The Effects of Thermal and Non-thermal Processing on Vitamin C, Carotenoids, Phenolic Compounds and Total Antioxidant Capacity in Orange Juice

The abundance of fresh drinks based on fruit juices, especially citrus juices, and minimally processed products allow consumers to ingest a wide variety of antioxidants in the diet, such as vitamin C, carotenoids, flavonoids and other phenolic compounds. Pulsed electric fields (PEF) and high hydrostatic pressure (HHP) are emerging technologies in the field of food preservation. They have the potential to pasteurize various foods non-thermally, and it has been verified that these new technologies guarantee the safety (death of microorganisms) and stability (PME) of juices, with less quality loss in the final product. The effect of non-thermal processing (PEF, HHP) and pasteurization on total phenolic compounds, total antioxidant activity, vitamin C and carotenoids of orange juice was studied. There was a statistically significant reduction (p<0.05) in Trolox equivalent antioxidant capacity (TEAC) when juice was processed by either of these treatments, but the decrease was higher after pasteurization. TEAC decreased during refrigerated storage (4°C) of the samples analysed. Vitamin C concentration did not change significantly after pasteurization and non-thermal treatment; during refrigerated storage. However, vitamin C decreased more in pasteurized juice than in juice treated by PEF and HHP. The vitamin A concentration in the refrigerated orange juice was affected less by non-thermal treatments than by conventional thermal treatments. Total phenolic compounds were always higher in the untreated orange juice, followed by juice treated by PEF and HHP and finally by pasteurized juice, although the differences were not statistically significant (p>0.05), and during refrigerated storage they remained practically constant in all samples. Furthermore, a juice with similar characteristics as fresh juice, while preserving the bioactive compounds which provide it with its wealthy properties, is obtained. _____________________________________________________________________________________________________________