15D-8 |
Carbon dioxide assisted low temperature extrusion for producing functional foods |
H. S. JEONG, Food Science & Biotechnology, Chungbuk Provincial Univ., Okchon, 373-800, South Korea and R. T. Toledo, Dept. of Food Science & Technology, Univ. of Georgia, Athens, GA 30602. Food supplements containing health-functional components are marketed in different forms and are increasing in popularity. A quick-melting tablet supplement can be the most convenient form which melts easily in the mouth therefore, no further swallowing is needed to ingest the product. Our objective in this work was to develop a low temperature extrusion process to produce a porous but non-friable tablet from mixtures of a binder and health-functional ingredient as opposed to the conventional high temperature tabletting process. Gaseous carbon dioxide was used to develop porosity in the product. Extrusion was carried out below 50oC to prevent discoloration of pigments and destruction of functional components. Mixtures including pre-gelatinized rice flour and corn starch, sucrose, and plant material in different proportions were extruded. Grape skin which has a high content of resveratrol, was used as the functional ingredient. Extrusion and formulation parameters were amount of grape skin, carbon dioxide pressure at the injection point, and ratio of pre-gelatinized rice flour to corn starch. Results showed that screw configuration using short pitch and reverse screw elements improved mixing, allowed extrudate expanion, and prevented back-flow of injected gas towards the feed port. 5-10% sugar addition prevented surface cracks during drying of the extrudate. Carbon dioxide injection pressure ranged from 0.4 to 0.6MPa. Pressures greater that 0.6MPa produced very high density extrudate, with poor compressive strength, irregular pore size and structure collapse after exiting the die. Expansion ratio by sectional area of extrudate was in the range of 2 to 16, bulk density 0.3-1.2g/cm3, porosity 0.2-0.7, water solubility index 5-20%, and water absorption index 3-10. Products produced at 0.4-0.6Mpa exhibited the lowest compressive strength values, ranging from 200 to 600N. Carbon dioxide assisted low temperature extrusion is suitable for products containing vitamins, pigments and bioactive components to minimize changes in functional components.
Session 15D, Food Engineering: Processing Technologies
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