Microencapsulation of chia seed oil in chia seed protein-gum complex coacervates
Creators: name: Timilsena, Yakindra Prasad
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 300699
subject: Food sciences not elsewhere classified
classificationCode: 400405
subject: Food engineering

description: Plant-based polyunsaturated fatty acids (PUFAs)-rich oils, such as chia seed oil (CSO), are considered as healthier and more sustainable alternative of fish oil; however, their chemical composition, thermal properties and stability are important aspects to be considered before their real application in foods. In this thesis, physical, chemical and thermal characteristics of CSO, which is comprised of 64.4% alpha linolenic acid (ω-3), 21.5% of linoleic acid (ω-6) and about 10% saturated fatty acids, is studied in details. The presence of substantially high concentration of PUFAs in CSO makes it highly susceptible to oxidation, and hence requires an effective encapsulation matrix to preserve it from oxidative degradation during processing and storage. Therefore, this study proposed to microencapsulate CSO using complex coacervates derived from interaction of a protein and a polysaccharide. CSO, CPI and CSG were extracted from fresh chia seeds. Important physicochemical and functional properties of CSO, CPI and CSG were determined and the process of formation of CPI-CSG complex coacervates was systematically optimised. CPI-CSG complex coacervates produced using the optimised process were used as shell materials to encapsulate CSO and produce liquid microcapsules, which were converted to powder form using spray drying. These microcapsule powders were characterised in terms of total oil, surface oil and oil stability during storage. Finally, simulated (in vitro) digestion studies were carried out to compare the digestibility pattern of unencapsulated chia seed oil and microencapsulated oil.<br><br>It was found that CPI and CSG formed complex coacervates at the pH of 2.7 and CPI-to-CSG ratio of 6:1. Transglutaminase cross-linked complex coacervates had high thermal stability and showed negligible mass loss when heated to 280ºC and these complex coacervates were more thermally stable than CPI and CSG. Microencapsulation of CSO using CPI-CSG complex coacervates as shell material at a core-to-wall ratio of 1:2 followed by spray drying produced powdered microcapsules with 6 times higher oxidative stability compared to that of the unencapsulated CSO. The complex coacervation process developed in this study showed very high encapsulation efficiency (93.9%), exceptionally high microcapsule yield (∼98%) and very low surface oil (2.1%) indicating great potential of CPI-CSG complex coacervates as an encapsulant of PUFA-rich oils. <br><br>In vitro digestion study showed that majority of encapsulated CSO (38 to 84%) was released in gastric stage by hydrolysis of CPI by pepsin and much smaller amount of it (15 to 23%) was released in intestinal stage. In addition, the degree of lipolysis of CSO encapsulated in CPI-CSG matrix was the slowest indicating it to be the better shell material than CPI and CSG.<br><br>Using CPI, CSG and CSO as model protein, gum and oil derived from a single plant, this study provided new understanding of the optimal coacervation parameters, thermal stability of the resultant complex coacervates and their effectiveness in encapsulating and enhancing the stability of the oil. This study also provided insights into the fact that complex coacervates are able to deliver oil better to the targeted site (intestine); thus, are able to act as suitable delivery vehicles for lipophilic ingredients.