National Center for Home Food Preservation according to the National Center for Home Food Preservation National Center for Home Food Preservation National Center for Food Preservation website safety guide General Canning Guidelines food acidity and processing methods other sites National Center for Food Preservation website commercial vinegars with 5% acetic acid according to the National Center for Home Food Preservation Acidity in Home Canned Foods From the NCHFP basic safety guidelines National Center for Home Food Preservation basic safe guidelines preserve food safely