In a fresh assault on bacterial contamination of food, some major U.S. meat processors have embraced a high-pressure processing technique that they say makes cold cuts, fruit and other edibles safer without affecting taste. Hormel Foods Corp., Perdue Farms Inc. and others are dunking prewrapped foods nto tanks of pressurized water - a process that kills salmonella, e.coli and listeria and allows food makers to add fewer preservatives.