61A-12 |
Phase behavior of inulin and amylopectin systems in high moisture environments |
J. E. ZIMERI, Department of Food Science, Rutgers University, 65 Dudley Rd., New Brunswick, NJ 08901 and J. L. Kokini. Inulin is a carbohydrate polymer added to food products as a supplement due to its nutritional properties. It can also be combined with water to produce the same texture and mouthfeel as fat in processed foods such as starch-based foods. Previous studies have indicated that in mixed amylopectin-inulin systems, relative crystallinity of the samples increased with increasing inulin content. Phase separation was confirmed by the existence of two independent glass transition temperatures. Since these findings applied to samples in limited moisture environments, studies need to be extended to more dilute systems. The objectives of this research were to start developing a ternary phase diagram that describes the interactions in inulin-amylopectin-water systems by studying the rheological properties of the individual components in high moisture environments. Inulin and amylopectin suspensions were prepared at concentrations ranging from 2 to 50% and from 0.5 to 20% (w/w, w.b.), respectively. These samples were heated to 90°C and stored at room temperature for 48 h. Steady shear and dynamic analyses were performed. Changes in G', G" and tan d were monitored with respect to temperature, confirmed by differential scanning calorimetry. Results showed that inulin and amylopectin were insoluble in water and presented shear-thinning behavior for most of the range of concentrations studied. Inulin formed dilute suspensions at 2% and strong, semi-crystalline gels at 40 and 50%. Amylopectin had characteristics of a dilute system at 2% and formed weak gels at higher concentrations. Above 2%, inulin presented lower viscosities and higher storage moduli than amylopectin. While amylopectin did not present any melting behavior at temperatures of 100°C, inulin had a wide melting region at concentrations of 40 and 50%. Inulin's ability to mimic fat's functionality in high-moisture, starch-containing foods will be determined in future studies, using present findings on the individual components' behavior as the knowledgebase.
Session 61A, Carbohydrate
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