Physical and functional properties of cheese powders affected by sweet whey powder addition before or after spray drying Denise Felix da Silva ⁎, Lilia Ahrné, Flemming Hofmann Larsen, Anni Bygvrå Hougaard, Richard Ipsen Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej 26, DK-1958 Frederiksberg C, Denmark abstract article info Article history: Received 12 May 2017 Received in revised form 18 August 2017 Accepted 3 October 2017 Available online 05 October 2017 Cheese powder properties are affected by the use of different cheese raw materials, addition of ingredients, spray drying and storage conditions. Sweet whey powder can be added after spray drying, in a dry mixing process, or before spray drying into the cheese feed to improve physical properties like flowability, particle size, color and reconstitution properties. This work focused on how addition of sweet whey powder before (co-sprayed) or after spray drying (dry mixed) affected the physical, flow, thermal and reconstitution properties of Danbo cheese powder. It was demonstrated that co-sprayed samples presented smaller particles, faster dissociation, better solubility and rehydration ability (by 1 H NMR relaxometry), whereas solid-state 13 C MAS NMR and differential scanning calorimetry were utilized to show that lactose was mainly amorphous for co-sprayed powders and mainly present as crystalline lactose monohydrate in dry mixed powders. Also, dry mixed showed the lowest flow functional coefficient and a weaker structure after rehydration (1:1 w/w). Rheological measurements indicated the presence of a stable and elastic network after rehydration. In conclusion, lactose state and particle size are the main factors affecting the properties of cheese powder added sweet whey powder. © 2017 Published by Elsevier B.V. Keywords: Cheese powders Nuclear magnetic resonance Lactose Reconstitution 1. Introduction Cheese powders are produced by spray-drying and are widely used as a multifunctional ingredient to provide an optimum combination of taste and texture in ready meals, sauces, creams, soups, etc. They can be pro- duced from a variety of cheeses such as Cheddar, Danbo, Camembert, or Gouda. During production the cheeses are comminuted, mixed with water and other ingredients, and heated to form a homogenous emulsion, termed cheese feed. Generally, the cheese feed is held at 60 °C for at least 1 h, pasteurized and then spray dried [1,2]. Cheese powder properties such as physical, thermal and rehydration properties can be affected by the use of different cheese raw materials, addition of ingredients, spray drying and storage conditions [1–4]. For example, the use of fillers, such as maltodextrin and whey powder in cheese powder production may reduce the raw material cost and im- prove the physical properties, especially the rehydration properties of powders [5]. Sweet whey powder is one of the most common filler ma- terials used in the food industry [6]. Sweet whey powder (SWP) is produced from liquid whey derived from the manufacture of cheese or rennet casein by coagulation of milk at pH of 6.0–6.5. Prior to spray drying, the lactose present in the sweet whey is crystallized in order to produce non-hygroscopic whey powder [7]. SWP is widely used in powder formulations to improve the physical quality of powders such as particle properties, flowability, and reconstitution abilities [8–11]. In cheese powders, SWP can be added before spray drying into the cheese feed, or after spray drying, in a dry mixing process, resulting in powders with e.g. different particle sizes and flowability. Most spray dried dairy ingredients contain lactose in an amorphous state [12]. Amorphous sugars are thermodynamically unstable and more susceptible to crystallization and to participation in Maillard reac- tions, consequently causing browning [12].Therefore, an understanding of the thermal reactions is important to predict the quality of dairy in- gredients [13]. Likewise, reconstitution is an important attribute of powdered ingredients and has been investigated using different methods such as light-scattering, microscopy, rheology and low field nuclear magnetic resonance (LF-NMR) spectroscopy [14–17]. More spe- cifically, rehydration is an important property for the final product and will depend on the structure and composition of a given dairy powder [18–20]. Only a few studies have investigated the characteristics of cheese powders, and they have mostly dealt with flavor properties [21,22]. Recently, Erbay and Koca [2] investigated the physical properties of cheese powder produced from white cheese and liquid whey or maltodextrin, and they concluded that the addition of maltodextrin re- sulted in cheese powders with high densities, optimum reconstitution properties, and low content of free fatty acids. Powder particles produced with liquid whey, were larger than the particles of powders produced without liquid whey addition, spherical, and uniform [5]. Powder Technology 323 (2018) 139–148 ⁎ Corresponding author. E-mail address: denise@food.ku.dk (D. Felix da Silva). https://doi.org/10.1016/j.powtec.2017.10.014 0032-5910/© 2017 Published by Elsevier B.V. Contents lists available at ScienceDirect Powder Technology journal homepage: www.elsevier.com/locate/powtec