Pumpkin seed flour (a cold-pressed by-product): characterization and rheological assessment in gluten-free bread premixes

Abstract

Cold-pressed oil production generates high-quality oil and a nutrient-rich press cake as a by-product. Cucurbita pepo seeds (var. styrica) are typically used for this purpose. This work aims to add value to the press cake by-product by characterizing the techno-functional, physicochemical, nutritional, and microstructural properties of pumpkin seed flour (PSF), and evaluating the impact of PSF on the pasting and rheological behaviour of gluten-free model premixes (rice flour based). Nutritionally, PSF contained 41% protein. Although lipids accounted for one-third of its composition (predominantly unsaturated fatty acids), PSF showed high oxidative stability. Regarding its techno-functional properties, PSF showed good emulsion activity (55%), high thermal emulsion stability (51%) and good water, oil, and organic molecule retaining capacities. Characterization of PSF and rice flour (RF) showed that the two flours complement each other when forming composite mixtures. In addition, the suitability of PSF for breadmaking was determined by evaluating its effect on the rheology of premixes. The premixes were prepared by substituting RF with PSF at 10%, 20% and 30%. The viscoamylograph showed that regardless of the substitution level, PSF formed premixes that were less susceptible to retrogradation and had the potential to enhance oven spring during baking. At 20% and 30% substitution, PSF also improved the rheological quality of the gluten-free dough models, acting similarly to xanthan gum. This effect could be related to the ability of PSF to retain water and to form emulsions. These results showed the aptitude of PSF to be included in formulations intended for gluten-free bakery products.