| 1. |
- Ortega-Ojeda, Fernando, et al.
(författare)
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Gel formation in mixtures of amylose and high amylopectin potato starch
- 2004
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 57:1, s. 55-66
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Tidskriftsartikel (refereegranskat)abstract
- The influence of amylopectin (Ap) (in the form of high amylopectin potato starch, HAPP) on the rheological properties of its mixtures with amylose (Am) has been studied in small-deformation oscillatory rheometry during relatively long times (6 h). The absence of HAPP granule remnants in the samples has been considered important; therefore HAPP, Am, and HAPP-Am mixtures have been prepared at 140degreesC. A higher amount of HAPP in the HAPP-Am mixture resulted in a lower value of G' of the formed systems. This trend was stronger at 10 and 8%, than at 6% total polysaccharide concentration. The rheological properties of the mixtures with the lowest amount of Am resulted in a theological behaviour that was similar to that of HAPP at identical concentration. With increasing Am concentration in the Am-HAPP mixtures, the behaviour was comparable to pure Am. HAPP did not seem to increase the effective concentration of Am and act as a precipitator. The frequency dependence of G'(n') strongly drop with increasing Am concentration until a certain ratio of Am:HAPP was reached, approaching zero. This implied a drastic liquid-solid transition, which was clearer at higher total polysaccharide concentrations. The values of G' for pure Am increased more rapidly and at considerably lower concentrations than for pure HAPP. For HAPP the decrease in n' with increasing concentration was gradual, in three different stages. First a strong decrease in n' and W to a more or less constant value (similar to0.5) and then, at the highest concentration, n' decreased even further, and approached zero. For Am, the values of n' decreased abruptly from similar to1 to similar to0 with increasing concentration, which implies a distinct liquid to solid transition. (C) 2004 Elsevier Ltd. All rights reserved.
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| 2. |
- Ortega-Ojeda, Fernando, et al.
(författare)
-
Gel formation in mixtures of hydrophobically modified potato and high amylopectin potato starch
- 2005
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 59:3, s. 313-327
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Tidskriftsartikel (refereegranskat)abstract
- The rheological properties of gels of hydrophobically modified potato starch (HMPot) and high amylopectin potato starch (HAPP) were studied by small deformation oscillatory rheometry. The hydrophobic modification consisted of octenyl succinate anhydride (OSA) chains grafted mainly on the amylopectin molecules. The theological behaviour of HMPot was different from the behaviour of native potato starch and HAPP. At concentrations higher than similar to15%, the moduli for HMPot starch were higher than for native potato starch and HAPP. A higher level of OSA Substitution led to lower moduli values. The gel formation of HMPot was slower than the gel formation of native potato starch and HAPP. This was explained by the formation of amylose-OSA inclusion complexes and OSA-OSA hydrophobic interactions. Decreasing concentrations of HMPot in HMPot-HAPP mixtures led to reduced moduli values, and a theological behaviour resembling that of HAPP. At HMPot concentrations lower than 50% in the HMpot-HAPP mixture, amylose or OSA seemed not to contribute to the network formation. Addition of sodium dodecyl sulphate (SDS) to HMPot reduced the moduli at lower concentrations (1%). Further increase in SDS concentration (2%) increased the moduli values. However, the moduli values were still lower than for pure HMPot. The decrease in the moduli when SDS was added is Suggested to be due to a replacement of OSA by SDS in the amylose-inclusion complex. The strengthening of the existing OSA-OSA hydrophobic interaction when further SDS was added, is explained by the formation of polymer-micelles. When SDS was added to native potato starch and HAPP the theological behaviour was different from that observed for HMPot starch. The moduli increased when SDS was added to native potato starch and HAPP. With increasing SDS concentration, the storage modulus (G') of native potato starch and HAPP increased to the same value. Consequently, the rheological properties of native potato starch and HAPP were suggested to be dominated by amylopectin and not by amylose. (C) 2004 Published by Elsevier Ltd.
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| 3. |
- Ortega-Ojeda, Fernando
(författare)
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Interactions between Amylose, Native Potato, Hydrophobically Modified Potato and High Amylopectin Potato Starches
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The behaviour of different starches and their mixtures was investigated using several analysis techniques, i.e. small-deformation oscillatory measurements (rheological measurements), differential scanning calo-rimetry (DSC), light microscopy, and UV spectrophotometry (turbidi-metry). Potato, waxy maize and barley starches were mixed two and two in different ratios and at different water contents (Paper I). In the DSC gelatinisation thermograms of the starch mixtures, thermogram characteristics of the individual starches were detected. The waxy maize-barley and potato-barley mixtures had the lowest retrogradation enthalpy values. The retrogradation enthalpy measured for most starch mixtures was equal to the calculated value assuming that each starch contributed to the enthalpy according to its proportion in the mixture. A simple, less time-consuming and non-chemical method for preparing starch samples was established (Paper II). Using light microscopy, no granules were observed after temperature treatments between 130-160 °C, thereby preventing the influence of granules or granule rem-nants on the rheological behaviour of starch samples could be avoided. The influence of granule remnants on the rheological properties of starch samples treated at 90 °C was observed, when compared to sam-ples treated at 140 °C (Paper III). Native potato starch gave higher moduli values than high amylopectin potato starch (HAPP), after both 90 and 140 °C treatments. A mixture of commercial amylose and HAPP gave lower storage modulus (G’) compared to native potato starch. The contribution of amylopectin to the rheological behaviour of blends with commercial amylose was investigated (Paper IV). In amy-lose-HAPP mixtures, higher amounts of amylose produced higher G’ values, and gave rheological behaviour similar to pure amylose sam-ples. The rheological behaviour of hydrophobically modified potato starch (HMPot) with two levels of substitution was studied, as well as its mixtures with HAPP or sodium dodecyl sulphate (SDS)(Paper V). At higher concentrations, the moduli for HMPot starch were higher than for native potato starch and HAPP. Increasing the octenyl succi-nate anhydride (OSA) substitution degree decreased the moduli values. HMPot showed slower gel formation than native potato starch and HAPP. Decreasing proportions of HMPot in mixtures of HMPot and HAPP reduced the moduli values, and produced a rheological behav-iour resembling that of HAPP. Amylose or OSA seemed not to con-tribute to the network properties in the HMPot-HAPP mixtures at HMPot proportions lower than 50 %. Adding of SDS to HMPot re-duced the moduli at the lower concentrations (1 %) investigated. An increase in SDS concentration to 2 % increased the moduli. Adding of SDS to native potato starch and HAPP led to an increase in the moduli. With increasing SDS concentration, the G’ values for native potato starch and HAPP became increasingly similar.
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| 4. |
- Ortega-Ojeda, Fernando, et al.
(författare)
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On the dispersion and small-amplitude oscillation measurements of high amylopectin potato starch.
- 2003
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 55:3-4, s. 121-121
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Tidskriftsartikel (refereegranskat)abstract
- Differential scanning calorimetry (DSC), optical microscopy and turbidity measurements were used to define experimental conditions (time, temperature and shearing) for dissolving high amylopectin potato starch (HAPP) granules. A simple, less time consuming and non-chemical method for preparing starch samples was established. Small-amplitude oscillation measurements were used to characterise the behaviour of the resulting solutions. The DSC, microscopy and turbidity experiments showed that preparing the samples at 140 °C was necessary to dissolve HAPP, with no further detectable granule structures. Rheological measurements showed that the storage (G') and loss (G'') moduli increased with concentration. At a HAPP concentration of 2 % G'' > G' and the system behaved like a diluted solution. The frequency dependence also decreased with increasing concentration. At 14 % HAPP, the system showed more gel-like properties with G' more or less independent of frequency.
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