Effect of Relative Humidity on Oxidation of Flaxseed Oil in Spray Dried Whey Protein Emulsions

Abstract

Flaxseed oil was emulsified in whey protein isolate (WPI) and spray-dried. Powder characteristics and oxidative stability of oil at relative humidities (RH) from RH approximately 0% to RH 91% at 37 degrees C were analyzed. Oil droplets retained their forms in drying and reconstitution, but the original droplet size of the emulsion was not restored when the powder was dispersed in water. The particles seemed to be covered by a protein-rich surface layer as analyzed by electron spectroscopy for chemical analysis (ESCA). Oxidation of flaxseed oil dispersed in the WPI matrix was retarded from that of bulk oil but followed the same pattern as bulk oil with respect to humidity. A high rate of oxidation was found for both low and high humidity conditions. The lowest rate of oxidation as followed by peroxide values was found at RH 75%, a condition that is likely to diverge significantly from the monolayer moisture value. A weak baseline transition observed for the WPI matrix in a differential scanning calorimetry (DSC) thermogram suggested a glassy state of the matrix at all storage conditions. This was not consistent with the observed caking of the powder at RH 91%. Scanning electron microscopy (SEM) images revealed a considerable structural change in the WPI matrix in these conditions, which was suggested to be linked with a higher rate of oxygen transport. Possible mechanisms for oxygen transport in the whey protein matrix under variable RHs are discussed.

Development of stable flaxseed oil emulsions as a potential delivery system of ω-3 fatty acids

“…Similarly, Kuhn and Cunha (2012) reported about 41.70 % increase in PV of free flaxseed oil, which increased from 0.420 to 0.714 meq peroxides/kg oil during 30 days of storage. The present results are in agreement with Karaca et al (2013), Partanen et al (2008) and Grattard et al (2002), who reported improved oxidative stability of flaxseed oil (in powder form) encapsulated by different proteins. Peroxide value of flaxseed oil in emulsions (prepared with 7.5-12.5 % WPC) remained well within the limit of up to 15 meq peroxide/kg oil under the Codex Alimentarius Commission (1999) standard for cold-pressed and virgin oils (Choo et al 2007).…”

Microencapsulation of babassu coconut milk

“…Comparing Figures 1a and 1b, it can be observed that hygroscopicity values were inversely proportional to the powder moisture content, i.e., products with lower moisture were more hygroscopic. This same behavior was reported by Tonon, Brabet and Hubinger, (2008) and Ferrari et al (2012) index, in triplicate (PARTANEN et al, 2008). The oil fraction was extracted from the powder samples with iso-octane/ isopropanol, and it was homogenized with a chloroform/ methanol (7:3) mixture, iron chloride, and an ammonium thiocyanate solution.…”

Interfacial protein engineering for spray-dried emulsions – Part II: Oxidative stability

“…Better oxidative stability at high RH has also been reported previously, when powders have contained protein in addition to maltodextrin or other carbohydrate constituents or have had only protein as wall material in spraydrying (Klinkesorn, Sophanodora, Chinachoti, McClements, & Decker, 2005) or freeze-drying (Ponginebbi, Nawar, & Chinachoti, 2000). Flaxseed oil encapsulated in whey protein using spray-drying had the lowest oxidation rate at RH 49% and 75% (Partanen et al, 2008). Correspondingly, conjugated linoleic acid encapsulated in whey protein concentrate/maltodextrin by spray-drying had the best stability at a w 0.821 (Jimenez et al, 2006), whereas dried emulsions prepared only with carbohydrates as wall material either by spray-drying (Drusch, Serfert, & Schwarz, 2006;Partanen et al, 2005) or by freeze-drying (Grattard, Salaün, Champion, Roudaut, & Le Meste, 2002) gave opposite results.…”

“…1 and 2). The commercial sunflower oil used in this study was relatively stable, which may explain lower impact of encapsulation than found previously with more oxidation sensitive oils, such as fish oil or flaxseed oil (Klinkesorn et al, 2005;Partanen et al, 2008). The effect of the RH on the oxidative stability of the bulk sunflower oil was low as expected because of the hydrophobic nature of the oil.…”

“…Our previous studies suggested a major difference between protein versus carbohydrate wall materials with respect to their ability to protect oil from oxidation at humid conditions (Partanen, Hakala, Sjövall, Kallio, & Forssell, 2005;Partanen et al, 2008). Proteins are more likely than carbohydrates to interact with lipids, based on their surface active properties, which allow them to serve as emulsifiers that can form an interfacial layer around oil droplets.…”