I performed a DSC analysis of rice starch samples to determine gelatinization enthalpy and peak temperature. I'm expecting a gelatinization temperature between 60 to 80 celsius. What could be the possible reasons for this pattern of the curve? Does this mean that my sample is degraded??
First, you need to be confident about the purity of your sample. Then, you have to dry your sample and heat it in the N2 environment at the flow rate of 20ml/min. Then put 8-10 mg of the sample in the aluminum dish and press it. Now, you can draw the DSC curve because your curve is irregular, and it is not correct.
Amir Sepehrianazar Moisture content of my sample is 14%. If I further dry the starch, for 8 mg how much water should be added to the aluminum dish before pressing?
You do not need to add water. If you work by DSC you need to pure and then dry the starch. DSC has a special dish for sample formation. You can use them. You do not have to add water for pressing.
@Amir Sepehrianazar
But starch gelatinization requires water and heat
I agree with Kavitha Susan Issac: gelatinization is defined as the melting of starch assisted by water. That means that presence of water is essential. Now the gelatinization properties of starch are dependent on the amount of water, as shown in the attachment. But generally, gelatinization temperature range and gelatinization enthalpy are independent of water content up to 60 %. [The reason for this is explained in the attachment and may be derived from the key publication of J.W. Donovan.] That is why generally a (dry) starch content somewhere between 25 and 33 % is selected. Depending on the type of the DSC instrument, endothermic peaks turn upwards or downwards.
Alunmina cups are suitable only to 100 degrees C or slightly higher. As cereal starch-water systems (including rice starch) show a secondary endotherm at ca 110 degrees C, due to the melting of the amylose-lipid complex, hermetically sealable stainless steel cups may be preferred. Weighing cups before and after the DSC experiment is recommended to check whether pan leakage has occurred.
Gelation tenpratire range and antalipy in 60% above neddent to water
DSC endotermic curve you can onbtain antalipy of your material
Gelation tenpratire range and antalipy in 60% above neddent to water
DSC endotermic curve you can onbtain antalipy of your material
Yes you must used minimum warter same other papers
And then obtained gelation amount
Peter A. M. Steeneken Amir Sepehrianazar I am getting positive correlation between amylose and enthalpy of gelatinization. Can you explain why this reverse phenomena is happening?
The relationship between amylose (Am) content and gelatinization enthalpy (E) is not straightforward and quite complex. One has to distinguish between intact granular starch and retrograded starch.
(1) Granular starch. Here, bundles of amylopectin (Ap) side-chains forms the framework of the semi-crystalline structure whereas Am is largely amorphous. Probably because Am and Ap are synthesized by separate enzyme systems: Am by granule-bound starch synthase (SSS) and Ap by a complex interplay of soluble starch synthase (SSS), starch branching enzyme (SBE) and isoamylase (IA). See Ball et al. (attached). One might think that high Ap means high E, but in fact correlations are scattered and differences in E rather small. This is because starches may differ in amylopectin architecture (chain-length distribution and branching degree) and also in crystalline type. For example: waxy and regular maize starch have A-type crystallinity and high amylose maize mutants have B-type crystallinity. See Jane et al. for some results (attached).
(2) Retrograded (= recrystallized) starch. At elevated water content gelatinized starch recrystallizes into the B-type, at low water content (or with added organic solvent) into the A-type. Am with its long linear chains should have the highest tendency for crystallization and one would expect a higher E at higher Am. However, this is not always what is observed. Recrystallized pure Am in water has melting temperature about 120 Celsius whereas retrograded starch starts melting already around 40 Celsius with rather low E which suggests (a) much less ordering in retrograded than in granular starch, (b) amylopectin participating in crystallization. In addition, in cereal starches Am may participate in Am-lipid complexes (thermoreversible and melting at about 100 Celsius). In this way Am may escape retrogradation to some extent.
Conclusion is that one may not expect straightforward correlations between %Am and E, not for granular and not for retrograded starch.
First we have to draw DSC and the low peak environment gives us an enthalpy and the peak environment that is up shows the networking factor for us. Jelly depends on the amount of network factor
First we have to draw DSC and the low peak environment gives us an enthalpy and the peak environment that is up shows the networking factor for us. Jelly depends on the amount of network factor
First we have to draw DSC and the low peak environment gives us an enthalpy and the peak environment that is up shows the networking factor for us. Jelly depends on the amount of network factor
First we have to draw DSC and the low peak environment gives us an enthalpy and the peak environment that is up shows the networking factor for us. Jelly depends on the amount of network factor
Peter A. M. Steeneken Thank you for detailed answer. Can I have your mail id for further discussion regarding starch chemistry? I am having so many questions related to starch chemistry and facing problem for interpretations. My mail id is [email protected] or [email protected]
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