Date

2022-1

Author

Arğün, Sinem

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Microfluidization has been gaining popularity as a size reduction process in recent years. Its application in food research has shown that reducing the particle size of food materials not only alters their structure but also develops their functional properties. Therefore, microfluidization technique was used in this study for olives to change the cell wall structure and decrease the size of oil droplets. The aim of this study is to develop a new value-added product (an olive powder) from olive with enhanced functionality and to characterize physical and stability properties of olive powder in water suspensions and to compare it with regular olive powders produced conventionally freeze drying. In the study, green, black and raw olive powders were produced with freeze drying following microfluidization at 1200 bar. Control samples were prepared without microfluidization. Peroxide values, antioxidant activity (DPPH assay), total phenolic content, lipolysis (free fatty acid content), color, moisture content and microscopic analysis (Scanning Electron Microscopy) were conducted for the powder samples. Stability measurements through Turbi Scan and rheological characterization were performed for the suspensions prepared from the powders at different concentrations. When the effect of microfluidization is investigated, it can be concluded that antioxidant activity was not affected significantly for all olive powders while total phenolic content decreased for green and raw olive powders. Among all olive powders, raw olive gave the highest antioxidant activity and phenolic content. In addition, raw olive gave the best results in peroxide values and free acidity experiments. In the microscopic analysis of olive powders, SEM images revealed that microfluidization results in finer particles which are self-encapsulated by trapping the oil droplets inside of the olive. Stability analysis and rheological measurements of olive powder suspensions showed that microfluidization process is a good way to obtain more stable suspensions having higher water holding capacity. Herschel-Bulkley model was found for the flow behaviors of olive powder suspensions. Microfluidized olive powder suspensions had higher elastic (G') and viscous (G'') moduli than unmicrofluidized ones because microfluidization produces more hydrophilic moieties and results in larger moduli values. To conclude, microfluidization technique helped to make the olive powder more stable compared to conventional olive powders.

Subject Keywords

Olive Powder, Microfluidization, Freeze Drying, Oxidation, Stability

URI

https://hdl.handle.net/11511/95453

Collections

Graduate School of Natural and Applied Sciences, Thesis