Evaluation of some cooking ingredients decontaminating selected vegetables from pesticide residues

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INTRODUCTION
Pesticide residues in food continue to be a matter of concern to humanity.The regulatory authorities in India are focusing on monitoring of pesticide residues in agricultural commodities to ensure food safety for consumers and for better international trade activities.A recent survey of different food commodities sold in different markets of Kerala showed that out of 16,948 samples studied, 290 (1.70%) samples contained residues of various insecticides at levels above those prescribed as safe by FSSAI (AICRP PR, 2012).
In vegetable samples (141 in number) and fruit samples (56 in number) collected from different locations in Kerala during the period of July to September 2014 under a separate programme of Government of Kerala and Kerala Agricultural University, 12 vegetable samples and five fruit samples had detectable level of pesticide residues.Residues in green chilli, yard long bean, curry leaf, coriander leaf, amaranthus, guava and pomegranate were at higher levels (PAMSTEV, 2014).
This growing concern about pesticide residues in agricultural commodities has demanded immediate government level interventions for solutions.For tackling the problem interventions can be at production, marketing and consumption stages.Most of the vegetables marketed in Kerala are produced outside this state, and hence intervention at production level is almost impossible.The next possibility is intervention at marketing stage ie. to collect statutory samples, test them in an accredited testing lab and to take legal action against the food business operator, including seizing of contaminated products.This also remain elusive due to the inadequate infrastructural facilities and complicated legal procedures.Therefore intervention at consumption stage is to be explored as a practical solution for the problem, ie. to standardize and popularize decontamination procedures that can be adopted just before cooking/consumption.
Several substances have been reported as effective in decontaminating agricultural products from pesticide residues.They mostly covered earlier pesticides and did not gain popularity and large scale adoption.Recently different decontaminating substances like common salt, vinegar, turmeric etc were tried in India and promising results were also reported (Abou-Arab, A. A. K., 1999, Gardenmo.net, 2011, Varghese and Mathew, 2013and Vijayasree et al., 2012).These studies do not cover the insecticide residues detected in Kerala in recent surveys and the methodology followed in the treatments also have not been standardized.In this context, two vegetables (okra and curry leaf) seen contaminated with insecticide residues in the surveys were treated with different decontaminating substances commonly used in cooking with a view to assessing the possible levels of decontamination.

Standardization of pesticide residue estimation
Certified Reference Materials (CRM) of different pesticides having purity ranging from 95.10 to 99.99 per cent were purchased from M/s Sigma Aldrich and stored in a freezer at low temperature, with light and moisture excluded.Solvents used in the study were all glass distilled before use.The analytical method for estimation of residues of pesticides has been validated by conducting recovery studies at three different fortification levels ie.LOQ, 5 x LOQ and 10 x LOQ using control samples (samples having pesticide residues below detectable levels).

Decontamination study
To study the effect of different decontaminating materials on removal of pesticide residues, two vegetables viz., okra and curry leaf were selected and the methodology adopted for the decontamination study was as follows.
Curry leaf plants available in the Instructional Farm, College of Agriculture, Vellayani were sprayed with the above mixtures of insecticide emulsions.Curry leaves collected 1 st day and 3 rd day after spraying were used for residue estimation.
The different decontaminating treatments in this experiment were tamarind 2 % (20g of tamarind pulp extracted in one litre water), common salt 2 % (20g of common salt dissolved in one litre water), turmeric powder 1 % (10g of turmeric powder suspended in one litre water), vinegar 2 % (20 ml of vinegar diluted in one litre water), luke warm water and water (untreated control).Samples of 100 g curry leaves and 250 g okra fruits were dipped individually in the treatments for fifteen minutes followed by washing in tap water.Samples were then cut into small pieces and then homogenized and the representative samples (25 g each) in three replicates were collected, residues in the samples were assessed.

Analytical procedure
The standard QuEChERS protocol was followed to prepare samples and the same was analyzed in a Gas Chromatograph equipped with 63 Ni Electron Capture Detector (ECD), fitted with DB-5 capillary column (dimethyl polysiloxane, 30 m x 0.25 mm i.d.x 0.5 μm film thickness)

Recovery study
Multi Residue Methods (MRM) for pesticide residue analysis was adopted for recovery studies.The results demonstrated that the method followed had a satisfactory analytical performance in terms of selectivity and linearity.Good linearity within the range of 0.01-0.5 mg kg -1 for the pesticides belonging to OP and SP insecticide groups was obtained.Satisfactory recoveries and RSDs were achieved for most of the pesticides evaluated even at the lowest level of fortification.The mean recovery of all the insecticides used were in the range 70 -110 Evaluation of some cooking ingredients decontaminating selected vegetables per cent and the repeatability of the recovery results, as indicated by the RSD < 20 % confirmed that the method is sufficiently reliable for pesticide residue estimation in curry leaf and okra.
Data relating to the removal of insecticide residues and results of statistical analysis of the data are presented in Table 1 to 8.

Removal of malathion residues:
The performance of different treatments on the residues of malathion on okra fruits and curry leafs is shown in table 1. Turmeric (residue 70.56% < in control) was the best and it was closely followed by tamarind (68.92%) and common salt (62.37%).In samples collected three days after spraying also efficacy of the treatments were in the same sequence, (the percentage reduction ranging from 63.89 to 57.10%).Vinegar, lukewarm water and water were comparatively ineffective, the percentage removal being in the range of 25.88% to 41.77% only.The removal of malathion residues in curry leaf samples harvested at both the intervals was very high in all treatments, the percentage removal being in the range of 69.64 to 95.78%.The residue of malathion in okra (0.31 mg kg -1 ) harvested on 3 rd day after treatment was only 38.75% of the residue in 1 st day sample (0.80 mg kg -1 ) and corresponding percentage in curry leaf was 32.72%.

Removal of chlorpyriphos residues (Table 2):
On okra samples sprayed with chlorpyriphos and collected one day after spraying tamarind (62.52% removal of residue) was the best closely followed by common salt (54.38%) and vinegar (50.67%).Same ranking of the treatments with the percentages of 60.22%, 54.38% and 47.30% on samples collected three days after spraying was observed.In the remaining treatments, the removal of residues ranged from 9.48 to 32.14% only.
In curry leaf harvested one day after spraying turmeric (82.93% residue removal) was the best treatment and it was closely followed by common salt (69.36%) and tamarind (66.05%).In samples collected on the 3 rd day after spraying tamarind (62.01%) was the best and it was followed by turmeric (47.38%).Common salt (38.86%) came superior to vinegar and water (34.12 and 34.22% respectively).The residue in okra fruits collected on 3 rd day after spraying (0.55 ppm) was only 34.8% of the residue level in samples collected one day after spraying (1.45 ppm).

Removal of quinalphos residues (Table 3):
The results of different treatments on quinalphos residues in okra fruits showed that tamarind, common salt, vinegar and turmeric which removed 65.30%, 63.14%, 54.79% and 52.88% residue from samples collected one day after spraying can be ranked as effective treatments.In the samples collected 3 days after spraying turmeric removed only 36.40% residue while the remaining treatments gave 51.48 to 61.31 per cent residue.All the treatments gave effective decontamination of curry leaf having quinalphos residues the percentages of removal in the 1 st day samples being 54.23 to 85.16% and in the 3 rd day samples the removal ranged from 50.90 to 69.30% except water which showed the removal of 40.55 per cent only.Evaluation of some cooking ingredients decontaminating selected vegetables The residue level on 3 rd day after spraying sample was 47.54% of the level in 1 st day sample for okra and corresponding figure for curry leaf was 36.7 per cent only.

Removal of profenophos residues (Table 4):
From samplesof okra collected one day after spraying with profenophos tamarind (73.25% removal), common salt (68.24%) and turmeric (50.60%) could be ranked as good decontaminants.But in samples collected three days after spraying turmeric gave only 41.68% removal while the percentages in the remaining treatments ranged from 52.77 to 65.65 per cent.Lukewarm water and water were relatively less effective.
In the case of curry leaf, samples collected one day after spraying all treatments removed the residues (51.06 to 88.52 per cent) effectively.Samples collected 3 days after spraying also showed good performance (50.95 to 67.52 per cent removal of residues) in all the treatments except common salt and water in which the percentage removal was 48.88 and 44.55% respectively.
Percentage of residues of profenophos in 3 rd day samples compared to the 1 st day samples was 34.89% in bhindi and 52.84% in curry leaf.

Removal of ethion residues (Table 5):
Tamarind; common salt and vinegar gave 64.03%, 59.73% and 56.06% removal of ethion residue from okra collected one day after spraying while in samples collected on the 3 rd day   Evaluation of some cooking ingredients decontaminating selected vegetables Values in parentheses are concentration of insecticides in mg kg -1 percentage removal were 59.73%, 59.62% and 52.52% respectively in common salt, tamarind and vinegar.In turmeric the removal was 41.39% and 42.38% removal only on 1 st and 3 rd day samples.In the case of curry leaf all treatments removed the residues effectively (57.25% to 86.99% removed from 1 st day samples and 57.15% to 67.0% removed from 3 rd day samples).
Ethion residue in okra harvested on 3 day waiting period was 58% of the residue in samples collected on the 1 st day of spraying.The corresponding residue content in curry leaf on 3 rd day was 65% of the residue in 1 st day samples.

Removal of cypermethrin residues (Table 6):
Removal of cypermethrin was relatively low 54.46% to 57.23% in 1 st day samples of okra fruits in treatments with tamarind, common salt and vinegar respectively while the corresponding percentages in 3 rd day samples were 52.18%, 45.61% and 50.25% respectively.In the case of curry leaf the removal percentage in treatments except water gave 58.84% to 89.37% removal in 1 st day sample and tamarind, vinegar and turmeric gave 53.7% to 59.51% removal in 3 rd day samples.In common salt and water treatments the removal of cypermethrin ranged from 36.26% to 49.17% only.The waiting period of 3 days followed in harvest of okra brought down the residue level to 63.6% of the 1 st day sample and corresponding reduction in curry leaf was 85.7%.

Removal of fenvalerate residues (Table 7):
Common salt was the best for the removal of fenvalerate residue (73.21%) and it was followed by vinegar (63.67%) and tamarind (56.15%).The corresponding removal in 3 rd day sample also was high (49.13% to 73.21%).In curry leaf all the treatments gave high removal in 1 st day sample (except water), percentages ranging from 64.95% to 90.25%.In the 3 rd day samples satisfactory removal was in tamarind (56.16%) and vinegar (52.69%) only.Residue in 3 rd day sample in okra was 61.7% of the 1 st day sample and in curry leaf corresponding residue was 66%.

Removal of methyl parathion residues (Table 8):
Common salt and tamarind alone were found good for removing methyl parathion residue from 1 st day sample of okra fruits while in other treatments residue removal ranged from 11.69% to 40.40% only.In the third day sample the removal in common salt alone was good (54.22%).In the remaining treatments the removal ranged from 11.70% to 37.46%.Regarding curry leaf, all treatments including water gave 50.68% to 74.43% removal in 1 st day samples.In 3 rd day sample the removal was below 50% in all treatments.The residue levels in 3 rd day samples of okra was 43.37% of the 1 st day sample and in curry leaf corresponding percentage was 39.84%.
Evaluation of some cooking ingredients decontaminating selected vegetables Values in parentheses are concentration of insecticides in mg kg -1

DISCUSSION
The data obtained from the experiments clearly show the effectiveness of the treatments in removing the insecticide residues in okra and curry leaf.From okra removal of malathion residue was comparatively better with tamarind, turmeric and common salt, while vinegar, lukewarm water and water were comparatively inferior.With chlorpyriphos residue, turmeric and water treatments were inferior to the rest of the treatments.Methyl parathion residue was best removed by tamarind and common salt while the remaining treatments were not effective.All the treatments except turmeric and water removed residues of qunalphos, profenophos, ethion, cypermethrine and fenvalerate.In the case of curry leaf the residue levels of insecticides were significantly higher than those of okra fruits.This might be due to lower bulk weight of curry leaf and consequent larger surface area available for holding the residues of insecticide for the same weight of the two commodities taken for the studies.The residues from curry leaf was being effectively removed by all treatments in the experiment including lukewarm water and water.The result bring to light the possibility of reducing the hazards of insecticide residues in vegetables by adopting simple and safe methods of decontamination in post harvest processing before cooking.Because of the variations in the performance with reference to the chemistry of insecticide, crop waiting period etc., standardization of separate techniques for different pesticides and for different commodities (identified through a farm-gate sample survey) may be necessary for tackling the problem.
The rapid fall in residues of different insecticides in samples collected 3 days after spraying when compared to the levels of residues in samples collected 1 day after spraying, highlights Values in parentheses are concentration of insecticides in mg kg -1 the importance of adopting recommended waiting periods in harvesting the crops after spray operations.This precaution clubbed with the adoption of proper decontamination practices may provide an effective method to solve the hazards of insecticide residues in agricultural commodities.Though the decontaminating effect of a lot of substances have been studied in the recent past the pesticide studied in this experiment and the crops chosen have not been covered in early studies.

Table 2 : Extent of removal of chlorpyriphos residues from okra fruits and curry leaves collected 1st day and 3rd day after spraying subjected to dipping in different treatment solutions for 15 min.
Values in parentheses are concentration of insecticides in mg kg -1

Table 3 : Extent of removal of quinalphos residues from okra fruits and curry leaves collected 1st day and 3rd day after spraying subjected to dipping in different treatment solutions for 15 min.
Pallavi Nair K. et.al.Values in parentheses are concentration of insecticides in mg kg -1

Table 4 : Extent of removal of profenophos residues from okra fruits and curry leaves collected 1st day and 3rd day after spraying subjected to dipping in different treatment solutions for 15 min
Values in parentheses are concentration of insecticides in mg kg -1

Table 8 : Extent of removal of methyl parathion residues from okra fruits and curry leaves collected 1st day and 3rd day after spraying subjected to dipping in different treatment solutions for 15 min.
Pallavi Nair K. et.al.