Effects of operating conditions on oil loss and structure of almond snacks

Abstract

An almond-and-wheat blend (about 1:2.5, dry basis) was extruded through a co-rotating twin-screw extruder with a barrel diameter of 25 mm. The effects of barrel temperature (69.77-120.23°C), dough moisture (26.64-33.36%) and screw speed (13.85-38.50 rad s )1 ) on specific mechanical energy, oil loss that occurs during extrusion process, pressure at the die and on complexing index, break strength, porosity and expansion ratio of extrudates were investigated using response surface methodology. The only variable that had a significant influence on oil loss was barrel temperature (the lowest oil loss, i.e. 0.06%, was obtained with the minimum barrel temperature). The worst product structure was obtained at barrel temperature less than 100°C. Yet, the highest values of porosity (18.47%) and expansion ratio (158.76%) were obtained at a barrel temperature of 120°C. Regression results showed a positive correlation (r 2 = 0.94) between oil loss, porosity and expansion degree values.

Study of starch-lipid complexes in model system and real food produced using extrusion-cooking technology

“…its increase caused an augment of fat loss, that could be attributed to the formation of bond between starch and lipid fraction (Table 3), which was not extractable with petroleum ether. Moreover, the highest values of barrel temperature favor the migration of fat fraction outside from mass extruded (De Pilli, Carbone, Derossi, Fiore, & Severini, 2008;De Pilli, Jouppila, et al, 2008).…”

Study on formation of starch–lipid complexes during extrusion-cooking of almond flour

“…Also in this case, the smallest values of break strength were obtained at high values of barrel temperature and feed moisture. This behaviour can be explained assuming that the lack of starch-lipid complex formation, at these operating conditions, gives a fragile structure to extrudate (Mercier et al, 1980;Bhatnagar and Hanna, 1994b;De Pilli et al, 2007). Deformability is an index of the energy opposed to the product at the applied strength.…”

“…2-4). Moreover, the highest values of barrel temperature favour both the melting of starch-lipid complexes that were formed during extrusion in the first stages of extrusion process and the migration outside fat fraction (De Pilli et al, 2005, 2007.…”

“…The appropriate range of processing parameters to extrude wheat flour and a blend with wheat and almond flours was chosen according to De Pilli et al (2007).…”

Microstructural and textural properties of puffed snack prepared from partially deffated almond powder and corn flour

“…Sun and Muthukumarappan () reported that increasing the content of defatted soy flour (10–30%) into corn flour decreased the ER of the product. ER of extrudate products is related to the formation of bubbles when cooked melts exit the die (De Pilli et al, ). On the other hand, according to De Pilli et al () results, the addition of lipids related to increase level of whole almond powder in extrudates formulations, might have influenced the character of starch matrix, so that it could no longer hold water vapour, resulting in lower ER.…”