Antioxidant capacity and colour stability of texture-improved canned strawberries as affected by the addition of rose (Rosa damascena Mill.) petal extracts

Abstract

Antioxidant capacity of texture-improved canned strawberries (TICS) was studied during storage depending on the addition of polyphenol-enriched extracts from rose (Rosa damascena Mill.) petal by-product. Furthermore, the pigment retention and surface colour evolution were monitored by HPLC–DAD analyses and CIEL⁎a⁎b⁎ measurements, respectively. The addition of rose petal extract (250–500ppm) strongly contributes to the antioxidant capacity of the canned strawberries, resulting in 15–54% (Trolox equivalent antioxidant capacity, TEAC assay) and 21–40% (ferric reducing antioxidant power, FRAP assay) higher values as compared to the control sample, even after 12weeks of storage. A significant pigment retention, i.e. 70–81% relative concentrations of pelargonidin 3-glucoside, was observed for the polyphenol-fortified strawberries during the fruit firming process and subsequent pasteurisation. Correspondingly, colour stability was improved since total colour difference (∆E*) values were smaller than that of the control sample. The results obtained demonstrate an enhancement of antioxidant capacity by application of rose petal extracts to texture-improved strawberries, thus are shown promising for development of new functional foodstuffs. This polyphenol fortification is also suitable from a technological point of view, supporting colour stability during the enzymatic fruit firming process.