Microencapsulation of flax oil with zein using spray and freeze drying
Introduction
There has been a growing interest in research, development and commercialization of functional food ingredients over the past decade (Day et al., 2009, Shahidi, 2009). The addition of ω-3 and ω-6 polyunsaturated fatty acids (PUFA) to functional food ingredients and their consumption in dietary supplements have experienced significant increases (O’Brien, 2009, Sanguansri and Augustin, 2007). These fatty acids have been associated with a variety of health benefits, such as reducing the risk of coronary heart diseases, hypertension, arthritis, and immune response disorders (Rubio-Rodríguez et al., 2010). Fish oil, flax oil, and more recently, algae oil, are the most commonly used sources of ω-3 fatty acids most commonly used (Rubio-Rodríguez et al., 2010). However, one of the major drawbacks of oils containing a high amount of PUFA is their rapid oxidation, which involves the formation of toxic products such as peroxides or undesirable off-flavor compounds (O’Brien, 2009).
The use of encapsulation technologies to retard or avoid the oxidation of these oils has been reported and it has drawn considerable attention in the food industry (Ahn, Kim, Lee et al., 2008, Ahn, Kim, Seo et al., 2008, Klaypradit and Huang, 2008, Klinkesorn and McClements, 2009, Kolanowski et al., 2009, Omar et al., 2009, Partanen et al., 2002, Ré, 1998, Sanguansri and Augustin, 2007, Velasco et al., 2006). Some of the commonly used coating materials for the microencapsulation of ω-3 fatty acids are proteins, lipids, polysaccharide gums and cellulose (Sanguansri & Augustin, 2007). However, the selection of an adequate coating material for PUFA depends on its capacity to stabilize and protect the oil from degradation during processing and storage conditions, and it also has to be approved for food use. Zein, the prolamin fraction of corn protein (Shukla and Cheryan, 2001), has long been recognized for its coating ability for the encapsulation of bioactive compounds (Hurtado-López and Murdan, 2006, Jónsdóttir et al., 2005, Liu et al., 2005, Parris et al., 2005, Zhong and Jin, 2009, Zhong, Jin, Xiao et al., 2008) and fish oil (Zhong, Tian, & Zivanovic, 2009). For lipid compounds, zein has been shown to adsorb fatty acids and produce zein sheets (Padua & Wang, 2009). Zein can also bind and enrobe lipids, keeping them from deteriorative changes. In addition, the antioxidant activity of zein has been studied in powder systems (Matsumura et al., 1994, Wang, Fujimoto et al., 1991, Wang, Miyazawa et al., 1991).
Flax oil is a good source of PUFA, especially linolenic acid (C18:3 ω-3) (Bozan & Temelli, 2002). However, this oil has low stability and high susceptibility to oxidation. Encapsulation of flax oil using zein as a coating material has not been reported in the literature. Therefore, the objective of this study was to evaluate the ability of zein to act as a microencapsulating agent for flax oil using spray and freeze drying, considering that Canada is the world’s largest flax producer. The effects of the concentrations of zein and flax oil were studied using Response Surface Methodology, Central Composite Design – Face Centered, in order to optimize the formulation to produce flax oil microcapsules. The microcapsules were analyzed for their microencapsulation efficiency, flowing properties and morphological characteristics.
Section snippets
Materials
Cold pressed and unrefined flax oil was obtained from a local market, Gold Top Organics (Edmonton, AB, Canada). Corn zein (NF F4400C Non-GMO/IP grade) was supplied by Freeman Industries LLC (Tuckahoe, NY, USA). Food grade anhydrous ethyl alcohol was purchased from Commercial Alcohols Inc. (Toronto, ON, Canada). Petroleum ether and hexane were acquired from Fisher Scientific (Ottawa, ON, Canada).
Fatty acid composition of feed flax oil
Linolenic acid (C18:3 ω-3) was the major fatty acid (59.85 ± 0.39 g/100 g), followed by oleic (C18:1) (16.04 ± 0.21 g/100 g), linoleic (C18:2) (15.86 ± 0.06 g/100 g), palmitic (C16:0) (5.17 ± 0.03 g/100 g) and stearic (C18:0) (3.07 ± 0.08 g/100 g) acids. The fatty acid composition of the flax oil was in agreement with the profiles previously reported by Bozan and Temelli (2002). The stability of the encapsulated flax oil and the changes in fatty acid composition over storage are the subject of
Conclusions
Flax oil microcapsules were produced using zein as a coating material by spray and freeze drying. Using the Central Composite Design – Face Centered, it was demonstrated that particle yield and microencapsulation efficiency were affected by the zein:flax oil ratio in the spray drying process. Particle yield was significantly affected by the zein concentration (linear, p = 0.008), while microencapsulation efficiency was affected by flax oil concentration (linear, p = 0.013). Furthermore, the
Acknowledgment
The authors are grateful to Alberta Agricultural Research Institute for financial support of this project.
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