Effects of suni-bug (Eurygaster spp.) damage on semolina properties and spaghetti quality characteristics of durum wheats (Triticum durum L.)

Abstract

Effects of suni-bug (Eurygaster spp.) damage on semolina properties and spaghetti quality characteristics of durum wheats (Triticum durum L.) were investigated. The semolinas obtained from sound (control), medium damage (around 20%) and high damage (around 40%) samples of five durum wheat cultivars (cvs. Diyarbakir, Firat, Ege, Svevo and Zenith) were processed into spaghetti. As the bug damage level increased, Glutograph stretch values of all cultivars decreased significantly probably due to deteriorative effects of bug damage on gluten quality. Glutograph relaxation values and gluten spread values of the damaged samples were considerably higher compared to those of sound samples in all cultivars, due to proteolytic degradation. The breaking force of the uncooked spaghetti samples decreased significantly with increasing bug damage level indicating that they were susceptible to breakage and not suitable for handling, packaging and shipment. Panel tests indicated significant deterioration in sensory properties (stickiness, firmness and bulkiness) generally at the medium damage level.

Deterioration in gluten quality supported the significant increases in total organic matter (TOM) and cooking loss values of the spaghetti samples with increasing damage levels.

Introduction

Durum wheat (Triticum durum L.) is one of the most important cereal crops in the world. It is suitable for manufacturing various food products. Pasta is the most common product made from durum wheat. It is also used for the preparation of bulgur, noodles, couscous and various types of bread in the Middle East and North Africa (Elias, 1995, Troccoli et al., 2000).

Cooking quality of pasta is the characteristic of greatest importance for consumers and, therefore, of greatest importance to durum wheat producers, breeders and processors. During pasta cooking, a weak or discontinuous protein matrix results in a protein network that is too loose and permits a greater amount of exudates to escape during starch granule gelatinization (Resmini and Pagani, 1983). The exudates form a surface of starch and the pasta becomes sticky (Feillet, 1988), giving pasta strands the tendency to clump. The variation in pasta cooking quality is due in part to the amount of protein present in semolina samples and in part to the intrinsic characteristics of these proteins (i.e. quality). There is a general agreement that protein content is the primary factor influencing pasta quality and that gluten strength is an important secondary factor (D'Egidio et al., 1990, Feillet and Dexter, 1996, Malcolmson et al., 1993, Matsuo et al., 1982, Novaro et al., 1993). However, there are some other factors with substantial negative influence on gluten quality of durum wheat such as the damage by Heteropterous insects. Hence, in the present study, it was intended to investigate the effects of suni-bug (Eurygaster spp.) damage on gluten quality characteristics and spaghetti cooking properties of durum wheats.

It is known that the pre-harvest attack of wheat by some Heteropterous insects gives wheat flour with reduced bread-making quality (Harriri et al., 2000, Lorenz and Meredith, 1988, Swallow and Every, 1991). The bug damaged wheat contains salivary secretion of insects, which contains proteolytic enzyme(s) (Paulian and Popov, 1980). The protease enzyme breaks down the gluten structure during mixing and fermentation resulting in poor rheological properties and bread with reduced volume and unacceptable texture (Every et al., 1998, Kretovich, 1944, Lorenz and Meredith, 1988, Sivri et al., 1998, Sivri et al., 1999). Flour milled from bug (Eurygaster spp., Aelia spp. and Nysius huttoni) damaged wheat exhibits weak dough properties and unsatisfactory baking quality due to enzymatic degradation of gluten proteins (Cressey and McStay, 1987, Every, 1992, Köksel et al., 2001, Matsoukas and Morrison, 1990, Sivri et al., 1998, Sivri et al., 1999, Sivri and Köksel, 1996). It has been reported that insect infestation affects the glutenin and gliadin fraction of wheat proteins, with increased specificity towards the high molecular weight glutenin subunits (Cressey and McStay, 1987, Perez et al., 2005, Rosell et al., 2002, Sivri et al., 1999).

Although some research publications are available related to the effects of suni-bug damage on gluten proteins, rheological properties and baking quality of bread wheats, we have not encountered any study on the effects of suni-bug damage on pasta quality characteristics. Hence, the present study was planned to investigate the effects of suni-bug damage on some semolina properties and spaghetti quality characteristics of durum wheats (T. durum L.).