Thermal treatments are commonly used to extend the shelf life of beverages but the heat can damage their nutritional profile. Undesirable effects include irreversible losses of nutritional compounds, undesirable changes in physicochemical properties, and alteration of their antioxidant properties.
For healthy drinks rich antioxidants, there is therefore a search on to find alternative processing techniques that extend shelf life without damaging nutrients.
Writing in Food Science and Technology, scientists at the University of Lleida in Spain set out to compare the effects of HIPEF and thermal technologies on a fruit juice – soy milk beverage stored at 4 °C.
To establish whether HIPEF is an acceptable alternative, they tracked how both processing techniques affected microbial stability, antioxidant properties, and various quality parameters.
Comparing the results obtained for HIPEF treatment (35 kV/cm, 4 μs bipolar pulses at 200 Hz for 800 or 1400 μs) and thermal pasteurization (90 °C, 60 s), the scientists concluded that HIPEF may be a good alternative treatment.
HIPEF processing for 800 μs ensured microbial stability for 31 days; but, by increasing the treatment time to 1400 μs shelf-life reached 56 days - a level in line with thermal processing.
During storage, vitamin C content and antioxidant capacity depleted with time, and but levels were higher in drinks processed by HIPEF than in those thermally treated.
Total phenolic content did not change significantly over time, but it was higher in the 1400 μs-HIPEF treated beverages than the thermally processed ones.
As for enzyme activity, peroxidase and lipoxygenase in HIPEF treated beverages were inactivated by 17.5–29 per cent and 34–39 per cent, respectively; whereas thermal treatment achieved 100 per cent and 51 per cent.
Color, soluble solids, pH, and acidity values were not significantly affected by the either processing treatment.
Based on these results, the scientists concluded that: “It is possible that HIPEF treatment may achieve similar microbial stability than thermal processing with a major retention of antioxidant properties in fruit juice– soy milk beverages.
“Nonetheless, there is a need for focused studies on the effects of HIPEF processing on different bioactive compounds, sensory and quality attributes of beverages containing fruit juices and soymilk during storage.”
Source: Food Science and Technology
Published online ahead of print: doi:10.1016/j.lwt.2010.01.015
Impact of high intensity pulsed electric field on antioxidant properties and quality parameters of a fruit juice–soymilk beverage in chilled storage
Authors: M. Morales-de la Peñaa, L. Salvia-Trujilloa, M.A. Rojas-Graü and O. Martín-Belloso