Original article The influence of inulin addition on the morphological and structural properties of durum wheat pasta Daniela Manno, 1 * Emanuela Filippo, 1 Antonio Serra, 1 Carmine Negro, 2 Luigi De Bellis 2 & Antonio Miceli 2 1 Dipartimento di Scienza dei Materiali – Universita` del Salento, Via per Monteroni, 73100 Lecce, Italy 2 Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali – Universita` del Salento, Via per Monteroni, 73100 Lecce, Italy (Received 3 April 2009; Accepted in revised form 24 July 2009) Summary The effect of the addition of different concentration of inulin fibre to durum wheat pasta was evaluated in terms of structure, texture and morphological characteristics. Inulin fibre fraction was incorporated into pasta at 5%, 10% and 15% inclusion rates. Changes to pasta quality were observed with inulin fibre fraction addition by scanning electron microscopy, X-ray diffraction and Raman spectroscopy methods. Investi- gation of pasta microstructure indicate a lowering in crystallinity increasing the inulin content and characterisation of starch gelatinisation events indicated that a combination of changes to the starch–protein matrix and the high water-binding capacity of inulin alters the physico-chemical properties and then the digestibility of the pastas. Keywords Dietary fibre, pasta, Raman spectroscopy, scanning electron microscopy, starch, X-ray diffraction. Introduction Pastas are a popular cereal commodity in Italy and European households and are considered to be low glycaemic index (GI) foods, eliciting low postprandial blood glucose and insulin responses and prolonged satiety with evident benefit effects on people with different pathologies (obesity, diabetes, altered lipidic metabolism; Bornet et al., 1987; Bjorck et al., 2000; Weickert & Pfeiffer, 2008; Sabanis & Tzia, 2009). The low GI of pasta can be linked to a reduced and relatively stable progressive liberation of sugars from pasta during digestion. This may be attributed, in part, to the compact structure of pasta resulting from the extru- sion process, which brings about a close protein network entrapping starch granules and thereby delaying amylol- ysis (Pagani et al., 1986; Fardet et al., 1999). Studies have illustrated that the glycaemic response of pasta can be lowered further, by the addition of soluble fibre including guar gum (Kim et al., 2006), and b-glucan (Yokoyama et al., 1997). In addition, inulin and oligofructose (the most common fructans) might reduce serum lipids because these fibres resist digestion in the upper gastro- intestinal tract and are fermented in the large intestine by indigenous bacteria (Davidson & Maki, 1999). Whole durum wheat is employed in traditional pasta manufacture because of the unique rheological proper- ties of its protein (Marconi et al., 2000). So that a partial or relevant substitution of durum wheat semolina with fibre material can result in negative changes to pasta quality, including increased cooking loss and loss of hardness (Edwards et al., 1995; Gelencse´r et al.,2008). One should strike the right balance between the amount of inulin that provides benefits and pasta quality. Although significant numbers of studies illustrate the benefit of consuming alternative fibre-rich products, there is a paucity of studies that document the changes to the physical–chemical properties of food products which includes alternative fibres. These changes have importance with regard to product palatability and consumer acceptance. The aim of this study was to assess the influence of inulin fibre fraction inclusion on durum wheat pasta morphological, structural and texture quality. To perform this study, we used the information obtained by low vacuum scanning electron microscopy (LVSEM), the X-ray diffraction (XRD) and the Raman microspectroscopy. By combining LVSEM with XRD and Raman spectroscopy reological, mor- phological, structural and molecular information can be obtained with great spatial resolution also at the microscopic level. All type of samples were analysed directly, in air, at ambient temperature, wet or dry, and in many cases without preliminary sample preparation. *Correspondent: Fax: 39 0832 297070; e-mail: daniela.manno@unile.it International Journal of Food Science and Technology 2009, 44, 2218–2224 2218 doi:10.1111/j.1365-2621.2009.02062.x Ó 2009 The Authors. Journal compilation Ó 2009 Institute of Food Science and Technology