Dog treat icing turning yellow

Any ideas on why my icing would turn yellow after a few days? I melt down yogurt chips and either use a little canola oil or paramount crystals to thin it a little. I then dip or coat the cookie with it. Then they go into a cookie case. After a few days, they start turning yellow. Could it be the lights in the case? The temperature or the air? Someone had told me it might be because the chips are old, but I've used brand new chips and had the same thing happen.

Chef's Answer ~ That sounds frustrating! There are a couple reasons why icing would change colors. First, the ingredients. When you add ingredients that have a color to themselves like margarine, butter, etc., it can alter the end color of the icing. So, as slight as it may be, canola oil does have a color, so for now I would stick to the paramount crystals.

Second, the temperature of the room, or in this case, the bakery case. If the area is warm, the icing gets softer, and this can cause the dog treat icing to deepen in color, or get darker.

Third, is humidity. It seems that the longer it takes for your icings to dry, which is controlled by humidity, the more you'll notice your icing getting darker.

These are all things to consider, and areas to start troubleshooting as to why your icing may be changing colors. Another thought is to purchase white food coloring to see if that aids your icing in remaining white. Also, lemon juice is suppose to bleach out icings and may help your white stay white.

I hope this helps! Happy Dog Treat Baking! :)