Effects of Xanthan Gum and Protein Isolates on the Functional Properties of Lablab Bean (Dolichos lablab) Seeds Starch

Abstract

Background and Objective: Lablab bean seeds (Dolichos lablab) contain high protein and resistant starch. The resistant starch possesses an important function for health. However, it has poor functional properties, so its use in food products is limited. The purpose of this study was to improve the functional properties of starch from lablab bean seeds by interacting it with proteins and gum xanthan. Materials and Methods: Starch was isolated from the flour that has been made free from fat and protein. The interaction between lablab bean seed starch with protein fraction and xanthan gum was conducted using the following steps: Five gram protein fraction was mixed with xanthan gum in the amounts of 0.1, 0.2 and 0.3 g and without xanthan gum as a control. The mixture was diluted in 100 mL water using a 250 mL beaker glass and was brought to a pH of 7 using 0.1 M NaOH . The solution was stirred for 10 min until homogeneous. A total of100 g (dry weight) of lablab bean seed starch was added to each treatment and stirred. In all treatments, the mixture was heated to 120°C for 2 h and cooled in a desiccator for 1 h. The flours were crushed and sieved with a (100 sized) mash and were observed. A randomized block design was used for this study. Results: The functional properties of starch after interacting with protein (5%) and gum xanthan (0.1-0.3%) were better than those without interaction, especially in functionality related to viscosity, swelling power, water holding capacity and emulsion capacity; however, the gelatinization temperature rose above 80°C while starch only requires 76°C. Conclusion: This study found that functional properties of starch interacted with 5% protein and 0.2% gum xanthan yielded the best flour. It is recommended to be used as an ingredient for food products such as noodles, bread, biscuits, snacks and others.