Degree of hydrothermal degradation in WSE was assessed by analyzing the composition of two phenolic compounds typically present in sunflower seeds, namely chlorogenic acid (CHA) and one of its hydrolythic derivatives – caffeic acid (CA).
Also, another aspect of hydrothermal degradation in WSE was studied, namely the decomposition (dehydration) of sugars to 5-HMF by measuring amount of formed 5-HMF during extraction.
Amounts of chlorogenic acid (wCHA), caffeic acid (wCA) and 5-hydroxymethyl furfural (w5-HMF) present in the WSE are presented in Table 3.
Compared to the total phenolics content, it can be observed that CHA is the main phenolic compound in WSE, however its content quickly starts to decrease with te at temperatures P100 C.
It seems that the ester bond present in CHA (unlike the ones present in the triglycerides) is not very stable in SubCW at
these conditions. At the same time the increase of CA with te can be observed, what indicates that the derivative of CHA (CA) is formed during extraction. Highest decomposition rate of CHA can be observed at 160 C, with the lowest obtained yield of wCHA after te = 5 min, which is 27.63 ± 0.66 mg/g ext. Although we would expect CA to have a similar rate of formation as the decomposition rate of CHA, we can observe that this is not the case.
More CHA is decomposed with te than CA is formed. Although further hydrothermal degradation of CA is likely to occur at 160 C, a more feasible explanation of this anomality is the previously mentioned extraction of phenolics (CA) to OE in the phase separation step.
CHA could probably not be extracted with non-polar phase (hexane) since its composition in WSE at 60 C does not change ovet te.
From Table 3 it can be also observed that 5-HMF is formed during extraction at the studied extraction conditions.
It seems that formation of 5-HMF occurs at TeP100 C, whereas at 60 C no 5-HMF is formed. Interestingly, the highest amounts of 5-HMF are obtained at 100 C, whereas at higher temperatures lower amounts are obtained. Also, at 130 C and 160 C a decrease of 5-HMF with te can be observed.
At 130 C the decrease of 5-HMF is visible after 30 min of extraction for all M/S ratios and at 160 C the decrease
can already be observed after 5 min of extraction.
This decrease in concentration could indicate the previously mentioned further hydrothermal degradation of 5-HMF to other products, such as organic acids (levulinic acid and formic acid).
Degree of hydrothermal degradation in WSE was assessed by analyzing the composition of two phenolic compounds typically present in sunflower seeds, namely chlorogenic acid (CHA) and one of its hydrolythic derivatives – caffeic acid (CA). Also, another aspect of hydrothermal degradation in WSE was studied, namely the decomposition (dehydration) of sugars to 5-HMF by measuring amount of formed 5-HMF during extraction.Amounts of chlorogenic acid (wCHA), caffeic acid (wCA) and 5-hydroxymethyl furfural (w5-HMF) present in the WSE are presented in Table 3. Compared to the total phenolics content, it can be observed that CHA is the main phenolic compound in WSE, however its content quickly starts to decrease with te at temperatures P100 C. It seems that the ester bond present in CHA (unlike the ones present in the triglycerides) is not very stable in SubCW atthese conditions. At the same time the increase of CA with te can be observed, what indicates that the derivative of CHA (CA) is formed during extraction. Highest decomposition rate of CHA can be observed at 160 C, with the lowest obtained yield of wCHA after te = 5 min, which is 27.63 ± 0.66 mg/g ext. Although we would expect CA to have a similar rate of formation as the decomposition rate of CHA, we can observe that this is not the case. More CHA is decomposed with te than CA is formed. Although further hydrothermal degradation of CA is likely to occur at 160 C, a more feasible explanation of this anomality is the previously mentioned extraction of phenolics (CA) to OE in the phase separation step.CHA could probably not be extracted with non-polar phase (hexane) since its composition in WSE at 60 C does not change ovet te.From Table 3 it can be also observed that 5-HMF is formed during extraction at the studied extraction conditions. It seems that formation of 5-HMF occurs at TeP100 C, whereas at 60 C no 5-HMF is formed. Interestingly, the highest amounts of 5-HMF are obtained at 100 C, whereas at higher temperatures lower amounts are obtained. Also, at 130 C and 160 C a decrease of 5-HMF with te can be observed. At 130 C the decrease of 5-HMF is visible after 30 min of extraction for all M/S ratios and at 160 C the decreasecan already be observed after 5 min of extraction. This decrease in concentration could indicate the previously mentioned further hydrothermal degradation of 5-HMF to other products, such as organic acids (levulinic acid and formic acid).
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