Technical and nutritional properties of vegetable enriched pasta utilising juice and pomace from spinach, red cabbage, beetroot and carrot : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

Abstract

Vegetable pasta may deliver health benefits by increasing vegetable intake. Previous studies only applied one form of vegetable to pasta formula to investigate their effect. For example, Padalino, Costa, Del Nobile, and Conte (2019) used powdered glass wort (Salicornia europaea) to improve the nutritional value of pasta. In contrast, SIPOS et al. (2017) evaluated the nutritional value and sensory quality of pasta enriched with beetroot juice and beetroot puree. Few comparisons were found between different forms at the same addition level. Therefore, this study investigated the replacement of semolina with juice, puree, and pomace of spinach, red cabbage, beetroot and carrot. The effect of replacement on technical and nutritional value was evaluated. The cooking loss of pasta made with spinach juice and spinach puree at 1 % substitution was the same as the control, while all other samples showed higher cooking loss. Spinach pasta was characterised by higher breaking force but lower breaking distance in the tensile test than the control, while all other pasta had a lower breaking force and breaking distance. Spinach pasta was generally firmer than the control. Red cabbage juice pasta was less firm than other forms of fortified pasta at 1 g/100 g substitution level. Spinach, red cabbage, beetroot and carrot juice are better colourants than puree or pomace as they change the colour of the pasta more dramatically at the same substitution level. The in vitro starch digestibility test show that spinach pomace 10%, red cabbage pomace 10%, beetroot pomace 10%, carrot pomace 10%, spinach juice 1%, spinach puree 2%, and beetroot puree 4% significantly reduced the area under the curve of the in vitro starch digestion. This reduction was due to a combined effect of decreased starch content, increased dietary fibre content and inhibition of α-amylase caused by vegetable material addition. Total phenolic content (TPC) and antioxidant capacity increased significantly on raw, cooked and digested samples of vegetable-fortified pasta compared to the control. The β-carotene content of spinach and carrot pasta samples (raw, cooked, and digested) was also higher than that of the control. At the same substitution level, the juice was more efficient in improving the antioxidant capacity of resultant pasta compared to puree or pomace. Mineral contents of vegetable-fortified pasta (raw and cooked) were also higher than the control. In general, at the same lower substitution level, juice and puree-enriched pasta samples generally exhibited better technical quality than pomace-enriched ones. The study exhibits that incorporating vegetable juice or puree to produce pasta results in a superior nutritional profile with a slight compromise of technical quality.