Effect of blanching methods and frozen storage on some quality parameters of turnip greens (“grelos”)

In this research, the effects of different blanching conditions and frozen storage on the stability of some quality factors in turnip greens (“grelos”) grown in the northwest of Spain were studied. The turnip greens were blanched in water, in water with different concentration of citric acid or in water with different concentration of ascorbic acid. The heat treatment was carried out at 90 °C for 1 or 2 min. Blanching in water reduced the content of total soluble solids, chlorophyll and total phenolics as well as the antioxidant activity of turnip greens. Blanching in water with citric acid caused the most important changes in pH values and titratable acidity. The use of ascorbic acid during the blanching process gave rise to a high antioxidant capacity of turnip greens. The chlorophyll loss depended on the type of acid and its concentration as well as on the blanching times. The use of acids in the blanching water minimized the loss of total soluble solids, antioxidant capacity and total phenolic during frozen storage.

► The controlled blanching contributes to the retention of nutrients in processed foods. ► In addition, blanching can increase the bioavailability of some nutrients. ► Some organic acids could be used to keep the qualities of the product during the processing. ► The citric acid and ascorbic acid in the blanching water minimized the losses during frozen storage.