Effects of Monoglyceride Content and Acyl Chain Length on Crystal Structure and Physical Properties of Cottonseed Oil Stearin

The investigation aimed to elucidate the influence of monoglyceride (MGs) content and acyl chain length on the crystal structure and physical properties of cottonseed oil stearin/monoglyceride (COS/MG) blends. Three MGs with distinct acyl chain lengths were investigated at five different concentrations. Compared to pure COS, the addition of MGs facilitated earlier nucleation in the samples. MGs with acyl chains structurally similar to those triglycerides (TGs) in COS promoted COS crystallization, whereas MGs with less similar acyl chains inhibited the crystallization. Regarding the crystal structure, the blends containing MGs with longer acyl chains exhibited a higher proportion of sub-α crystals. Moreover, MGs actively participated in the formation of lamellar structures in the COS. When the acyl chains of MGs closely resembled those high-melting TGs in COS, MGs intercalated into these TGs lamellae, resulting in mixed lamellar arrangements. Modifications to the crystal structure consequently altered the crystal micromorphology. In the COS/MG blends, the MGs initially crystallized to serve as nucleation sites, leading to the subsequent crystallization of COS and generating numerous smaller crystals than those in pure COS. Increasing the MGs content progressively influenced the micromorphology, which was ultimately dominated by MGs crystals. This increase of MG content enhanced solid fat content (SFC), the mean crystal size, fractal dimension, and hydrogen bonding interactions, forming a denser crystalline network characterized by increased hardness and improved oil binding capacity. At identical MG concentrations, differences in the micromorphology, fractal dimension, and SFC of the COS/MG blends led to distinct physical properties. This study would provide theoretical insights to support the formulation and development of COS-based plastic fats.