Java Properties object to String

I have a Java Properties object that I load from an in-memory String, that was previously loaded into memory from the actual .properties file like this:

this.propertyFilesCache.put(file, FileUtils.fileToString(propFile));

The util fileToString actually reads in the text from the file and the rest of the code stores it in a HashMap called propertyFilesCache. Later, I read the file text from the HashMap as a String and reload it into a Java Properties object like so:

String propFileStr = this.propertyFilesCache.get(fileName);
Properties tempProps = new Properties();
try {
    tempProps.load(new ByteArrayInputStream(propFileStr.getBytes()));
} catch (Exception e) {
    log.debug(e.getMessage());
}
tempProps.setProperty(prop, propVal);

At this point, I've replaced my property in my in-memory property file and I want to get the text from the Properties object as if I was reading a File object like I did up above. Is there a simple way to do this or am I going to have to iterate over the properties and create the String manually?