Multivariate comparison of the Brabender viscograph and the rapid visco analyser using cross-linked starch

The relation between two viscographs, the Brabender Viscograph and the Rapid Visco Analyser (RVA), has been determined by using multivariate statistics. The viscographs determine the properties of cross linked starch products by measuring a viscogram, i.e., the viscosity change during a well defined process of heating. With a Brabender viscograph it takes 50 min to measure the specifications of one sample, an RVA performs a similar temperature cycle in 10 min. The shorter measuring time should make the RVA more suited for process analysis than the Brabender Viscograph, provided that both viscograms give comparable information. A method is presented which establishes the correlation between the viscograms and predicts the Brabender characteristics from the RVA measurement. Viscograph measurements were performed with a set of 60 cross-linked potato starch products. The products were made by setting the levels of reagent, swelling inhibitor, reaction temperature and reaction time. The products were measured on both viscographs, each with its own optimized operating method. All four factors significantly affected the Brabender and RVA viscograms. Principal component analysis showed that the viscograms could be reduced to two principal components. The first principal component is the weighted mean viscosity, the second shows whether the peak viscosity is still present. The relation between Brabender and RVA was analyzed with partial least squares. The analysis shows a strong correlation between both viscographs and the Brabender Viscosities could be predicted from an RVA viscogram.