1 ISSN: 2040-4565 © 2015 The Authors doi: 10.1255/jsi.2015.a2 This licence permits you to use, share, copy and redistribute the paper in any medium or any format provided that a full citation to the original paper in this journal is given, the use is not for commercial purposes and the paper is not changed in any way. JOURNAL OF SPECTRAL IMAGING JSI Hyperspectral to multispectral imaging for detection of tree nuts and peanut traces in wheat flour Puneet Mishra, a,* Ana Herrero-Langreo, b Pilar Barreiro, a Jean Michel Roger, b Belén Diezma, a Nathalie Gorretta b and Lourdes Lleó a a Department of Ingeniería Rural, ETSI Agrónomos, Avda. Complutense s/n Universidad Politécnica de Madrid (UPM), CEI Moncloa, 28040 Madrid, Spain. E-mail: puneet.mishra@alumnos.upm.es b Irstea, UMR ITAP, 361 Rue J.F. Breton, 34196 Montpellier Cedex 5, France In current industrial environments there is an increasing need for practical and inexpensive quality control systems to detect the foreign food materials in powder food processing lines. This demand is especially important for the detection of product adulteration with traces of highly allergenic products, such as peanuts and tree nuts. Manufacturing industries dealing with the processing of multiple powder food products present a substantial risk for the contamination of powder foods with traces of tree nuts and other adulterants, which might result in unintentional ingestion of nuts by the sensitised population. Hence, the need for an in-line system to detect nut traces at the early stages of food manufacturing is of crucial importance. In this present work, a feasibility study of a spectral index for revealing adulteration of tree nut and peanut traces in wheat flour samples with hyperspectral images is reported. The main nuts responsible for allergenic reactions considered in this work were peanut, hazelnut and walnut. Enhanced contrast between nuts and wheat flour was obtained after the application of the index. Furthermore, the segmentation of these images by selecting different thresholds for differ- ent nut and flour mixtures allowed the identification of nut traces in the samples. Pixels identified as nuts were counted and compared with the actual percentage of peanut adulteration. As a result, the multispectral system was able to detect and provide good visualisa- tion of tree nut and peanut trace levels down to 0.01% by weight. In this context, multispectral imaging could operate in conjuction with chemical procedures, such as Real Time Polymerase Chain Reaction and Enzyme-Linked Immunosorbent Assay to save time, money and skilled labour on product quality control. This approach could enable not only a few selected samples to be assessed but also to extensively incorporate quality control surveyance on product processing lines. Keywords: hyperspectral, multispectral, near infrared (NIR), index, chemometrics, nuts, allergy, adulteration Introduction A nut is a fruit composed of a hard shell and an edible seed. Tree nuts (TNs) are usually used to describe a wide range of seeds except peanuts, mostly from trees, with a tough seed coat or shell. With high-energy content and positive global health impact, TNs are nutrients that have been present for centuries in the human diet. Nuts in general are concentrated sources of dietary energy, as well as sources of unsaturated fatty acids, various micronutrients and fibre. 1 However, over recent decades they have increasingly been found to induce adverse health effects with allergenic reactions. The need for recognition of allergies has been rising in the industrialised world since the middle of the last century. In addition, the prevalence of food allergies has grown rapidly over the past 10 years. 2 Peanuts and TNs are common food allergens and are P. Mishra et al., J. Spectral Imaging 4, a2 (2015) Received: 13 January 2015 n Revised: 5 June 2015 n Accepted: 7 June 2015 n Publication: 24 June 2015 open access Paper Presented at HSI 2014, Hyperspectral Imaging and Applications, Coventry, UK