Genetical, Biochemical and Technological Parameters Associated with Biscuit Quality. II. Prediction Using Storage Proteins and Quality Characteristics in a Soft Wheat Population

The present research aims to study the genetic, biochemical and technological characteristics of the Portuguese soft wheat landrace «Barbela» population. Several new HMW-GS and ω-gliadins that characterise this population were identified. The potential of this local variety for biscuit production was evaluated using 150 derived pure lines cultivated over three consecutive years. The use of various indirect tests and storage protein analysis allowed us to select 98 lines to study biscuit value (sweet-biscuit). The sweet-biscuit parameters studied were the speed and energy of dough extrusion, cooking time, dough temperature, and biscuit mass before and after cooking, length, thickness, width, density and surface appearance of the biscuit. These parameters were related to the technological characteristics as evaluated by mixograph and alveograph analysis as well as grain hardness, starch damage levels, protein content, relative viscosity of the pentosans, storage protein alleles, Zeleny test, flour yield and thousand kernel weight of grains. As the «Barbela» lines were all of the soft type, our study demonstrated that grain hardness did not significantly influence the parameters of the biscuit test. Multiple regression analysis showed that protein content was the main variable accounting for the quality potential of the soft wheats selected for biscuit value. Protein content was negatively correlated with machinability (the ratio of extrusion speed/energy of dough extrusion), length and surface appearance of the biscuit. Moreover, the relative viscosity of the water-soluble pentosans was important for several biscuit parameters such as surface appearance and extrusion time. The variables of the mixograph generally correlated well with several biscuit parameters. Conversely, alveograph parameters did not show any significant correlation with the biscuit test. The variation observed in «Barbela» lines for extrusion energy, length, density and surface appearance in the biscuit test were significantly influenced by the Glu-1 locus. This study allowed us to define additional criteria for predicting sweet biscuit value in a soft wheat progeny.