Application of FT-Raman Spectroscopy and Chemometric Analysis for Determination of Adulteration in Milk Powder

Abstract

In this work, FT-Raman spectroscopy is explored as a rapid technique for the assessment of the milk powder quality. Based on information provided by Raman spectra of samples adulterated with starch and whey, a quantitative method is developed to identify the fraud, using Partial Least Squares regression (PLS). In regression models using PLS the results are satisfactory, and such models can be used to identify and quantify samples presenting whey and starch in milk powder at concentrations of 2.32% and 1.64% (w/w), respectively. In the whey determination, the obtained values in the PLS model of the new samples are compared with those obtained by the spectrophotometric method of acid ninhydrin. This result shows that there is no significant difference with the 95% level of confidence between the values provided by the PLS regression method and the acid ninhydrin. The present work shows Raman spectroscopy as an analytical tool which can be used in quality control of milk powder, even in fraud processes, and the calculated figures of merit such as sensitivity, accuracy, limit of detection and limit of quantification clearly demonstrate this potential use. Although the multivariate models developed are not strictly quantitative, especially for low concentrations, they can be used as screening methods for routine analysis, as showed by this work. The authors wish to thank CNPq, FAPEMIG, CAPES, and FINEP (Brazilian agencies) for financial support. This work is a collaboration research project of members of the Rede Mineira de Química (RQ-MG) supported by FAPEMIG.

Review of validation and reporting of non-targeted fingerprinting approaches for food authentication

“…For instance, McIntrye et al compared the ethanol content derived from the fingerprinting model of NIR spectra with those revealed by univariate calibration of one wavelength [82]. Furthermore, De Almeida et al compared the predicted percentages of whey in adulterated milk powder, derived from a PLS model based on NIRspectroscopy fingerprints, with a photometric method of acid ninhydrin, an established screening method for this purpose [83]. Similarly, fingerprinting predictions were compared with results directly revealed by a standard chemical analysis for peroxide and iodine determination in adulterated avocado oils [54].…”

“…In five of the investigated studies, the trueness of the fingerprinting approaches was evaluated by comparing model prediction results to those derived by another analytical approach [54,[82][83][84]. For instance, McIntrye et al compared the ethanol content derived from the fingerprinting model of NIR spectra with those revealed by univariate calibration of one wavelength [82].…”

Alkaline Solubilization of Chicken Tissues Monitored by Raman Spectroscopy Followed by Pb Determination by GF AAS

“…Another interesting study 19 that also employed chemometric methods combined to FT-Raman spectroscopy verified the adulteration of milk powder samples, commercialized in Brazil, by starch additions.…”

“…Therefore, it offers analytical opportunities for many areas of production, quality inspection and control, including food industry. [19][20][21][22] Lopez-Diez et al 21 proposed a method to evaluate the potential of Raman spectroscopy allied to chemometrics to detect adulterations in olive oil by very closely related oils.…”

“…Importantly, the frequency variation corresponds to the energy difference between two vibrational states of the molecule, and may be assigned to functional groups. 19 In addition, Raman spectroscopy is a versatile and rapid technique, which makes possible the simultaneous determination of more than one component, without the need for samples pre-treatment step so that there is no generation of toxic waste products. Therefore, it offers analytical opportunities for many areas of production, quality inspection and control, including food industry.…”