Microbiota fermentation characteristics of acylated starches and the regulation mechanism of short-chain fatty acids on hepatic steatosis

Starches acylated with specific short-chain fatty acids (SCFAs) have the potential to provide specificity in SCFA delivery. It is well documented that SCFAs are involved in lipid metabolism, but the underlying mechanism is still unclear. For characterizing the fermentation properties of acylated starches with various SCFAs in terms of SCFA production, three different acylated starches were prepared following the esterification of high amylose maize starch (HAMS) using acetic anhydride, propionic anhydride and butyric anhydride, respectively. Compared with HAMS, the gut microbiota fermentation of acetylated, propionylated and butylated starches specifically increased the production of acetic acid, propionic acid, and butyric acid, respectively, indicating that the introduced acyl group can be effectively released during the fermentation process. Furthermore, the utilization of these starches generated more total SCFAs, suggesting that they can be effectively fermented by the microbiota as a carbohydrate substrate. Study on an in vitro model of cultured rat hepatocytes indicated that either mixed SCFAs or butyrate play an important role in regulating lipid metabolism via activating AMPK and PPAR signaling pathways, implying the importance of butyrate in the improvement of lipid metabolism and accumulation. This study may provide further understanding of the individual function of the corresponding SCFA.

Manipulation of the internal structure of starch by propionyl treatment and its diverse influence on digestion and in vitro fermentation characteristics

High amylose maize starch (HAMS) and waxy maize starch (WMS) were modified by propionylation and their corresponding physicochemical characteristics, digestion and fermentation properties were studied. The results indicated that two new peaks related to methylene (2.20 ppm) and methyl (0.97 ppm) in the NMR spectrum were formed, indicating the occurrence of propionylation, and this was further confirmed by the formation of a characteristic absorption at 1747 cm^-1 in the FTIR spectrum. The propionylation led the modified starch having a lower electron density contrast between the crystalline and amorphous flakes, resulting in the formation of a more compact structure following the increased degrees of substitution (DS). The propionylated starch also had a higher thermal stability and hydrophobicity. These structural changes increased the content of resistant starch (RS) and reduced the predicted glycemic index. More importantly, the gut microbiota fermentation properties indicated that the propionylation of the starch can not only increase the yield of propionate, but also increase the concentration of total short-chain fatty acids (SCFAs). This study highlights a new approach to significantly enhance the RS content in starch, together with an increased SCFA generation capacity.

Effect of acetyl esterification on physicochemical properties of chick pea (Cicer arietinum L.) starch

Acetyl esterification of isolated Bengal gram starch was carried out using acetic anhydride as reactant. Modification of native starch at variant concentrations of acetic anhydride (6, 8 and 10 %, w/w) resulted in modified starch with 2.14, 3.35, 4.47% acetyl content and 0.082, 0.130 and 0.176° of substitution (DS) respectively. The acetyl esterification of native starch brought significant changes in physicochemical properties with respect to pasting behavior, granule morphology, thermal properties and retrogradation profile. Acetyl modifications of native starch increased swelling capacity, water absorption power and oil absorption capability by 17, 13 and 20 % respectively. Acetylation has decreased pasting temperature, pasting time, final viscosity and set back viscosity due to increase in amylsoe content, hydrogen bonding and porosity of starch granule. The acetyl modification was confirmed by IR spectra with the presence of an ester carbonyl group (C = O) at 1720.3 cm(-1) and absorption band at 174.8 cm(-1). In DSC evaluation there was decrease in To, Tp, Tc and ΔH of acetylated starch than native starch which resulted in reduced retrogradation by 56 %.

Effect of acetylation, oxidation and annealing on physicochemical properties of bean starch

Black and Pinto bean starches were physically and chemically modified to investigate the effect of modification on digestibility and physicochemical properties of bean starch. The impact of acetylation, oxidation (ozonation) and annealing on the chemical composition, syneresis, swelling volume, pasting, thermal properties and digestibility of starches was evaluated. The physicochemical and estimated glycemic index (eGI) of the Black and Pinto bean starches treated with ozone were not significantly (P>0.05) different than that of their respective control starches. Annealed starches had improved thermal and pasting properties compared to native starches. Acetylated starches presented reduced syneresis, good pasting properties and lower eGI. Also, all modified starches had increased levels of resistant starch (RS). Therefore, the digestibility and physicochemical properties of bean starch were affected by the type of modification but there were no significant (P>0.05) differences between the Black and Pinto bean starches.