Digestion characteristics of 5 kinds of polyphenols-containing wheat starches and their effects on noodle leaves quality

The study aimed to investigate the effects of polyphenols on wheat starch digestion characteristics and starch digestive enzyme activity, by selecting polyphenols with better from proanthocyanidins, tannic acid, quercetin, rutin, and catechin for incorporation into dried noodle leaves. Changes in the in vitro digestion characteristics and various quality indicators of the dried noodle leaves were then measured. The results showed that among the five polyphenols, tannic acid and proanthocyanidins had more significant inhibitory effects on starch digestion. With the addition of 5% tannic acid and proanthocyanidins, rapidly digestible starch (RDS) was significantly reduced to 2.61%±0.44% and 1.10%±0.22%, respectively, while resistant starch (RS) increased to 91.17%±1.11% and 87.82%±0.63%, respectively, enhancing the starch’s resistance to digestion. Among the five polyphenols, tannic acid exhibited the strongest inhibitory effect on α-amylase, with an inhibition rate of 85.53%±2.21% at a mass concentration of 1.0 mg·mL^-1, followed by proanthocyanidins, which had an inhibition rate of 81.82%±2.02% at the same mass concentration. Proanthocyanidins demonstrated the strongest inhibitory effect on α-glucosidase, with an inhibition rate of 78.27%±1.48% at a mass concentration of 3.0 mg·mL^-1, with tannic acid at the same mass concentration showed a much lower inhibition rate of 29.11%±1.07% against α-glucosidase, indicating poor effectiveness. Therefore, proanthocyanidins were selected for follow-up experiments. The addition of proanthocyanidins increased the hardness of the dried noodle leaves, with the cooking loss first increasing and then decreasing, while the water absorption rate showed an opposite trend. The L^* value (brightness) decreased significantly, and the sensory scores were reduced. When the addition level was 5.0%, the glycemic index (GI) of dried noodle leaves was reduced to 68.47 (medium GI food), suggesting potential applications of proanthocyanidins in low-GI staple foods of diabetics. However, the addition should not exceed 1.5%, as equal to or exceeding this level. Thus, the optimal addition level of proanthocyanidins was determined to be 1.0%, at which the GI of the dried noodle leaves could be reduced to 77.08, and the dried noodle leaves exhibited good quality indicators. This provides a reference for the application of proanthocyanidins in low-GI foods.