Node.js - Set a mongoose object field to empty according to request payload

So I have a number of Mongoose models in my web app. I want to be able to set the fields as empty when the payload of a PUT request contains that data as empty. I am not sure what i have written above makes much sense so ill try to explain through the code I have.

if(req.params.iId){
        Industry.findById(req.params.iId, function(err, industry){
            if (err){
                return res.send(500, {
                    message: getErrorMessage(err)
                });
            }
            if (!industry){
                return res.send(204, {
                    message: 'No industry found, Cannot Update'
                });
            }

            industry.industry = req.param('name');
            industry.updated = Date.now();

            industry.save(function(err, newIndustry) {
                if (err) {
                    return res.send(500, {
                        message: getErrorMessage(err)
                    });
                } else {

                    newIndustry.__v = undefined;
                    newIndustry.withEffectTo = undefined;
                    newIndustry.withEffectFrom = undefined;
                    if(isResponseJson){
                        res.json(industry);
                    }else{
                        res.jsonp(industry);
                    }
                }
            });
        });
    }

From the client side a send a JSON payload of the form:

{
     "industry":""
}

Through this payload, I intend to set the particular Industry objects industry field to empty, not caring about whatever value of previously had. The problem is when I send this payload it causes no change and the object keeps whatever value it previously had. I know that setting that particular value to undefined and then saving it would do the trick (another related question)

but i have a number of request parameters in other models and how do i set there fields as empty when a corresponding empty value for their key is obtained from the request payload. Any help would be really appreciated.