Products of thermolysis of potato starch treated with hydrochloric and citric acids as potential prebiotics

Abstract

New starch preparations were produced by thermolysis of potato starch in the presence of inorganic (hydrochloric) and organic (citric) acids at 150 °C for 3 h and 180 °C for 1 h. The resulting dextrins were physicochemically and structurally characterised and analysed for their resistance to enzymatic digestion in vitro. Moreover, dextrins were tested as products with potential prebiotic properties, selectively stimulated growth and activity of beneficial bacteria, band not contributed to growth of undesirable intestinal microflora. It was found that depolymerisation of the starch was not accompanied by significant chemical modification. Citric acid acted as activator or catalyst for repolymerisation and polycondensation of glucose polymers with low molecular weight saccharides to form non-digestible products. The studies indicated possibility of preparation of well-soluble dextrins, with low water binding capacity, of low pH and very low viscosity, containing about 80% of molecules with weight average molecular weight of 3,500 g/mol (average degree of polymerisation @ 22), with reduced caloric value in comparison to native starch, as a result of their resistance to enzymatic hydrolysis. Microbial studies revealed that beneficial Lactobacillus and Bifidobacterium, in the presence of dextrins prepared with citric acid, were able to dominate the environment in the common culture with other bacteria isolated from human faeces. The results confirmed the possibility of applying dextrins, prepared under specific conditions, as soluble dietary fibre and after fulfilment of additional requirements – also prebiotics.