Effects of anticaking agents and storage conditions on the moisture sorption, caking, and flowability of deliquescent ingredients Rebecca A. Lipasek a , Julieta C. Ortiz a , Lynne S. Taylor b , Lisa J. Mauer a, ⁎ a Department of Food Science, Purdue University, 745 Agriculture Mall Drive, W. Lafayette, IN 47907, USA b Department of Industrial and Physical Pharmacy, Purdue University, 575 Stadium Mall Drive, W. Lafayette, IN 47907, USA abstract article info Article history: Received 15 August 2011 Accepted 18 October 2011 Keywords: Deliquescence Powder blends Physical stability Moisture sorption isotherms Deliquescent highly soluble crystalline ingredients are prone to caking and dissolution when they are stored above a certain relative humidity (RH) but exhibit minimal moisture adsorption below this RH. Anticaking agents are added to improve the flowability of powders and to prevent or reduce caking. The objective of this study was to determine the effects of anticaking agents on the moisture sorption behavior, flowability, and caking characteristics of deliquescent ingredients and blends thereof. Single deliquescent food ingredi- ents (sodium chloride, sucrose, fructose, and citric acid) and binary systems (sodium chloride blended with sucrose, fructose, or citric acid) were used as the host powders, and silicon dioxide, calcium silicate, and calcium stearate were the three anticaking agents studied. Moisture sorption isotherms were generated to investigate the water–solid interactions of the anticaking and host powders. Following controlled RH stor- age treatments, caking was assessed by the sieve test and flowability by avalanche power and avalanche angle measurements. Formulation had variable effects on deliquescence behavior and moisture sorption, while formulation, storage RH, length of storage, and RH cycling all significantly affected the physical stability of the powder blends. Calcium stearate was the most effective anticaking agent at reducing moisture sorption and delaying the onset of deliquescence, as well as maintaining the flowability properties of all powders tested. In particular, calcium stearate was able to substantially alter the moisture sorption behavior of blends of deliquescent ingredients, which are inherently more susceptible to the deleterious effects of moisture due to deliquescence lowering. The results are of great significance because they show that the effectiveness of an anticaking agent in preventing moisture-induced caking depends on the complexity of the host powders as well as on the interaction with environmental moisture. Thus, the type of anticaking agent added to a deli- quescent ingredient must be tailored to the host powder to enhance product quality and stability. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction The phenomena of deliquescence and deliquescence lowering have been linked to chemical and physical instabilities in powdered food in- gredients and blends (Lipasek, Taylor, & Mauer, 2011; Mauer & Taylor, 2010). Deliquescence is a first order moisture-induced temperature- dependent phase transformation from solid to solution that occurs at a specific relative humidity (RH 0 ) for crystalline deliquescent ingredi- ents, including common food ingredients such as salts, sugars, organic acids, and vitamin C (Mauer & Taylor, 2010; McNaught & Wilkinson, 1997; Zografi & Hancock, 1994). At RHs below RH 0 , deliquescent solids adsorb minimal amounts of water, less than 3 molecular layers (Mauer & Taylor, 2010; Nokhodchi, 2005) of moisture at the surface via hydrogen bonding (Thiel & Madey, 1987). Increasing the RH above RH 0 causes the solid to dissolve in the condensate film, and complete solid dissolution and solution dilution will occur if the environmental RH is maintained above RH 0 (Zografi & Hancock, 1994). The kinetics of deliquescence increases as the RH increases above RH 0 (Mauer & Taylor, 2010). Deliquescence lowering occurs when two or more deli- quescent powders are in physical contact and the RH increases above the deliquescent point of the blend (RH 0mix ), which is lower than the RH 0 of any of the individual components (Salameh, Mauer, & Taylor, 2006). The extent of deliquescence lowering is not affected by the rela- tive composition of the two ingredients in the blend (Salameh et al., 2006); however, complete dissolution of both ingredients in a binary blend held at the RH 0mix will occur only at the eutonic composition (Seinfeld & Pandis, 1998). Caking of food powders is a common problem that occurs during processing, handling, and storage and can contribute to reduced product quality and functionality, lumps, agglomeration, poor rehydration and Food Research International 45 (2012) 369–380 Abbreviations: RH, relative humidity; RH 0 , deliquescence point of an individual crystalline ingredient; RH 0mix , deliquescence lowering point of a blend of crystalline ingredients; N, sodium chloride; S, sucrose; SiD, silicon dioxide; CSi, calcium silicate; CSt, calcium stearate. ⁎ Corresponding author. Tel.: + 1 765 494 9111; fax: + 1 765 494-7953. E-mail address: mauer@purdue.edu (L.J. Mauer). 0963-9969/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2011.10.037 Contents lists available at SciVerse ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres