Lecture 15: PH treatments, Insect Control, Chilling and Freezing Injuries Flashcards
what is one of the major causes of PH losses of produce?
insect infestation
describe insect infestation
- 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
how is the spread of insects prevented?
- 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
what does CFIA stand for?
canadian food inspection agency
how does CFIA protect plants and animals from pests/diseases?
has controls, restrictions and prohibitions on entry of plants, animals and products
how can you import meats and F/V?
- must have a certificate or permit
what is the goal of regulations?
to prevent entry and establishment of exotic or non-indigenous orgaisms that pose a risk to plant life or health
what does APHIS stand for?
animal plant health inspection service
what is APHIS responsible for?
for regulating import/export and movement within the US of commodities that are subject to quarantine restrictions
similar to AAFC/CFIA
what is AAFC?
agriculture and agri-food canada
what is the goal of phytosantiary treatments?
- to achieve probit-9 control
- 99.9968% mortality of target insect/pests
- 3 survivors per 100000 treated
- around 5 log reduction
describe quarantine treatments
physical or chemical treatment given to a commodity to ensure destruction of insects of all stages of their growth (eggs, alrvae, pupae and adults)
what are 4 quarantine treatments for insects used in USA and canada?
- fumigation
- cold treatment
- heat treatment
- irradiation
describe fumigation
- early and most popular method of insect control
- produce is subjected to gas fumigants in fumigant chambers under controlled temp, time and conc
what does conc and treatment time of fumigant depend on?
- insect species, degree of contamination
- produce compatibility and quantity of produce
what is fumigation similar to? how are they different?
- similar to ethylene ripening procedure
- diff: fumigation has slightly modified procedure w/ diff gases
what are common fumigants?
ethylene dibromide (EDB)
methyl bromide (MB)
phosphene
ethylene oxide
what is EDB?
ethyleme dibromide
- common fumigant
- used to be popular, but is now banned for domestic use due to effect on ozone layer
describe cold treatment
what produce can this be used for?
- 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)
why were heat treatments less often used?
why are they more popular now?
- 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
vapor heat is slow b/c of presence of what?
air
why is hot water dip more effective than vapor heat?
- vapor heat is slower due to air presence
- water has better heat transfer
- temp control is easy
- distribtion is more uniform
hot water dip is effect against what?
insects and molds
what is the primary disadvantage of hot water dip?
heat sensitivity of many fruits to temp required for effectiveness
what are some treatment variations?
high temp air fumigation + refrigeration
cold treatment + fumigation
waxing
edible coating
how do chilling and freezing injuries affect post harvest handling?
b/c they don’t permit the most effective use of temp which is the most imp parameter for suppressing post harvest decay
define chilling injury
permanent and irreversible physiological damage to chilling sensitive commodity
results from exposure of plant tissue to temp below a certain level
what are the 2 classes of crops based on chilling sensitivity?
- non-chilling sensitive commodities
2. chilling sensitive commodities
what are symptoms of chilling injury?
- 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
what are ways to alleviate chilling injuries?
- treatment prior to storage: treatment with calcium dip = makes produce more resistant to chilling injury
- seed germination at lower temp
- treatment during storage: intermittent exposure to higher temp; use control atmosphere; use low pressure storage or hypobaric storage
define freezing/frost injury
temp specific injury to commodities stored at temp below freezing points
how can you alleviate freezing injuries?
not much can be done
- avoid freezing temp (stay right above freezing temp)
- use of CA conditions
