Food and Bioprocess Technology

, Volume 12, Issue 5, pp 751–768 | Cite as

Influence of Inlet Drying Air Temperature and Milk Flow Rate on the Physical, Optical and Thermal Properties of Spray-Dried Camel Milk Powders

  • Jackline Akinyi OgollaEmail author
  • Boris Kulig
  • Liliana Bădulescu
  • Michael Wandayi Okoth
  • Günter Esper
  • Jutta Breitenbach
  • Oliver Hensel
  • Barbara Sturm
Original Paper


The influence of milk flow rate and inlet drying air temperature on the physical, optical and thermal properties of laboratory spray-dried camel milk powders is investigated. The physical, thermal and optical properties of laboratory spray-dried camel milk powders at three inlet drying air temperatures (110, 120 and 130 °C) and two milk flow rates (166 and 248 cm3/h) were evaluated. These properties are fundamental to understanding the quality, stability, final application and portability of the milk powders. Following this, the results were compared to commercial milk powder (CMM). Specifically, we evaluated the influence of the inlet drying air temperatures and feed rates on the reconstitution properties, particle properties, bulk, colour and thermal properties. Using response surface methodology (RSM), the findings indicated that the inlet drying air temperatures significantly influenced moisture content, and the L* a* b* colour properties (p < 0.0001) of the powders. However, the bulk and reconstitution properties were significantly influenced by the milk flow rate (p < 0.0001). The thermograms of all the milk powders had three endothermic peaks and two shifts. The onset of the glass transition increased in temperature with decreasing moisture content of the powders varying from 37.49 to 44.21 °C. Scanning electron microscopy (SEM) images of the laboratory spray dried powders were hollow and collapsed compared with the commercial samples which were spherical and rough with small cracks, dents and pores. The results demonstrated that both the inlet drying air temperature and the milk flow rate influenced the thermal, optical and physical properties of laboratory spray-dried powders.


Camel milk powder Spray drying Physical properties Colour properties Thermal properties 



The first author, Jackline Akinyi Ogolla would wish to acknowledge Katholische Akademische Ausländer-Dienst (KAAD) for her research stay in Germany. This study is part of Global food supply (GlobE) project – RELOAD (FKZ 031A247 A) funded by the German Federal Ministry of Education and Research (BMBF) and the RE4Foods project (EP/L002531/1) funded by the Engineering and Physical Sciences Research Council (EPSRC), UK. The authors gratefully acknowledge their financial contributions. The authors further wish to thank Dr. Helen McKee for proofreading the manuscript.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.

Supplementary material

11947_2019_2243_MOESM1_ESM.docx (20 kb)
ESM 1 (DOCX 20 kb)


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Authors and Affiliations

  • Jackline Akinyi Ogolla
    • 1
    Email author
  • Boris Kulig
    • 1
  • Liliana Bădulescu
    • 2
  • Michael Wandayi Okoth
    • 3
  • Günter Esper
    • 4
  • Jutta Breitenbach
    • 4
  • Oliver Hensel
    • 1
  • Barbara Sturm
    • 1
    • 5
  1. 1.Faculty of Organic Agriculture. Department of Agricultural & Biosystems EngineeringUniversity of KasselWitzenhausenGermany
  2. 2.Faculty of Horticulture. Department of Bioengineering of Horti-Viticultural SystemUniversity of Agronomic Sciences and Veterinary Medicine of BucharestBucharestRomania
  3. 3.College of Agriculture and Veterinary Sciences. Department of Food Science, Nutrition and TechnologyUniversity of NairobiNairobiKenya
  4. 4.Department of Food TechnologyFulda University of Applied SciencesFuldaGermany
  5. 5.School of Natural and Environmental SciencesNewcastle UniversityNewcastle upon TyneUK

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