Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem Short communication Circannual changes in major chemical composition of bulk dromedary camel milk as determined by FT-MIR spectroscopy, and factors of variation Péter Nagy a, ⁎ , Judit Juhász a , Jenő Reiczigel b , Gábor Császár c , Róbert Kocsis c , László Varga d a Emirates Industry for Camel Milk and Products, Farm and Veterinary Department, PO Box 294236, Dubai, United Arab Emirates b Department of Biomathematics and Informatics, University of Veterinary Medicine, 2 István Street, 1078 Budapest, Hungary c Hungarian Dairy Research Institute, 24 Lucsony Street, 9200 Mosonmagyaróvár, Hungary d Department of Food Science, Faculty of Agricultural and Food Sciences, Széchenyi István University, 15-17 Lucsony Street, 9200 Mosonmagyaróvár, Hungary ARTICLE INFO Keywords: Camel Dromedary Raw milk Chemical composition Seasonal variation ABSTRACT We monitored the major chemical composition of bulk dromedary camel milk by FT-MIR spectroscopy over a 5- year period. The results highly correlated with those determined with reference methods (r > 0.985, p < 0.001). Production parameters showed significant (p < 0.001) seasonal and yearly changes. The overall mean fat, protein, lactose, solids-not-fat, and total solids concentrations of bulk dromedary camel milk were 2.87%, 2.94%, 4.15%, 8.00%, and 10.69%, respectively. Month of the year, year of the study, and level of production had a strong influence on bulk milk chemical composition and yield of milk components; however, the relative effect of season on composition was greater (proportion of variance app. 50%) compared to that of other factors of variation. The highest and lowest values were measured during winter and summer, respectively. Circannual variation in major milk components was associated with environmental conditions (photoperiod, temperature), whereas it was independent of nutritional factors. 1. Introduction With an overall milk production of 2.86 million metric tons in 2014, dromedary camels are among the top five dairy animal species globally. Although camel milk is available in large quantities in the arid and semi-arid regions of Asia and Africa, most of the milk is consumed lo- cally and does not enter supply chains (FAO, 2018). However, the camel dairy industry has gone through major changes over the last 15 years and an ever-increasing quantity of raw camel milk is processed commercially. As a result, more and more new camel milk-based dairy foods are developed and marketed all over the world (Varga, Süle, & Nagy, 2014; Nagy and Juhasz, 2016). Industrial production of camel milk necessitates the continuous monitoring of the physicochemical composition of raw milk for quality management purposes. Moreover, it is important to understand the role of various factors affecting milk composition and the processing char- acteristics of bulk camel milk collected at different times of the year. However, studies on bulk or pooled dromedary camel milk are scarce. Only few papers analyzing composite milk samples do exist (Kouniba, Berrada, Zahar, & Bengoumi, 2005; Haddadin, Gammoh, & Robinson, 2008; Ismaili, Saidi, Zahar, Hamama, & Ezzaier, 2016). The majority of the available literature focuses on chemical composition and other parameters in milk samples collected from individual dromedaries throughout lactation (Zeleke, 2007; Aljumaah et al., 2012; Musaad, Faye, & Al-Mutairi, 2013). In most previous studies, camel milk composition was determined by primary chemical methods (Mehaia, Hablas, Abdel-Rahman, & El- Mougy, 1995; Al haj and Al Kanhal, 2010). Electronic milk testing in- struments based on ultrasound (Al-Saiady et al., 2012; Musaad et al., 2013), thermo-optical technology (Aljumaah et al., 2012), or mid-in- frared (MIR) spectroscopy (Zeleke 2007; Ahmad et al., 2012) have re- cently been applied for camel milk analysis, but none of these sec- ondary electronic methods have been calibrated for dromedary camel milk. The objectives of this study were (1) to monitor changes in con- centration and yield of major chemical components of bulk dromedary camel milk over a 5-year period at the world’s largest commercial dairy camel operation, and (2) to evaluate the effect of different factors (year, season, stage of lactation, level of production) on bulk milk composi- tion. We hypothesize that environmental factors (i.e. photoperiod, temperature) play a pivotal role in influencing the composition of bulk dromedary camel milk destined for processing. In addition, we report https://doi.org/10.1016/j.foodchem.2018.11.059 Received 20 August 2018; Received in revised form 26 October 2018; Accepted 10 November 2018 ⁎ Corresponding author. E-mail addresses: peter@camelicious.ae (P. Nagy), jutkajuhasz@gmail.com (J. Juhász), reiczigel.jeno@univet.hu (J. Reiczigel), gcsaszar@mtki.hu (G. Császár), rkocsis@mtki.hu (R. Kocsis), varga.laszlo@sze.hu (L. Varga). Food Chemistry 278 (2019) 248–253 Available online 10 November 2018 0308-8146/ © 2018 Elsevier Ltd. All rights reserved. T