Comparison of pasting and rheological properties of rice flours and cross-linked waxy rice starches using the Rapid Visco Analyser and dynamic rheometer

Abstract

The pasting and rheological properties of rice flour and starch are critical for assessing functional and structural qualities of food products. This study aimed to develop a method for assessing the distinct pasting properties of rice flours from short-, medium-, and long-grain cultivars with varying amylose contents, and native and cross-linked waxy rice starches by the oscillatory rheometer equipped with a parallel plate geometry. In contrast to the standard procedure by the Rapid Visco Analyser (RVA), which requires ∼3 g of sample and only measures the pasting properties, the oscillatory rheometer allows for the sequential analysis of pasting and rheological properties with smaller sample sizes as low as 25 mg. When 200 mg or 25 mg of flour or starch were used, the oscillatory rheometer obtained similar pasting profiles to the RVA and assessed the viscoelastic behavior of the resulting pastes, which correlated with the amylose content. Using 25 mg of sample, with a 0.4 mm gap, allowed for the differentiation of the storage moduli across varying levels of cross-linking. A smaller gap size relative to the sample amount, e. g. 100 mg of sample with a 0.5 mm gap, did not distinguish the pasting profiles of rice flours with similar amylose contents, possibly due to excessive granule swelling and breakdown. This study highlights the capability of the oscillatory rheometer to characterize starch functionality, offering a robust method for sequentially analyzing pasting and viscoelastic properties of limited samples, such as those from breeding programs.