Text Box: For some understanding of the C.perfringens varieties active in SRB starters, Rtech was asked to perform DNA analyses on flour, corn meal, and cheese initiated starters.  As before, dry starter set-ups were delivered to Rtech where they were hydrated, incubated, and subjected to DNA analysis.  The set-ups comprised 1/2 Cup Robin Hood flour, 1/2 Teaspoon baking soda, 1/2 Campden tablet, and 2 Tablespoons cornmeal, or 1/4 Cu-Inch cheddar cheese, or nothing for the flour-only set-up; Rtech personnel added hot water.  Interestingly, in contrast to the corn meal starter with  9,700,000 CFU/ml, the flour-only starter had but 850,000 CFU/ml while the cheese-based starter rang up 1,600,000,000 CFU/ml.

 The DNA analysis report concluded that only the cheese-based perfringens (similarity rating at 0.92) was positively identified as Type A Clostridium perfringens of bovine origin.  Corn meal perfringens similarity to the bovine perfringens was 0.76 and flour-only 0.73.  Per Rtech: "A similarity of >0.85 indicates positive identification of the genus and species for the isolate.  Similarities of < or = 0.85 indicate a close relationship to that genus but do not indicate a positive identification for the isolate."  Compared to one-another, the perfringens variants best similarity of 0.67 occurred between cheese and flour-only with a score of 0.52 between corn meal and flour-only. 

 The Rtech database has a limited number of C.perfringens patterns with some identified as Type A bacteria but the type (B, C, D, or E) is unknown for the rest.  Bacteria found in  the corn meal and flour-only starters probably are Type A variants also though they are different from one-another.  My limited data set confirms variability to be the persistent character of Clostridium perfringens.

 A practical starter or proliferation of Clostridium perfringens will develop from plain white flour as noted.  Starters also arise on straight corn meal, whole wheat flour, and triticale, etc. suggesting that perfringens needs only a ready supply of proteinaceous material together with proper temperature and moisture.  Starters based on white flour and an initiator may have two or more perfringens variants active with one or more coming from each source (flour, initiator).  Perhaps hybrid variants are created.  Many more DNA analyses are necessary to crack this conundrum.

 White potato, raw, baked, or boiled, is often included in published SRB starter recipes.  In my experience, potato-based starters fail as often as they succeed.  The character of the starter and subsequent bread seems identical to that arising on many other materials abetted by a Campden tablet.  Starters will not develop when potato or corn starch is substituted for flour in a Campden augmented mix.

Text Box: Many, if not most, published recipes for SRB starters specify some quantity of sugar  and milk.  As part of the attempt to increase cheesy odor in starters and bread, various quantities of dry and liquid milk as well as cane and corn sugar were used in corn meal based starters.  No significant effect was achieved.  Except as they might influence flavor of the finished loaves, sugar and milk seem neither beneficial nor detrimental to SRB starters.

Bicarbonate of soda (baking soda) is strikingly beneficial.  Action will arise on starter mixes lacking soda, but it is slow in developing and relatively weak.  Baking soda apparently buffers the acid produced as C.perfringens proliferates perhaps to sustain congenial conditions for perfringens activity.