Effects of processing and storage on pesticide residues in foods.

Pesticides are chemicals frequently used in agriculture to obtain maximum yield and improve product quality. Thousands of active ingredients and formulations of different pesticides are commercially available. Besides their advantages, a major disadvantage of pesticides is their residues, even though strict maximum residue limits have been set for each pesticide and permitted agricultural commodity. Permanence of pesticide residues on agricultural products depends on several factors such as the properties of pesticide, formulation, and applied concentration. Light, temperature, plant morphology, and plant growth factors are also effective in determining permanence. Degradation effects of the processing treatments rely on the dissolution of pesticides in the surrounding atmosphere, hydrolysis, microbial degradation, oxidation, penetration, and photo-degradation. Various steps applied during food processing, such as washing with water or other aqueous solutions, peeling, chopping, pickling, heat treatments, and processes such as drying, canning, fruit juice and concentrate production, malt, beer and wine production, oil production, and storage have certain effects on the presence of pesticide residues as well. Only washing with water can remove pesticide residue up to 100%, depending on the location of residue, residence time on food, water solubility of residue, washing temperature, and agents used to increase effectiveness. Besides washing, skin removal or peeling is one of the most effective treatments for residue removal, especially on non-systemic pesticides. During cooking, residues might be evaporated or hydrolyzed. Effects of storage temperature on reduction are related to volatilization, penetration, metabolism of pesticide, moisture content, and microbial growth, if any. In refrigerated or frozen storage, residues are stable or degrade slowly. Drying may increase the residue content because of the concentration, but in sun-drying reduction may occur because of photo-degradation. Clarification and filtration may eliminate residues retained in suspended particles. The degradation product, however, may be more toxic than the initial compound in some cases.