Durum semolina spaghetti is known to have a low-moderate glycaemic index but the impact of various processing variables during the manufacture and cooking of pasta does affect pasta structure and potentially could alter starch digestion. In this study, several process variables were investigated to see if they can impact the in vitro starch digestion in spaghetti while also monitoring the pasta’s technological quality. Cooking time had a large impact on pasta starch digestion and reducing cooking from fully cooked to al dente and using pasta of very high protein content (17%), reduced starch digestion extent. The semolina particle size distribution used to prepare pasta impacted pasta quality and starch digestion to a small extent indicating a finer semolina particle size (<180 µm) may promote a more compact structure and help to reduce starch digestion. The addition of a structural enzyme, Transglutaminase in the pasta formulae improved overcooking tolerance in low protein pasta comparable to high protein pasta with no other significant effects and had no effect on starch digestion over a wide protein range (8.6–17%). While cold storage of cooked pasta was expected to increase retrograded starch, the increase in resistant starch was minor (37%) with no consequent improvement in the extent of starch digestion. Varying three extrusion parameters (die temperature, die pressure, extrusion speed) impacted pasta technological quality but not the extent of starch digestion. Results suggest the potential to subtly manipulate the starch digestion of pasta through some processing procedures.

In Australia, adoption of reduced tillage and stubble retention cropping systems by growers to conserve soil moisture has seen an increase in the prevalence of the disease Fusarium crown rot (FCR) caused by the stubble-borne fungal pathogen Fusarium pseudograminearum. Durum wheat is particularly susceptible to FCR, exhibiting significant yield and quality losses in the presence of infection. Increasing rates of nitrogen (N) application at sowing exacerbates FCR. However, to achieve the desired grain protein and quality suited to pasta manufacturing, N application is necessary, and this creates a dilemma for growers. The purpose of this study was to investigate the effects of FCR infection in the presence of different N fertiliser application rates in durum wheat varieties on the yield and technological quality. Two durum varieties were evaluated at the same location over two seasons (2020 and 2021). These seasons were characterised by being wetter than normal and showed different responses to FCR and N application. Three rates of FCR inoculation and five rates of N fertilizer were applied (varying according to season) at sowing. In general, the 2021 season showed better responses to applied N regarding the yield and technological properties, with no impact from FCR. The FCR inoculation, while resulting in significant infections in 2020 (15–36-fold increase) and in 2021 (~45-fold increase), had no impacts on the yield or grain quality in 2021, while in 2020, the yield was reduced (24.9%), with variable effects on the technological properties. The 2021 season showed much more responses to applied N (grain protein increased by ~24%). Jandaroi was found to maintain its kernel vitreosity at all protein levels (mean of 88.5%), obtaining the premium grade, while DBA Lillaroi did not (mean vitreosity of 76.6%) and could be downgraded if N application was insufficient. However, higher N application rates needed to achieve more than 12% protein lead to a reduction in dough strength, with Jandaroi maintaining its dough strength much better (2.7% reduction in the gluten index) than DBA Lillaroi (18.2% reduction in the gluten index). This was related to the lower glutenin/gliadin (Gli/Glu) ratio in response to applied N at sowing in Jandaroi, which helped retain kernels with a high vitreousness. This suggests genetics plays an important role in a genotype’s response to N fertilisation and should be considered when selecting a genotype where higher premium grades are desirable.

In Australia adoption of reduced tillage and stubble retention cropping systems to conserve soil moisture by growers has seen an increase in the prevalence of the disease Fusarium crown rot (FCR) caused by the stubble-borne fungal pathogen Fusarium pseudograminearum. Durum wheat is particularly susceptible to FCR expressing significant yield and quality losses in the presence of infection. Increasing rates of nitrogen (N) application at sowing exacerbates FCR. However, to achieve the desired grain protein and quality suited to pasta manufacture, N application is necessary and this creates a dilemma for growers. The purpose of this study was to investigate the effects of FCR infection in the presence of different N fertiliser application rates in durum wheat varieties on yield and technological quality. Two durum varieties were evaluated at the same location over two seasons (2020 and 2021). These seasons were characterised by being wetter than normal and showed different responses to FCR and N application. In general, the 2021 season showed better responses to applied N with no impact of FCR. The FCR inoculation while it resulted in significant infection, it had no impacts on yield or grain quality in 2021 while in 2020 yield was reduced and only gluten index was reduced. Jandaroi was found to hold its kernel vitreosity at all protein levels obtaining the premium grade while DBA Lillaroi did not and would suffer downgrade if N application was insufficient. However, higher N application rates needed to achieve 12% + protein saw a reduction in dough strength with Jandaroi holding its dough strength much better than DBA Lillaroi. This was related to the lower glutenin/gliadin (Gli/Glu) ratio in response to applied N at sowing in Jandaroi which helped retain kernels with high vitreousness. This suggests genetics plays an important role in a genotype response to N fertilisation and should be considered when selecting a variety where higher premium grades are desirable.