of the produce

Answer 27

becomes unappealing

Question 28

Condensation can promote

Answer 28

microbial growth, integrity loss for the package

Question 29

Respiration Rate-senescence

Answer 29

Senescence of fresh produces is proportional to respiration rate

Question 30

respiration rate is

Answer 30

Temperature dependent and affected by modified atmosphere

Question 31

Respiratory quotient (RQ) is

Answer 31

the ratio of CO2 produced to O2 consumed (assumed=1)

Question 32

RQ<1 when

Answer 32

reduced lipids are used for respiration

Question 33

RQ>1 when

Answer 33

organic acids are used for respiration

Question 34

Transpiration

Answer 34

The loss of water from fruits or vegetables (living cells) in a form of vapor

Question 35

transpiration is esential because

Answer 35

i) ʻcreates suction force and helping in ascent of sapʼ ii) ʻaffects water and minerals absorption through roots iii) ʻtranslocation of plant food from one part to another iv) ʻdissipates excess solar energy received by plantʼ and etc

Question 36

Factors influencing transpiration:

Answer 36

Temperature Surrounding gases (type and level) Cultivar Relative humidity (minimize VPD) Light Air movement Nature of surface coatings Physical injury, etc

Question 37

Gases-CO2 -help to

Answer 37

inhibit microbial growth

Question 38

co2 known to

Answer 38

increase firmness in certain fresh produces

Question 39

Higher composition (>15%) of co2 has known to

Answer 39

induce off-flavor development (fermentative metabolism)

Question 40

Nitrogen help to

Answer 40

inhibit microbial growth Retain package from being collapsed Prevent oxidation Replace air

Question 41

Oxygen-reduced lvl was reported ot help in

Answer 41

delaying the softening and pigment development

Question 42

ethylene

Answer 42

s used to control ripening process of fruits

Question 43

Produces high in ethylene MUST BE STORED SEPARATELY

Answer 43

than produces low in ethylene

Question 44

climacteric Fruits

Answer 44

1. Ripening process continues after harvest 2. Some produces large amount of ethylene

Question 45

Non-climacteric Fruits

Answer 45

1. Must ripen on the plant 2. Exposure to ethylene after harvest can deteriorate the quality faster

Question 46

Acetylene-an alternative to ethylene

Answer 46

Economical alternative to ethylene and commonly used in less developed countries

Question 47

Combination of CO2 and O2 is

Answer 47

s common for active modified atmosphere applications

Question 48

Packaging Materials

Answer 48

help in prolonging the shelf life of fruits and vegetables

Question 49

Provide protection and containment

Answer 49

for distribution purposes of fruits and vegetables

Question 50

packaging material example

Answer 50

Vented corrugated boxes Vented clamshell?