Tomasz Zięba

Properties of corn starch subjected hydrothermal modification

Abstract The objective of this study was to determine the effect of heating a water dispersion of corn starch to various temperatures, followed by its freezing and defrosting, on selected properties of re-formed starch pastes. A suspension of starch was heated to various temperatures ranging from 59 to 94°C, and afterwards frozen and defrosted. The differential scanning calorimetry (Mettler Toledo, 822E) thermal characteristics of starch pre-heated to temperatures not inducing complete pasting revealed transitions of: (I) retrograded amylopectin, (II) non-pasted starch, (III) amylose-lipid complexes, (IV) retrograded amylose, and (V) highly thermostable starch structures. The application of higher temperatures during heating caused disappearance of transitions II and V. The increase of pre-heating temperature induced firstly a decrease and then stabilization of the swelling power as well as a successive decrease in starch solubility. Pastes pre-heated to temperatures over 79°C contained large macroparticles that were increasing viscosity of the re-formed starch paste (their size was positively correlated with viscosity value).

The influence of freeze-dried red and purple potatoes on content of bioactive polyphenolic compounds and quality properties of extruded maize snacks

Taking into account, that freeze-dried red and purple potatoes are a rich source of polyphenols, mostly anthocyanins, it seems reasonable to utilise such raw material, free of gluten, to produce gluten-free snacks based on maize, by means of extrusion. The aim of the study was to analyse the content of bioactive polyphenols in extruded maize snacks with varying share of freeze-dried red and purple potatoes of the varieties Magenta Love and Blue Star, and to evaluate their antioxidant potential. Additionally the analysis of consumer acceptance of such products was performed. It was observed, that maize extrudates with a share of freeze-dried red and purple potatoes are an innovative, valuable pro-health product which could be used by healthy consumers, but also by the people with certain dietary disorders, such as celiac disease. Application of 25% share of freeze-dried red potatoes Magenta Love variety to extrudates proved to be the best in terms of content of bioactive compounds and antioxidant activity. Also the colour, high sensory scores and improved texture properties suggest that such a product could be well accepted on the market.