Browsing by Author "Gabucan, Ma.Heidi"

The literature review highlighted the principles of microencapsulation and spray drying, with emphasis on the properties of highly oxidizing oils, protein interface modification, and mechanism of lipid oxidation. The major aim of the research was to study the chemical and physical stability of microencapsulated flaxseed oil (MFSO) during storage under controlled relative humidity conditions (0%, 11%, 33%, 54%, and 75%RHs) and compare the results to bulk flaxseed oil (FSO). Microencapsulation was done by spray drying of non-cross linked (NCL) and transglutaminase cross-linked (CL) Na-caseinate FSO emulsions. Oxidative stability was examined through changes in physical and chemical properties of MFSOs and FSO as influenced by different RHs and storage periods. Chemical analyses were used to analyze the peroxide value (PV), fatty acid profile, γ-tocopherol, carotenoid and chlorophyll, phenolic compounds, and secondary oxidation products (hexanal and propanal) in MFSOs and FSO. Degree of secondary oxidation was determined by static headspace gas chromatography while the morphology of MFSOs was examined by scanning electron microscopy. Results showed that at dry condition (0%RH), surface lipids of CL and NCL MFSOs were unstable and more susceptible to oxidation after 17 weeks storage. Release of hexanal and propanal were higher for NCL than CL microencapsulated flaxseed oil which suggested that interfacial cross-linking of Na-caseinate was efficient. At high moisture condition (75%RH), MFSOs were oxidatively stable owing to their low PVs and structural transformation from porous structure to agglomerates or sticky form. High amounts of alpha-linolenic acid and γ-tocopherol were detected in FSO and MFSOs, and only minor losses occurred throughout storage period and under different RHs. FSO also contained considerable amounts of carotenoid and phenolic compounds but low in chlorophyll content. Oxidative stability of interface and matrix elucidated that humidity conditions considerably influenced the chemical and physical properties of CL and NCL MFSOs.