Fermentability of Novel Type-4 Resistant Starches in In Vitro System

Abstract

Resistant starches are non-digestible starches that are fermented in the colon by microbiota. These carbohydrates are prebiotic and can be beneficial to consumer health. Many types of resistant starch exist with varying physical properties that may result in differences in fermentability. The objective of this research project was to compare potential prebiotic effects and fermentability of four novel resistant starches using an in vitro fermentation system and measuring changes in total gas production, pH, and formation of SCFAs (short chain fatty acids). Fecal donations were collected from seven healthy volunteers. Four novel resistant starches, modified potato starch (MPS), modified tapioca starch (MTS), and modified maize starches (MMS-1 and MMS-2), were analyzed and compared to polydextrose and short chain fructooligosaccharides (FOS) as controls. After twenty-four hours of fermentation, MPS and MTS responded similarly in gas production (74 mL; 70.6 mL respectively), pH (5.93; 5.93 respectively), and SCFA production (Acetate: 115; 124, Propionate: 21; 26, Butyrate: 29; 31 μmol/mL respectively). While MMS-1 had similar gas production and individual SCFA production, the pH was significantly higher (6.06). The fermentation of MMS-2 produced the least amount of gas (22 mL), with a higher pH (6.34), and lower acetate production (78.4 μmol/mL). All analyzed compounds were fermentable and promoted the formation of beneficial SCFAs.

Novel Resistant Starch Type 4 Products of Different Starch Origins, Production Methods, and Amounts Are Not Equally Fermented when Fed to Sprague‐Dawley Rats

“…Thus, the amounts of RS4 as total fiber were well within the human fiber requirement in our rat model. The third difference in production of the RS4 products was the modification of the starch to produce RS4, which was by phosphate cross‐linking or acid hydrolysis and heat treatment . We therefore propose these three mechanistic differences in the RS4 products that might determine fermentability, which include the origin of the starch, the amount of starch available for fermentation, and the different methods of production used for the RS4 products.…”

“…In fact, in vitro studies have shown that products made with 1,3 gylcosidic bonds between glucose molecules were not digestible, but the glucans were digested during in vivo studies in chickens, rats, and humans (unpublished data). This further emphasizes the importance of not just performing in vitro analyses, but always performing in vivo studies to assess true fermentation and physiological effects of a particular product …”

“…This suggests that bacteria utilization of the starches is not completely dependent on the amount of RS4 in the diet alone, but also on the structural differences of the starches. RSA, RSC, and RSD were chemically modified by distarch phosphate cross‐links, while RSB underwent acid hydrolysis and heat treatment . Without the application of chemical constituents or cross‐linkages, acid hydrolysis and heat treatment likely produces RS4 by breaking existing chemical bonds by hydrolysis followed by alteration of the bonds with heat, which cause a structural change that renders the starch indigestible.…”

“…RS3 is nongranular, “retrograded amylose” found in foods that are cooked and then cooled such as potatoes and puddings. Resistant starch type 4 (RS4) is chemically‐modified starch generated by several different methods, including the addition of ester cross‐links between starch molecules, the addition of chemical constituent groups, or by acid hydrolysis and heat treatment . These methods alter the chemical and physical properties of the starch which reduce its digestibility by preventing enzymatic accessibility and/or degradation .…”

Butyrylation of Maize and Potato Starches and Characterization of the Products by Nuclear Magnetic Resonance and In Vitro Fermentation

“…Our esterified starch samples were not pre-digested with enzymes, according to the AOAC method (AOAC 991.43) prior to the in vitro fermentation since it is typically practiced in these types of study designs [ 32 ]. We only had small amounts (below 500 mg) of esterified starches available and the pre-digestion procedure would not have left enough material to conduct triplicate in vitro fermentations subsequently.…”