Every approach to substitute another fat for trans-containing partially hydrogenated fats in product applications is doomed to fail if one tries only to match the properties of the fat. With such a substitution only a limited set of the physical properties can be matched. Consequently the substitution process has to be based on a deep understanding of the application at hand. Consideration should also be given to how far it is acceptable that the change in fat composition is accompanied by a perceivable change of the product.
Starting from the simple end, chemical stability is based mainly on the absence of PUFA. Therefore alternative high stability oils, as used in frying applications, should also have a limited amount of PUFA. Another condition related to chemical deterioration is related to products containing enzymes, such as those present in herb preparations. Products containing herbs and significant amounts of medium-chain fatty acids such as lauric or myristic acid tend to develop a soapy taste over time through lipolysis.
In applications that rely on partially hydrogenated fats for structure, three aspects of the TFA are key to their success. These are the excellent crystallization behavior, the steep melting profile and the reliable formation of small crystals with the consequent high structuring effectiveness of the solid material. Consequently, successful substitutes will in the first place need to form small crystals to maintain product structure and stability. For manufacturing processes under more or less quiescent conditions with relatively low supersaturation, as for example found for bouillon cubes, it is necessary that the crystallization from a slurry to a solid mass proceeds in a comparable timeframe to the TFA-containing reference. Crispness and form stability of the product and the absence of stickiness are important attributes in the further manufacturing or packing of products.
Manufacturing processes with high supersaturation and high shear are related to high throughput and intrinsically to polymorphic transitions. These applications, such as spreads, necessitate that the substituting fat undergoes the polymorphic transition quickly. TFA containing fats undergo the polymorphic transition very quickly, often in less than 100 s. As the throughput of the manufacturing process scales inversely with the transition time, unless the hardware configuration of the manufacturing equipment is changed, dramatic increases of the transition time are prohibitive. As the final consumer remains king, obviously no substitution scenarios should yield a deterioration of properties perceived by the consumer, such as mouthfeel.
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