Aprianita, Aprianita (2010) Assessment of underutilized starchy roots and tubers for their applications in the food industry. Research Master thesis, Victoria University.

Abstract

Physicochemical properties of flours and starches isolated from tubers and roots commercially available in Australia and traditionally produced in Indonesia were investigated in this study. The results showed that these flours and starches may be utilized in certain food applications. Raw starchy materials from Australia included taro, yam, and sweet potato. Due to its narrow particle size distribution (1-64 μm), taro flour would be better suited in applications which require improved binding and reduced breakability. The paste of sweet potato flour and starch had higher clarity compared to those of yam and taro. All flours and starches showed variable pasting behavior. In general, all starch samples had higher viscosity than that of flour samples. Taro flour had the highest viscosity among other flour samples. Yam flour and starch were more stable against heat and mechanical treatments. An apparent shear thinning behavior was observed from the extracted mucilage. Concentration dependant flow behavior of all mucilage samples was successfully fitted by the (Ostwald) Power Law, Hershel Buckley, and Casson models. Meanwhile, flours and starches isolated from tubers and roots grown in Indonesia also had properties suitable for certain food applications. Compared to other flour samples, cassava and canna flours contained the highest amount of total starch (TS). Taro starch had the lowest amount of TS among other starch samples with 75.44%. The highest amount of amylose was observed from yam and canna flours (25.24 and 23.19%, respectively). Among starch samples, canna starch contained the highest amylose content (30.38%), while taro had the lowest (7.64%). In terms of protein content, arrowroot flour had the highest amount (7.70%), in contrast to cassava flour which had the lowest (1.51%). Compared to other flours, canna and konjac flour were the most slowly digested which indicated by their high amount of resistant starch (RS). Canna starch had the highest swelling power and viscosity than other starches and flours. The clearest paste was observed from cassava flour and starch as opposed to konjac starch which was the most opaque paste. Subsequently, physicochemical properties of composite flours made of wheat flours at different protein contents (low and high protein contents) and canna or konjac flours at different level substitution (0, 25, 50, 75, and 100%) were prepared and analyzed. Compared to that of wheat flour alone, the increasing level of canna flour from 0-100% significantly increased the amount of RS but decreased protein content of wheat-canna composite flours. This substitution did not alter the TS, amylose, and amylopectin contents of these mixtures. Changes of physicochemical properties were also observed in wheat-konjac composite flours. The increasing amount of konjac flour decreased the TS, amylose, amylopectin, and protein content of the mixtures. Substitution of wheat flour with 75% of canna or konjac flours in HPWC (High Protein Wheat-Canna), HPWK (High Protein Wheat-Konjac), and LPWK (Low Protein Wheat-Konjac) increased the swelling power of these mixtures at 80 and 90◦C. In general, substitution of wheat flour with up to 50% of canna or konjac flours significantly decreased viscosity of composite flours. Further increase of canna or konjac flours did not cause any other observable decline. In addition, the substitution of wheat flour with canna or konjac flours increased the gelatinization temperature of all composite flours.

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