*3.2. Polyphenolic Compounds Composition*

The total polyphenolic compounds content in PEP ranged from 34.66 to 47.65 g/100 g db and differed due to the drying technique and parameters applied for their dehydration (Table 2) [5]. In general, the highest total content of identified polyphenolic compounds was noted after SPD, which was almost 19% higher when compared to FD, and is regarded as the technique that preserve bioactive compounds the most. Similarly, the highest retention of polyphenolic compounds in sugar-free extracts, submitted to SPD, was noted in case of chokeberry [11] and cranberry [27], which pointed to this dehydration method as being successfully used when the retention of selected polyphenolic compounds is concerned.



Freeze drying (FD); Vacuum drying 40 ◦C (VD 40 ◦C), 60 ◦C (VD 60 ◦C), 80 ◦C (VD 80 ◦C); Spray drying (SPD); different letters (a,b,c,d) within the rows indicate significant differences between samples (*p* ≤ 0.05; LSD Tukey test).

Going into the details, the major group of polyphenolic compounds present in PEP consisted of five identified phenolic acids, among which the chlorogenic and 3-feruoylquinic acids were dominant. The highest retention of these constituents was noted after SPD. As previously observed [5], the drying processes led to the degradation of phenolic acids within the increase of the temperature during VD, except methyl 3-caffeoylquinate. Interestingly, the increase in the temperature during VD up to 80 ◦C, followed by SPD (170 ◦C) resulted in, respectively, 29-, and 16-times higher content of this compound in the powders when compared to those gained after FD. In case of flavonols, processing during which the temperature above 40 ◦C (VD 40 ◦C, VD 60 ◦C, VD 80 ◦C and SPD) caused a strong degradation of quercetin-3-*O*-galactoside, the application of such conditions caused an increase in the content of quercetin-3-*O*-glucoside when compared to FD. This might be connected with the thermally-induced release of this constituent during drying. In general, the SPD process resulted in better retention of flavonols being almost 20% higher when compared to FD. In the current study, three anthocyanins

had been identified and their content followed the same patterns as the above-mentioned groups of polyphenolic compounds.
