On the Dispersion and Small-Amplitude Oscillation Measurements of High Amylopectin Potato Starch
| Main Authors: | , , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0038-9056 |
| Online Access: | http://www.viks.sk/chk/star_3_4_03_138_149.doc |
| Abstract: | Summaries. This article is the second part of research on amylose-lipid complexes, where the first article dealt with monoglycerides. Here, a variety of fatty acids with chain lengths between 3 and 22 carbons and with varying degree of unsaturation were studied regarding their ability to form amylose-lipid complexes. In the present paper it is intended to investigate the formation of different fatty acid- amylose complexes under conditions that are not optimised for complex formation. Such conditions are common in the processing of starch. Differential scanning calorimetry (DSC) was used to analyse transition temperatures and enthalpies \\\{H\\\}. The transition enthalpy H was taken as a measure of the quantity of the complexes in the samples. Except for the two shortest fatty acids (propionic and butyric acid), all the fatty acids showed DSC-peaks corresponding to transition of amylose-lipid complexes. Form II complexes, i.e. the crystalline form of the complex, were also formed for all fatty acids with a chain length of >=12, even with polyunsaturated fatty acids. In this investigation, the amount and type of complexes formed do not reflect equilibrium conditions, but are instead a result of the rate of all the different sub-processes involved in complex formation, and these are influenced by the availability of the fatty acids and the heat treatment. The highest amounts of complexes were created by arachidonic and docosahexaenoic acid when the sample had not been subjected to any previous heat treatment. Heat treatment of the sample changed this and for heat treated samples the saturated palmitic and stearic acid yielded highest total amount of complexes. However, the ratio between complexes of form II and form I differed between the fatty acids complexes and during extended temperature treatment, most form II complexes were created by arachidonic and linoleic acid. Comparing the results from each fatty acid to the corresponding monoglyceride (with chain lengths of 10-18), it can be concluded that fatty acids seem to form complexes more easily than monoglycerides do, but monoglycerides create complex form II more easily than fatty acids, especially in case of shorter-chain lipids. Conclusion. This study showed that for complexes formed between fatty acid anions and amylose the temperature of dissociation was only marginally affected by the previous heat treatment of the sample. On the other hand the amount and type of complexes formed were strongly effected by the temperature conditions. For both complex forms, the heat stability increased with chain length, and decreased with unsaturation, similarly as for monoglycerides. All fatty acids created complexes with amylose, except for C3 and C4 where no DSC endotherms were detected. During heat treatment at 100 °C, complex form II was created with every fatty acid, unsaturated as well as saturated, with chain length >=12. The polar head was important for the tendency to create form II complexes; they were hardly created by the shorter fatty acids (C10 and C12), in contrast to corresponding monoglycerides, which have been shown to form II complexes easily. Heat treatments favoured complex formation in general for the fatty acid soaps. In the case of uncharged fatty acids the effect of short heat treatment, the only type tested in this work, was not beneficial for complex formation and for the long chains the amount of complex in fact seemed to decrease after the second scan. The shorter heat cycle mainly favoured increased formation of form I complexes even though a certain amount of form II complexes also was formed. The longer heating cycle will first of all favour formation of complex II, the effect being larger for the long fatty acids soaps than for the short ones. The amount of complex I is often higher than if no heat treatment has been performed, but in all cases lower than what was seen for a short heat treatment. Thus, the longer heat treatment favours formation of complex II on the expense of form I. All unsaturated fatty acids created more complexes than the saturated ones did during the first scan of non heat treated samples; the highest H was determined for the very long polyunsaturated fatty acids, C20:4 and C22:6. |
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| ISSN: | ISSN 0038-9056 |
