Effects Of Ultrasound On The Crystallization Behavior And Physicochemical Properties Of Fats

Palm oil is widely used in shortening and margarine production.In the producing process,the palm oil based blends may present some disadvantages,for example crystallization slow,crystal particles bulky,become harder after storage.As a new technique,ultrasound showed great potential in the aspect of oil crystallization.Pure fat and water-in-oil system were the objects of this paper,which were the imitators of shortening and margarine.The effect of ultrasonic power(47.5,95,190,and 285 W)and ultrasonic time(30,60,120,and 240 s)on the crystallization behavior were studied,together with the physicochemical properties of the crystallization production.The crystallization behavior included crystallization rate,microstructure,polymorphism and so on.The physicochemical properties include viscosity,hardness,oxidation stability,composition and the melting enthalpy of the crystallized productions.Firstly,the crystallization behavior of mixture(POL:POSt:SBO=49:33:18)was studied.Crystallization rate was improved after ultrasound.Crystal particles became smaller and more crystals appeared after the same time.Both ?? crystals and ? crystals were contented before and after HIU,and the content of ?? crystals improved after the appliance of HIU.Triglycerides were piled up based on double-chain-length which was known from long spacings of XRD.All these improving effects became stronger as the ultrasonic power became bigger and the ultrasonic time became longer.Secondly,the physicochemical properties of mixture were studied.Mixture samples became harder after HIU.Viscosity of mixture samples reduced.Improving effects became stronger as the ultrasonic power became bigger and the ultrasonic time became longer.The DSC results were consistent with the XRD results.Oxidation stability became worse.Besides,content of triglycerides reduced which may due to the discomposing of triglycerides.Finally,the crystallization properties of water-in-oil samples were studied.The results of the water-in-oil samples showed the same affecting trend as the pure fat system.Crystal particles became more and smaller,and the content of ?? crystals improved,the hardness became bigger,and the viscosity reduced after HIU.And all these improving effects became stronger as the ultrasonic power became bigger and the ultrasonic time became longer.But because of the water's addition,the hardness and viscosity values of water-in-oil samples were lower compared with samples of the pure fat under the same HIU conditions.