Abstract
In lipid-based food products, fat crystals are used as building blocks for creating a crystalline network that can trap liquid oil into a 3D gel-like structure which in turn is responsible for the desirable mouth feel and texture properties of the food products. However, the recent ban on the use of trans-fat in the US, coupled with the increasing concerns about the negative health effects of saturated fat consumption, has resulted in an increased interest in the area of identifying alternative ways of structuring edible oils using non-fat-based building blocks. In this paper, we give a brief account of three alternative approaches where oil structuring was carried out using wax crystals (shellac), polymer strands (hydrophilic cellulose derivative), and emulsion droplets as structurants. These building blocks resulted in three different types of oleogels that showed distinct rheological properties and temperature functionalities. The three approaches are compared in terms of the preparation process (ease of processing), properties of the formed systems (microstructure, rheological gel strength, temperature response, effect of water incorporation, and thixotropic recovery), functionality, and associated limitations of the structured systems. The comparative evaluation is made such that the new researchers starting their work in the area of oil structuring can use this discussion as a general guideline.Practical applicationsVarious aspects of oil binding for three different building blocks were studied in this work. The practical significance of this study includes (i) information on the preparation process and the concentrations of structuring agents required for efficient gelation and (ii) information on the behavior of oleogels to temperature, applied shear, and presence of water. This information can be very useful for selecting the type of structuring agents keeping the final applications in mind. For detailed information on the actual edible applications (bakery, chocolate, and spreads) which are based on the oleogel systems described in this manuscript, the readers are advised to refer our recent papers published elsewhere. (Food & Function 2014, 5, 645–652 and Food & Function 2014, 5, 2833–2841).
Highlights
The functionality and desirable texture properties of commonly consumed lipid-based food products are governed by the underlying colloidal network of fat crystals that is responsible for trapping liquid oil into a 3D “gel-like” structure [1]
The building blocks can be formed by single component or mixture of components and the formation of building blocks could be achieved through direct method or indirect method in case of hydrophilic polymers where dried microstructures are created by stripping off the water from hydrated polymer solutions [2, 7, 8, 11,12,13]
It is widely used material in food and pharmaceutical fields as coating, glazing, and film forming agent [14, 15]. It is composed of a complex mixture of polar and nonpolar components consisting of long chain fatty acids, wax esters, fatty alcohols, and alkanes [16]
Summary
The functionality and desirable texture properties of commonly consumed lipid-based food products are governed by the underlying colloidal network of fat crystals that is responsible for trapping liquid oil into a 3D “gel-like” structure [1]. The oil structuring in this case is caused due to the limited solubility of high melting TAGs in the oil, upon cooling a hot solution, the TAG molecules crystallize out of the liquid broth forming crystals that interact together to form a network [2, 3]. This conventional way of oil structuring relying on the use of fat crystals or crystalline TAG molecules as building blocks suffers from two basic shortcomings. The building blocks can be formed by single component or mixture of components (mixed systems) and the formation of building blocks could be achieved through direct method (usually by dispersing gelator molecules in oil medium at high temperatures followed by cooling) or indirect method in case of hydrophilic polymers where dried microstructures are created by stripping off the water from hydrated polymer solutions [2, 7, 8, 11,12,13]
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