Formation and Microstructures of Whipped Oils Composed of Vegetable Oils and High-Melting Fat Crystals

This paper reports the experimental results of processes used for the formation of whipped oils composed of vegetable oils (salad oil) and high-melting fat crystals [fully hydrogenated rapeseed oil rich in behenic acid (FHR-B)]. No emulsifier was added to form this whipped oil. Microprobe FT-IR spectroscopy, synchrotron radiation microbeam X-ray diffraction (SR-mu-XRD), polarized optical microscopy, and differential scanning calorimetry (DSC) were employed to observe fine fat crystal particles of the most stable polymorph of beta (beta-fat crystal), FHR-B, and their adsorption at the air-oil surface before, during, and after the formation of the whipped oil. The results obtained revealed the following: (1) The preparation of an organogel composed of salad oil and small fibrous beta-fat crystals using a special tempering procedure was a prerequisite for forming whipped oil. (2) The beta-fat crystals were adsorbed at the air-oil surface to encapsulate the air bubbles during the formation process of whipped oil. (3) The values of overrun of the whipped oil reached > 200 % after an aeration time of 30 min at 20 A degrees C. (4) The SR-mu-XRD experiments demonstrated that the lamellar planes of the beta-fat crystals near the air-oil surface were arranged almost parallel to the air-oil surface plane. The present study provides the first evidence that tiny fat crystal particles may cause aeration in liquid oils without the addition of other whip-assisting substances such as emulsifier crystals.