Characterization, Functional Applications and Cytotoxicity of the Piliostigma reticulatum gum

Abstract

Thirty samples of mature dry seeds of Piliostigma reticulatum (Carob) trees were collected from the areas around Nyala town – southern Darfur state, Sudan, during the seasons 2014, 2015 and 2016. The seeds were dehusked; the germ and gum were separated manually. Physicochemical characterization and toxicity of the gum and germ samples were studied . Rheological, emulsification and some thickening application properties of Piliostigma reticulatum gum were also studied. The results obtained, showed mean values for the moisture (4.03%) , ash (3.09%) , water holding capacity (2.64 % ) , nitrogen content (2.75%) and protein content( 17.19%) for the gum , while for the germ the moisture ( 5.6%) , ash (7.21 %) , Water holding capacity( 1.93% ) , nitrogen content( 10.94% ) and protein content (68.38 %). Both gum and germ are insoluble, in cold-water and organic solvents. The solubility at 60 °C of gum sample in H2O, 0 .1 M Na2CO3 and 0.5 M NaHCO3 were 8.2%, 48.9% and 80% respectively, and gelled using 0.5MNa2B4O7 and 0.1 M NaOH. Whereas that of germ sample in H2O , 0 .1 M Na2CO3 , 0.5 M NaHCO3 , 0.5 MNa2B4O7 , 0.1 M NaOH , 0.5 M NaOH and 1M NaOH were 22.7%, 53.5% ,60% ,81% ,46.5% , 69% and 74% respectively . Elemental analysis shows that, both gum and germ are rich in potassium, calcium, phosphorus and silicon, but have low contents of sodium, zinc and manganese. Percent averages of sugar composition of the gum is mannose (42.58%) , galactose (20.27% ) and ribose(1.79 %) , while percent sugar composition of germ is glucose (3.4%) , fructose(6.9%) and sucrose (5.6%) . Amino acid content of gum and germ were determined .The results showed the presence of fifteen amino acids namely, Asparagine , Threnine , Serine , Glutamine , Proline , Glysine , Alanine , Valine , Methionine , Leucine , Tyrosine , v Phenylalanine , Histidine , Lysine and Arginine. Rheological properties of the gum reveal a non-Newtonian behavior. At low concentrations 1, 2 and 3% (w/w) at 25 °C the behaviour is shear thinning while at concentration 5 % (w/w) the behaviour is shear- thickening. The viscosity at different temperatures was measured at concentration 3% (w/w), the result showed that the viscosity was decreased as temperature increased. Rheological study properties of the Corn Starch – Piliostigma reticulatum gum mixture result showed that shear thinning behaviour. Emulsification studies of Piliostigma reticulatum gum showed that the gum has less emulsifying stability and larger droplet size. Thickening application studies of gum in Yogurt and Baking, results showed that in Yogurt it is good thickening and stabilizing agent and improve the quality of bread .Toxicological study of Piliostigma reticulatum gum and germ on two types of cancer human cells lines, was undertaken to assess the safety of using the germ and gum as food additives. The results showed that Piliostigma reticulatum germ is harmful and the gum has no toxic effect.