Frozen berries are not harmful. The nutrients are locked in at peak freshness which makes frozen berries an excellent affordable, nutritious option. Buyers must, however, make sure to rinse and then boil their frozen berries for exactly a minute to destroy any potential contaminants. Frozen berries, especially those of the imported variety, are one of the highest-risk foods for carrying foodborne pathogens like norovirus, Listeria monocytogenes, Salmonella, E. Coli, and other enteric viruses and bacteria