University of Liege / University of Agricultural Sciences and Veterinary Medicine, Liege / Cluj-Napoca, Belgium / Romania
Doctorat en sciences agronomiques et ingénierie biologique
[en] halva ; tahini ; colloidal stability ; oxidative stability ; near infrared spectroscopy ; rheology ; particle size distribution
[en] Prior to the experimental part of this work, a literature review related to the aim of this thesis was realized. Firstly, it describes the balanced nutritional composition of sunflower seeds and their applications as food industry raw materials. It follows the state of the art of sunflower halva manufacturing with emphasis on the main issues encountered during processing. Consequently, as the researches concerning sunflower halva type products are very limited, it was decided to consolidate the identified quality problems (i.e., oil separation problem and rancidity during storage) background by given basic principles concerning foods physical properties (e.g., rheology, particle size distribution), as well as food products colloidal and oxidative stability basics. Moreover, fundamentals of NIR spectroscopy and chemometrics give the background for a proposal of an alternative nondestructive and rapid method to assess lipid oxidation in sunflower halva type products.
Firstly, the experimental part of this thesis focuses on comparing the physico-chemical properties of different particle size tahini prototypes including also the industrial reference in order to understand tahini behavior and structure. Studying the physico-chemical properties of different granulometries tahini samples allows, for the first time, the prediction of a schematic sunflower tahini structure – knowledge needed to understand physical and oxidative instability for this type of products. Moreover, the experimental work aimed to assess the influence of particle size distribution, storage time and temperature on sunflower tahini colloidal and oxidative stability. Furthermore, during this work there were developed two new methodologies, a laser diffraction method to determine particle size distribution of sunflower tahini, as well as a near infrared rapid method coupled with chemometrics to assess in situ sunflower tahini oxidative status.