Crystallization Kinetics in Industrial Fats: The Effect of Substituting Stearic Acid for Palmitic Acid in Fats Containing Lauric Acid

Abstract

This study explores the crystallization kinetics in multicomponent and lauric acid-containing fat blends. The role of the dominating saturated fatty acid (palmitic versus stearic acid) was explored. The blends contained predominantly three main triglyceride groups: trisaturated triglycerides (H3), trisaturated/medium-chain triglycerides (H2M), and monounsaturated triglycerides (H2U). Each group contains more than one triglyceride. This grouping was used as a compositional framework to compare trends across model and commercial systems. The impact of H3 content (8% vs 4%) and dominant saturated fatty acid (palmitic versus stearic acid) on crystallization was investigated using differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS/WAXS). To further our understanding of the crystallization kinetics in ternary mixtures, symmetrical academic replicates (true ternary blends) PPP-PLaP-POP and SSS-SLaS-SOS in rapeseed oil were studied. All samples were analyzed during cooling and short isothermal holding to capture initial differences in mixed crystal formation/cocrystallization. Results revealed a multistep crystallization process, with commercial blends displaying a long-persisting α-phase coexisting with β′ and β phases. The multiple β′ phases differed in composition and dissolution temperature. In contrast, academic blends showed a short-lived α-phase followed by late recrystallization into the β phase. Blends containing a higher amount of H3 triglycerides (8%) exhibited a strong recrystallization into a β phase, indicating that the H3 content exceeded the limit for H3 inclusion into a mixed crystalline phase with H2M and other groups. The transition into β was slowed down in the S-based systems. Overall, the H3 level played a greater role in the P-based systems with no β phase in C4-P─the P-based commercial system containing 4% of H3. This renders the factors dominant saturated fatty acid and H3 level interrelated. The academic blends demonstrated relatively simple crystallization and melting behavior with a drastic difference to the commercial systems observed in SAXS/WAXS. These findings emphasize the difficulty in simplifying the triglyceride composition in fat crystallization. Still, breaking down industrial fat crystallization into the main triglycerides proved to be a useful approach to further our understanding.