|LU, LU - Washington State University|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2014
Publication Date: 1/1/2015
Publication URL: http://handle.nal.usda.gov/10113/60578
Citation: Lu, L., Baik, B.-K. 2015. Starch characteristics influencing resistant starch content of cooked buckwheat groats. Cereal Chemistry. 92(1):65-72.
Interpretive Summary: High resistant starch (RS) content, in addition to dietary fibers present in groats, contributes to the low-calorie, high fiber food status of buckwheat. Six buckwheat cultivars exhibiting high, medium, and low RS content of cooked groats were selected and starches were isolated to determine their functional properties in order 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 cultivars, respectively. Cultivars of high RS content exhibited greater amylose leaching during cooking than cultivars of low RS content. Cultivars of low RS content exhibited relatively high amylose-lipid complex determined using a differential scanning calorimeter (DSC). Gelatinization enthalpy and degree of amylopectin retrogradation determined using DSC was not related to RS content. An evident relationship was observed between RS content of cooked groats and amylose retrogradation determined by gel texture analysis and syneresis test. High amylose content, high amylose leaching capacity, low amylose-lipid complex and high amylose retrogradation all appear to be responsible for high RS content of cooked buckwheat groats.
Technical Abstract: Enzyme resistant starch (RS), owing to its health benefits such as colon cancer inhibition, reduced glycemic response, reduced cholesterol level, prevention of gall stone formation and obesity, has received an increasing attention from consumers and food manufacturers, whereas intrinsic and extrinsic factors affecting the content of RS in processed foods are still not well understood. The present study elucidated the influence of starch characteristics on RS content of cooked buckwheat groats. Both apparent and actual amylose content were significantly related to RS content of cooked buckwheat. Amylose leaching capacities of buckwheat starches were highest in RS cultivars, less in medium RS cultivars and lowest in low RS cultivars. The crystallinity of native buckwheat starches showed little influence on RS content of cooked buckwheat groats. Amylose-lipid complex may negatively affect the formation of RS of cooked buckwheat groats by preventing amylose leaching and retrogradation. Starch gel hardness, cohesiveness, and springiness and syneresis illustrated a positive relationship between amylose retrogradation and RS content. High amylose content, high amylose leaching capacity, low amylose-lipid complex and high degree of amylose retrogradation all contributed to high RS content of cooked buckwheat groats.