Effects of soaking, steaming and vacuum microwave heating on structure and physical property of quick cooking Job’s Tear

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Aumaporn Arlai
Siriya Kietbunsri


Job’s Tears is one of the most fruitful nutritional foods. However, it consumes a lot of cooking time prior to consumption. If the cooking time of Job’s Tears could be reasonably reduced, it would be more convenient and an incentive to consumers to eat more Job’s Tears. The main objective of this study is to reduce cooking time of Job’s Tears by reducing its moisture with vacuum microwave heating. The experiments were conducted by soaking (6 and 7 h) and steaming (at 100oC for 20 and 30 min), after which the grains were dehydrated by vacuum microwave (60, 80 and 100% power). It was found that increased soaking and steaming times decreased percentages of water uptake and cooking time, whereas increasing the microwave power levels did not. The lightness (L*) changed significantly with increased soaking-, steaming- and power conditions. Scanning electron micrographs (SEM) showed the absolute change in starch granules, becoming more honeycomb-like in structure and formed fractures after strong treatment. Based on these results, the optimal treatment for precooked Job’s Tears grains consisted of soaking for 7 h, steaming for 30 min and drying at 80% microwave power. By using these combining parameters, the reduction of the cooking time by about 53.3% while still maintaining good sensory qualities (data not shown), was achieved.


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Arlai, A., & Kietbunsri, S. (2017). Effects of soaking, steaming and vacuum microwave heating on structure and physical property of quick cooking Job’s Tear. Interdisciplinary Research Review, 12(1), 16–21. https://doi.org/10.14456/jtir.2017.3
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