Comparing Alternative Processing Methods in Tomatoes
BY DAVID DESPAIN
Whether in a salsa, on a pizza, or in a salad, tomatoes are best enjoyed by consumers when they’re perceived as fresh. The downside to traditional heat treatment in tomatoes and any other fresh foods to kill bacteria is the resulting degradation of “freshness” characteristics and quality.
Fresh food producers have a number of alternatives to conventional thermal processing at their disposal. However, there have been few studies that evaluate the strengths and weaknesses of these options on specific fresh food products such as diced tomatoes or tomato purees.
Now, a USDA-NRI-funded study involving Ohio State University in partnership with North Carolina State University, University of California-Davis, and the U.S. Army Natick Soldier Center compared four alternative processing technologies on a single food source: tomatoes. On Wednesday, June 27, scientists presented data from the study to industry professionals at the 2012 IFT Annual Meeting in Las Vegas.
The methods evaluated and discussed in the session included ohmic, continuous flow microwave, batch-type microwave, and high-pressure processing. The study’s results were unique because they offered a side-by-side comparison of advanced thermal and the most significant nonthermal processing methods.
The study’s data revealed only minor differences from the alternative or nonthermal technologies. All were effective in reducing the target organism Bacillus coagulans. There were few differences noted in terms of content of phenolics, organic acids, and color profiles. As for sensory and nutritional characteristics, semi-continuous flow microwave offered better retention of vitamin C while high-pressure processing helped to better retain “fresh” characteristics.
Were the study’s results meaningful enough to purchase an expensive piece of machinery?
“I don’t think so,” said Patrick Dunne of the Combat Feeding Program and Consumer Research Team, U.S. Army Natick Soldier Research. However, he added, a problem with the study was the choice of evaluating tomatoes. For example, he said, if the study had evaluated, say guacamole, perhaps it would have revealed a very different picture, where high-pressure processing would be strongly preferred over the advanced thermal processing methods.
Sadir Sastry, of Ohio State University, agreed that the study had limitations that made it difficult to truly glean whether or not one process was more advantageous over another. There were several variables involved, he said, and the choice for an alternative process must ultimately be left up to the discretion of the food scientists involved in a specific fresh food application.
