| A whey-based puffed snack food was produced on a twin-screw extruder to determine the effect of varying starch type, protein type, and protein concentration on the physical, chemical, and sensory characteristics of a second-generation snack food. Two starch types (normal corn starch and pregelatinized waxy starch) and two whey protein concentrate types (regular and instantized) were chosen. Each combination of starch and protein was extruded in triplicate at three protein concentrations: 16%, 32%, and 40%.; Physical (expansion ratio, breaking force, density, color, and air cell size) and chemical (moisture content, water absorption index, water solubility index, total soluble protein, water-soluble protein, and water-soluble carbohydrate) characteristics were examined. Starch type and protein level were found to significantly affect the characteristics of the extrudates. Both increasing protein and use of normal cornstarch significantly reduced extrudate expansion ratio (p < 0.0001, p = 0.0003), air cell size (p < 0.0001, p = 0.0002), and water solubility (p < 0.0001, p = 0.0078), and increased extrudate density (p < 0.0001, p < 0.0001), hardness (p < 0.0001, p = 0.0069), and color (p < 0.0001, p = 0.0481).; For normal corn extrudates, the effect of the starch was likely modified by the presence of an amylose-protein complex. A relationship between total soluble protein and water-soluble carbohydrate values was seen to exist for these extrudates. This suggests the complex is covalent in nature.; Based upon physical analyses, three combinations were chosen for sensory analysis (normal cornstarch at 32% protein, pregelatinized waxy starch at 32% protein, and pregelatinized waxy starch at 40% protein). Mean hedonic scores were in the range of 5--6, "Neither Like nor Dislike" to "Like Slightly." Panelists rated the normal cornstarch extrudate higher than either of the pregelatinized waxy extrudates on the characteristics texture (p < 0.0001), flavor (p = 0.0277), aftertaste (p < 0.0001), and overall acceptability (p = 0.0005). |
