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DNA barcoding debars adulterants in traded spices
Monday, 06 March, 2017, 08 : 00 AM [IST]
Spices being low volume high value commodities are reported to be adulterated with plant- based as well as synthetic adulterants. Processed foods including spices such as spice powders often result in the loss of any morphological diagnostic features of the species, increasing the possibility of fraudulent substitutions or adulteration. The conventional analytical tools are inefficient in this regard. Regulatory agencies, food processors and consumers are all interested in detecting or tracing out adulterants or authenticating raw materials of food products in order to satisfy food quality and safety requirements (Lees, 2003; Che Man et al., 2005).
With globalisation of trade, the role of standards and conformity assessment are of paramount importance especially in spices and its value-added products because the non-tariff agreements such as Sanitary and Phytosanitary (SPS) and Preshipment Inspection (PSI) agreements insist that the product(s) is safe, free from adulterants and has the desired quality (Dhanya and Sasikumar, 2010). Adulterants of any nature in exported commodities also adversely affect the legendary fame of Indian spices and thereby hamper the nation’s prestige. Though acceptable levels of many of the synthetic adulterants are available, there is paucity of faster and efficient methods to trace out the plant-based adulterants in spices, especially in value-added items like spice powders. The adulterants in spices assume the proportion of health hazards for end-consumers.
Though there are few analytical tools available to detect plant-based adulterants in the traded spice, they have either low resolution power or are not faster or high throughput (Dhanya and Sasikumar, 2010). The CBOL Plant Working Group (www.barcoding.si.edu/plant_working_group.html) stressed the usefulness of DNA barcoding in plant species identification, especially for critical groups (Hollingsworth et al., 2009). DNA barcoding uses short sequences of DNA to discriminate species since genetic variation among the species exceeds than that within species (Herbert et al., 2003).
DNA barcoding is put into use to detect the plant-based adulterants in traded spices such as black pepper powder, cinnamon and turmeric at Indian Institute of Spices Research. Though many vegetative adulterants such as papaya seed, wild Piper species etc. are reported as adulterants in traded black pepper, DNA barcoding method could detect chilli as an adulterant in traded black pepper for the first time. The barcoding loci psbA-trnH and rbcL proved to be very useful in this regard (Parvathy et al. 2014). HPLC analysis supplemented the finding. This work attracted international attention (Annex-1). Probably unscrupulous elements may be finding it lucrative to recycle the exhausted black pepper (the black pepper left after the extraction of the pungent principles) as value-added black pepper (powder), fortified with other pungent substances like chilli.
Adulteration of traded cinnamon (True cinnamon or Indian cinnamon-Cinnamomum verum) with other Cinnamomum species bearing morphological resemblance to the target commodity by default or design has become a problem of concern. Of late, C. verum barks are adulterated with a rougher, thicker, cheaper and less aromatic bark of the morphologically similar C. cassia (syn. C. aromaticum) having a bitter and burning flavour. C. cassia is reported to contain 1% coumarin, a naturally occurring flavouring substance banned by the US Food and Drug Agency known to cause kidney and liver damage in rodents (Lungarini et al., 2008). Some isolated incidents of hepatotoxicity to humans by coumarin intake were also reported by World Health Organization (WHO, 1995). The barcoding locus rbcL could detect the presence of C. cassia in two of the market samples out of the five studied thereby confirming the presence of C. cassia adulteration in commercial samples of true cinnamon (Swetha etal. 2014). This work too attracted global attention (Annex-2).
Turmeric (Curcuma longa L.) is increasingly become important as a medicinal herb besides its classical label as a spice, dye and cosmetic plant. However, traded turmeric powder is reported to be adulterated or substituted with Yellow shotty or ‘Manja kuva’(Curcuma zedoaria),cassava starch and so on. The easy availability coupled with low price of C. zedoaria may induce turmeric powder manufacturers in deliberate mixing of C. zedoaria with C.longa. C. zedoaria is reported to be toxic (Lakshmi et al., 2011) and mixing it in turmeric powders may cause health hazards or reduce the perceived medicinal value of turmeric, ultimately eroding the consumer confidence. Substances such as cassava starch, wheat, rye and barley may be deliberately adding to increase the bulkiness of the commodity for economic gain, contrary to the label claims. Recently we could detect the presence of Curcuma zedoaria and cassava starch in one sample each out of the 10 branded market samples of turmeric powder studied, using the barcode locus, ITS. (Parvathy et al. 2014-communicated).
Barcoding was used for the authentication of star anise (Ilicium verum) from its closely related adulterant species like I. micranthum, I. simonsii, I. modestum, I. jgadifengpi, I. henryi, andI. dunnianum var. latifolium (Meizi et al., 2012).
Gismondi et al. (2013) has proposed the use of DNA barcoding as a traceability tool for commercial saffron samples. A study was conducted using different Crocus species using loci viz. rbcl, matK, psbA-trnH and ITS. ITS locus was found to be ideal for discriminating C. sativus (true saffron sample) from other species. This method could also differentiate between saffron samples of European and Italian origin.
Purity of a natural product is the cornerstone of its perceived biological efficacy besides taste and aroma. Though authentication of value-added herbal product such as spice powders from unethical activities like product substitution, adulteration, use of fillers, mislabelling is a daunting task, the DNA barcoding methods may provide an answer to this challenge in the coming days.
• Che Man YB, Syahariza ZA, Mirghani MES, Jinap S and Baker J. (2005). Analysis of potential lard adulteration d in chocolate and chocolate products using fourier transform infrared spectroscopy. Food Chemistry, 90:815-819.
• Dhanya K and Sasikumar B. (2010). Molecular marker based adulteration detection in traded food and agricultural commodities of plant origin with special reference to spices. Current Trends in Biotechnology and Pharmacy, 4:454-489.
• Gismondi, A., Fanali, F., Labarga, J.M.M., Cailoa, M.G., Canini, A. 2013. Crocus sativus L. genomics and different DNA barcode applications. Plant Systematics and Evolution, 299: 1859-1863.
• Hebert, P. D. N., Cywinska, A., Ball, S. L., & de Waard, J. R. (2003). Biological identification through DNA barcodes. Proceedings of the Royal Society of London, 270, 313–321.
• Hollingsworth ML, Clark A, Forrest LL, Richardson JE, Pennington RT, Long D, Cowan R, Chase MW, Gaudeul M and Hollingsworth PM. (2009 a). Selecting barcoding loci for plants: evaluation of seven candidate loci with species level sampling in three divergent groups of land plants. Molecular Ecology Resources, 9:439–457.
• Lakshmi S, Padmaja G and Remani P. (2011). Antitumour effects of Isocurcumenol isolated from Curcuma zedoaria rhizomes on human and murine cancer cells. International Journal of Medicinal Chemistry, Article ID 253962, doi:10.1155/2011/253962.
• Lees, M (Ed.) (2003). Food authenticity and traceability. Woodhead Publishing Ltd.Cambridge, UK. p. 612.
• Lungarini S, Aureli F and Coni E. (2008). Coumarin and cinnamaldehyde in cinnamon marketed in Italy: a natural chemical hazard. Food Additives and Contaminants 25:1297-1305.
• Meizil, L., Hui, Y., Kun, L., Pei, M., Wenbin, Z., Ping, L. (2012). Authentication of Illicium verum using a DNA barcode psbA-trnH. Journal of Medicinal Plants Research, 6: 3151-3161.
• Parvathy VA, Swetha VP, Sheeja TE and Sasikumar B.(2014). DNA barcoding detects plant based adulterants in traded turmeric powder. (communicated).
• Parvathy VA, Swetha VP, Sheeja TE, Chempakam B, Leela NK and Sasikumar B. (2014). DNA barcoding to detect chilli adulteration in traded black pepper. Food Biotechnology. 28:25–40.
• Swetha, V.P., Parvathy, V.A., Sheeja, T.E. and Sasikumar, B. (2014). Isolation and amplification of genomic DNA from barks of Cinnamomum. Turkish Journal of Biology, 38: 151-155.
• World Health Organization(WHO). (1995). Coumarin: A strong association with hepatotoxicity. WHO Drug Info 9:159.
(The author is principal scientist and head, Crop Improvement and Biotechnology Division, ICAR-Indian Institute of Spices Research, Kerala. He can be contacted at firstname.lastname@example.org)
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