Authentication of capsicum using chromatographic techniques and chemometric methods

Abstract

The discrimination of the geographical origins and varieties of chili peppers by using chromatography and spectroscopy to separate and analyze capsaicinoids, volatile compounds, and TPC components of chili peppers were studied. The combination of multivariate techniques such as principal component analysis (PCA), cluster analysis (CA), and linear discriminant analysis (LDA) were applied to the analytical data to monitor the chili pepper profiles and construct a mathematical model to aid in the identification of the origins and varieties of the chili pepper samples. The chili samples were classified into 3 major groups include the hot chili peppers (Capsicum annum Linn.), the bird chili (Capsicum frutescens Linn.), and the chili spur pepper (Capsicum annuum Linn. Varacuminatum Fingerh.), based on their varieties and geographical origins. The result show that the content of capsaicin and dihydrocapsaicin of bird chili peppers has the greatest content (2.51- 5.31 g kg-1 and 0.74 -1.50 g kg-1 dry weight respectively), followed in order of decreasing concentration by hot chili peppers (1.35 - 3.10 g kg-1 and 0.52 - 1.06 g kg-1 dry weight, respectively), chili spurs pepper (0.11- 0.26 g kg-1 and 0.01 - 0.04 g kg-1 dry weight, respectively). The VOCs analysis showed that the volatile compounds of the three varieties of chili pepper samples have different qualities and quantities according to their varieties. In chili peppers from various origins have similar VOCs but different quantities. The total phenolic content analysis showed that the total phenolic content of the hot chili peppers (2.25 – 2.75 mg gallic acid/100 g FW) was higher than those of the others, whereas the bird chili peppers and the chili spur peppers were 2.00 – 2.27 mg gallic acid/100 g FW and 1.10 – 1.52 mg gallic acid/100 g FW, respectively. The discrimination of geographical origins and varieties of chili peppers samples indicated that CA can be clearly differentiated the varieties of chili peppers at distance 0.4 and the origins of chili peppers at distance 0.2-0.3. In PCA showed that all chili peppers sample clustered according to their variety and origins. Each of the varieties and origins of chili peppers have organic composition markers that are unique to each species. Original group of samples can be predicted with 100% correction by cross-validating LDA.