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What is pesticide residues ?

When a crop is treated with a pesticide, a very small

amount of the pesticide, or its metabolites or

degradation products, can remain in the crop until

after it is harvested.

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why do they turn up in our food?

to control the growth of weeds

– used by farmers

or prevent crop damage by insects, rodents and molds.

– used on food crops after harvest to prolong their storage life.

– used on animal farms to control insect pests

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HARMFUL EFFECTS OF PESTICIDE

RESIDUES To the Environment

water systems

Pollute the air.

insect species

Harming beneficial soil microorganisms

worms

Weakening plant root systems and immune systems.

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Do Processed Foods Have Less

Pesticides Than Fresh Foods?

Generally, yes.

Reason:

Growers : don’t need to ensure that their foods are cosmetically perfect

Processors : consumer demand for foods with minimal pesticide residues

Processing : reduce pesticide residues

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EFFECT OF PROCESSING ON

PESTICIDE RESIDUES

Reduce

pesticide

residues

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METHODS USE TO REMOVE PESTICIDE

RESIDUES.

Washing

Peeling

Hulling

Trimming

Cooking + Stir-frying

Canning

Freezing

Drying

Infusion

Parboiling

Storage

Chemical solution

Neutral solutions

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Washing

Surface residues simple washing operations

systemic residues present in tissues will be little affected

the proportion of residue that can be removed by washing declines with time

Hot washing and blanching cold washing

commercial washing Domestic rinsing

EX:

Washing rice grains with water removed approximately 60% of the chlorpyrifos residues

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Washing+ cooking: apple to sauce 98%

Washing and drying

Washing and peeling

Washing, peeling and juicing

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the effectiveness of washing in removing residues depends upon

four factors

the location of the residue

the age of the residue

the water solubility

the temperature

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Peeling

residues are confined to the outer surfaces removal in peeling, hulling or trimming operations

Peeling fresh fruits such achieves virtually complete removal of residues from the fruit.

avocado

bananas

citrus

kiwifruit

mango

Pineapple

Peeling methods:

Chemical peeling (mostly lye peeling)

mechanical peeling (mainly abrasion peeling),

steam peeling

freeze peeling

Residues of systemic pesticides can enter the flesh of crop!

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Peeling and cooking

Peeling + blanching affect organophosphorous organochlorine

Peeling + frying

Reason: stability of organochlorines to heat treatment

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Hulling

The hulls of cereal grains generally contain the

majority of pesticide residues from any field

treatments.

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Trimming

removal of either inedible parts or parts with defects, or for cutting the raw material to a size that is suitable for further processing.

Ex: Pirimiphos methyl residues in rice were reduced 70 percent and 90 percent by husking and polishing,

respectively

Husking of corn (maize) removed 99 percent of the residues from field treatments with tetrachlorvinphos

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Cooking and canning

Pesticide residues depend on:

time

temperature

degree of moisture loss

whether the system is open or closed

the heat degradation and volatilization of residues

EX:

Only 13 percent of parathion residues on tomatoes were found in canned juice or ketchup.

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Stir-frying

Pesticide residues can be effectively decreased by stir-frying

These can be reduced upto 49 and 53 percent by peeling and frying

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freezing

Freezing : slows food decay

slow most chemical reactions

EX

Freezing of tomatoes decreased the pesticide residues from 5 to 26 percent after

six days and 10 to 31 percent after 12 days of pesticide contamination

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Drying

Drying has been found to reduce the pesticide residues considerably.

EX: Sunlight drying lead to around 50% decline in bitertanol residues from 0.50 ppm present at harvest

Drying of grapes lead to 64.2–71.9% losses of methamidophos possibly due to evaporation of the

pesticide during the process

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infusion

Tea: 64% processing…….. 36%remain........... 16%of the pesticide is transferred to cup-infusion

The transfer of quinalphos to the infusion could be due to its solubility in water

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Parboiling

means precooking of rice within the husk.

Parboiling : hydrating padd + heating to cook the rice + drying of the rice

high temperature (100 C)…. inactivation or degradation of pesticides

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Storage

long term (3–36 months)

Grains stored at ambient temperatures

in bulk silos

insecticides may be applied post-harvest to reduce losses from storage pests.

pesticides can migrate through to the bran and germ

Storage + milling Reduced pesticide residues

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EFFECT OF CHEMICAL SOLUTIONS

ON PESTICIDE RESIDUES

Acidic solutions

citric acid

acidic solution ascorbic acid

acetic acid

hydrogen peroxide

at a concentration of 5 and 10 percent for 10 minutes reduction of pesticide residues.

Acidic solutions neutral and alkaline solutions

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Alkaline solution

Solutions of NaOH, acetic acid, potassium dichromate

Dipping of fruits in NaOH solution removed 50 to 60 percent surface residues of pyrethroids

compared to 40 to 50 percent removal by hydrolytic degradation with NaOH and a

detergent solution removed 50 to 60 percent residues omate and soap are used as

decontaminating agents

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Ozonation

Ozone because of its powerful oxidizing property is effectively applied in drinking

water and waste water treatment

Tap water treatment + ozonated water treatments significantly reduced the

pesticide residues on vegetables, as compared to no-wash treatment

pesticide residues

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Neutral solutions

Sodium chloride (NaCl) solution

28 to 93% organochlorines

100 % organophoshates

NaCl concentration pesticide residues

5 and 10 % NaCl

solution for 15 minutes

rubbed by hand

water was decanted

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What Can You Do?

Grow some of your food using organic methods.

Buy organic food.

Wash and scrub all fresh fruits, vegetables

Eat less or no meat.

Trim the fat from meat.

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References:

1)Ahmed, A., Randhawa, M. A., Yusuf, M. J., & Khalid, N. (2011). EFFECT OF PROCESSING ON PESTICIDE RESIDUES IN FOOD CROPS-A REVIEW.Journal of Agricultural Research, 49(3).

2) Holland, P. T., Hamilton, D., Ohlin, B., & Skidmore, M. W. (1994). Effects of storage and processing on pesticide residues in plant products. Pure and Applied Chemistry, 66(2), 335-356.

3) Krieger, R. I., Brutsche-Keiper, P., Crosby, H. R., & Krieger, A. D. (2003). Reduction of pesticide residues of fruit using water only or plus Fit™ Fruit and Vegetable Wash. Bulletin of environmental contamination and toxicology, 70(2), 0213-0218.

4) Hyder, K. (2006). GMP and HACCP for tree nuts and dried fruit processing plants in Afghanistan. Submitted to: USAID Prime Contractor: Chemonics International Inc., Rebuilding Agricultural Markets Program (RAMP). p, 1-17.

5) Pandey, P., Raizada, R. B., & Srivastava, L. P. (2010). Level of organochlorine pesticide residues in dry fruit nuts. Journal of Environmental Biology, 31(5).

6) Kaushik, G., Satya, S., & Naik, S. N. (2009). Food processing a tool to pesticide residue dissipation–A review. Food Research International, 42(1), 26-40.

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