Abstract
Noodles are widely consumed in China, which can be cooked in different ways. The effects of different cooking methods (boiling, steaming, microwave heating, stir-frying and frying) on the resistance starch (RS) content and digestive properties (digestion rate, digestibility and estimated glycemic index (eGI) value) of noodles were investigated. The RS content was greatly affected by the cooking time, and it was varied when the noodles were optimally cooked using different cooking methods. The RS contents of the microwaved and stir-fried noodles were relatively high (0.59%–0.99%), but it was lower (0.43%–0.44%) in the boiled and steamed noodles. Microwaved noodles showed the slowest digestion rate and the lowest eGI. Due to the limited water within fried noodles, none RS was found in the fried noodles, whereas stir-fried noodles showed RS5 formation from the XRD and DSC results. Compared with boiled and steamed noodles, the microwaved noodles showed a more compact morphology without porous holes on the surface, whereas fried noodles showed irregular morphology. The results indicated that the digestive properties of noodles made with the same ingredients can be greatly altered by using different cooking methods, and the digestive properties of different cooked noodles are worthy of confirmation using in vivo analysis.
Highlights
Noodles are staple foods for many Asian countries [1]
Starch is the major ingredient of noodles, which can be classified as rapidly digestive starch (RDS), slowly digested starch (SDS) and resistant starch (RS) [2] based on the digestion rate and extent in the human digestive tract
The decrease in the RS content with longer cooking time could be explained by the higher degree of gelatinization of the starch within noodles, as the starch gelatinization peak (69.61 ◦ C, Table 1) from all noodles under the optimum conditions were lost
Summary
Noodles are staple foods for many Asian countries [1]. Starch is the major ingredient of noodles, which can be classified as rapidly digestive starch (RDS), slowly digested starch (SDS) and resistant starch (RS) [2] based on the digestion rate and extent in the human digestive tract. RS is the starch that cannot be absorbed in the small intestine of healthy individuals [3], but it can be utilized by microorganisms in the colon [4]. RS1 is the starch that is physically inaccessible to digestion by entrapment in a non-digestible matrix. RS2 is composed of native starch granules of selected botanical sources. RS3 is retrograded starch and is created when gelatinization is followed by a retrogradation process.
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