Starch Paste Stickiness is a Relevant Native Starch Selection Criterion for Wet-end Paper Manufacturing
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/star_9_03_381_389.doc |
| Abstract: | Summaries. The correct choice of selection and quality criteria is critical for most starch applications. In this study, a set of different potato starches, selected for a large variation in natural phosphate content and final viscosity, was cationised and tested in a laboratory scale wet-end paper manufacturing process. Analysis of further parameters expected to be critical for processing, including amylose content and starch granule size, was also performed. Since no significant correlation was found between any of these parameters and paper processing, further attempts were made to find structural or physico-chemical explanations for the paper processing performance. Hence, several additional parameters of the starches were determined including amylopectin chain length pattern, phosphate substitution, molecular size distribution, pasting-texture properties and fragility of the gelatinised granules. Among these parameters, the best correlation found to paper filler retention was stickiness of the starch as measured by texture analysis. The starches that performed best in the paper trials showed rapid granule bursts that could be readily estimated from the width of the pasting curve peaks. Light microscopy of non-soluble remnant starch obtained after gelatinisation of starch under dilute conditions revealed a high proportion of broken granular structures. It is hypothesised that the degree of phosphorylation, together with a hitherto unknown molecular parameter that is related to starch granule fragility, determines starch paste stickiness, which in turn is an important parameter for wet-end paper manufacturing. Conclusions. Among the number of starch structural and physical parameters analysed, the best correlation to paper filler retention was found to be the stickiness of the starch measured by texture analysis. Parameters with possible relationships to starch stickiness were therefore investigated in more detail. The low non-soluble remnant yield and narrow RVA peaks obtained for starches with high starch phosphate content indicated that starch phosphate induces more efficient starch granule burst. Kuras starch, however, which was the best starch with respect to combination of filler retention and breaking length, had a high phosphate content but a lower remnant yield and narrower RVA peak than expected from the starch phosphate content. B652, being next best, had a moderate starch phosphate content and also showed the same characteristics. It may be speculated that these two starches had inherently weak granule surfaces and that this property resulted in rapid and general granule burst and high stickiness. Light microscopy of starch granule remnants indicated that the ratio between intact and disrupted starch remnants in the starch preparations was related to the stickiness of the starch. Despite a thorough structural determination of the starches and fractions thereof, it was not possible to exclusively assess the detailed molecular constituents related to high stickiness and good paper filler retention of these starches. |
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| ISSN: | ISSN 0038-9056 |
