{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,17]],"date-time":"2026-01-17T23:31:21Z","timestamp":1768692681306,"version":"3.49.0"},"reference-count":30,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2024,9,30]],"date-time":"2024-09-30T00:00:00Z","timestamp":1727654400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"province of Gelderland"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A minimally invasive needle refractometer is presented for sugar content measurements within produce. A passive sampling cap structure was developed that improves the reliability of the device by avoiding interfering back reflections from the flesh of the produce. It is explained that factory calibration may not be needed for this type of refractometer, potentially reducing production costs. Also demonstrated is an iterative method to correct for temperature variations without the need for an integrated model for how the refractive index changes with temperature for different levels of sugar concentration. The sensor showed a typical standard deviation of 0.4 \u00b0Bx for a 10-s-long measurement and was validated against a prism refractometer, showing an average offset of (0.0\u00b10.1) \u00b0Bx. In addition, the potential for using the device to investigate sugar distributions within a single fruit sample is demonstrated.<\/jats:p>","DOI":"10.3390\/s24196336","type":"journal-article","created":{"date-parts":[[2024,9,30]],"date-time":"2024-09-30T10:00:47Z","timestamp":1727690447000},"page":"6336","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Fibre Refractometry for Minimally Invasive Sugar Content Measurements within Produce"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6865-5693","authenticated-orcid":false,"given":"Mark A.","family":"Zentile","sequence":"first","affiliation":[{"name":"IMEC the Netherlands, OnePlanet Research Center, Bronland 10A, 6708 WH Wageningen, The Netherlands"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5823-270X","authenticated-orcid":false,"given":"Peter","family":"Offermans","sequence":"additional","affiliation":[{"name":"IMEC the Netherlands, OnePlanet Research Center, Bronland 10A, 6708 WH Wageningen, The Netherlands"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-2859-6682","authenticated-orcid":false,"given":"David","family":"Young","sequence":"additional","affiliation":[{"name":"IMEC the Netherlands, OnePlanet Research Center, Bronland 10A, 6708 WH Wageningen, The Netherlands"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1717-7294","authenticated-orcid":false,"given":"Xu U.","family":"Zhang","sequence":"additional","affiliation":[{"name":"IMEC the Netherlands, OnePlanet Research Center, Bronland 10A, 6708 WH Wageningen, The Netherlands"}]}],"member":"1968","published-online":{"date-parts":[[2024,9,30]]},"reference":[{"key":"ref_1","unstructured":"OECD (2018). Guidelines on Objective Tests to Determine Quality of Fuit and Vegetables, Dry and Dried Produce, OECD. Technical report."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"228","DOI":"10.1007\/s10762-011-9863-9","article-title":"Nondestructive Measurement of Sugar Content in Apples by Millimeter-Wave Reflectometry","volume":"33","author":"Oda","year":"2012","journal-title":"J. Infrared Millim. Terahertz Waves"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Yang, Z., Pathak, P.H., Sha, M., Zhu, T., Gan, J., Hu, P., and Mohapatra, P. (2019, January 15\u201318). On the feasibility of estimating soluble sugar content using millimeter-wave. Proceedings of the IoTDI \u201919: International Conference on Internet-of-Things Design and Implementation, Montreal, QC, Canada.","DOI":"10.1145\/3302505.3310065"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Walsh, K.B., Blasco, J., Zude-Sasse, M., and Sun, X. (2020). Visible-NIR \u2018point\u2019 spectroscopy in postharvest fruit and vegetable assessment: The science behind three decades of commercial use. Postharvest Biol. Technol., 168.","DOI":"10.1016\/j.postharvbio.2020.111246"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1016\/j.ifset.2013.04.016","article-title":"Advanced applications of hyperspectral imaging technology for food quality and safety analysis and assessment: A review\u2014Part II: Applications","volume":"19","author":"Wu","year":"2013","journal-title":"Innov. Food Sci. Emerg. Technol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"339235","DOI":"10.1016\/j.aca.2021.339235","article-title":"All-in-one: A spectral imaging laboratory system for standardised automated image acquisition and real-time spectral model deployment","volume":"1190","author":"Mishra","year":"2022","journal-title":"Anal. Chim. Acta"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"651","DOI":"10.1631\/BF02840975","article-title":"Measurement of sugar content in Fuji apples by FT-NIR spectroscopy","volume":"5","year":"2004","journal-title":"J. Zhejiang Univ. Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1007\/s11099-015-0163-9","article-title":"Measurements of reflectance and fluorescence spectra for nondestructive characterizing ripeness of grapevine berries","volume":"54","author":"Buschmann","year":"2016","journal-title":"Photosynthetica"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1016\/j.postharvbio.2006.09.006","article-title":"Hyperspectral laser-induced fluorescence imaging for assessing apple fruit quality","volume":"43","author":"Noh","year":"2007","journal-title":"Postharvest Biol. Technol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1016\/j.jfoodeng.2009.02.020","article-title":"Multivariate calibration of mango firmness using vis\/NIR spectroscopy and acoustic impulse method","volume":"94","author":"Valente","year":"2009","journal-title":"J. Food Eng."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"417","DOI":"10.1071\/AR04299","article-title":"Assessment of internal quality attributes of mandarin fruit. 2. NIR calibration model robustness","volume":"56","author":"Guthrie","year":"2005","journal-title":"Aust. J. Agric. Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"338771","DOI":"10.1016\/j.aca.2021.338771","article-title":"Handling batch-to-batch variability in portable spectroscopy of fresh fruit with minimal parameter adjustment","volume":"1177","author":"Mishra","year":"2021","journal-title":"Anal. Chim. Acta"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2047","DOI":"10.1063\/1.1139513","article-title":"Optical fiber refractometer","volume":"58","author":"Meyer","year":"1987","journal-title":"Rev. Sci. Instrum."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1900094","DOI":"10.1002\/lpor.201900094","article-title":"A Comprehensive Review of Optical Fiber Refractometers: Toward a Standard Comparative Criterion","volume":"13","author":"Urrutia","year":"2019","journal-title":"Laser Photonics Rev."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Cano-Vel\u00e1zquez, M.S., Hendriks, A.L., Picelli, L., van Veldhoven, R.P.J., and Fiore, A. (2023). Temperature-Compensated Solution Concentration Measurements Using Photonic Crystal Fiber-Tip Sensors. Sensors, 23.","DOI":"10.3390\/s23187703"},{"key":"ref_16","unstructured":"Cano-Vel\u00e1zquez, M.S., Buntinx, S., Hendriks, A.L., Van Klinken, A., Li, C., Heijnen, B.J., Dolci, M., Picelli, L., Abdelkhalik, M.S., and Sevo, P. (2024). Beyond spectral resolution in optical sensing: Picometer-level precision with multispectral readout. arXiv."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1962","DOI":"10.1088\/0957-0233\/13\/12\/321","article-title":"A fibre optic Fresnel ratio meter for measurements of solute concentration and refractive index change in fluids","volume":"13","author":"Chang","year":"2002","journal-title":"Meas. Sci. Technol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"579","DOI":"10.1016\/j.snb.2007.04.008","article-title":"Fresnel-reflection-based fiber sensor for on-line measurement of solute concentration in solutions","volume":"126","author":"Su","year":"2007","journal-title":"Sens. Actuators B Chem."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"035004","DOI":"10.1063\/1.3698293","article-title":"Fresnel-reflection-based fiber sensor for high-temperature measurement","volume":"83","author":"Pan","year":"2012","journal-title":"Rev. Sci. Instrum."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1571","DOI":"10.1109\/JSEN.2012.2236751","article-title":"Simple Fiber-Optic Refractive Index Sensor Based On Fresnel Reflection and Optical Switch","volume":"13","author":"Xu","year":"2013","journal-title":"IEEE Sens. J."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"987","DOI":"10.1111\/nph.16084","article-title":"Fiber-optic refractometer for in vivo sugar concentration measurements of low-nectar-producing flowers","volume":"224","author":"Aronne","year":"2019","journal-title":"New Phytol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1505","DOI":"10.1109\/LPT.2011.2162825","article-title":"On-Chip Arrayed Waveguide Grating Interrogated Silicon-on-Insulator Microring Resonator-Based Gas Sensor","volume":"23","author":"Yebo","year":"2011","journal-title":"IEEE Photonics Technol. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Zhang, X.U., Faber, D.J., Post, A.L., van Leeuwen, T.G., and Sterenborg, H.J.C.M. (2019). Refractive index measurement using single fiber reflectance spectroscopy. J. Biophotonics, 12.","DOI":"10.1002\/jbio.201900019"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Zhang, X.U., Post, A.L., Faber, D.J., van Leeuwen, T.G., and Sterenborg, H.J.C.M. (2017). Single fiber reflectance spectroscopy calibration. J. Biomed. Opt., 22.","DOI":"10.1117\/1.JBO.22.10.100502"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1683","DOI":"10.1088\/0957-0233\/15\/9\/002","article-title":"Measurement of the refractive index of liquids at 1.3 and 1.5 micron using a fibre optic Fresnel ratio meter","volume":"15","author":"Kim","year":"2004","journal-title":"Meas. Sci. Technol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"947","DOI":"10.1364\/AO.55.000947","article-title":"Refractive indices of common solvents and solutions at 1550 nm","volume":"55","author":"Saunders","year":"2016","journal-title":"Appl. Opt."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"195","DOI":"10.1081\/JFP-120017815","article-title":"Temperature and Concentration Dependence of Density of Model Liquid Foods","volume":"6","author":"Balaban","year":"2003","journal-title":"Int. J. Food Prop."},{"key":"ref_28","unstructured":"Zentile, M., Zhang, X., Offermans, P., Young, D., and Tibbe, A. (2022). A Probe, a System and a Method for Analysis of a Liquid in a Mixture of the Liquid and Solid Substance. (4 312 017 A1), European Patent."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2419","DOI":"10.1002\/fsn3.1109","article-title":"Effects of distribution of sugars and organic acids on the taste of strawberries","volume":"7","author":"Ikegaya","year":"2019","journal-title":"Food Sci. Nutr."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2715","DOI":"10.1021\/jf981079i","article-title":"Visualization of Sugar Content in the Flesh of a Melon by Near-Infrared Imaging","volume":"47","author":"Sugiyama","year":"1999","journal-title":"J. Agric. Food Chem."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/19\/6336\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T16:07:46Z","timestamp":1760112466000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/19\/6336"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,9,30]]},"references-count":30,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2024,10]]}},"alternative-id":["s24196336"],"URL":"https:\/\/doi.org\/10.3390\/s24196336","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,9,30]]}}}