Development of Nondestructive Detection Method for Adulterated Powder Products Using Raman Spectroscopy and Partial Least Squares Regression

Abstract

This study was conducted to develop a non-destructive detection method for adulterated powder products using Raman spectroscopy and partial least squares regression(PLSR). Garlic and ginger powder, which are used as natural seasoning and in health supplement foods, were selected for this experiment. Samples were adulterated with corn starch in concentrations of 5-35%. PLSR models for adulterated garlic and ginger powders were developed and their performances evaluated using cross validation. The    and  of an optimal PLSR model were 0.99 and 2.16 for the garlic powder samples, and 0.99 and 0.84 for the ginger samples, respectively. The variable importance in projection (VIP) score is a useful and simple tool for the evaluation of the importance of each variable in a PLSR model. After the VIP scores were taken pre-selection, the Raman spectrum data was reduced by one third. New PLSR models, based on a reduced number of wavelengths selected by the VIP scores technique, gave good predictions for the adulterated garlic and ginger powder samples.

Nontargeted Analytical Methods as a Powerful Tool for the Authentication of Spices and Herbs: A Review

“…FT‐Raman (1064 nm) was, however, used successfully ( R 2 = 0.93) to quantify the content of metanil yellow in turmeric at concentrations of adulterant higher than 1% (Dhakal et al., ). Similar results were found for the prediction of starch content in garlic powder ( R 2 = 0.96), ginger powder ( R 2 = 0.91) (Lee et al., ), and onion powder ( R 2 = 0.96) (Lee et al., ) using spectral information provided by a Raman instrument (785 nm).…”

“…Raman spectroscopy (Figure ) is a variation of analytical vibrational spectroscopy that can be successfully used to control the authenticity and quality of food (Table ). This technique is not affected by water content and can even be used to analyze food through its packaging such as glass or plastic (Lee et al., ).…”

“…In this group are found those adulterants that can share physical similarities such as granulometry and color, and that commonly have a lower economic value than spices. Perhaps one of the most used adulterants is starch (Lee et al., ; Lee, Lohumi, Cho, Kim, & Lee, ; Lohumi et al., ; Su & Sun, ). Starch is a highly consumed carbohydrate and is found as a natural reserve in many foods such as wheat, potatoes, cassava, and sweet potatoes, among others, and its price as native starch is very low (Cruz‐Tirado et al., ).…”

Garlic adulteration detection using NIR and FTIR spectroscopy and chemometrics

“…Adulteration of garlic is most likely to occur in the powdered form. Garlic powder has the potential to be adulterated with any white powder with talc and chalk powder being identified (Brehaut, 2017) as well as starch as adulterants employed (Lee et al, 2014, Lohumi et al, 2015a.…”

“…For the detection of garlic adulteration, Fourier transform infrared (FTIR) was used in the development of a competent method to detect corn starch adulteration in garlic powder with partial least squares regression (PLSR) and variable importance projection (VIP), resulting in an R 2 value of 0.95 and standard error of prediction of 2.56 (Lohumi et al, 2015a). A method for the detection of corn starch in garlic was also developed using Raman with PLSR and VIP with an R 2 value of 0.99 and a standard error of correction of 2.16 (Lee et al, 2014). Although a targeted quantitative method has the potential to detect adulteration at lower percentage levels there is also a need for a non-targeted method to detect unknown white powders as well as known adulterants.…”