30E-15 |
Effects of fats with different melting points on starch extrudate expansion and comparison with microwave expansion |
A. Thewessen1, C. I. MORARU2, and J. L. Kokini2. (1) Wageningen University, Wageningen, Netherlands, (2) Food Science Department, Rutgers University, New Brunswick, NJ 08901 Sales of snack foods are continuously increasing in the U.S. and worldwide, with extrusion being one of the main manufacturing techniques. The texture and mouthfeel of extruded snacks depend greatly on their ingredients and expanded volume. Fats have the ability to improve the sensory properties of cereal snacks, and at the same time affect the degree of expansion. Liquid fats are reported to decrease expansion in extrusion, microwave heating and baking. In case of solid fats, although some studies reported they are able to improve the expansion of baked and microwaved products, very limited information exists about their effects on extrudate expansion. The objective of this study was to investigate the effects of fats with different melting points on direct expansion of amylopectin and to compare them with the effects on expansion by microwave heating. Canola oil, solid hydrogenated soybean fat and polyethylene wax were mixed with amylopectin at the levels of 0, 2, 4, 6, 8, and 10% (w/w) and the mixtures were expanded using a twin-screw extruder. The samples were analyzed for expansion ratio, fat content, bulk density, texture and structure. Addition of hydrogenated soybean fat resulted in increased expansion of the extrudates. Maximum expansion occurred at 6% hydrogenated soybean fat, at the same level where maximum expansion by microwave heating took place. Both canola oil and wax addition resulted in decreased expansion of the starch matrix. For the wax containing samples, lower expansion was caused mainly by collapse. Fat addition had a significant impact on the mechanical properties of the extrudates, both due to its contribution to expansion and to a softening effect. Understanding the effects of different types of fats on starch extrudate expansion can help elucidate the mechanisms that control expansion.
Session 30E, Food Engineering: Rheology and texture
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