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 similar to 7%
is needed to lower GI which corresponded to an amylose content of similar to 58%.
