Extruded pellets were prepared from normal corn starch using a corotating twin‐screw extruder (25:1 L/D ratio, 31 mm diameter screw), and then expanded by heating in a conventional microwave oven for 70 sec. The effects of gelatinization level and moisture content of the extruded pellets on the morphology and physical properties of the microwave‐expanded products such as puffing efficiency, expansion bulk volume, and bulk density were investigated. The expanded shape and air cell structure differed according to the degree of gelatinization of the pellets. Maximum puffing efficiency and expansion volume with the pellets containing 11% moisture were achieved at 52% gelatinization. For this level of gelatinization, starch was extruded at 90°C barrel temperature. In addition, the moisture content of the pellets critically affected the expansion behavior. The maximum puffing efficiency and expansion volume were achieved in a moisture range of 10~13%. For optimum product shape and uniform air cell distribution, the pellets should undergo sudden release of the superheated vapor during the microwave‐heating. The expansion by microwave‐heating was optimized at ≈50% gelatinization.
The objective of this study was to evaluate the qualities of Topokki Garaedduk by different moisture ratios (rice flour : water=1:0.3, 1:0.4, 1:0.5). Topokki Garaedduk was investigated in terms of its moisture, texture, and sensory properties. The moisture content of Topokki Garaedduk was increased. The hardness, chewiness, and cohesiveness of Topokki Garaedduk significantly decreased with increased moisture ratios, however springiness and adhesiveness were not significantly changed. Water absorption of Topokki Garaedduk was increased and solid content showed no significant differences with increasing moisture ratio. A sensory evaluation showed that the moistness of Topokki Garaedduk increased, while hardness, and springiness decreased with increasing moisture ratios. The overall acceptability of Topokki Garaedduk at the 1:0.4 ratio of rice flour : water scored highest at 6.92 among the samples (p<0.05). The correlation coefficient between sensory moistness and moisture content was significantly increased (R 2 =0.91). As a result of this study, Topokki Garaedduk with an additional 40% moisture content (rice flour : water=1:0.4) had the most suitable quality properties.
Pumpkin (Cucurbita sp.) is a widely consumed fruit as it has high carotenoid content and
medicinal value, but has a relatively short shelf life and prone to microbial spoilage.
Various drying techniques have been introduced to the industry to preserve pumpkinbased products. During the drying process, products are prone to serious decay caused by
changes in temperature, thus affecting the physical or chemical properties of the product.
The objective of this study was to determine the effects of different drying methods on the
physical properties and proximate composition of pumpkin powder produced from
different parts of the fruit. Samples were made using unpeeled pumpkin and parts of the
fruit, i.e. skin, flesh and seed and were dried using different drying methods, i.e. oven (80°
C), rapid hot air oven (80°C) and freeze dryer (-110°C). The dried samples were then
milled and sieved at approximately 250 µm and 710 µm in diameter. Different drying
methods had a significant influence on the physical and chemical properties of the
samples (p<0.05). Rapid hot air drying showed a promising impact on the production of
pumpkin powder resulting in powder with a moisture content of 5.61-6.89%, particle size
of 122.98-256.46 µm, and density of 304.80-724.69 kg/m3
. These results were better than
freeze-dried powders. Proximate composition values of samples dried using rapid hot air
were also found to be better than oven-dried powder with a protein content of 9.86-
31.54% and fat content of 3.88-34.93%. In conclusion, rapid hot air-dried powder showed
the best quality in terms of physical properties and proximate composition.
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