How do you add a JToken to an JObject?

I'm trying to add a JSON object from some text to an existing JSON file using JSON.Net. For example if I have the JSON data as below:

  {
  "food": {
    "fruit": {
      "apple": {
        "colour": "red",
        "size": "small"
      },
      "orange": {
        "colour": "orange",
        "size": "large"
      }
    }
  }
}

I've been trying to do this like this:

var foodJsonObj = JObject.Parse(jsonText);
var bananaJson = JObject.Parse(@"{ ""banana"" : { ""colour"": ""yellow"", ""size"": ""medium""}}");
var bananaToken = bananaJson as JToken;
foodJsonObj["food"]["fruit"]["orange"].AddAfterSelf(bananaToken);

But this gives the error: "Newtonsoft.Json.Linq.JProperty cannot have multiple values."

I've actually tried a few different ways but can't seem to get anywhere. In my example what I really want to do is add the new item to "fruit". Please let me know if there is a better way of doing this or a simpler library to use.