Browsing by Subject "expansion"

Malnutrition is a common problem in Peruvian highlands and in Bolivia. Amaranth, quinoa and kañiwa are pseudocereals cultivated in these areas and regarded as good sources of protein and non-saturated fatty acids. The literature review deals with the nutritional and technological properties of amaranth, quinoa and kañiwa. The aim of this investigation was to: (1) prepare gluten free corn-based extrudates containing amaranth, quinoa and kañiwa (20% of solids), (2) study the effects of independent extrusion variables on the physical properties of the extrudates and (3) evaluate lipid stability during storage by measuring hexanal production. Extrudates were made in 4 separate trials using a small scale co-rotating twin screw extruder. Experiments were performed using Box-Behnken?s experimental design in which independent extrusion variables were water content of mass (15, 17 and 19%), screw speed (200, 350 and 500 rpm) and temperature of the die (150, 160 and 170 °C). Samples were collected and their physical properties were analyzed (sectional expansion index, hardness and water content). Ground and whole extrudate samples were stored in open headspace vials at 11 and 76% RH for a week (exposure time) before being sealed and stored for 0, 2, 5 and 9 weeks at room temperature in the absence of light. Hexanal content was analyzed using headspace gas chromatography. The highest sectional expansion index (SEI) and the lowest hardness were achieved when the water content of mass was 15%, screw speed 500 rpm and temperature of the die 160 °C. Extrudates containing amaranth had the highest SEI (7.6) while extrudates containing quinoa and kañiwa had SEIs of 6.1 and 5.1, respectively. Pure corn extrudates (reference sample) had the lowest SEI (4.5). Extrudates containing kañiwa and pure corn extrudates presented the lowest (28 N/mm) and highest hardness (89 N/mm), respectively. In storage studies, ground extrudates (except samples containing quinoa) showed comparatively higher hexanal production than whole extrudates exposed to 11 and 76% RH. Whole extrudates exposed to 76% RH showed very low hexanal production during storage. This study proved that it was possible to add amaranth, quinoa and kañiwa to extruded corn snacks and achieve higher expansion than that of pure corn extrudates. Indeed, the results obtained from the evaluation of lipid oxidation during storage suggest a remarkable stability of whole extrudates after being exposed to high relative humidity. Further studies on lipid stability for longer storage would be highly desirable.