Application Of Cold Plasma Technique For The Degradation Of Fungicides And Quality Evaluation Of Tomato(Lycopersicon Esculentum Mill) Fruit

The application of agrochemicals in modern agricultural practices is significant to increase the crop production and to protect the crops against various pest attacks and fungal diseases.However,the excessive use of these agrochemicals and their residual presence on agricultural products have become a major environmental and human health concern globally.Therefore,degrading of the agrochemical residues in agricultural products is necessary to ensure the consumers health.In recent years,cold plasma（CP）technology has received a widespread attention as a novel,eco-friendly,efficient and sustainable food processing technology.CP has proven to be an effective method for microbial decontamination,surface modification and degradation of the residues of agrochemical and other industrial processes.The degradation of the agrochemical residues is based on the excited reactive species formed during plasma generation such as reactive oxygen and nitrogen species（RONS）and other hydroxyl（^●OH）radicals.These reactive species undergo several chain reaction and form ozone（O₃）and hydrogen peroxide（H₂O₂）,which have been identified as key species for degrading agrochemical residues in agricultural products.Fruits and vegetables specially tomato（Lycopersicon esculentum Mill.）fruits are vital part of a healthy diet because of the existence of important amount of nutrients and minerals.Therefore,understanding the interaction between plasma and agrochemicals become necessary in fruit and vegetables.（1）The main focus of the 1^st study was to investigate the impact of dielectric barrier discharge（DBD）on the degradation of anilazine fungicide residues in tomato juice at 0,1,2,3,4 and 5 min treatment time respectively.The findings revealed that the concentration of the residues was significantly decreased by increasing the treatment time and the optimal residues degradation was 65%at 5 min.The quality attributes of the tomato juice after 5 min treatment showed a decrease in p H from 4.28 to 4.18 and an increase in total soluble solids（TSS）from 5.70 to 6.70.Moreover,the total phenolic content,antioxidant activity,total flavonoid content and color value of the treated samples were slightly changed compared with untreated samples.The findings confirm that DBD plasma is an effective and time saving method for degrading fungicide residues in fruit juice.（2）In the 2^nd study,the main aim of the investigation was to evaluate the effect of plasma activated liquid（PAL）including plasma activated water（PAW）and plasma activated buffer solution（PABS）to reduce chlorothalonil（CTL）and thiram（THM）fungicide from tomato fruits.PAL was obtained using distilled water and buffer solution,which was then activated with radio frequency（RF）plasma jet with atmospheric air and argon（Ar/O₂）as feed gases.The reactive species observed in the plasma jet includes reactive oxygen and nitrogen（RONS）such as O,O_2,N,N₂and^●OH,which enhanced the acidification,increased oxidation potential（ORP）,electrical conductivity（EC）and NO₂ of PAL,and played a vital role in the degradation of fungicide residues.The outcome of the study concluded that the PAL acquired by using atmospheric air as the feed gas,CTL concentration was reduced by85.3%and 74.2%and THM residues reduced by 79.47%and 72.21%after treatments with PAW₁₀ and PABS₁₀,respectively.In addition,increasing the activation time caused a significant reduction in fungicide residues.Furthermore,CTL and THM residues were also reduced while increasing the activation time of PAL using Ar/O₂ as the feed gas,the concentrations of CTL residues were reduced by 75.07%and 69.89%for PAW₁₀and PABS₁₀,respectively,and THM residues reduced by 65.89%and 61.91%for PAW₁₀and PABS₁₀,respectively.Moreover,washing with the activated PAL had no negative impact on the quality of fruits.（3）In the 3^rd study,the key purpose of the investigation was to assess the effect of the combined treatments（PAL-U）of PAL including PAW and PABS with ultrasound（U）for degrading chlorothalonil fungicide residues in tomato fruits.The focus of the study was to compare the effect of ultrasound,individual PAL and PAL-U treatments for the residual degradation of fungicide.The PAL was activated by atmospheric plasma air jet（APAJ）using treatment time of 1,3,5,and 10 min.For the individual treatment,tomato fruits were immersed in PAL for 15 min and for the combined treatment,the fruits were immersed in PAL then subjected to ultrasound treatment for 15 min.The results showed that the synergistic effect of PAL-U effectively reduced the residues compared with individual PAL or ultrasound treatment alone.The fungicide residues were reduced significantly（p≤0.05）by 89.28%and 80.23%after treatment with PAW₁₀-U and PABS₁₀-U,respectively,compared with the reductions of 48.76,85.30 and 74.20%for individual treatments of ultrasound,PAW₁₀ and PABS₁₀,respectively.The degradation pathway of fungicide was also observed.On the other hand,the assessment of the quality characteristics showed that immersing tomato in PAL and PAL-U had no significant effects on the quality.（4）In the last part,the focus of the study was to assess the impact of PAL,PA-U and ultrasound treatment alone（U）for the degradation of chlorothalonil fungicide residues from tomato fruits during 12 days of storage period.For this investigation,the PAL including PAW and PABS obtained by distilled water and buffer solutions were activated with RF plasma jet using treatment time of 5 and 10 min.The high-performance liquid chromatography（HPLC）findings confirmed that PAW₁₀ and PABS₁₀ treatments significantly（p≤0.05）reduced the fungicide residues by 74.11%and 85.43%respectively,compared with89.29%and 80.30%for PAW₁₀-U and PABS₁₀-U,respectively.After 12 days of storage,the residues were reduced by 91.52,89.14,97.26 and 93.14%for PABS,PAW,PABS-U₁₀ and PAW-U₁₀,respectively.In addition,the quality attributes of the tomato fruits were also evaluated during the storage period and the findings revealed that the treatments had no significant effect on the quality compared with control samples.The present study is the first study,which reports on the application of DBD plasma to degrade anilazine fungicide in tomato juice and PAL including PAW and PABS for CTL and THM in tomato fruits.For the first time,the synergistic application of PAL combined with ultrasound treatment（PAL-U）as a promising approach for fungicide degradation was provided.In addition,the residual degradation in agricultural product after treatment with PAL was below the maximum residual limits,thus showing potency of the approach.Moreover,we also provided the degradation pathway of the fungicides after treatment showing the structure of intermediates.The study concluded that PAL and PAL-U treatments are effective and less time-consuming methods for removing pesticide residues without compromising the quality of products,thereby paving the way for up-scale treatments at industrial levels.Lastly,it is suggested that PAL and PAL-U could be a safe and effective degradation method for agrochemical residues in agricultural products with the potential for large scale applications in food processing industries.