Ohmic heating could up juice quality
proved to be a good way of improving the flavour quality of orange
juice while extending sensory shelf life. The findings could point
to a more efficient way of extending juice shelf life, reports
Simon Pitman.
The scientists, Shirly, Leizerson and Eyal Shimoni from the Technion-Israel Institute of Technology, have just published their findings in two reports in the Journal of Agriculture and Food Chemistry, with early findings indicating that the sensory shelf life of orange juice could be extended to more than 100 days, doubling expectancy compared to pasteurization methods.
Ohmic heating uses electricity to rapidly and uniformly heat food and drink, resulting in less thermal damage to the product. The technology has been around since the early 1900s, but it was not until the 1980s that food processing researchers began investigating the possible benefits to the industry.
The scientists compared pasteurized orange juice, which had been heated at 90 C for 50 second, with orange juice that was treated at 90, 120 and 150 C for 1.13, 0.85 and 0.68 seconds in an ohmic heating system.
The scientists reported the microbial counts showed complete inactivation of bacteria, yeast and mould for both pasteurization and ohmic heating.
The experiment found that for all examples retention of both pectin and vitamin C was reported similar. Likewise both treatments prevented the growth of micro-organisms for 105 days, compared to fresh orange juice.
However, where the ohmic heated samples proved much stronger was in the preservation of flavours and and the general taste quality over a period of time. The scientists tested five representative flavour compounds - decanal, octanol, limonene, pinene and mycrene. Testing showed that levels of these compounds were significantly higher in the ohmic treated samples after storage than in the pasteurized examples.
The scientists' results found that the only adverse reaction that the ohmic treated orange juice had was that it increased browning in the juice, although this was not reported to be visible, until after 100 days. Conversely the appearance of the ohmic samples was said to be visibly less cloudy.
The implications of the findings to the juice industry could be wide-reaching as quality is a major driving force for a product that is often marketed in the premium category. If the cost of implementation proves competitive then this could become a serious contender to pasteurization methods.
