Trans fats don't affect taste - human taste buds don't activate for any fat molecule.

Trans fats were used because they keep longer, unsaturated fats go rancid in air, hydrogenated fats (which contain some portion of trans fats) keep better. Saturated fats (e.g. butter) can keep for very long times.

For packaged food like this, the oils used would (previously) be hydrogenated so they could push the expiration dates out and avoid waste. Now, they just either use saturated fats directly or add extra preservatives.