Management of pesticide residues in grapes

Abstract

The study on ‘Management of pesticide residues in grapes’ was carried out at Pesticide Residue Research and Analytical Laboratory (PRRAL), Department of Entomology, College of Agriculture, Vellayani and farmers field, Theni district of Tamil Nadu during the period 2022-24. The main objectives of the study were to monitor the pesticide residues in grapes, to evaluate the decontamination methods and to assess the effect of processing on the removal of pesticide residues in grapes. Monitoring studies to find out pesticide residues in farm gate samples were conducted at Theni district of Tamil Nadu and market samples were collected from various districts of Kerala. Monitoring studies revealed that 100 per cent of farm gate and market samples of grapes were detected with pesticide residues. Out of 27 pesticides detected, 17 were insecticides and 10 were fungicides. The detected insecticides include eight organophosphates, four neonicotinoids, two synthetic pyrethroids, one each from diamide, tetramic acid derivative and IGR. Among the processed products, 37.50 per cent of ball grapes and raisins samples were found to be contaminated. No residues were detected from squash and wine samples. Buprofezin, malathion, carbendazim, metalaxyl, tebuconazole and pyraclostrobin, difenoconazole and penconazole were the pesticides detected below FSSAI MRL. A laboratory experiment was conducted to evaluate the effectiveness of various decontamination methods in removing pesticide residues from grapes. Organically grown grape vines at fruiting stage were selected from Cumbum, Theni district of Tamil Nadu. The selected vines with fruits were uniformly applied with a mixture of 11 pesticides (at double the recommended dose) selected based on data obtained from monitoring studies. Grapes were harvested 48 hours after spraying, subjected to decontamination treatments and analysed for residues. The result showed that soaking grapes in 2% sodium carbonate solution for 10 min followed by washing two times with water was effective in removal of pesticide residues (43.15-84.71 %). The second superior treatment was soaking grapes in lukewarm water (45.26-79.33 %). In radiation treatment, treated grapes were exposed to different levels of gamma radiation 0.50, 1.00 and 1.50 kGy and two different UV radiations - UV A (365 nm) and UV B (312 nm) at 5 and 10 min each. It was observed that gamma radiation 1 kGy was 98 effective in removing pesticide residues by 46.67-83.25 per cent followed by gamma radiation 0.5 kGy 19.28-66.95 per cent. Treated grape samples were processed into squash, wine, ball grapes and raisins following the standard protocol and the extent of removal of pesticide residues due to processing was calculated. The results showed that processing of grapes into wine had maximum removal of pesticide residues 56.55-100 per cent followed by ball grapes (44.63-91.99 %). Sensory acceptability studies were conducted for sensory parameters like appearance, colour, texture, taste, aroma and overall acceptability of the decontaminated and processed products of grapes. It was carried out by a panel of 30 judges of different age group and they evaluated using hedonic scale ratings using Kendall’s W test. Similar ratings were assigned to all the parameters by the evaluators for both decontaminated and processed products of grapes. To conclude, monitoring studies of grapes revealed that 100 per cent of farm gate and market samples, as well as 37.50 per cent of processed products, contained pesticide residues. Decontamination studies showed that soaking grapes in 2% sodium carbonate solution followed by soaking in lukewarm water for 10 min, resulted in the highest removal of pesticide residues. Among radiation treatments, gamma radiation at 1 kGy was found to be an effective method for eliminating pesticide residues from grapes. Among processing methods, wine making showed the maximum removal of pesticide residues, followed by ball grapes.