Heat-moisture treatment under mildly acidic conditions alters potato starch physicochemical properties and digestibility.
Potato starch was subjected to heat-moisture treatment (HMT; 120 °C, 3 h) under mildly acidic conditions (pH 5, 6, or 6.5 [control]) at moisture levels of 15, 20 or 25%. HMT starches exhibited significantly delayed pasting times and reduced overall paste viscosities, amylose leaching, and granular swelling characteristics relative to native starch, as well as enhanced levels of thermo-stable resistant starch (≈24%). HMT appeared to alter/enhance short-range chain associations (FT-IR) within amorphous and/or crystalline regions of starch granules. However, the extent of physicochemical change and RS enhancement during HMT was most facilitated by a mildly acidic condition (pH 6) at higher treatment moisture levels (20 or 25%). These conditions promoted limited hydrolysis of amylopectin molecules, primarily at α-(1→6) branch points, likely enhancing mobility and interaction of starch chains during HMT. Thus, a slightly acidic pH might reduce conditions and/or timeframe needed to impart physicochemical changes and reduced digestibility to potato starch.
School of Food Science, University of Idaho, P.O. Box 442312, Moscow, ID 83844, United States. Electronic address: tvand@paran.com.
Jong-Yea
JY
Kim
Kerry C
KC
Huber
D000687:Amylopectin / Q000737:chemistry*; D000688:Amylose / Q000737:chemistry; D006358:Hot Temperature; D006813:Humidity; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D011198:Solanum tuberosum / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013213:Starch / Q000737:chemistry*; D014783:Viscosity; D014961:X-Ray Diffraction
D013213:Starch; D000688:Amylose; D000687:Amylopectin
Acid; Crystallinity; Digestibility; Properties; Resistant starch; Starch physical modification; pH