Abstract'Murtilla' (Ugni molinae Turcz) is a native Chilean species that belongs to the Myrtaceae family. It produces a small, globular fruit with pleasant flavor and recognized antioxidant activity. Convective hot-air and freeze drying are important techniques for fruit preservation, but their effect on murtilla fruit polyphenols and antioxidant activity has not yet been studied simultaneously. The objective of this study was to compare the effect of convective hot-air drying at 65 and 80 ºC and freeze drying on total polyphenol content (TPC), total anthocyanin content (TAC), polyphenols and anthocyanins of the Red Pearl-INIA variety of fresh murtilla fruits as measured by HPLC and antioxidant activity (DPPH and ABTS). The freeze dried fruit retained higher values for TPC (2192.4 mg/100 g d.w.), TAC (13.4 mg/100 g d.w.), polyphenols (79.02 mg/100 g d.w. by HPLC) and anthocyanins (0.188 mg/100 g d.w. by HPLC) than the murtilla dried by convective hot-air at both 65 and 80 ºC. The application of all treatments showed a positive increase in the DPPH (2945.4 to 3677.6 μmol TE/100 g d.w.) and ABTS (2664.8 to 3397.2 μmol TE/100 g d.w.) antioxidant activity of the dried murtilla compared to the DPPH (2111.1 μmol TE/100 g d.w.) and ABTS (2247.8 μmol TE/100 g d.w.) of the fresh fruit. Freeze drying was the best technique for the retention of polyphenols and antioxidant activity from the fresh murtilla fruit. Therefore, freeze drying is recommended over convective hot-air drying at 65 and 80 ºC when these bioactive compounds need to be preserved.
Polyphenol content and antioxidant activity in murtilla (Ugni molinae Turcz) fruit from three genotypes (the 14-4 genotype and the Red Pearl-INIA and South Pearl-INIA varieties) were studied over five growing seasons. Our results showed significant differences in total polyphenol content among yearly harvests. The lowest value (283 ± 72 mg GAE/100 g dw) was obtained for the 14-4 genotype in the 2008 harvest, and the highest value (2,152 ± 290 mg GAE/100 g dw) was observed for the variety South Pearl-INIA in 2007. The lowest value for antioxidant activity (2,234 ± 337 µmol TE/100 g dw) was obtained for the Red Pearl-INIA variety in 2008, and the highest value (4,073 ± 76 µmol TE/100 g dw) was observed for the 14-4 genotype in 2007. There was a significant effect of genotype and growing season on polyphenol content, antioxidant activity and dry matter content for the murtilla fruits evaluated in this study, but additional studies examining other abiotic and biotic factors are required to fully explain causality.
Murtilla (Ugni molinae Turcz) fruit has a unique aroma; along with its pleasant sweet flavour, this has stimulated its commercial development in international markets. This development, however, requires the application of suitable conservation methods. Five different packaging treatments for murtilla fruit (Red Pearl‐INIA variety) conservation were evaluated at 0 °C for 60 days. The treatments consisted of two types of packaging [polyethylene terephthalate (PET) punnets and low‐density polyethylene (LDPE) bags] and the application of an edible coating of carboxymethyl cellulose to the fruits. The incorporation of the aqueous extracts of murtilla leaves from the 18‐1 and 27‐1 ecotypes into the carboxymethyl cellulose edible coating was also evaluated for its antimicrobial effects. There was a significant (p < 0.05) reduction in the moisture content, a significant weight loss and an increase in soluble solids when the murtilla fruit was packed only in a PET punnet. However, with the other four treatments, in which an LDPE bag and edible coating were used, the moisture content (76.8–74.4 g/100 g) and soluble solids (15.6–17.8 ºBrix) in the fruit remained stable during storage. Low weight loss (1.64–2.25%) occurred in the fruits that received treatments with the LDPE bag and edible coating. Under experimental conditions and from operational facilities, packaging in PET punnets with an LDPE bag was the best alternative to preserve the murtilla fruit at 0 °C for 60 days. Copyright © 2013 John Wiley & Sons, Ltd.
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