Lecture 15: PH treatments, Insect Control, Chilling and Freezing Injuries

Question 1

what is one of the major causes of PH losses of produce?

Answer 1

insect infestation

Question 2

describe insect infestation

Answer 2

• most damage occurs when produce is on field
• after post harvest, spoilage of produce by insects is not much, but produce can carry insects as eggs or larvae –> which stay dormant –> eggs will become insects when favorable conditions exists

Question 3

how is the spread of insects prevented?

Answer 3

• through import control procedures
• includes treatments to produce originating from geographical locations
• quarantine treatments
• it is up to the exporting countries to meet all quarantine reqs of the importing country

Question 4

what does CFIA stand for?

Answer 4

canadian food inspection agency

Question 5

how does CFIA protect plants and animals from pests/diseases?

Answer 5

has controls, restrictions and prohibitions on entry of plants, animals and products

Question 6

how can you import meats and F/V?

Answer 6

• must have a certificate or permit

Question 7

what is the goal of regulations?

Answer 7

to prevent entry and establishment of exotic or non-indigenous orgaisms that pose a risk to plant life or health

Question 8

what does APHIS stand for?

Answer 8

animal plant health inspection service

Question 9

what is APHIS responsible for?

Answer 9

for regulating import/export and movement within the US of commodities that are subject to quarantine restrictions

similar to AAFC/CFIA

Question 10

what is AAFC?

Answer 10

agriculture and agri-food canada

Question 11

what is the goal of phytosantiary treatments?

Answer 11

• to achieve probit-9 control
• 99.9968% mortality of target insect/pests
• 3 survivors per 100000 treated
• around 5 log reduction

Question 12

describe quarantine treatments

Answer 12

physical or chemical treatment given to a commodity to ensure destruction of insects of all stages of their growth (eggs, alrvae, pupae and adults)

Question 13

what are 4 quarantine treatments for insects used in USA and canada?

Answer 13

1. fumigation
2. cold treatment
3. heat treatment
4. irradiation

Question 14

describe fumigation

Answer 14

• early and most popular method of insect control

- produce is subjected to gas fumigants in fumigant chambers under controlled temp, time and conc

Question 15

what does conc and treatment time of fumigant depend on?

Answer 15

• insect species, degree of contamination

- produce compatibility and quantity of produce

Question 16

what is fumigation similar to? how are they different?

Answer 16

• similar to ethylene ripening procedure

- diff: fumigation has slightly modified procedure w/ diff gases

Question 17

what are common fumigants?

Answer 17

ethylene dibromide (EDB)
methyl bromide (MB)
phosphene
ethylene oxide

Question 18

what is EDB?

Answer 18

ethyleme dibromide

• common fumigant
• used to be popular, but is now banned for domestic use due to effect on ozone layer

Question 19

describe cold treatment

what produce can this be used for?

Answer 19

• were commodity is exposed to a low temp long enough to cause destruction of the insect
• effective against insects in tropical regions
• produce must be tolerant of temp regime for required duration (not good for chilling sensitive commodities)

Question 20

why were heat treatments less often used?

why are they more popular now?

Answer 20

• less used due to development of effective fumigants that are cheaper, effecter and faster than heat
• now they are more used b/c consumers worry about use of chemicals in food from fumigation

Question 21

vapor heat is slow b/c of presence of what?

Answer 21

air

Question 22

why is hot water dip more effective than vapor heat?

Answer 22

• vapor heat is slower due to air presence
• water has better heat transfer
• temp control is easy
• distribtion is more uniform

Question 23

hot water dip is effect against what?

Answer 23

insects and molds

Question 24

what is the primary disadvantage of hot water dip?

Answer 24

heat sensitivity of many fruits to temp required for effectiveness

Question 25

what are some treatment variations?

Answer 25

high temp air fumigation + refrigeration

cold treatment + fumigation

waxing

edible coating

Question 26

how do chilling and freezing injuries affect post harvest handling?

Answer 26

b/c they don’t permit the most effective use of temp which is the most imp parameter for suppressing post harvest decay

Question 27

define chilling injury

Answer 27

permanent and irreversible physiological damage to chilling sensitive commodity

results from exposure of plant tissue to temp below a certain level

Question 28

what are the 2 classes of crops based on chilling sensitivity?

Answer 28

1. non-chilling sensitive commodities

2. chilling sensitive commodities

Question 29

what are symptoms of chilling injury?

Answer 29

• surface discoloration, lesions, pitting
• internal discoloration (browning)
• appearance of H2O soaked areas
• tissue breakdown and softening
• failure of fruit to ripen in normal pattern
• increase susceptibility to microbial attack
• loss of characteristic flavors, aromas, sprouting abilities

Question 30

what are ways to alleviate chilling injuries?

Answer 30

1. treatment prior to storage: treatment with calcium dip = makes produce more resistant to chilling injury
2. seed germination at lower temp
3. treatment during storage: intermittent exposure to higher temp; use control atmosphere; use low pressure storage or hypobaric storage

Question 31

define freezing/frost injury

Answer 31

temp specific injury to commodities stored at temp below freezing points

Question 32

how can you alleviate freezing injuries?

Answer 32

not much can be done

• avoid freezing temp (stay right above freezing temp)
• use of CA conditions