Effect of Hot-Air Drying and Vacuum Drying on Oxalate Contents of Limnophila Aromatica and Limnophila Geoffrayi
Keywords:Hot-air, Vacuum drying, Rice paddy herb, Vegetables, Soluble oxalate
This study investigated the total, soluble and insoluble oxalate contents of two rice paddy herbs (Limnophila aromatica and Limnophila geoffrayi) as affected by hot-air and vacuum drying methods at different temperatures (50, 60, 70, and 80°C). Overall, the lowest content of soluble oxalate was observed which a high temperature (70 and 80°C) of hot-air dried samples (3.47 and 3.14 mg/g DW in L. geoffrayi and 11.39 and 11.75 mg/g DW in L. aromatic, respectively), while soluble oxalate content was highest in the high temperature (80°C) vacuum dried samples (5.84 mg/g DW in L. geoffrayi and 18.23 mg/g DW in
L. aromatica, respectively). With an increase in drying temperature, there was significantly decreased soluble oxalate content in the hot-air dried samples, while oxalate content increased in the vacuum dried samples. Total oxalate contents had slight changes with the same trend for soluble oxalates. On the other hand, insoluble oxalate content showed a contrasting effect with the soluble and total oxalate content. In addition, the results showed that the soluble and total oxalate contents for various drying temperatures for the
L. geoffrayi species were significantly lower than for the L. aromatica species. Hot-air drying at 70°C provided the optimal results with respect to the content of soluble oxalates.
Borghi, L., Meschi, T., Maggiore, U. and Prati, B. 2006. Dietary therapy in idiopathic nephrolithiasis. Nutrition Reviews. 64:301–312.
Budaraga, I.K. 2017. Processing taro tubers (Colocasia esculenta (L) Schott) become flour as efforts to increase community revenues in mentawai region. International Journal of Life Sciences Research. 5(2):62–70.
Do, T.L. 1999. Vietnamese medicinal plants, Medicine Publishing House, Hanoi, Vietnam.
Grases, F., Costa-Bauza, A. and Prieto, R.M. 2006. Renal lithiasis and nutrition. Nutrition Journal. 5:23.
Haines, P.J. 2002. Principles of thermal analysis and calorimetry. The Royal Society of Chemistry.
Holloway, W.D., Argall, M.E., Jealous, W.T., Lee, J.A. and Bradbury, J.H. 1989. Organic acids and calcium oxalate in tropical root crops. Journal of Agricultural and Food Chemistry. 37:337–341.
Jangam, S.V. and Mujumdar, A.S. 2010. Classification and selection of dryers for foods.
In L.C.L.S.V. Jangam, A.S. Mujumdar (Eds.). Drying of Foods, Vegetables and Fruits. 1:59–82.
Jaya, S. and Das, H. 2003. A vacuum drying model for mango pulp. Drying Technology. 21:1215–1234.
Judprasong, K., Charoenkiatkul, S., Sungpuag, P., Vasanachitt, K. and Nakjamanong, Y. 2006. Total and soluble oxalate contents in Thai vegetables, cereal grains and legume seeds and their changes after cooking. Journal of Food Composition and Analysis. 19:340–347.
Kumoro, A.C. 2012. Development of efficient calcium oxalate removal techniques from taro corms. Prosiding SNST ke-3 Tahun. 6–11.
Massey, L.K. 2007. Food oxalate: factors affecting measurement, biological variation, and bioavailability. Journal of the American Dietetic Association. 107:1191–1194.
Mitra, J., Shrivastava, S.L. and Rao, P.S. 2011. Process optimisation of vacuum drying of onion slices. Czech Journal of Food Sciences. 29:586–594.
Noonan, S.C. and Savage, G.P. 1999. Oxalate content of foods and its effect on humans. Asia Pacific Journal of Clinical Nutrition. 8:64–74.
Pan, Y.K., Zhao, L.J., Hu, W.B. 1999. The effect of tempering–intermittent drying on quality and energy of plant materials. Drying Technology. 17:1795–1812.
Perera, C.O., Hallett, I.C., Nguyen, T.T. and Charles, J.C. 1990. Calcium oxalate crystals: the irritant factor in kiwifruit. Journal of Food Science. 55:1066–1069.
Praveen Kumar, D.G., Umesh Hebbar, H., Sukumar, D. and Ramesh, M.N. 2005. Infrared and hot-air drying of onions. Journal of Food Processing and Preservation. 29:132–150.
Proctor, D.L. 1994. Grain storage techniques - Evolution and trends in developing countries. Food and Agriculture Organization of the United Nations (FAO), Rome.
Reis, F.R., Lenzi, M.K. and Masson, M.L. 2012. Effect of vacuum drying conditions on the quality of yacon (smallanthus sonchifolius) slices: process optimization toward color quality. Journal of Food Processing and Preservation. 36:67–73.
Sahari, M.A., Hamidi-Esfehani, Z. and Samadlui, H. 2008. Optimization of vacuum drying characteristics of date powder. Drying Technology. 26:793–797.
Savage, G.P., Vanhanen, L., Mason, S.M. and Ross, A.B. 2000. Effect of cooking on the soluble and insoluble oxalate content of some New Zealand foods. Journal of Food Composition and Analysis. 13:201–206.
Scholz, E. 1984. Karl fischer titration: determination of water. Springer: New York.
Simpson, T.S., Savage, G.P., Sherlock, R. and Vanhanen, L.P. 2009. Oxalate content of silver beet leaves (Beta vulgaris var. cicla) at different stages of maturation and the effect of cooking with different milk sources. Journal of Agricultural and Food Chemistry. 57: 10804–10808.
Suksamrarn, A., Poomsing, P., Aroonrerk, N., Punjanon, T., Suksamrarn, S. and Kongkun, S. 2003. Antimycobacterial and antioxidant flavones from Limnophila geoffrayi. Archives of Pharmacal Research. 26:816–820.
Wanyo, P., Siriamornpun, S. and Meeso, N. 2011. Improvement of quality and antioxidant properties of dried mulberry leaves with combined far-infrared radiation and air convection in Thai tea process. Food and Bioproducts Processing. 89:22–30.