Abstract
The effect of temperature (35, 50, and 60°C) on the rehydration behavior of microwave‐dried amaranth (Amaranthus dubius) leaves was investigated. Leaves were dried at 700 W power level before rehydrating in water. The higher the rehydration temperature, the higher the equilibrium moisture content of the leaves, although the effect was not statistically significant. The increase in rehydration ratio was significant only as temperature increased from 50 to 60°C. The process was adequately described by the Peleg sorption model, with the Peleg rate constant (K 1) and the Peleg capacity constant (K 2), both decreasing as rehydration temperature increased. While the color difference (ΔE) between fresh leaves and leaves rehydrated at 35°C was significantly higher than for the leaves rehydrated at 50 and 60°C, this difference was not visible. Cooking of leaves occurred beyond 120 min at the higher rehydration temperatures . Based on the results, rehydration of microwave‐dried leaves was successfully carried out at 35°C, however, rehydrated leaves were darker than the fresh leaves. Increasing the temperature to 50°C improved the rehydration capacity and the color of the leaves, however, cooking of leaves occurred by the second hour of the process.
Highlights
The genus Amaranth consists of approximately 60 plant species, some of which are used as food grain, leafy vegetables, and ornamentals (Borneo & Aguirre, 2008)
They found that betel leaves rehydrated at the lower temperatures of 25 and 40°C mostly resembled fresh leaves compared with leaves that were rehydrated at 80°C
Amaranth leaves were successfully rehydrated in water at 35–60°C
Summary
The genus Amaranth consists of approximately 60 plant species, some of which are used as food grain, leafy vegetables, and ornamentals (Borneo & Aguirre, 2008). Vegetable amaranth (Amaranthus sp.) grows in the Caribbean and is widely used throughout the region interchangeably with spinach (Spinacia oleracea L) as a leafy green. Interest in extending the shelf life and adding value to this perishable leafy green led to research work on the microwave drying, and subsequent rehydration of amaranth leaves. Previous research works on dried amaranth have focused primarily on quality and nutrient content of the dried material (Aletor & Abiodun, 2013; Fathima, Begum, & Rajalakshmi, 2001; Peter, Elizabeth, Judith, & Hudson, 2014; Rodriguez, Perez, Romel, & Dufour, 2011) and Borneo and Aguirre (2008) looked at the use of the ground, dried amaranth leaves in green pasta as a spinach substitute. Previous research works on dried amaranth have focused primarily on quality and nutrient content of the dried material (Aletor & Abiodun, 2013; Fathima, Begum, & Rajalakshmi, 2001; Peter, Elizabeth, Judith, & Hudson, 2014; Rodriguez, Perez, Romel, & Dufour, 2011) and Borneo and Aguirre (2008) looked at the use of the ground, dried amaranth leaves in green pasta as a spinach substitute. Akonor and Amankwah (2012) and Singh, Singh, Singh, Singh, and Singh (2014) looked at various aspects of drying kinetics of sun and solar-dried amaranth and Fathima et al (2001), Rajeswari, Bharati, Ramchandranaik, and Naganur (2013) and Pati, Pardeshi, and Shinde (2015) investigated the microwave-drying potential of amaranth leaves
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