DisplayTitle

Starch Characteristics Influencing Resistant Starch Content of Cooked Buckwheat Groats

^†Corresponding author. Phone: +1.330.263.3891. E-mail: byungkee.baik@ars.usda.gov
¹School of Food Science, Washington State University, Pullman, WA 99164, U.S.A. ²USDA-ARS-CSWQRU, Soft Wheat Quality Laboratory, OARDC–Ohio State University, 1680 Madison Ave., Wooster, OH 44691, U.S.A.

Cooked buckwheat groats are suggested to contain a greater amount of resistant starch (RS) than cereal grains. High RS content, in addition to dietary fibers present in groats, contributes to the low-calorie, high-fiber food status of buckwheat. Six buckwheat genotypes exhibiting high, medium, and low RS content of cooked groats were selected, and starches were isolated to determine their functional properties to explore the possible cause of high RS content of cooked buckwheat groats. Apparent and actual amylose contents were 27.4 and 31.6–34.5% in high, 27.4–28.6 and 32.5–33.7% in medium, and 21.4–25.6 and 24.5–32.0% in low RS genotypes, respectively. Genotypes of high RS content exhibited greater amylose leaching based on total starch content during cooking than genotypes of low RS content, mainly because of higher amylose content in the former than latter. Genotypes of low RS content exhibited a relatively high content of amylose-lipid complexes, as determined with a differential scanning calorimeter (DSC). Gelatinization enthalpy and degree of amylopectin retrogradation determined with a DSC were not related to RS content. An evident relationship was observed between RS content of cooked groats and amylose retrogradation determined by gel hardness (r = 0.91, P < 0.05), cohesiveness (r = 0.89, P < 0.05), and syneresis (r = 0.88, P < 0.05). Increases in starch amylose content, amylose leaching capacity, and amylose retrogradation, as well as a decrease in the amount of amylose-lipid complexes all appear to be related to high RS content of cooked buckwheat groats.