Which ingredient in Italian bread gives it that great taste?

I'm assuming this is not a speciality Italian bread such as Panettone or Pan d'oro. It's a regular bread loaf.

Hard to know for sure, but in all likelihood, the missing taste is due to short rise times and yeast type. Most of the taste in bread is developed, not put in.

As suggested in the comments, the ingredients are bread flour (usually tipo 00 or 0), water, yeast, and salt. Tuscan bread has no salt. and sometimes, there is olive oil to prevent the dough from developing a skin. The notes below might be useful:

• A French baker I work with, always keeps some of yesterday's dough and mixes it with today's dough. This means an exponentially small amount of the dough can be years old. He also performs three rises (two punch-downs).

• Let your biga rest in colder temperatures for a couple of days so the enzymes can do their work and develop taste.

• Get yeast from a baker. The instant yeast at the grocery store is ok but the commercial yeast can work better with the longer ferments. A famous natural bread baker in our area uses 2500 year old yeast from Egypt. (the head baker has a heck of story on how he got his hands on this yeast). Strict Neapolitan Pizza makers use Ischia starter for their dough.

Peter Reinhart explains Italian breads really well in The Bread Baker's Apprentice

I would guess the big thing that separates supermarket Italian bread from homemade bread is that frequently, the dough isn't made on the premises; it's usually shipped in frozen and baked at the bakery counter. While I wouldn't recommend freezing the shaped dough, an overnight rest in the fridge (like you'd do for NY-style bagels or artisanal baguettes) will probably get you a lot closer to what you're looking for.

One thing you might want to look at is the recipe for Cuban bread from La Segunda bakery in Tampa. (Note that the amount of yeast in the recipe seems way too high for dry yeast.) One interesting aspect about Cuban bread that it seems to have in common with supermarket bread is that the crust and texture are fairly smooth. With Cuban bread, that means a long, mechanized kneading cycle; I've even heard of people using pasta machines for the kneading process. (Seems like overkill to me...) I'd also stick with bread flour, as industrial bakers seem to prefer high protein content. The Italian 00 flour makes excellent bread, but I don't think it's what you want.

The last part is the giant rack ovens they use in supermarkets. For that, I have no substitute to offer. You could buy your own convection oven, although you might have to dig around to find one that's actually worth buying.

if the bread you are talking about is crispy, extra virgin olive oil could be the clue ;)

There are a few things that haven't been mentioned that may make a difference:

• Salt: many commercial breads have loads of salt in them, that difference in flavor may just be more salt. The type of salt can make a difference too, you could try sea salt or kosher salt. Adding more salt isn't that healthy, but it may make the difference. Don't go overboard though, try adding a 25% more to a recipe and see what you think.
• Flour: the grains used in the making of flour are different in Europe from the US, that may make a flavor difference
• Water: believe it or not, water can make a big difference to the flavor of bread (or other foods). NYC has soft water from the catskills, and it is one of the reasons bread and pizza there is so good. Most municipal water in the US is hard water which I've found to make a definite difference. Try filtering your water with a brita or similar product, or using bottled mountain spring water
• Yeast strains: the yeast you get in the store is only one strain, artisan bakers may be using their own strains, or strains you can't get in a store. You can get other yeasts online, or make your own natural yeast starter to get a different flavor

Probably time. Good bread takes at the very least 6 hours between mixing together the ingredients and retrieving the final product from the oven.

Use sourdough starter. It will improve the flavor of your bread. See how to make your own sourdough starter here.

Also make a slow fermentation on the refrigerator. The slower the better is the flavor.

You can add a bit of rye flour for a more "rustic" Italian Bread taste. I think that's probably the missing ingredient.

i use barley malt and malted milk powder and the smallest amount of tumeric for color

Accidentally made what I would call Italian bread, attempting a variation on a familiar recipe. This was my 37th loaf in two years, mostly various NO-KNEAD breads (using Steve Gamelin's no-knead books and video-- I cannot knead, and have no mixers.) My favorite bread is a Rustic loaf (made 17 times), the origin for which is lost in antiquity--the recipe calls for regular active dry yeast and is ready in 3 1/2 hours--I mean from mixing the dough to baked to cooled and on the table. I wondered what would happen if I were to use rapid/instant/quick granulated yeast instead,with an all-night rise (18 to 24 hours--I waited only 18.) Only the yeast was changed, but again, I couldn't knead it, so the next day I floured the dough by rolling it around in the bowl and dumped it right into an oiled Lodge cast iron skillet for the second-day rise of 2 hours (I don't enjoy baking with the "hot pot" method). Upped the oven temp from 425 to 450, wish I hadn't--the lower temp might have given more "oven spring." But as it was, it turned out to be a beautiful loaf, crispy crust, lovely grain, and with a scent just like you get when opening a bag of bakery Italian bread--at least to me. The recipe I used: 2 c cool water in big bowl, stirred in 1 1/2 tsps. non-iodized salt (I think 2 tsps. would have been better) and 1/2 tsp of the instant granulated yeast, and last, 4 c bread flour. Covered with wet-and-wrung-out double-layer flour sack and plastic, to keep crust from forming (and sprayed the sack lightly with water next morning too). I was having a lot of trouble with crust forming--hence the flour sack trick has solved that problem. Hope somebody finds this of interest. Nothing like baking bread to soothe the soul... Carol

P.S. Baked for 40 minutes uncovered. Cooled completely before slicing.

Use a starter! It adds flavor. You can let it sit out overnight, and for better flavor, make a starter and keep it in the fridge for whenever you need it. Just remember to subtract the starter ingredients from your total ingredients. For crust, use steam for the first half of your baking time.