Document Type : Research Article
Authors
Department of Food Science and Technology, Sari Agricultural Sciences and Natural Resources University, Iran.
Abstract
Introduction: The Phaseolus Vulgaris on a global scale of cultivation has been categorized in the first rank and considered as the seventh staple food in the world. Proteins are usually classified into 3 groups including flours with 50 to 65 percent protein, concentrate with 65 percent protein and isolates with over 90 percent protein. Protein concentrate is produced by defatted flour through removal of soluble sugars, soluble fiber and minor compounds by alcohol, water or diluted acid with pH around 4-4.8. Protein isolate is affected by further refining processes compared to protein concentrate. In addition to the importance of the nutritional properties, crop proteins have a key role as a functional agent in the formulation of food products. Solubility, water binding capacity, oil absorption capacity, emulsifying and foaming abilities are noticed as the main functional properties. One of the specific and unique varieties of beans is Phaseolus Vulgaris var (aroos bean). The aim of this study was to determine the chemical composition of flour and bean protein isolate. In addition, some of the functional properties such as emulsification properties, foaming and stability as well as the effect of pH and ionic strength on above-mentioned characteristics were investigated.
Materials and Methods: The seed of Phaseolus Vulgaris and refined soybean oil (0ila) were purchased from Sari local supermarket. Phaseolus Vulgaris protein isolate was extracted and obtained powder was kept in impervious polyethylene plastic bags against moisture and air and placed at -18 ° C until analysis. The efficiency was calculated based on the sediment. Also, chemical composition and purity of the isolates were determined. Some functional properties, including emulsifying properties and foaming capacity at pH 4, 7, 8 and 10 were tested; and impact of the ionic strength of NaCl in concentrations of 0, 0.5 and 1 molar were examined. The results of all treatments were expressed based on the average of triplicate. Means were subjected to analysis of variances (one way-ANOVA) using (SPSS Statistics version 16) software program. Differences among the mean values of the various treatments were determined by Duncan test and the significance was defined at p < 0.05. The graphs were drawn using Excel software.
Results and Discussion: Phaseolus Vulgaris had 9% protein isolate efficiency and purity of 89.06%. The amount of protein in Phaseolus Vulgaris flour was less than the amount of protein that has been reported for other crops. While in terms of purity, protein isolate was similar to legumes in other studies. Foaming ability and emulsifying properties of Phaseolus Vulgaris protein isolate at 7 = pH were 42% and 65%, respectively. The value of this parameter using exposure to alkaline region and keeping far from the isoelectric point at pH = 10 were risen to the highest amount of 70.23% and 77.33%, respectively. During 90 minutes, stability of emulsions and foams were gradually decreased. With increasing of NaCl concentrations, foaming capacity and emulsifying properties were significantly reduced. Considering the efficient functional of Phaseolus Vulgaris protein isolate, further investigation required in order to be used in the formulation of meat products, cakes, cookies, crackers, sauces and soups.
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