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FS 303 > Postharvest Physiology & Respiration > Flashcards

Postharvest Physiology & Respiration Flashcards

1
Q

List the three stages of development of fruits.

A

1 - Growth
2 - Maturation
(Climacteric)
3 - Senescence

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2
Q

Describe the growth stage

A

Cell enlargement

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3
Q

Describe the Maturation Stage

A
  • Growth ends
  • Ripening begins
  • Seeds develop
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4
Q

Describe the Senescence stage

A
  • Degradation process
  • Seeds released
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5
Q

What hormone triggers ripening?

A

ethylene

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6
Q

Does ripening continue after detachment from the plant?

A

yes

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7
Q

What changes occur during ripening?

A
  • colour changes
  • texture changes (firm to soft)
  • Flavour changes ( highly acidic to less acidic + low sweetness to high sweetness)
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8
Q

What is the Climacteric stage?

A

the final physiological process that marks the end of fruit maturation and the beginning of fruit senescence

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9
Q

What occurs during the climacteric stage?

A

increased ethylene and a rise in cellular respiration

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10
Q

What is the defining point of the climacteric stage?

A

a sudden rise in the respiration of the fruit

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11
Q

Why is the climacteric stage optimal for consumers?

A
  • marks the peak of edible ripeness
  • best taste and texture for consumption
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12
Q

What is chlorophyll?

A

A bright green pigment that is oil soluble

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13
Q

What is the importance of chlorophyll?

A

Critical in photosynthesis ( formation of glucose from CO2 and water)

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14
Q

How does fruit ripening affect chlorophyll?

A
  • Chlorophyll degradation
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15
Q
A
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16
Q

What are carotenoids?

A

Yellow, orange and red pigments that are oil soluble.

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17
Q

When do caraoenoids become visible?

A

Only after chlorophyll degradation

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18
Q

True of false: biosynthesis stops after harvest

A

False - it continues after harvest

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19
Q

Carotenoids are sensitive to oxidation : what happens

A
  1. Loss of vit. A activity
  2. Loss of antioxidant activity
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20
Q

What is significant about Lutein?

A

Potentially effective against macular degeneration

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21
Q

What are flavonoids?

A

Group of phytonutrients found in fruits and vegetables responsible for their colours

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22
Q

Flavonoids can also be antioxidants, what are their benefits?

A

Anti inflammatory and immune function

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23
Q

What are the four most significant enzymes in tomatos?

A

1 - Polygalacturonase (PG)
2 - Pectin methylesterase (PME)
3 - Beta-galactosidase (B-GALase
4 - Pectate lyase (PL)

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24
Q

Function of Polygalacturonase

A

Depolymerize pectin by hydrolyzing glyosidic bonds

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25
Q

Function of Pectin methylesterase

A

Remove methyl ester groups and as a result increase carboxylic residue

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26
Q

Function of Beta-galactosidase

A

-cleave terminal galactose residues
-Loss of galactose from wall polysaccharides occurs throughout fruit development and accelerates the onset of ripening

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27
Q

Function of Pectate lyase

A

Randomly cleave demethylesterfied polygalacturonate

28
Q

What is significant about the permeable membrane in osmosis?

A

Permeable to water but not to solutes

29
Q

What is osmosis?

A

When water moves across a membrane from a low solute concentration to a high solute concentration

30
Q

What does osmosis create?

A

Osmotic pressure

31
Q

How is osmotic equilibrium established?

A

Established by water moving through a membrane

32
Q

What do you call a low solute concentration solution? What do the cells look like?

A

hypotonic (cells swollen)

33
Q

What do you call a high solute concentration solution? What do the cells look like?

A

hypertonic (cells shriveled)

34
Q

What do you call a solution that has reached osmotic equilibrium? What do the cells look like?

A

isotonic (cells keep tone)

35
Q

What causes tissue softening?

A

Pectin depolymerization by enzymes that results in a loss of structure

36
Q

How can firmness be measured?

A

Texture Analyzer

37
Q

What pH are fruit and vegetables?

A

Highly acidic

38
Q

How does the pH change during ripening? What does this affect?

A
  1. The amount of organic acids decrease, increasing pH (less acidic)
  2. Affects colour
39
Q

How is sweetness changed during ripening?

A
  1. Starch degrades into sugar, increasing soluble solids and changes sugar/acid ration = change in flavour
40
Q

pH of tomato juice?

A

pH 4

41
Q

What is sweetness in fresh produce determined by?

A

soluble solids

42
Q

How are soluble solids analyzed

A

use of a refractometer

43
Q

How does a refractometer work?

A
  • measures refractive index in degree Brix (%)
44
Q

What is the unit Degrees Brix used for? Examples?

A
  1. measures % sugar content of aqueous solutions
  2. sugars in juices, wines, soft drinks
45
Q

What happens when a fruit has more pectin vs. less pectin?

A

More = hard
Less = soft

46
Q

How do ripe fruits increase sugar?

A

Break down of starch

47
Q

What is respiration?

A

The enzymatic oxidation of glucose -> oxygen and water

48
Q

What is the purpose of respiration?

A

To release the chemical energy stored in C-H bonds

49
Q

What is the function of ATP?

A

It captures the released energy and stores it to be used by the cell

50
Q

How do the energy content of molecules change with oxidation?

A

They decrease

51
Q

What are the three stages of Aerobic respiration (detail in notes) . Where do they take place?

A

1 - Glycolysis (no O2 required) - cytoplasm
2 - Krebs Cycle (Mitochondria)
3 - Electron transport chain (Mitochondria)

52
Q

What are the three stages of Anaerobic respiration?

A

1 - Glycolysis can occur (no O2)
2 - Fermentation (cytoplasm) - ethanol + NAD in plants; lactic acid + NAD in animals

53
Q

What is the significance of NAD +?

A

crucial to glycolysis - cell death without it

54
Q

Can you use all of the anaerobic energy?

A

No, anaerobic respiration leaves a lot of energy (in the lactate or ethanol molecules) that the cell cannot use and must excrete

55
Q

What is the metabolic waste product of cellular respiration?

A

CO2

56
Q

Define cellular respiration

A

The biochemical pathway where energy from the chemical bonds in food molecules is released to be reused for the essential processes of life.

57
Q

What happens to the respiration in fruit and veg after harvest?

A

it continues

58
Q

What happens at a faster respiration rate?

A

Faster chemical process and supplies deplete quickly (rotting) - slower rate can increase shelf life

59
Q

What factors does respiration rate depend on?

A

Type of produce, temp, air quality, ripening (ethylene), damages etc.

60
Q

What enzyme is related to ripening

A

ethylene

61
Q

Provide examples for fast, moderate and slow respiration rates in food:

A

F: broccoli
M: strawberries and yellow apples
S: Apples, tomatoes, grapefruit

62
Q

What is the general rule for the relationship between respiration rate and temperature?

A

Lower temp = lower reaction rate (respiration, oxidation, enzyme reaction)

63
Q

How can you slow down respiration using air quality?

A
  • lower oxygen levels; increase CO2 levels
64
Q

How can air quality negatively impact Fruit and Veg?

A

No oxygen = decay or fermentation (quality degraded by off flavour)

Too much CO2 = damage F&V

65
Q

How can you make sure to optimally store produce?

A

1 - Air circulation (maintain uniform temp and stacking can affect circulation)

2 - Air quality
2a) moisture content 2b) off flavour/odor can be absorbed by products ( air circulation system requires filtering)

3 - controlled atmosphere

66
Q

What is used to measure color?

A

Hunter scale

FS 303 (12 decks)

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