{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,13]],"date-time":"2025-12-13T07:09:36Z","timestamp":1765609776578,"version":"build-2065373602"},"reference-count":36,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2017,3,18]],"date-time":"2017-03-18T00:00:00Z","timestamp":1489795200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Non-destructive subsurface detection of encapsulated, coated, or seal-packaged foods and pharmaceuticals can help prevent distribution and consumption of counterfeit or hazardous products. This study used a Spatially Offset Raman Spectroscopy (SORS) method to detect and identify urea, ibuprofen, and acetaminophen powders contained within one or more (up to eight) layers of gelatin capsules to demonstrate subsurface chemical detection and identification. A 785-nm point-scan Raman spectroscopy system was used to acquire spatially offset Raman spectra for an offset range of 0 to 10 mm from the surfaces of 24 encapsulated samples, using a step size of 0.1 mm to obtain 101 spectral measurements per sample. As the offset distance was increased, the spectral contribution from the subsurface powder gradually outweighed that of the surface capsule layers, allowing for detection of the encapsulated powders. Containing mixed contributions from the powder and capsule, the SORS spectra for each sample were resolved into pure component spectra using self-modeling mixture analysis (SMA) and the corresponding components were identified using spectral information divergence values. As demonstrated here for detecting chemicals contained inside thick capsule layers, this SORS measurement technique coupled with SMA has the potential to be a reliable non-destructive method for subsurface inspection and authentication of foods, health supplements, and pharmaceutical products that are prepared or packaged with semi-transparent materials.<\/jats:p>","DOI":"10.3390\/s17030618","type":"journal-article","created":{"date-parts":[[2017,3,20]],"date-time":"2017-03-20T11:39:09Z","timestamp":1490009949000},"page":"618","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":21,"title":["A Spatially Offset Raman Spectroscopy Method for Non-Destructive Detection of Gelatin-Encapsulated Powders"],"prefix":"10.3390","volume":"17","author":[{"given":"Kuanglin","family":"Chao","sequence":"first","affiliation":[{"name":"Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, 10300 Baltimore Avenue, Building 303 BARC-East, Beltsville, MD 20705, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sagar","family":"Dhakal","sequence":"additional","affiliation":[{"name":"Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, 10300 Baltimore Avenue, Building 303 BARC-East, Beltsville, MD 20705, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jianwei","family":"Qin","sequence":"additional","affiliation":[{"name":"Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, 10300 Baltimore Avenue, Building 303 BARC-East, Beltsville, MD 20705, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yankun","family":"Peng","sequence":"additional","affiliation":[{"name":"National R&amp;D Centre for Agro-Processing, China Agriculture University, 17 Qinghua East Road, Haidian, Beijing 100083, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Walter","family":"Schmidt","sequence":"additional","affiliation":[{"name":"Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, 10300 Baltimore Avenue, Building 303 BARC-East, Beltsville, MD 20705, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Moon","family":"Kim","sequence":"additional","affiliation":[{"name":"Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, 10300 Baltimore Avenue, Building 303 BARC-East, Beltsville, MD 20705, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Diane","family":"Chan","sequence":"additional","affiliation":[{"name":"Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, 10300 Baltimore Avenue, Building 303 BARC-East, Beltsville, MD 20705, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,3,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"539","DOI":"10.1080\/05704928.2011.593216","article-title":"Applications of Raman spectroscopy in agricultural products and food analysis: A review","volume":"46","author":"Yang","year":"2011","journal-title":"Appl. Spectrosc. Rev."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1696","DOI":"10.1021\/ac062223z","article-title":"Noninvasive authentication of pharmaceutical products through packaging using spatially offset Raman spectroscopy","volume":"79","author":"Eliasson","year":"2007","journal-title":"Anal. Chem."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1016\/j.jfoodeng.2013.09.025","article-title":"Prototype instrument development for non-destructive detection of pesticide residue in apple surface using Raman technology","volume":"123","author":"Dhakal","year":"2014","journal-title":"J. Food Eng."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Dhakal, S., Chao, K., Schmidt, W., Qin, J., Kim, M., and Chan, D. (2016). Evaluation of turmeric powder adulterated with metanil yellow using FT-Raman and FT-IR spectroscopy. Foods, 5.","DOI":"10.3390\/foods5020036"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1016\/j.jpba.2012.09.016","article-title":"Assessment of the performance of a handheld Raman device for potential use as a screening tool in evaluating medicines quality","volume":"74","author":"Hajjou","year":"2013","journal-title":"J. Pharm. Biomed. Anal."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.forsciint.2010.03.020","article-title":"Forensic and homeland security applications of modern portable Raman spectroscopy","volume":"202","author":"Izake","year":"2010","journal-title":"Forensic Sci. Int."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"195","DOI":"10.1155\/2006\/738186","article-title":"Biomedical applications of Raman and infrared spectroscopy to diagnose tissues","volume":"20","author":"Krafft","year":"2006","journal-title":"Spectroscopy"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"563","DOI":"10.1002\/jrs.1688","article-title":"Non-invasive probing of pharmaceutical capsules using transmission Raman spectroscopy","volume":"38","author":"Matousek","year":"2007","journal-title":"J. Raman Spectrosc."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1016\/j.jpba.2008.01.013","article-title":"Non-invasive quantitative assessment of the content of pharmaceutical capsules using transmission Raman spectroscopy","volume":"47","author":"Eliasson","year":"2008","journal-title":"J. Pharm. Biomed. Anal."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1211","DOI":"10.1366\/000370207782597085","article-title":"Quantitative transmission Raman spectroscopy of pharmaceutical tablets and capsules","volume":"61","author":"Johansson","year":"2007","journal-title":"Appl. Spectrosc."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"3690","DOI":"10.1039\/c2an35443h","article-title":"Transmission Raman measurement directly through packed corn kernels to improve sample representation and accuracy of compositional analysis","volume":"137","author":"Shin","year":"2012","journal-title":"Analyst"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"8097","DOI":"10.1021\/jf301247w","article-title":"Protein and oil composition predictions of single soybeans by transmission Raman spectroscopy","volume":"60","author":"Schulmerich","year":"2012","journal-title":"J. Agric. Food. Chem."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"393","DOI":"10.1366\/0003702053641450","article-title":"Subsurface probing in diffusely scattering media using spatially offset Raman spectroscopy","volume":"59","author":"Matousek","year":"2005","journal-title":"Appl. Spectrosc."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1016\/j.forsciint.2011.05.016","article-title":"Spatially offset Raman spectroscopy (SORS) for the analysis and detection of packaged pharmaceuticals and concealed drugs","volume":"212","author":"Olds","year":"2011","journal-title":"Forensic Sci. Int."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"899","DOI":"10.1039\/b705029a","article-title":"Subsurface probing of calcifications with spatially offset Raman spectroscopy (SORS): Future possibilities for the diagnosis of breast cancer","volume":"132","author":"Stone","year":"2007","journal-title":"Analyst"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"926","DOI":"10.1364\/OL.34.000926","article-title":"Spatially offset Raman spectroscopy of layered soft tissues","volume":"34","author":"Keller","year":"2009","journal-title":"Opt. Lett."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"255","DOI":"10.1366\/13-07215","article-title":"A novel approach for subsurface through-skin analysis of salmon using spatially offset Raman spectroscopy (SORS)","volume":"68","author":"Afseth","year":"2014","journal-title":"Appl. Spectrosc."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1016\/j.postharvbio.2012.04.008","article-title":"Nondestructive evaluation of internal maturity of tomatoes using spatially offset Raman spectroscopy","volume":"71","author":"Qin","year":"2012","journal-title":"Postharvest Biol. Technol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"437","DOI":"10.1002\/jrs.4825","article-title":"A line-scan hyperspectral Raman system for spatially offset Raman spectroscopy","volume":"47","author":"Qin","year":"2016","journal-title":"J. Raman Spectrosc."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1875","DOI":"10.1002\/jrs.2335","article-title":"Application of portable Raman spectroscopy and benchtop spatially offset Raman spectroscopy to interrogate concealed biomaterials","volume":"40","author":"Hargreaves","year":"2009","journal-title":"J. Raman Spectrosc."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1921","DOI":"10.1021\/ac00142a008","article-title":"Detection of capsule tampering by near-infrared reflectance analysis","volume":"59","author":"Lodder","year":"1992","journal-title":"Anal. Chem."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1016\/j.jpba.2012.04.023","article-title":"A multidisciplinary approach for the analysis of an adulterated dietary supplement where the active pharmaceutical ingredient was embedded in the capsule shell","volume":"67\u201368","author":"Lanzarotta","year":"2012","journal-title":"J. Pharm. Biomed. Anal."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"374","DOI":"10.1007\/s11694-016-9316-1","article-title":"Raman spectral imaging for quantitative contaminant evaluation in skim milk powder","volume":"10","author":"Dhakal","year":"2016","journal-title":"J. Food Measur. Charact."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1425","DOI":"10.1021\/ac00014a016","article-title":"Interactive self- modeling mixture analysis","volume":"63","author":"Winding","year":"1991","journal-title":"Anal. Chem."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/j.chemolab.2004.06.009","article-title":"A new approach for interactive self-modeling mixture analysis","volume":"77","author":"Winding","year":"2005","journal-title":"Chemom. Intell. Lab. Syst."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"998","DOI":"10.1016\/j.foodchem.2012.10.115","article-title":"Simultaneous detection of multiple adulterants in dry milk using macro-scale Raman chemical imaging","volume":"138","author":"Qin","year":"2013","journal-title":"Food Chem."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Dhakal, S., Chao, K., Qin, J., Kim, M., Peng, Y., and Chan, D. (2017). Identification and evaluation of composition in food powder using point-scan Raman spectral imaging. Appl. Sci., 7.","DOI":"10.3390\/app7010001"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1016\/S0003-2670(01)00909-6","article-title":"Self-modeling mixture analysis of Raman microspectrometric investigations of dust emitted by lead and zinc smelters","volume":"446","author":"Batonneau","year":"2001","journal-title":"Anal. Chim. Acta"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1927","DOI":"10.1109\/18.857802","article-title":"An information theoretic-based approach to spectral variability, similarity and discriminability for hyperspectral image analysis","volume":"46","author":"Chang","year":"2000","journal-title":"IEEE Trans. Inf. Theory"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"4560","DOI":"10.1021\/j100267a029","article-title":"Crystalline Urea: Evidence for vibrational delocalization","volume":"89","author":"Liapis","year":"1985","journal-title":"J. Phys. Chem."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"398","DOI":"10.1366\/14-07600","article-title":"Continuous temperature- dependent Raman spectroscopy of melamine and structural analogs detection in milk powder","volume":"69","author":"Schmidt","year":"2015","journal-title":"Appl. Spectrosc."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1016\/j.molstruc.2005.08.018","article-title":"Vibrational and theoretical studies of non- steroidal anti- inflammatory drugs ibuprofen [2-(4-isobutylphenyl) propionic acid]; Naproxen [6- methoxy-\u03b1-methyl-2-napthalene acetic acid] and Tolmetin acids [1-methyl-5-(4-methylbenzoyl)-1H-pyrrole-2-acetic acid]","volume":"783","author":"Jubert","year":"2006","journal-title":"J. Mol. Struct."},{"key":"ref_33","first-page":"187","article-title":"The adsorption behavior of buffered aspirin monitored by Raman and surface-enhanced Raman spectroscopy","volume":"6","author":"Andronie","year":"2014","journal-title":"HVM Bioflux"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1060","DOI":"10.1520\/JFS14050J","article-title":"Characterization of acetaminophen: Molecular microanalysis with Raman microprobe spectroscopy","volume":"41","author":"Pestaner","year":"1996","journal-title":"J. Forensic Sci."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"621","DOI":"10.1038\/370621a0","article-title":"Structure at 2.4A resolution of F1- ATPase from bovine heart mitochondria","volume":"370","author":"Abrahams","year":"1994","journal-title":"Nature"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"2399","DOI":"10.1021\/ja0356176","article-title":"Raman spectroscopic characterization of secondary structure in natively unfolded proteins: \u03b1-synuclein","volume":"126","author":"Maiti","year":"2004","journal-title":"J. Am. Chem. Soc."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/3\/618\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:30:43Z","timestamp":1760207443000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/3\/618"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,3,18]]},"references-count":36,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2017,3]]}},"alternative-id":["s17030618"],"URL":"https:\/\/doi.org\/10.3390\/s17030618","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2017,3,18]]}}}