From Plums to Prunes:  Influence of Drying Parameters on Polyphenols and Antioxidant Activity

Abstract

Prunes, which are industrially obtained by dehydrating fresh plums at 85-90 degrees C for 18 h, contain higher levels of phenolic compounds than most other fruits. Prune phenolics have shown beneficial effects on human health. Reports are available in the literature on ascorbic acid, phenol composition, and antioxidant activity of fresh plums and prunes, but there is a lack of publications on the influence of drying parameters on the phenolic compounds and antioxidant activity. A study was carried out on two plum cultivars using two sets of air-drying temperatures: (i) air temperature at 85 degrees C until 50% of prune moisture level and then the temperature was lowered to 70 degrees C; (ii) air temperature at 60 degrees C. Whole fresh and dried fruits were assessed for phenolics (catechins, hydroxycinnamic acids, anthocyanins, and flavonols), ascorbic acid, and antioxidant activity (all parameters were calculated on a dry matter basis). Analysis of data shows that chlorogenic and neochlorogenic acid changes were affected by both process parameters and cultivar. Drying destroyed anthocyanins, and there was a significant decrease in flavonols. Ascorbic acid was drastically reduced in relation to process temperature. The most striking result was that drying at 85 degrees C doubled antioxidant activity in both cultivars, while contradictory results were found for 60 degrees C processed plums.

Characterization of Plum Procyanidins by Thiolytic Depolymerization

“…The flavan-3-ol monomers (-)-epicatechin and (+)-catechin were detected in the crude extracts for GG-C, GG-V, and GJ samples, with (+)-catechin being highly preponderant, while in M and GG-F samples, only (+)-catechin was identified. Other studies of plums also describe (+)-catechin as the main monomeric flavan-3-ol detected, with (-)-epicatechin being present in smaller amounts (13)(14)(15). Procyanidin B7 [dimer of (-)-epicatechin and (+)-catechin with a C4-C6 linkage] was identified only in the three samples of the GG variety.…”

Selected cultivars of cornelian cherry (Cornus mas L.) as a new food source for human nutrition

“…Nevertheless, in this case the effect on total values of antioxidant activity is problematic (Gil et al, 2002). This can also be associated with a considerably variable content of vitamin C due to the effect of the year, the degree of ripeness, manipulation, processing, etc (Piga et al, 2003). In addition, it is possible that the levels of other components participating in the formation of antioxidant activity may be rather variable and for that reason the momentary content of phenolic substances is considered to be the most important coefficient of correlation with antioxidant activity in fruits (Gil et al, 2002;Chun and Kim, 2004;Vizzotto et al, 2006) and vegetables (Valsikova and Belko, 2004).…”

Antioxidant activity and sensory changes of strawberry tree fruits during cold storage and shelf life

“…Antioxidant activity was evaluated using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). A diluted and filtrated sample obtained as reported by Piga et al (2003) was used and the antioxidant activity was expressed with the following -OD -3 min -1 g -1 DM, in the Equation:…”