Flavour retention in sodium caseinate e Carboxymethylcellulose complex coavervates as a function of storage conditions T. Koupantsis, A. Paraskevopoulou * Laboratory of Food Chemistry and Technology, School of Chemistry, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece article info Article history: Received 30 November 2016 Received in revised form 15 February 2017 Accepted 2 March 2017 Keywords: Complex coacervation Flavour encapsulation Sodium caseinate Retention Glycerol Tannic acid abstract Flavour retention in freeze-dried complex coacervates prepared with sodium caseinate and carboxy- methylcellulose was followed over storage for 20 days at two relative humidities (0 and 54%) and temperatures (25 and 45  C). Beta-pinene was used as a model volatile compound. Avrami’s equation mathematical model was equipped to describe the correlation between release rate and storage time. In general, volatile’s retention in the dried powder was considerably affected by the storage conditions along with the wall material characteristics (e.g. protein/polysaccharide ratio, presence of reticulating agents, i.e. glycerol and tannic acid) as a greater rate of release was observed at high relative humidity (RH) and temperature values and low biopolymer addition levels. Moreover, the Arrhenius activation energy E a was reduced by increasing RH from 0 to 54% while it got either positive or negative values indicating that the release of b-pinene was either related or not to temperature. Rehydration of dried powders in high humidity air conditions and the induced reduction of their effective surface area may account for the decrease of b-pinene retention. Glycerol addition resulted in higher retention of the volatile compound in the powder stored at low RH and temperature (0% RH, 25  C) as compared to other storage conditions, which was further confirmed by the remarkable increase of half-life release t 1/2 from 29 to 9303 days, as this was calculated from the Avrami’s equation mathematical model. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Flavour encapsulation is a common way to satisfy the demand for improved flavour performance and shelf-life stability in many food systems. In general, encapsulation provides protection for a flavour by reducing losses in flavour intensity and quality through prevention of degradation (due to exposure to light or oxygen) or retardation of its evaporation. Additionally, encapsulation provides a means for controlled release, as well as conversion of a liquid flavour into a solid powder. Various techniques (e.g. spray-drying, spray-chilling, melt in- jection, etc.) have been developed to perform encapsulation of a flavour. Between them complex coacervation is considered partic- ularly suitable for the entrapment of sensitive flavour materials within a protective matrix. This process commonly occurs between biopolymers with opposite electrical charges (i.e. proteins and polysaccharides). It is accomplished by phase separation (biopolymer-rich phase vs. phase depleted in both biopolymers) and the successive deposition of the newly formed coacervate phase around the so-called “core material” (Gouin, 2004) by inducing media modifications (i.e. pH adjustment and/or protein/ polysaccharide ratio) (Paraskevopoulou & Kiosseoglou, 2013). Various combinations of proteins with polysaccharides have been employed for flavour encapsulation by complex coacervation including gelatin/gum arabic for mustard seed essential oil, laven- der oil, peppermint oil, turmeric oleoresin, (Dong et al., 2008; Peng et al., 2014; Xiao, Liu, Zhu, Zhou, & Niu, 2013; Zuanon, Malacrida, & Telis, 2010), soy protein isolate e gum arabic for sweet orange oil, (Jun-xia, Hai-yan, & Jian, 2011), whey protein concentrate with gum arabic or mesquite gum for chia essential oil, orange oil flavour or lemon juice flavour (Rodea-Gonz alez et al., 2012; Weinbreck, Minor, & de Kruif, 2004). Additionally, milk proteins (i.e. sodium caseinate (CN) and whey protein isolate (WPI)) and carboxymeth- ylcellulose (CMC) have been successfully used in a previous study to stimulate the encapsulation of b-pinene by complex coacerva- tion (Koupantsis, Pavlidou, & Paraskevopoulou, 2014). The addition of reticulating agent, i.e. glycerol and tannic acid, led to the prep- aration of microcapsules with either enhanced (in the case of glycerol) or unaffected (in the case of tannic acid) encapsulation * Corresponding author. E-mail address: adparask@chem.auth.gr (A. Paraskevopoulou). Contents lists available at ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd http://dx.doi.org/10.1016/j.foodhyd.2017.03.006 0268-005X/© 2017 Elsevier Ltd. All rights reserved. Food Hydrocolloids 69 (2017) 459e465