Biobased colloids for food preservation and fragrances microencapsulation

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Wang, Xue
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Electronic thesis
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Colloids exhibit properties intermediate between suspensions and solutions therefore enabling their unique applications in foods, pharmaceuticals, cosmetics, coatings, water treatment and more. Emulsions are one of the most important type of colloids. As meta stable dispersions, emulsions must be stabilized with emulsifying agents such as surfactants to introduce kinetic stability to combat the thermodynamic instability. As the use of synthetic surfactants has drawn increasing concerns for their environmental and health implications, biosurfactants, especially sophorolipids and their derivatives, stand out due to their unique properties such as the ability to be produced at high titers (>300 g/L), antimicrobial activities and low toxicity. The first portion of the thesis is based on the development of biobased colloidal systems using sophorolipid derivatives for food preservation. Sophorolipid butyl ester (SLBE), which is naturally derived and has the potential to both stabilize o/w emulsions and provide antimicrobial activity, is used as the surfactant for preparing hydrocolloid-based coatings/films for potential applications of food packaging. The interactions of SLBE with different oil (oregano/olive oil) mixtures and biopolymers [γ-poly(glutamic acid), γ-PGA, and chitosan, CH] was investigated. During this study, it was revealed that SLBE stabilizes o/w emulsions over 30 days with oil concentrations at least 10 times that of the surfactant. Furthermore, CH is a highly effective emulsion stabilizer with apparent favorable interactions with SLBE. These promising results of SLBE-CH interactions can be used as a platform for developing antimicrobial films/coatings for food preservation. The second portion of the thesis is based on the development of oil encapsulation systems from biobased and safe precursor molecules. Microencapsulation is widely used to encapsulate solid, liquid, and gaseous substances to prevent evaporation of volatile compounds and to achieve controlled release; however, there is increased pressure on microcapsule manufacturers to develop encapsulation systems that follow green chemistry principles and use safe biobased materials. Here, we describe interfacial polymerization encapsulation of a fragrance oil. Diphenolic acid (DPA), prepared from cellulose-derived levulinic acid and phenol, was used as a replacement for bisphenol-A. The resulting diepoxy resin DGEDP-esters were incorporated in the fragrance oil phase and, upon reaction with the aliphatic diamine hexamethylenediamine (HMDA) or chitosan oligosaccharides (COS), formed capsule walls. The emulsifiers, gum arabic (GA), polyvinyl alcohol, sophorolipid butyl ester and polyvinyl pyrrolidone/polyquaternium-11 cosurfactant system were investigated to determine their ability to support emulsion formation and interfacial polymerizations. GA at 2.5 wt% stands out among the four emulsifiers as it provides both good emulsion stability and capsule formation. The effect of DGEDP-methyl ester/HMDA ratios on various capsule properties was studied. The preferred HMDA concentration is 1 wt% since there is a sufficient concentration of HMDA to react with DGEDP-methyl ester at interfaces to create capsule walls with a relatively high crosslinking density without bridging of oil capsules to form aggregates. Furthermore, DGEDP-esters with various structures were synthesized and used as oilsoluble monomers in interfacial polymerizations to study their structure-property relationships. Use of DGEDP-ME and DGEDP-MG led to the formation of compactly crosslinked capsules walls with high microencapsulation efficiency (EE > 95%). Besides, COS cured capsules exhibit good acid stability compared to HMDA cured capsules. These observations demonstrate that DGEDPester/HMDA and DGEDP-ester/COS are promising biobased alternatives for isocyanate and formaldehyde approaches for oil encapsulation.
August 2021
School of Science
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Rensselaer Polytechnic Institute, Troy, NY
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