Abstract
Pitaya (Stenocereus griseus) juice, obtained from fresh pitayas, was processed using a continuous ultraviolet-C (UV-C) light (57 µW/cm 2 ) system. Juice was processed at five flow rates (0.46, 3.28, 6.57, 16.49 and 30.33 mL/s) and five treatment times (5, 10, 15, 20, and 25 min). Fresh juice was used as control. Some physicochemical (pH, total soluble solids, color, and betalains), antioxidant (total phenolic compounds and antioxidant activity), and microbiological (aerobic mesophylls bacteria and yeasts plus molds) characteristics were assessed in fresh and UV-C processed juices. It was observed that the UV-C treatments did not affect pH and total soluble solids in juice. The total change in color (E) increased as treatment times increased; however, E values were reduced at high flow rates. The betalains and total phenolic compounds contents were reduced as flow rates and treatment times increased; consequently, the antioxidant activity lessened in juice. A maximum reduction of 2.11 and 1.14 log cycles was observed for mesophylls and yeasts plus molds, respectively, in the UV-C light treated pitaya juice.
Highlights
Emerging technologies such as high hydrostatic pressure, pulsed electric fields, ultrasound, and ultraviolet light have been used to obtain food products with characteristics similar to fresh products that consumers are demanding today
Luna (2006) reported values of total soluble solids in the range 10-17.25% (w/w). pH and phenolic compounds content in pitaya juice were similar to those reported for cacti fruits (Nurliyana, Syed, Mustapha, Aisyah & Kamarul, 2010) other than pitaya
The content of betalains in pitaya juice was higher than the amount reported for other red-pigmented fruits (Repo de Carrasco & Encina 2008; Castellanos & Yahia, 2008)
Summary
Emerging technologies such as high hydrostatic pressure, pulsed electric fields, ultrasound, and ultraviolet light have been used to obtain food products with characteristics similar to fresh products that consumers are demanding today. The short-wave ultraviolet-C light is a physical method that does not generate chemical residues in the food and today is used for water and surfaces disinfection (Quek & Hu, 2008). The UV-C light (254nm) is easy to use for disinfection purposes of liquid foods. It has lethal effects on micro organisms such as bacteria, viruses, protozoa, yeasts, and molds (Begum, Hocking-Ailsa & Miskelly, 2009). The absorption of UV-C light generates electronic changes that may cause breaking of the DNA bonds; microbial cells could be compromised. The photoproducts (pyrimidine nucleotide bases), generated by the application of UV-C light, block the DNA transcription and replication; even more, inhibits cell functions that may cause the cell death (Guerrero-Beltrán & Barbosa-Cánovas, 2004)
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