Starch thermal transitions comparatively studied by DSC and MTDSC

Abstract

The gelatinisation process of waxy starch was studied using both differential scanning calorimetry (DSC) and modulated temperature DSC (MTDSC). It was revealed that the results from the two techniques, especially the onset gelatinisation temperature, were slightly different, which may be due to the MTDSC principle and the mechanism of starch gelatinisation. Thus, it is suggested to avoid using MTDSC alone in the characterisation of starch thermal transitions especially in a quantitative way. However, MTDSC has the advantage in understanding the gelatinisation mechanism since it can separate the capacity change (reversible thermal event) from kinetic components (irreversible event). The stepwise change on reversible heat flow measured by MTDSC during gelatinisation was considered due to the phase transition of highly constrained starch polymer chains in granular packing. On the other hand, the glass transition of gelatinised starch (also thermoplastic starch) could not necessarily be detected by conventional DSC or MTDSC. However, by using a high‐speed DSC method, the extremely weak glass transition of the gelatinised starch with low moisture content could be enlarged and detected, which confirms the existence of glass transition of the gelatinised starch with low moisture content. This knowledge is helpful in the processing of starch‐based foods and polymeric materials.

Green Development of Biodegradable Films Based on Native Yam (Dioscoreaceae) Starch Mixtures

“…Reducing the T g of starch films is important to prevent the formation of cracks and pinholes due to brittleness . Although it is important to mention that the T g of the films cannot be lower than the storage temperature, or the starch recrystallizes (that is, amylose and amylopectin reassociation into crystalline segments) causing loss of flexibility due to rigidity . The films developed in this study, except for samples 5 and 7, could be applied to products that need or stay at temperatures below 46 °C without thermal damages to the coating properties.…”

“…On the contrary to the decrease which occurred in the T g after mixing the starches, the melting temperature ( T m ) was increased for the films obtained from the starch mixtures with values ranging from 140.99 °C (sample 7) to 169.92 °C (sample 10), except for sample 9. These observations could be due to the variable sizes of starch granules and to the transition of amylopectin microcrystallites that composes the matrix of the film. In our previous work, the granules size range were determined.…”

“…Biodegradable films can be obtained from a variety of native polymers such as starch, cellulose, collagen, chitosan, gelatin, and others, from their mixtures or from isolated amylose and amylopectin components . For that reason, films can be obtained with materials which present thermoplastic properties implying that they can be thermally processed becoming melted or rubbery at a lower temperature than the decomposition temperature …”

Starch-based nano-biocomposites

“…weak mechanical properties, poor long-term stability, and high water sensitivity). Formulation development and understanding of starch thermal [1][2][3][4][5] and rheological [6][7][8][9][10][11] properties could be the keys to solve these critical problems. Further, various starch-based blends and biocomposites have been developed, showing improved performance [12][13][14][15].…”

Thermoplastic Starch

“…At The University of Queensland (UQ), we have focused on many fundamental aspects in starch processing, including understanding of fundamentals of native starch [10,[119][120][121], starch degradation during extrusion [5,108], processing rheology of TPS [122], effects of starch type and chemical modifi cation on the processing and properties [23,31]; development of new TPS polymer blend products [123][124][125][126], optimisation of the related processing [127], understanding of performance of TPS by post-processing environmental conditions [128][129][130]; as well as the very recent work on plasticisation of starch using novel plasticisers [131]. Product wise our research has focused on the development of water soluble rigid sheet products and blown fi lms for dry goods packaging and water resistant injection moulding grades for moulding applications [132].…”