Analysis of herbs and spices
Analysis of herbs and spices is a critical process in ensuring their quality, safety, and efficacy. There are several methods used for analyzing herbs and spices, including sensory evaluation, chemical analysis, and microbiological analysis. In addition to these methods, there are also various regulations and standards that govern the analysis and quality of herbs and spices.
Spices are any dried part of a plant other than the leaves used to season and flavour a recipe without being the main ingredient; herbs are the leaves of plants used in cooking, either fresh or dried. Most spices derive their flavour from volatile oils and, in some cases, from a combination of oils and resinoids known as oleoresins. The characteristic flavour of a spice comes from a combination of different chemical constituents — alcohols, phenols, aldehydes, esters, terpenes and alkaloids — present in varying proportions.
The quality of spices and herbs is assessed through both intrinsic (chemical) and extrinsic (physical) characteristics. Beyond flavour, certain quality standards are mandated: pesticide residue, aflatoxin, heavy metals, solvent residues, sulfur dioxide and microbiological quality. The regulatory bodies governing this space include ASTA (American Spice Trade Association), FDA, AGMARK and BIS (Bureau of Indian Standards).
A working analytical programme for a spice processing plant covers several groups of tests. General analytical methods include sieve analysis, bulk index/bulk density (manual and machine method), moisture by distillation method, and total ash. Extraction techniques to determine essential oil content include the modified Clevenger method, the Lee and Ogg method, and estimation of steam volatile oil. Physical properties measured are specific gravity, optical rotation, refractive index, solubility in alcohol and evaporation residue. Oleoresin is estimated by the ceramic fibre filter method, by analysis of constituents specific to each spice, and by high-performance liquid chromatography (HPLC) — total extracts or oleoresins reflect the flavour profile more closely than volatile oil alone. Antioxidant potential is estimated by the DPPH radical scavenging assay, and fibre by determining the non-volatile ether content.
For export, physicochemical qualities remain the most important factor. These properties differ depending on the variety and on agroclimatic conditions during cultivation, harvest and post-harvest operations — which is why a plant's testing regime has to be matched to the material it actually receives, not to a generic specification.