Short-chain fatty acids refer to acids with carbon chain length less than 6, also known as volatile fatty acids, including acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, which can bring many beneficial functions to the body, such as enhancing intestinal barrier function, improving immune function, regulating blood sugar, and inhibiting obesity.

    Starch-lipid complex is a type V complex formed by hydrophobic interaction between amylose and lipids, and belongs to (type 5 resistant starch RS5), which is of great significance to human health. RS5 has a positive effect on the regulation of intestinal flora and metabolites in vivo and in vitro, reducing intestinal pH, increasing the production of (short-chain fatty acids SCFAs), promoting the growth of beneficial bacteria and reducing the number of harmful bacteria.

    Nutritional properties of starch-lipid complex

    Starch and lipids form a single helical structure and specific function through hydrophobic interaction under certain conditions, such as the natural starch-lipid complex in corn particles, the complex formed during cooking and food processing. Starch and lipids are both important energy sources and essential nutrients for the human body, and they have specific metabolic pathways and physiological functions in the human body. When starch and lipids form a stable single helix structure, they will have functional characteristics such as thermal stability, anti-digestibility, and nutritional characteristics such as controlling obesity, regulating blood sugar, regulating intestinal flora, and protecting the intestinal environment.

    Studies have shown that starch-saturated fatty acid complex can reduce the adverse effects of saturated fatty acids on intestinal flora, improve the relative abundance of beneficial bacteria and promote the balance of intestinal flora. It has functional properties such as thermal stability, anti-digestibility and nutritional properties such as controlling obesity, regulating blood sugar, regulating intestinal flora and protecting intestinal environment. It has the potential to overregulate fermentative metabolites and intestinal microbial composition and improve colon health.

    According to the study in this chapter, when starch is combined with saturated fatty acids with different carbon chain lengths, as the fatty acid chain length increases, the fewer complexes are formed, and the CI value also decreases. The starch-saturated fatty acid complex had similar and slow fermentation rates throughout the fermentation process, and the gas production at the fermentation end point was basically the same, both of which were 12.2mL. The concentration of acetic acid and propionic acid was higher than that of HAMS and DS, and the concentration of butyric acid was higher than that of FOS. However, the fermentation characteristics such as gas production and SCFAs production concentration had no significant relationship with the length of fatty acid carbon chain in the complex. By 16SrRNA sequencing, it was found that the effects of starch-saturated fatty acid complex and its corresponding saturated fatty acid complex on the bacterial community structure were significantly different after 24h fermentation, and the bacterial community structure of all starch-containing samples, samples 12C and 14C, and samples 16C and 18C showed relatively similar phenomena, and the differences among them were also large. The results of PCA analysis showed that the starchy saturated fatty acid complex was far away from SFAs and closer to HAMS and DS, and significantly increased the relative abundance of Roseburia, which may be related to the fact that the starchy saturated fatty acid complex can promote the high butyric acid concentration of 28~33mM. The experimental results showed that the fatty acid chain length had little effect on the in vitro fermentation characteristics of RS5, and the starch-saturated fatty acid complex had a relatively slow fermentation rate. However, in terms of bacterial community structure, different starch-saturated fatty acid complexes had different effects on the bacterial community structure. Among them, the bacterial community structure of sample SL-18C was very similar to that of DS. They both promote the growth of beneficial bacteria, especially probiotics that produce butyric acid.