Giampaolo Blanda

CZE separation of strawberry anthocyanins with acidic buffer and comparison with HPLC.

Anthocyanins, the major colourants of strawberries, are polar pigments that are positively charged at low pH. Herein, we have assessed a new analytical method for the separation of anthocyanins using CZE. Acidic buffer solutions (pH <2) were employed in order to maintain pigments in the cation flavylium form and achieve high molar absorptivity at 510 nm. These spectral properties enabled us to identify strawberry anthocyanins in a preliminary stage by detection in the visible range, although the method was optimised at 280 nm to obtain the best S/N. The effects of buffer composition highlighted the necessity of adding an organic modifier to the running buffer to obtain a suitable separation. The electrophoretic method permitted the separation of the three main anthocyanins of strawberry extracts, namely pelargonidin 3-glucoside (Pg-glu), pelargonidin 3-rutinoside and cyanidin 3-glucoside. The electrophoretic results, expressed as retention time and separation efficiency of the major anthocyanin (Pg-glu), were compared to those achieved in HPLC, the analytical technique traditionally used for the investigation of anthocyanins in vegetable matrix. The content of Pg-glu in strawberries (cv. Camarosa), calculated with HPCE and HPLC methods, resulted respectively in 11.41 mg/L and 11.37 mg/L.

Mass transfer and phenolic profile of strawberries upon refrigerated osmodehydration.

Whole strawberries were osmodehydrated at low temperature (5 °C) in a sucrose syrup (500 g/kg of solution) for different processing times (24, 48, 72, 96, and 120 h); after the treatment, water loss, solid gain, and weight reduction were recorded. Next, the osmodehydrated samples were frozen, and after a 5-month storage at −18 °C they were analyzed for drip loss, titratable acidity, refractometric index, pH, and sensory acceptance. The phenolic profile of the samples was characterized by means of high performance liquid chromatography (HPLC). After thawing, osmodehydrated samples presented a high acceptability for consumers. In addition, they presented drip loss values that were inversely correlated with the processing time, with 120-h samples presenting negligible drip loss after thawing. The processing time influenced the final quality of strawberries, and samples treated for 24–48 h were very suitable for direct consumption after thawing, in substitution of fresh strawberries. The samples treated for 72–120 h also presented characteristics that may render them suitable for applications in the food industry.