Influence of jet-cooking temperature and ionic strength on size and structure of cationic potato amylopectin starch as measured by asymmetrical flow field-flow fractionation multi-angle light scattering

Asymmetrical flow field-flow fractionation (AsFIFFF) in combination with multi-angle light scattering (MALS) was applied to cationic potato amylopectin (CPAP) to investigate how molar mass, root-mean-square (r.m.s.) radius and shape was influenced by different conditions of jet-cooking. The effect of different jet-cooking temperatures in the range 110 degrees C - 140 degrees C was studied in an excess steam jet-cooker. This equipment is used in the industry for dissolution of starch and starch derivatives before technical application. The effect of different ionic strengths conditions was examined in the range of 10-200 mM. The weight-average molar mass decreased from about 34 x 10(7) g/mol to 2.6 x 10(7) g/mol when the jet-cooking temperature was increased from 110 degrees C to 140 degrees C. Concurrently the root-mean-square radius decreased from ca 380 nm to 90 nm. The decrease in size was reflected by a decrease in viscosity with increasing temperature. The root-mean-square radius was reduced when increasing the ionic strength. This decrease in size was correlated with a decrease in viscosity. Conformation and Kratky plots showed that at low ionic strength (<= 10 mM) CPAP behaved as a flexible chain with high degree of branching, close to hyperbranching. Increase of the ionic strength gave a more compact structure and changes in the internal structure were observed as well. Consequently, by using AsFIFFF - MAILS the effect of technical processing on the molar mass, molecular radius, conformational structure, and shape could be determined in a size region where standard methodology commonly fails.