Evaluation of chemical and physicochemical properties of dietary fibers extracted from dry bean and chickpea

Legume products such as dry bean, chickpea, peas and lentil have high level of dietary fibre and their dietary fibre fractions are potential functional food ingredients. Altough legume production level is very high in Turkey and the world, dietary fibre intake is not at adequate amount. Dietary fibre is one of the most valuable nutrient for human health because of the positive effects on gastrointestinal system, decreasing glisemic index, cardiovascular disease. There are a lot of studies which are proven the positive health effects of dietary fibre on human health. Legumes contain high amount of dietary fibre in their structures. Dietary fibre is a healthy food additives which has positive effects on especially digestive system, cholesterol and blood sugar. Also, dry bean and chickpea are the most common legumes in Turkey and the most of other countries in the world. Dietary fibres extracted from food legumes are used to improve viscosity, sensory analysis and shelf life of food products. There are a lot of studies about the addition of dietary fibre isolates to bakery products, beverages, chocolates, milk and milk products, meat and meat products, pastas and soups. Generally they add to bakery products because of the high water holding capacities. Thus, shelf life is extended and the economic product loss is reduced. They also used for increasing the viscosity and improve the stability in beverage products. To provide the homogenity, soluble dietary fibres such as pectin and inulin are used in beverage products. Consequently, for all their positive effects on health, there is an increasing trend in product development to integrate legume's dietary fibres into foods such as baking products, dairy products, beverages and meat and meat products. Moreover, physicochemical properties of legume's dietary fibres that are swelling capacity (SC), oil holding capacity (OHC), water holding capacity (WHC), density and emulsion capacity are very important properties for the food production processes. In the food industry, physicochemical properties are the advantages and very important parameters for the processes. The aim of this study is extraction of the dietary fibre from dry bean and chickpea which are the most abundant varieties of legumes by a suitable methods for the usage in food industry and evaluation of that fibres according to chemical and physicochemical properties. Also investigate their purity, chamical composition and some physochemical properties. Dry beans and chickpeas were obtained by Assocation of Agricultural Products, Grains Processing and Packaging Industries (PAKDER) in the scope of the project. Dietary fibre content was extracted and then chemical composition anlysis and some physicochemical analysis were applied to dietary fibre isolates and raw legumes. In the previous studies, hull and cotyledon could not seperated efficiently each other. Because of that, some modifications applied to existing methods and efficiency was increased. Seperated cotyledon and hull amounts are 90,8% cotyledon and 9,2% hull from chickpea and 91,5% cotyledon and 8,5% hull from dry bean. Soluble dietary fiber and insoluble dietary fiber extraction is made from milled cotyledon flours of dry bean and chickpea. Hulls separated from cotyledon are estimated as insoluble dietary fiber because of their high amount of insoluble fibre content. Consequently, total dietary fiber isolate amount that includes soluble dietary fiber isolate of cotyledon, insoluble dietary fiber isolate of cotyledon and hull was calculated as 16,6% from chickpea and 13,7% from dry bean. Chemical composition analysis such as protein, fat, ash and moisture are applied to extracted dietary fibre isolates, cotyledon flours, hulls and raw dry beans and chickpeas. According to that compositional analysis; composition of dry bean insoluble dietary fibre isolate is 6,5% moisture, 3,4% fat, 2,8% ash, 16,4% protein and 70,9 %carbonhydrate; composition of dry bean soluble dietary fiber isolate is 4,4% moisture, 0,6% fat, 4,9% ash, 22,7% protein and 67,4% carbonhydrate; composition of chickpea insoluble dietary fibre isolate is 6,2% moisture, 2,6% fat, 2,1% ash, 17,4% protein, 71,8% carbonhydrate; composition of chickpea soluble dietary fibre is 7,3% moisture, 0,4% fat, 7,4% ash, 19,8% protein and 65,1% carbonhydrate; composition of chickpea cotyledon flour is 19,2% moisture, 4,1% fat, 2,9% ash, 21% protein and 52,8% carbonhydrate, composition of dry bean cotyledon flour is 21,3% moisture, 2,5% fat, 3,9% ash, 22,2% protein and 50,2% carbonhydrate, composition of chickpea hull is 10,6% moisture, 1,9% fat, 3,2% ash, 7,5% protein and 76,8% carbonhydrate; composition of dry bean hull is 15,5% moisture, 1,4% fat, 2,9% ash, 2,9% protein and 77,3% carbonhydrate, composition of raw chickpea is 10,1% moisture, 4,1% fat, 2,9% ash, 21% protein and 61,9% carbonhydrate; composition of dry bean is 11,1% moisture, 2,5% fat, 3,9% ash, 20,3% protein and 62,2%carbonhydrate. Additionally, sugar profile analysis was applied to dietary fibre isolates. According to results, glucose and sucrose are found to be predominant in soluble dietary fibres for both dry bean and chickpea isolate. Also, glucose was the predominant monomer for insoluble dietary fibre isolates extracted dry bean and chickpea. Dietary fibre and protein analysis were made to both of extracted soluble dietary fibre isolates and insoluble dietary fibre isolates, cotyledon flours and separated hulls to determine the composition. According to results of the dietary fibre and protein analysis, dry bean insoluble dietary fibre isolates contain 69,6% dietary fibre and 16,4% protein; dry bean soluble dietary fibre isolates contain 67% dietary fibre and 22,7% protein; chickpea insoluble dietary fibre isolates include 71,2% dietary fibre and 17,4% protein and the chickpea soluble dietary fibres include 63% dietary fibre and 19,8% protein. Additionally, chickpea hulls have 76,6% dietary fibre and 7,5% protein contents, dry bean hulls have 73,9% dietary fibre and 2,9% protein content. This results indicate that protein could not eliminated entirely with this method because for the protein elimination, isoelectric protein precipitation method is applied and protease enzym is not used. Low amount of protein content in the extracted dietary fibre isolates might be an advantage for usage of the fibers in food industry as an alternative ingredient for food processes. Also the final product cost of the fibre isolates might be decreased with this method because only one enzyme is used at a little amount. Moreover, physicochemical analysis which are swelling capacity, oil holding capacity, water holding capacity, density and emlsion forming capacity were applied to both soluble and insoluble dietary fibres. According to results of the oil holding capacity analysis, insoluble dietary fibre extracted from chickpea cotyledon have the highest amount of oil holdinf capacity (8,4 g/g sample). It is determined that, insoluble dietary fiber extracted from dry bean cotyledon has 8 g/g sample and soluble fibre extracted from cotyledon of chickpea has 2,6 g/g sample oil holding capacity. Legumes fibres are used in meat and meat products. According to the results of the oil holding capacity analysis, the insoluble dietary fibre isolates from both dry bean and chickpea can be used in meat products because of the high oil holding capacity If the swelling capacities are compared, insoluble dietary fibre extracted from chickpea cotyledon is have the highest value as 10 ml/g sample. The swelling capacities of the insoluble dietary fibre extracted from dry bean cotyledon, the soluble dietary fibre extracted from dry bean cotyledon and the soluble fibre extracted from cihckpea cotyledon are 4,3 ml/g sample, 3,7 ml/g sample and 1,8 ml/g sample. The water holding capacity of insoluble dietary fibre extracted from chickpea cotyledon have the highest value as 10,2 g/g sample, if it is compared to other dietary fibres. Insoluble dietary fibre extracted from dry bean cotyledon has 7 g/g sample, soluble dietary fibre extracted from dry bean cotyledon has 1,1 g/g sample and soluble dietary fibre extracted from chickpea has 0,9 g/g sample water holding capacity. The water holding capacity is the indicator that is shown the usage of dietary fibre isolates as a functional ingredient. High water holding capacity results in increasing the viscosity and providing the modification of textural structure. The swelling and water holding capacities of dietary fibre isolates are indications of their physiological role for gut function and controlling the glucose levels of blood. Emulsion forming capacities of dry bean soluble dietary fibre isolate, chickpea soluble dietary fibre isolate, dry bean insoluble dietary fibre isolate, chickpea insoluble dietary fiber isolate were determined as 39%, 29%, 17%, 15%. This results show that emulsion capacities of soluble dietary fibre isolates are higher than insoluble dietary fibres isolates. The densities of dietary fibre isolates are determined by direct density and bulk density analysis. According to results, the direct densities of dry bean soluble dietary fibre isolate and chickpea soluble isolate were found as 0,52 g/ml and 0,61 g/ml. 0,15 g/ml and 0,19 g/ml are the densities determined for dry bean insoluble dietary fibre isolate and chickpea dietary fibre isolate. The physiological structure is an indicator for the densities. Soluble dietary fibre isolates have an heavy and powder structure while the insoluble fibre isolates have piece by piece and light structure because of the density differences. Within the scope of the extraction of the dietary fibres with high purity, applied isolation method for insoluble and soluble dietary fibres from dry bean and chickpea was achieved with highly purity. Howewer there are protein, ash, moisture and fat content at low amounts compared to dietary fibre contents in the isolates. Also isolation method has at least amount of enzyme usage because it is desired for the usage as food ingredients in the food industry with low cost.