Probably, these two modes of drying would have resulted in some changes in the active ingredients in pepper. You can extract these two grades of pepper and subject the extracts to chromatography analysis with MS detector. The difference in composition between the two can be thus studied.
Dear Sir. Regarding your question about the best analytical method by which sun and heat (machine) dried pepper can be differentiated very clearly. You can use the procedures of Association of Official Analytical Chemists (AOAC, 1995) . For more details the following below links may help you in your analysis: