Lipid shortenings are usually composed of a mixture of oils from a number of sources such as un-hydrogenated, partially, and fully hydrogenated oils, as well as emulsifiers, and other additives. Canola, cottonseed, lard, palm, soybean, and tallow are typical edible oils used for the production of shortenings. Because of the relatively high number of influencing factors, it is quite challenging to understand the effect of molecular composition, processing conditions, additives, and emulsifiers on physical functionality (Humphrey, Moquin, and Narine, 2003). One of the significant components in shortenings, margarine, and specialty products are plastic vegetable oils and fats. It is well known that the solid-like behavior of plastic fats is due to the presence of a fat crystal network (Litwinenko et al., 2002). In terms of the rheological analysis, shortenings are semi-plastic materials that are capable of creating the desirable textural properties in fatty-based foods (Hakimzadeh et al., 2020). Moriya et al. investigated the effect of solid fat content on the G′ and G″ of margarine and found that the G′ and G″ increased linearly with the increase in the solid fat content in a double-logarithmic plot, independent of the type of margarine (Moriya, Hasome, and Kawai, 2020). Bakery shortening has the ability to impart texture, tenderness, and taste to baked products. Shortening functionality depends on crystallization behavior, melting profile, and viscoelastic properties (Saghafi et al., 2018). Texturizing a shortening to improve its plasticity is usually achieved by a chilling process in which the melted fat is rapidly cooled in a chilling unit. Crystallization under shear not only improves the plasticity and texture of the mixture, it also removes the heat of crystallization from the sample (Ahmadi and Marangoni, 2009; Erickson, 1990). The nature of the crystal network, including its spatial distribution, and the number, size, and shape of its constituent microstructural elements can be dramatically altered by changes in crystallization conditions (Litwinenko et al., 2002). The effect of cooling in a surface scraping heat exchanger system on dynamic fat crystallization and physicochemical properties of puff pastry shortening was studied. The results revealed that crystallization temperature affected the rheological properties as well as the hardness of the produced shortenings (Nguyen et al., 2021). The scraped surface heat exchanger consists of a steel shaft rotating in a tube that is cooled externally by boiling ammonia. The rotating shaft is fitted with scraper blades which at high rotation speeds are pressed against the cooled inner surface by centrifugal force (Haighton, 1969). To minimize the post-crystallization phenomenon in order to ensure the development of the proper crystal structure and desired plasticity, the cooling and working stages must be prolonged (Alexandersen, Ghazani, and Marangoni, 2020; Masuchi et al., 2014). Accessing the desirable texture and functionality of shortenings could be accomplished by some modification processes, including hydrogenation, fractionation, blending, and chemical or enzymatic interesterification of fats and oils (Saghafi et al., 2018). Hydrogenation of unsaturated fatty acids in edible oils allows for the conversion of liquid oils into semi-solid or solid fats. These fats are characterized by altered melting and textural characteristics and a higher oxidative stability (Litwinenko et al., 2002). Ahmed et al. reported the physiochemical properties of a model shortening. Moreover, the rheological properties of soybean oil, as well as partially and fully hydrogenated soybean oil, were determined (Ahmed et al., 2020).
Rheological properties and texture in bakery shortening and margarine directly affect the quality aspects, physical appearance, sensory evaluation, and texture of baked goods as finished products (Saghafi et al., 2019). A comparison of lipid shortening application as a function of molecular ensemble and shear showed that changes in melting and crystallization behavior of shortening systems could be significantly affected by manipulating the amounts of triacylglycerols containing specific fatty acids (Humphrey and Narine, 2004).
Investigating the effect of the crystallization regime on the macroscopic rheological and sensory properties of shortening was the aim of this study. Through working on a fixed formulation, it was attempted to determine the extent of the influence of crystallization process parameters on the final shortening texture, as well as storage and elastic attributes. The effects of the cooling rate, agitation, and filling temperature on the functional properties of shortenings including adhesiveness, hardness, plasticity, and homogeneity as well as the storage modulus (G’) and loss modulus (G’’) were assessed. Although there have been few studies in which the fat mixture composition with or without considering an isolated crystallization factor has been investigated, the main focus of the current work was the crystallization process parameters and their interactions, which have never been investigated in similar research.