University of Khartoum

Physico chemical and structural characterization of germinated and cooked lentils (Lens culinaris Medic)

Physico chemical and structural characterization of germinated and cooked lentils (Lens culinaris Medic)

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Title: Physico chemical and structural characterization of germinated and cooked lentils (Lens culinaris Medic)
Author: Sulieman, Mashair Ahmed
Abstract: Legumes such as lentil contain a high concentration of proteins, carbohydrates and make an important contribution to human diet in many countries. Lentil is a nutritious food legume cultivated for its seeds which have a relatively higher content of protein and calories compared to other legumes, it is a protein\\\\\\\\ calorie crop. Four lentil cultivars were used in this study, three of which are Sudanese (Rubatab,Nadi and Selaim),obtained from Elhudaiba Research Station ,the fourth one (Indian) is obtained from Khartoum North market. Proximate composition showed moisture content ranging from 6.4-10.3%, ash 2.7-3.7% ,fat 1.9-2.4% ,fibre 1.2-4.1% and protein 32.4-35.6%.Solubility of lentil protein was determined at pH values1-12 and sodium chloride concentrations 0.2-1N; minimum protein solubility was observed at pH 5.0.The protein was coagulated at the isoelecteric pH(5.0).Protein isolate were obtained for Nadi and Selaim.The isolates had 80% protein content and functional properties of lentil protein isolates were studied. Lentil protein has good functional characteristics with emulsification activity of 75.3-62.94% and emulsion stability was 41.4-46.3% and has lower foaming capacity with higher stability. The total protein was highly dispersible with a water absorption capacity of 1.9-2.2 ml H2O/g protein. Oil absorption capacity of 1.9-2.0 ml oil/g protein and bulk density of 1.4 g/ml. Lentil with high protein content has acceptable functional properties which makes it a promising protein source in food systems and its high nitrogen solubility and less than 1% fat content a characteristic generally needed for textured product like meat. Also, lentil can be incorporated in beverages and infant formula. Sudanese lentil cultivars (Rubatab, Nadi and Selaim) were germinated for 3 and 6 days. The germinated seeds were dried and milled. Proximate composition, phytic acid content, phytase activity and hydrocholoric acid (HCl) extractability of minerals were determined .During germination crude fat and fiber increased, whereas nitrogen free extract (NFE) and food energy decreased. Phytic acid content decreased significantly (pX04; .05) with an increase in germination time Germination resulted in a decrease in total phytate phosphorus with correspondingly marked increase in non-phytate phosphorus. Total and extractible mineral elements estimated in this study (phosphorus, calcium, iron, magnesium) were positively correlated with duration of germination except copper and zinc. Germination for 3 days increased phytase activity significantly (pX04; 0.05) for all cultivars. Phytase activity of Rubatab cultivar continued to increase up to 6 days germination, however for Nadi and Selaim cultivars it slightly decreased. In order to obtain lentil seeds with high phytase activity low phytic acid and high mineral extractability, germination for not more than 3 days is recommended. In studying the effect of germination on the amino acid content results indicate that germination increase partly of or all essential and nonessential amino acids with slight variation between cultivars. In Selaim cultivar, germinating seeds for 3 days increased the proportion of all essential amino acids except methionine; increasing the period of germination to six days decreased amino acid content, this was observed for histidine, lysine and arginine. This result was also observed for Rubatab cultivar in which the content of essential amino acids was increased due to germination except methionine and lysine. In Nadi cultivar germination for three days increased the essential and nonessential amino acids. Generally all lentil cultivars were low in their content of sulfur amino acids : methionine and cystine. The effect of cooking on protein digestibility, protein fractions and their electrophoretic characteristic for lentil cultivars was investigated. Cooking significantly (p X04; 0.05) reduced the protein digestibility using pepsin and/or pancreatin. Pepsin digestibility of raw seeds ranged from 44.6 to 52.1% and that of both pepsin and pancreatin ranged from 81.8 to 99.9%. Cooking reduced the protein digestibility of the cultivars and was found to range from 22.3 to 19.7% when pepsin was used and ranged from 77.1 to 88.2% when both pepsin and pancreatin were used. The major protein in lentil was albumin followed by globulin. Cooking significantly (p X04; 0.05) decreased the albumin fraction. This decrease was accompanied by significant increment in the glutelin fractions. SDS–PAGE electrophoresis of cooked lentil protein fractions showed that lentil protein was altered quantitatively and qualitatively due to cooking. Numbers of subunits of total protein in lentil cultivars before cooking ranged from 17 to 19 bands. However, after cooking they decreased and ranged from 13 to 16 bands. The effect of cooking was most pronounced in the prolamins fractions and its subunits were reduced from 4 to 2 with a high molecular weight of 56.0 kDa.
URI: http://khartoumspace.uofk.edu/handle/123456789/12912
Date: 2015-06-16


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