Non-Invasive Detection of Adulterated Olive Oil in Full Bottles Using Time-Domain NMR Relaxometry

Poliana M Santos,Carlos Manuel S Lobo,Flávio Vinicius C Kock,André S Carvalho,Maiara S Santos,Luiz Alberto Colnago

doi:10.5935/0103-5053.20160188

Poliana M Santos, Carlos Manuel S Lobo + Show 4 more

Open Access

https://doi.org/10.5935/0103-5053.20160188

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Abstract

A fast procedure using time-domain nuclear magnetic resonance (TD-NMR) to detect olive oil adulteration with polyunsaturated vegetable oils in filled bottles is proposed. The 1H transverse relaxation times (T2) of 37 commercial samples were measured using low-field nuclear magnetic resonance (LF-NMR) spectrometer and a unilateral nuclear magnetic resonance (UNMR) sensor. Results obtained with LF-NMR revealed better feasibility when compared with the UNMR sensor, with higher signal-to-noise (S/N) ratio and larger difference in the T2 decays. Principal component analysis (PCA) exhibited tight and well-separated clusters of pure olive oil (OO), pure soybean oil (SO), and blends of OO/SO (adulterated samples). Soft independent modeling of class analogies analysis (SIMCA) classification model indicated that five brands of olive oil commercialized in Brazil were adulterated with polyunsaturated fatty acids, further confirmed by high-resolution NMR. Overall, LF-NMR provided a fast procedure for screening olive oil authenticity directly in the sealed bottles.

Highlights

Olive oil stands out as the most expensive edible oil and is among the most frequently adulterated food products.[1,2] Olive oil is often adulterated with cheaper vegetable oils, including soybean, corn, sunflower, cotton, hazelnut, peanut, palm and many others.[1,2,3,4] Such practice is unfair to consumers, and to the honest farmers and olive oil industries
Five hundred relaxation curves were average in unilateral nuclear magnetic resonance (UNMR) signals the S/N ratios were approximately ten-fold lower than those obtained with low-field nuclear magnetic resonance (LF-NMR) spectrometer
No differences in the T2 values were observed between olive oil (OO) and soybean oil (SO) samples analyzed in the UNMR sensor

Summary

Introduction

Olive oil stands out as the most expensive edible oil and is among the most frequently adulterated food products.[1,2] Olive oil is often adulterated with cheaper vegetable oils, including soybean, corn, sunflower, cotton, hazelnut, peanut, palm and many others.[1,2,3,4] Such practice is unfair to consumers, and to the honest farmers and olive oil industries. The T2 relaxation curves collected in the LF-NMR spectrometer and in the UNMR sensor were normalized (as to the maximum amplitude of the first echo) and analyzed by exponential fitting, inverse Laplace transform (ILT), principal component analysis (PCA), and soft independent modeling of class analogies (SIMCA). The analysis performed in the LF-NMR showed a visible difference in the T2 relaxation times of the two oils (Figure 1b).

Results

Conclusion