Mongoose : Inserting JS object directly into db
If you use a plugin like this with mongoose (http://tomblobaum.tumblr.com/post/10551728245/filter-strict-schema-plugin-for-mongoose-js) you can just put together an array in your form, like newitem[item_title] and newitem[item_abv] -- or item[title] and item[abv]
You could also just pass the whole req.body if the elements match up there. That MongooseStrict plugin will filter out any values not explicitly set in your schema, but it still leaves checking types and validation up to mongoose. With proper validation methods set in your schema, you will be safe from any injection attacks.
EDIT: Assuming you have implemented the plugin, you should be able to use this code.
app.post('/items/submit/new-item', function(req, res){ new itemModel(req.body.formContents).save(function (e) { res.send('item saved'); });});