Through-packaging analysis of butter adulteration using line-scan spatially offset Raman spectroscopy technique

Authors: LOHUMI, SANTOSH - Chungnam National University; LEE, HOONSOO - Us Forest Service (FS); Kim, Moon; Qin, Jianwei - Tony Qin; CHO, BYOUNG-KWAN - Chungnam National University

Submitted to: Analytical and Bioanalytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2018
Publication Date: 6/22/2018
Citation: Lohumi, S., Lee, H., Kim, M.S., Qin, J., Cho, B. 2018. Through-packaging analysis of butter adulteration using line-scan spatially offset Raman spectroscopy technique. Analytical and Bioanalytical Chemistry. https://doi.org/10.1007/s00216-018-1189-1.
DOI: https://doi.org/10.1007/s00216-018-1189-1

Interpretive Summary: Although spectroscopic methods have been used for quality analysis of foods, the applications have been limited for analyzing foods through packaging materials. We modified our newly developed line-scan Raman hyperspectral imaging system to apply a spatially offset spectroscopic method to facilitate nondestructive authentication of foods through packaging materials. In this study, the technique was used to assess butter adulteration with margarine through two different packaging covers. The results showed that while conventional spectroscopic approach cannot penetrate the packaging covers, limiting its use in quality analysis of packaged food , our method yielded excellent results for butter adulteration through the commercial packaging covers. We envision that the technique can be used to develop high-throughput analysis for quality and authentication of various packaged agricultural products which would benefit packaged food processing industries.

Technical Abstract: Conventional backscattering Raman spectroscopic technique for food quality analysis is limited to surface inspection and highly affected by the superficial turbid layer of food and biological materials. The development of spatially offset Raman spectroscopy (SORS), which collects Raman spectra from a series of surface positions laterally offset from the excitation laser, has enabled deep noninvasive chemical characterization of a range of materials. In this study, we modified our newly developed line-scan Raman hyperspectral imaging system to facilitate SORS analysis using line-laser illumination to obtain Raman spectra of layered food samples. The developed SORS technique was used to quantify butter adulteration with margarine through two different packaging covers. An optimal offset distance was experimentally determined to penetrate the packaging covers and effectively collect Raman signals from butter samples. A multivariate calibration model of partial least square regression (PLSR) analysis was executed on the preprocessed data to predict the presence of margarine. The results revealed that while conventional backscattering Raman spectroscopy cannot penetrate the packaging covers, limiting its use in quality analysis of packaged food, SORS analysis yielded excellent results for detecting butter adulteration through the packaging covers of commercial butter samples. This is the first demonstration of a macro-scale line-scan SORS technique, which can be considered a high-throughput system because of the use of line-laser (~14 cm) that enables the collection of SORS spectra from many samples in a single scan. We expect that this novel line-scan SORS technique can be used to develop high-throughput and real time analysis techniques for quality and authenticity analysis of various packaged agro-products.