Can anyone help me with desem?

I use a slightly different recipe, but I think I can help.   By day 3 or 4 you should see bubbles in the desem if it is split in half.  I don't think you need to worry too much about smell.

If you get no bubbles, it is probably because you don't have enough yeast growing.  This tends to occur when the pH is too high and results in a dough that doesn't rise.

Here's what I do (adapted from Bread Alone and I'm still tweaking it but it works)

Day 1: 3/4 c flour + 1/2 c orange juice (helps grow yeast)

Day 2: Day 1 + 3/4 c flour + 1/2 c orange juice

Day 3: Day 2 + 3/4 c flour + 1/2 c orange juice

Day 4: Day 3 + 1/2 c flour + 1 tsp salt

fold into a boule

place onto a floured cloth in a large bowl 

let it rise at room temp 12 h

flip the risen dough form out onto a baking surface

Slash the dough 

Bake with steam for 25-30 min, 500oF 

Yes, only 4 days, actually only 3 and a half because the last day is just a 12 h rise followed by a half hour of baking.

I used OJ from concentrate by any OJ should work.  I learned the the OJ trick from SouroLady, who is also on this site.  Apparently, all the OJ does is make the dough slightly acid, which helps grow the wild yeast.

When I followed this recipe earlier this week I could not taste the orange in the final loaf.  Nonetheless, I am thinking of cutting back on the orange juice as I tinker with the recipe.

 Finally, I should mention that the flour I used was 50% whole wheat and 50% white bread flour.

Technically this is not a desem but a Pain Levain.  I don't know if there's much of a difference.  For me the key to this class of European sourdoughs is getting it slightly sour-- I want something like a yogurt sour not a vinegar sour.

and P.S.--Don't forget to fold the dough!

Good luck.  It's worth the work.  It took me years to figure this out but it was worth every minute.