Pasteurization of Cider for Mead

Just wondering what the details on using pasteurized cider versus unpasteurized cider in my mead. I just added about three delicious apples. The mead we made with 15lbs of honey, water and Lalvin yeast--pretty basic. I want to add about a gallon of cider to fill the space in the carboy. I'm picking up some freshly squeezed cider tomorrow at 7 am without preservatives and unpasteurized. would it be alright just to dump it straight into the mead? should i worry about bacteria or wild yeasts?

three "yellow delicious" apples****

Treat the cider with a campden tab and wait for a day before you add it to your mead.
Ideally if the Lalvin is active it should overpower any wild yeasts but I would go the campden route.

Don't worry about it...just pitch it in. I make my cider and cyser with fresh pressed, unpasturized, unsulfated cider haven't had an issue with wild yeast or bacteria yet. I've been making a cider and a cyser every year for the past 3 years.
Cider recipe: 5 gal cider w/ 3 lbs honey (and some cinnamon, allspice, and cloves)...add yeast and go. Cyser recipe: 5 gal cider, 1 gal honey...add yeast and go.

I second biochemedic's opinion. While there are likely wild yeast strains mixed in with your fresh juice, an established strain of commercial wine yeast, already actively fermenting, will very likely make it next to impossible that any wild strain will take off. Which Lalvin yeast are you using? Some of them possess an ability to produce natural "killer factor" proteins that annihilate sensitive wild strains, and most wild strains are sensitive. That little naturally selected advantage works to our advantage when we use a K-factor yeast strain.

If your mead is already fermented the alcohol will prevent the wild yeast from being active. The unpasteurized juice will have lactic acid bacteria and if you haven't used sulfite on the mead previously, your cider could possibly go through malolactic fermentation if you don't add some KMeta when the yeast fermentation is done.

Thanks for the advice. I just threw it into the mead w/o any campden tabs. I got the first gallon to come out--so it is THE freshest possible. I poured it in using a funnel and within an hour there was a mass of bubbles starting to form. I was wondering. I read that if you add fruit to the ferment you might have to punch out the cap let the CO2 out so the yeast doesn't die. D'you think I'll have to punch it out? or just let it be? I'm more for the latter.

The yeast won't die from the CO2 (you have to have about 7 atm of pressure to kill them), however, if you have a fruit cap, and you don't punch it down or stir/swirl to break it up it can cause the fermentation temp to rise too high creating a harsher mead or potentially harming the yeast (in extreme cases). Potentially more of a problem is that if you leave a fruit cap alone and allow the top of the fruit to stay out of the alcohol bath, spoilage organisms may set up house. So if you have a fruit cap, take the time to manage it.

With apple juice, since you are using juice and not whole fruit, there usually isn't too much of a cap to worry about.

Medsen

Adding on to the don't do anything to the cider. I've made two batches of cyser by putting 15lbs of honey into 5 gallons of fresh pressed, unfiltered, non-pasteurized, sulfite free cider. No issue with either batch, and it drops clear exceedingly fast. I do add nutrients and degas, but don't fine/filter.

That much cider and honey makes it a super sweet dessert cyser, but it's been very popular!