Resistant starch (RS) in foods has positive benefits for potentially alleviating lifestyle diseases. RS is correlated positively with starch amylose content. This study aimed to see what level of amylose in durum wheat is needed to lower pasta GI. The silencing of starch synthases IIa (SSIIa) and starch branching enzymes IIa (SBEIIa), key genes involved in starch biosynthesis, in durum wheat cultivar Svevo was performed and spaghetti was prepared and evaluated. The SSIIa and SBEIIa mutants have a 28% and 74% increase in amylose and a 2.8- and 35-fold increase in RS, respectively. Cooked pasta was softer, with higher cooking loss but lower stickiness compared to Svevo spaghetti, and with acceptable appearance and colour. In vitro starch digestion extent (area under the digestion curve) was decreased in both mutants, but much more in SBEIIa, while in vivo GI was only significantly reduced from 50 to 38 in SBEIIa. This is the first study of the glycaemic response of spaghetti prepared from SBEIIa and SSIIa durum wheat mutants. Overall pasta quality was acceptable in both mutants but the SBEIIa mutation provides a clear glycaemic benefit and would be much more appealing than wholemeal spaghetti. We suggest a minimum RS content in spaghetti of ~7% is needed to lower GI which corresponded to an amylose content of ~58%.

中文翻译：

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控制硬粒小麦直链淀粉含量可以降低意大利面条的血糖指数吗？


食品中的抗性淀粉（RS）对于减轻生活方式疾病具有积极的作用。 RS与淀粉直链淀粉含量呈正相关。这项研究的目的是了解硬粒小麦中的直链淀粉含量需要多少才能降低面食的血糖指数。对硬粒小麦品种 Svevo 中参与淀粉生物合成的关键基因淀粉合成酶 IIa (SSIIa) 和淀粉分支酶 IIa (SBEIIa) 进行沉默，并制备和评估意大利面条。 SSIIa和SBEIIa突变体的直链淀粉分别增加了28%和74%，RS增加了2.8倍和35倍。与 Svevo 意大利面相比，煮熟的意大利面更软，烹饪损失更高，但粘性更低，并且具有可接受的外观和颜色。两种突变体的体外淀粉消化程度（消化曲线下面积）均降低，但 SBEIIa 中的降低幅度更大，而 SBEIIa 中的体内 GI 仅从 50 显着降低至 38。这是对由 SBEIIa 和 SSIIa 硬粒小麦突变体制备的意大利面条的血糖反应的首次研究。两种突变体的整体意大利面质量都可以接受，但 SBEIIa 突变提供了明显的血糖益处，并且比全麦意大利面更有吸引力。我们建议，意大利面条中的 RS 含量最低需要达到 7% 左右才能降低 GI，这对应于 58% 左右的直链淀粉含量。