Abstract
Full-fat and defatted coconut protein concentrates containing 27.80% and 30.20% proteins (on a dry weight basis), respectively, were prepared from freeze-dried coconut meal samples. Selected functional properties such as: nitrogen solubility, emulsion and foaming properties were determined. Nitrogen solubility was measured in the range of PH 2.0-12.0 in three dispersion media including water, 0.1M NaCl (low salt) and 1.0M NaCl (high salt). The emulsion properties of the protein concentrates were measured at varying PH values (2.0-10.0) and sample concentrations. Foaming properties were determined using same parameters including the use of additives (NaCl solutions and carbohydrates). Below and above the isoelectric PH (4.0-5.0) the nitrogen solubility increased. The coconut protein samples showed a fairly high solubility (more than 54.0% and 53.0%) for full-fat coconut protein concentrate (FFC-PC) and defatted coconut protein concentrate (DFC-PC), respectively at pH 2.0. FFC-PC sample had maximum solubility (more than 73%) at 10.5 and minimum solubility (13.2%) at PH 4.0. On the alkaline PH scale, FFC-PC sample had maximum solubility of more than 43% at PH 10.5 in high salt (1.0M NaCl) solution while DFC-PC sample had maximum solubility of 50.2% in 1.0M NaCl solution and more than 80% in low salt (0.1M NaCl) dispersion medium. The emulsions prepared had good stability. A maximum of 92.5ml/g protein of emulsification capacity, at PH 10.0 and minimum of 45.3ml/g protein at PH 4.0 were obtained for FFC-PC while DFC-PC had a maximum EC of 86.4ml/g protein. FFC-PC samples produced significantly (P≤0.05) higher emulsion capacities than DFC-PC samples at all the dispersion PH and sample concentrations investigated. The FFC-PC samples had a significantly low foaming capacity than the DFC-PC samples at all the tested PH values. Similarly, the foaming capacities of FFC-PC and DFC-PC decreased with increasing PH of the sample medium. Both FFC-PC and DFC-PC foams collapsed completely, after 3hr standing at ambient temperature. Foaming was concentration dependent. The FFC-PC and DFC-PC foams increased sharply at 0.2% NaCl content of the sample slurries and progressed steadily to a peak of 92.0% and 113% in FFC-PC and DFC-PC samples respectively in 0.8% NaCl solution and then declined gradually with increased salt concentration. Addition of polymeric carbohydrates (sucrose, corn starch, gum acacia and pectins) significantly improved foaming properties of the protein concentrates but the foam stabilities were not significantly affected. Keywords: Coconut, Protein, Solubility, Foaming, EmulsionAJFAND Vol. 8 (2) 2008 pp. 170-191
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