The mucilage of okra (Abelmoschus esculentus (L.) Moench), containing high amount of gum and pectin, possesses the structure of rhamnogalacturonan which has thickening properties [1,2]. Pectin in okra is a low-methoxy type, which forms gel with calcium ion at low sugar concentration. The aim of this research is to study the application of okra's extract as a thickening agent and to reduce sucrose content in strawberry jam. Firstly, the optimum temperature for the extraction of the okra was investigated. Physical analyses were determined by % yield, flowing distance (viscosity) and color values (Hunter L* a* b*). It was found that at four different extracting temperatures, i.e, 50, 60, 70 and 80 °C, the optimum temperature for the extraction was 60 °C. Then, gelation properties of the okra's extract were investigated in 3 different concentrations of sucrose at 50, 60 and 70% (by weight of okra's extract) and 3 different concentrations of calcium chloride at 2, 2.5 and 3% (by total weight). Secondly, the physical analysis results showed that the sugar content at 50% and the calcium chloride concentration at 2% had the highest viscosity. Finally, an appropriate ratio of the okra's extract to reduce sucrose content in strawberry jam was further studied at either 60:40, or 40:60, or 80:20 (by sucrose weight) and the pectin content was varied at 0.5 and 1% (by total weight). The jam with the ratio of sucrose to okra's extract at 40:60, and of pectin at 0.5%, possessed the highest spreadability and the lowest viscosity. Additionally, at this concentration the sensory scores in appearance and spreadability were higher than those of the control.
[1] Woolfe, M.L, Chaplin, M.F. and Otchere, G. J. Sci. Fd Agric. 1977; 28: 519 – 529.
[2] Bhat, U.S, Tharathan, R.N. Starch 1987; 39: 165 – 167.
