Preparations And Properties Of Pectin And Superfined Powder From Abelmoschus Esculentus (L.)

Okra, Abelmoschus esculentus (L.) is a nutrient-rich vegetable with a variety of good medicinal value, like anti-fatigue and lowering serum cholesterol. Currently it has attracted more and more concern. This paper takes okra pods as raw material, mainly studies the extraction process of the pectin from the okra, the rheological property, the preparation of superfined okra powder and its physicochemical property and the adsorption of cholesterol. The results provide a theoretical basis for the further development of okra as functional food.The optimal conditions of pectin extraction were optimized as:liquid-solid ratio 42:1,extracting time 64 min, extraction temperature 60℃ and pH 3.9. Under this condition, the extraction rate of pectin was verified as 2.68±0.005%. The molecular weight of okra pectin is 5.94 × 103 kDa tested by HPLC.Based on the results by the Fourier transform infrared spectrometer, the okra pectin showed two absorption peaks within 1610-1630 and 1720-1740-1 cm-1, which is typical peak of carboxylic ester and uronic acid respectively.The intrinsic viscosity [η]of okra pectin was determined as 1656 mL/g. The apparent viscosity of okra pectin solution increased with the increment of pectin concentration and the sucrose concentration, while decreased with increasing temperature and shear rate. Experiments showed that the apparent viscosity of okra pectin solution was highest at pH 5.0, diminished with the raise or decrease of pH value. At a liquid-solid ratio more than 1.0% w/w in aqueous solution, the pectin extracted from okra presented non-Newtonian shear-thinning behavior and could be well described by the Cross model. Okra pectin is a typical weak gel, and lower temperature and higher concentration were helpful to gelation.The okra superfine powder were obtained using high pressure pulverizer, and the average particle size reached 18.69μm.The results showed that superfine grinding technology could efficiently pulverize the particles to submicron scaled. The differences of particle characteristics and total flavonoids extraction amount between crude powder and superfine are significant.The optimum conditions for the adsorption of cholesterol by okra superfined powder were as following:1.50 mg/mL initial cholesterol concentration,1:30 (m/V) solid-to-liquid ratio,60 min and 25℃. Under these conditions, the maximum adsorption quantity reached 39.40 mg/g. The adsorption process was dynamically and thermodynamically analyzed. The results indicated that the physical adsorption held a dominant position in the adsorption process and easily occurred. Besides, surface absorption played a leading role at low cholesterol concentrations, but both surface adsorption and intraparticle diffusion were dominant at high cholesterol concentrations. The results are useful for the application of okra and related functional products in the food industry.