Any scientific evidence to support "no metal utensils or bowls" for sourdough?

Personally I have tried ss utensils and bowls and non-ss utensils and bowls and have noticed zero difference.  Even tried some blind taste tests and no one could tell a difference. 

Nuff said!

Do what works for you.  My starter is going on 5 years.  I bake two loaves every 10 days or so.  I store the starter in either glass or crockery.  I use stainless steel spoons, stainless steel bench scrapers and a stainless steel bowl.  I bake in cast iron.  It works for me. 

Agree, do what works best for you.  Not to long ago, the "stainless" was not what it should have been and the acids that develop during fermentation reacted with these metals and made some discolored, ill tasting by products.  Most of todays metals are fine to use, but there are some cheap products out there that could react to long exposure to raw dough.  Not all stanless is created equal.

Here's the science: Sourdough is made sour by acids. Acids react to metals.

Now, for the analysis: This can be bad if the starter or dough is left for too long of exposure, but from what I've read, and also from my personal experience, there is no problem using metal spoons, bowls, scrapers, etc. to process your dough, as long as there is not a long enough exposure for the acids to react badly with the metals. How long is too long is very subjective and also depends on how acidic your dough is and what kind of metal it is in contact with. For me, it means I don't store my starter or dough in metal containers, but I use metal utensils and bowls, like Ambimom. But, as Ambimom and others have said, do what works for you.

I think in earlier times, iron and tin coated materials were used and reacted with the acid causing problems and later stainless was thrown into the metal mix.

But long ago I remember some cheap ss flatwear and bowls, which would get small rust spots on them, mostly when something acidic would remain in contact for a long time. I don't recall seeing anything like this for many years, and have used SS for all bread making.

The composition of SS varies greatly. Magnetic bowls, and induction friendly pans, have only chromium added, and the less there is, the more likely the rusting. Non-magnetic have nickel and chromium - the numbers you see on many pans 18/10 are the percenteges of these metals. These are more corrosion resistant, though these days, the magnetic ones are plenty stainless for our needs.

Dave

Aluminum was used a lot more in mixing bowls, drinking cups, and utensils in the past than now. Aluminum and acid do not work well together. Decent stainless steel bowls should be fine as a rule. I tend to use stoneware bowls and stainless steel utensils.

This article describes how stainless steel removes onion, garlic and fish odors from your hands by attracting the sulfur molecules (that cause the odors). 

Why Stainless Steel Erases Garlic's Aroma - Huffington Post

http://www.huffingtonpost.com/2012/03/13/eliminating-garlic-smell_n_1341413.html

So stainless steel reacts with some foods. Maybe there is something to the old saying about not letting sourdough touch metal? I hope it's not removing flavor or odor from sourdough, we usually want to increase that, not decrease it. ;-)

Are there perhaps certain alloys of Al formulated to resist acids? My 1970s Presto hand-cranked dough kneader employs both an aluminum vessel and hook, neither of which ever seem to show the least amount of discoloration or pitting. Am actually surprised how sparkly bright it has all stayed, considering the low pH of some of my SDs — have even added grapefruit juice to some batches, and often work the dough ball over the course of an hour. Though perhaps the product of any chemical reaction on the surface of the Al would get absorbed and blended into the dough before I'd ever notice? Eww. 

Have also purchased supposedly SS utensils from Wallyworld for my campsite upstate and seen them rust here and there, so guess there's no accounting for quality. OTOH, upscale dough mixers mostly all come with SS bowls and implements, no problems there. Incidentally, when Braun updated their Kitchen Center they dumped the plastic mixing bowl for stainless, and all agreed it was much improved. Never had a problem with the older bowl myself, but do look forward to testing out the SS version I have on order.

Happy mixing everybody. 

Is it one of those gold anodized Presto dough kneaders? I had one, once upon a time. I suspect that the anodizing might have protected it from the acids.

The nice thing about stainless steal bowls - and ceramic - is that they don't have fats adhere to them. Try making meringue in an old plastic bowl.

No, unfortunately my Presto is not gold anodized, but is/was painted Harvest Gold, yech. Obviously though some kind of alloy, is much shinier than the aluminum Presto pressure cooker of an earlier generation I had inherited, which was a dull grey and very difficult to clean — could scour that pot endlessly to no avail. OTOH, the interior of the Dough Kneader, and its hook, could almost pass for brushed stainless steel.

Just bought some eggs. When my Braun mixer arrives, will try out some meringues on the thirty year old plastic bowl, should be interesting.

Make sure the utensils you get are 18/10 or 18/8 stainless steel. If it doesn't state what it is, it may be 18/0, which will rust and stain. Those two numbers refer to the amount of chrome and nickel that make up the stainless steel. This is not just a plating, this is the makeup of the stainless all the way through.
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Explanation about stainless steel numbers from Ebay:
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"The first number is the amount of chromium that is contained in the stainless, i.e., 18 is 18% chromium.
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The second number is the amount of nickel, i.e., 8 stands for 8% nickel.
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So 18/8 means that this stainless steel contains 18% chromium and 8% nickel.
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18/10 is 18% chromium and 10% nickel. The higher the numbers the more corrosion resistant the material.
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18/0 is a misleading designation due the fact there is no nickel in 18/0."

18/0 stainless steel will rust and stain. 

The used (20? 30? YO) Braun K-1000 I scored on eBay arrived today. Came with a huge variety of stainless steel implements, out of which just the ice crushing blender blade had a few tiny speckles of rust, that scrubbed off fairly easily. Read where Saber supplies Braun's FP blades; dunno if that is true but they are supposed to be great quality. The slicing blade was still so sharp, it shredded my poor old dish brush.

Did as YK suggested and tested the large plastic mixing bowl and SS whisk on some meringue. The egg whites formed beautiful crests, so guess either the previous owner was super circumspect about maintaining the equipment, or Braun molded the vessel from some fat-resistant polymer. Bosch must do something similar with their plastic mixer sets.

The dough hook on the Braun is of the "European" design, with a plastic body and SS arms. Gonna try whipping up a batch of SD bagels later, see what happens. Hope no kaboomy.