A study was carried out to determine the stability of the anthocyanins
at different working temperatures in the microwave system.
To determine stabilities of anthocyanin type compounds,
their recoveries were determined in the samples of grape skins of
the Tintilla de Rota variety in a 20 min extraction in the microwave
system. To do this, approximately 2 g of sample were subjected to
an extraction with 25 mL of methanol:water (50/50) at different
temperatures between 50 and 150 C, using 500W system power.
A comparison was made of the chromatographic areas of the 11
compounds detected, comparing them with the extracts which
showed the highest concentrations of each of the determined
anthocyanins.
As can be seen in Fig. 1, the temperature which produced the
best recovery of anthocyanins from grape skins was 100 C, with
recoveries found to be lower at temperatures above 100 C. This
indicates that degradation must occur in compounds of this type
when those temperatures are used. Therefore, 100 C is the maximum
temperature to be used in developing the microwave assisted
extraction method.
It can also be observed that there is no clear difference between
glucosides (compounds 1–5) and the acyl derivatives (compounds
6–11). Rather, they all showed similar characteristics: a sudden decrease
in recovery, of approximately 50–60% in all cases, on
increasing the temperature from 100 to 125 C.
A study was carried out to determine the stability of the anthocyanins
at different working temperatures in the microwave system.
To determine stabilities of anthocyanin type compounds,
their recoveries were determined in the samples of grape skins of
the Tintilla de Rota variety in a 20 min extraction in the microwave
system. To do this, approximately 2 g of sample were subjected to
an extraction with 25 mL of methanol:water (50/50) at different
temperatures between 50 and 150 C, using 500W system power.
A comparison was made of the chromatographic areas of the 11
compounds detected, comparing them with the extracts which
showed the highest concentrations of each of the determined
anthocyanins.
As can be seen in Fig. 1, the temperature which produced the
best recovery of anthocyanins from grape skins was 100 C, with
recoveries found to be lower at temperatures above 100 C. This
indicates that degradation must occur in compounds of this type
when those temperatures are used. Therefore, 100 C is the maximum
temperature to be used in developing the microwave assisted
extraction method.
It can also be observed that there is no clear difference between
glucosides (compounds 1–5) and the acyl derivatives (compounds
6–11). Rather, they all showed similar characteristics: a sudden decrease
in recovery, of approximately 50–60% in all cases, on
increasing the temperature from 100 to 125 C.
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