Abstract
Many food products are subjected to quality control analyses for detection of surface residue/contaminants, and there is a trend of requiring more and more documentation and reporting by farmers regarding their use of pesticides. Recent outbreaks of food borne illnesses have been a major contributor to this trend. With a growing need for food safety measures and “smart applications” of insecticides, it is important to develop methods for rapid and accurate assessments of surface residues on food and feed items. As a model system, we investigated detection of a miticide applied to maize leaves and its miticidal bioactivity over time, and we compared two types of reflectance data: fourier transformed infrared (FTIR) data and hyperspectral imaging (HI) data. The miticide (bifenazate) was applied at a commercial field rate to maize leaves in the field, with or without application of a surfactant, and with or without application of a simulated “rain event”. In addition, we collected FTIR and HI from untreated control leaves (total of five treatments). Maize leaf data were collected at seven time intervals from 0 to 48 hours after application. FTIR data were analyzed using conventional analysis of variance of miticide-specific vibration peaks. Two unique FTIR vibration peaks were associated with miticide application (1,700 cm−1 and 763 cm−1). The integrated intensities of these two peaks, miticide application, surfactant, rain event, time between miticide application, and rain event were used as explanatory variables in a linear multi-regression fit to spider mite mortality. The same linear multi-regression approach was applied to variogram parameters derived from HI data in five selected spectral bands (664, 683, 706, 740, and 747 nm). For each spectral band, we conducted a spatial structure analysis, and the three standard variogram parameters (“sill”, “range”, and “nugget”) were examined as possible “indicators” of miticide bioactivity. We demonstrated that both FTIR peaks and standard variogram parameters could be used to accurately predict spider mite mortality, but linear multi-regression fits based on standard variogram parameters had the highest accuracy and were successfully validated with independent data. Based on experimental manipulation of HI data, the use of spatial structure analysis in classification of HI data was discussed.
Highlights
Many food products are subjected to quality control analyses before sold to consumers, and there is a trend of requiring more and more documentation and reporting by farmers regarding their use of pesticides
In the pairwise contrasts for each time interval between miticide application and rain event, we found a consistent significant effect of miticide treatment, while effects of rain event and/or addition of surfactant appeared to have negligible and/or inconsistent effects on the performance of the miticide (Table 1)
The two analytical approaches used in this study require certain equipment capabilities but both are non-destructive procedures that require a minimum of sample preparation, and they both have the potential of providing results real-time
Summary
Many food products are subjected to quality control analyses before sold to consumers, and there is a trend of requiring more and more documentation and reporting by farmers regarding their use of pesticides. Reflectance-based quality control systems are becoming increasingly more versatile, robust and more affordable. Precision agriculture [6,7], food quality and safety [8,9,10,11], and pharmaceutical industries [12] are just some of the areas in which reflectance-based analysis is becoming increasingly important. The driving factors behind widespread implementation of reflectance-based systems are: (1) data is acquired, processed and analyzed real-time due to increasingly faster and more powerful telecommunication systems and computer processing, (2) data acquisition is non-destructive, (3) labor intensive chemical procedures and/or qualitative/subjective evaluation procedures can be automated and replaced by quantitative standards, and (4) the technology is becoming increasingly cost-effective
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