Fate of Pesticide Residues on Raw Agricultural Crops after Postharvest Storage and Food Processing to Edible Portions

Although the established MRLs for processed and ready to eat food are limited to present and concern mainly the processed commodities where the residue could be found concentrated, regulatory attention has been focused on this issue the last decade and a current confrontation practice is the perspective of the processing factors (P f 's) establishment to be used with already specified MRL's of pesticides in RAC's (Codex Alimentarius Commission, 2007).P f is defined as the ratio of the residue level in processed commodity to the residue level in RAC or in the commodity to be processed.The aim of this chapter is to review the main types of post-harvest and processing practices that typically RAC's are being subjected prior their consumption and point out the effects that these processes cause on the fate of pesticide residues that may persist on and in RAC's after harvest.The main chemical, biochemical and physical phenomena in which pesticide residues take part in during these processes and the parameters that may influence these phenomena would further be discussed, through the latest published data on this topic. Mechanisms and factors affecting the fate of pesticide residues during storage and food processingThe most important mechanisms that may lead in of a possible residue alteration during storage and other household and industrial food preparation processes of RAC are summarized as follows: 1. Dissolution.The dissolution of a pesticide residue may take place during the washing of RAC, grape vinification, tea preparation and boiling and theoretically is related with the water solubility of the pesticide residue.Other factors such as the type of formulation applied, temperature, initial concentration of the pesticide residue on RAC, pesticide Kow, ionic strength and pH of the aqueous media and the nature of RAC may further affect the pesticide dissolution mechanism in a certain food preparation process.2. Heat degradation.Frequently a number of pesticides undergo degradation, polymerization and other reactions by heating.The reactions proceed at a greater rate in the liquid phase rather than in solid state.Thermal unstable compounds (e.g.atrazine, alachlor, aldicarb, captan, daminozide, dimethoate, dodine, lenacil, phorate, and others) may significant reduced by the formation of their degraded products during cooking and oven-drying of the processed RAC.Heat may also affect almost all pesticide eliminating mechanisms occur during RAC processing (dissolution, hydrolysis, penetration, volatilization, microbial degradation, metabolism and enzymatic transformation).3. Hydrolysis.Hydrolysis is one of the basic processes of most pesticides elimination through the different storage and food preparation processes of RAC.Most pesticide residues may by hydrolyzed during typical RAC processing depending on the water added or the moisture on RAC, pH, temperature and pesticide's concentration.Pesticide compounds with functionalities such as carbamate, amide, urea, thiocarbonyl and imino group are more readily hydrolyzed in the presence of trace amounts of acid and/or base during the different processes of food preparation.4. Metabolism (enzymatic transformation); Microbial degradation.The enzymatic transformation of pesticides is mainly the result of biotic processes mediated by plants and microorganisms.Penetrated pesticides may be further metabolized during the storage of fresh fruits and vegetables.Microbial degradation is the breakdown of pesticides by microorganisms.It occurs when fungi, bacteria, and other microorganisms consume pesticides along with other substances.Microbial degradation is usually www.intechopen.com