Acetylated, propionylated or butyrylated starches raise large bowel short-chain fatty acids preferentially when fed to rats.

Maize starch was acylated with acetic, propionic or butyric anhydride to produce the corresponding acylated starch. In the first experiment, butyrylated starch at a degree of substitution (DS) of 0.25 (i.e., 1 acyl unit per 4 glucosyl units) was fed to rats for 3 d. Cecal and distal colonic SCFA concentrations were 170 and 78% higher, respectively, in rats fed the butyrylated starch. However, the greatest increase was in butyrate with corresponding increases of 460 and 212%. Subsequently, acetylated, propionylated or butyrylated starches with DS of approximately 0.18 were prepared on a larger scale. Body weight gain did not differ between rats fed these acylated starches or a control starch for 14 d. Large bowel pH was significantly lower and digesta mass significantly higher throughout the large bowel in rats fed the acylated starches. Cecal + distal colonic starch averaged 12 mg in rats fed the control starch and 103, 134 and 135 (pooled SEM = 6) mg in rats fed acetylated, propionylated or butyrylated starch, respectively. Large bowel SCFA concentrations and pools were significantly higher in rats fed the three acylated starches and were disproportionately greater in the SCFA that had been esterified to the starch. In the cecum, acetate, propionate and butyrate pools were 280, 690 and 1060% higher, respectively, in rats fed the corresponding acylated starch than in those fed the control diet. In the distal colon, the corresponding increases were 320, 940 and 1370%. These data indicate that acylated starches are resistant starch (RS) and raise large bowel SCFA, apparently through bacterial release of the esterified fatty acid and fermentation of the residual starch.