You can try this solution:
In content variable pass the map as mvel. Following is the sample map:
[ 'reminderInterval' : new String("#{reminderInterval}"),
'report' : new String( "#{report}")
];
And in human task handler(WSHumanTaskHandler or CommandBasedWSHumanTaskHandler) modify executeWorkItem(WorkItem,WorkItemManager) method. Add following lines at bottom part of the method before serialisation:
ContentData content = null;
String contentString = workItem.getParameter("Content").toString();
//evaluate mvel
ExpressionCompiler compiler = new ExpressionCompiler(contentString.trim());
ParserContext context = new ParserContext();
context.addPackageImport("java.lang");
Map<String, String> contentObject =(Map<String, String>) MVEL.executeExpression(compiler.compile(context));