The Fresh Loaf

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The Pineapple Juice Solution, Part 1

Debra Wink's picture
Debra Wink

The Pineapple Juice Solution, Part 1

You know what they say... Life is a journey. But have you ever been pulled down a path that you otherwise would have walked on by? That's what happened to me when I started playing with sourdough. I didn't even like sourdough, or so I thought until about seven and a half years ago. I was watching the food network one day, and Daniel Leader appeared as a guest on Cooking Live. He was demonstrating how to make a sourdough starter from nothing but flour and water. How fascinating! I had no idea you could do that. Bread science was nowhere in the curriculum when I went to university almost 30 years ago, let alone sourdough. But for someone with a microbiology degree and a passion for baking, sourdough is the perfect marriage of two loves. I had to try it for myself. And so began the journey. The path so far has taken some surprising twists and turns, and led to meeting many interesting people along the way. Including Peter Reinhart, who has been nothing but gracious and supportive throughout, and who is ultimately responsible for getting me to sit down and record this story in my own words. Now, back to the beginning...

In early 2002, I was a member of the King Arthur Baking Circle, a message board for baking enthusiasts. With this brand new interest in sourdough, I found myself reading all of the threads under that category. In March another member, Pat Doucette began posting of the difficulties she was having in getting a starter going. She had tried a few different recipes with no success. Now she was following the formula in The Bread Baker's Apprentice and... still no luck. Newly armed with all of the advice that she was getting from others on the forum, she started over. And once again, she got results that were nothing like the book describes. But a pattern was becoming clear. On the second day, her seed cultures would fill with bubbles and expand to over three times the starting volume when minimal growth was expected. And then do nothing on the third and fourth days when they were supposed to be expanding more and more. They came on strong and then died at the same point each time. A pattern holds a clue, so I offered to do the procedure myself and see if I could reproduce what she was seeing. I followed the directions to the letter and, lo and behold, my results duplicated Pat's perfectly. I may be the only person on the planet who would be excited about this, but it gave me something to study and troubleshoot. There was something unexpected going on at the microbial level. Living things are funny that way, and microorganisms don't always follow directions.

One by one, other people on the message board began to speak up and post that they had experienced the same thing. In fact, it seemed that many more saw that scenario than the one described in the book. This phenomenon had nothing to do with local strains of lactobacilli and yeast as some had surmised, because Pat was making starter in Massachusetts and I was in Missouri. Others chiming in represented various regions of the country from coast to coast. This pattern is apparently quite common. We ran the gamut of theories on why yeast were coming on like gangbusters, only to quit and become non-responsive. We tested each theory by trying different flours at various points, increasing the feeding frequency, changing the hydration and water source, cooling it down, and anything else that anyone thought might help. But in the end, nothing fixed the problem, and the results weren't making much sense to me.

At that point, I had to do what microbiologists do when things don't add up---go back to the microscope and take a look. That meant packing up my starters, taking them to work, and having to answer all the curious questions about what I was doing and why. But the microscope answered a few of my questions, and that day proved to be the turning point. No wonder things didn't make any sense! We were operating on the assumption that we were growing yeast. What I found was that there were no yeast or lactobacilli to be seen anywhere in all the activity of day two. Not a single one. But it was like a three-ring circus in there---different kinds of bacteria, some round, some rod-shaped, some motile, some not. Some were spinning, some were twirling, some flipping or zigzagging, and some were just darting back and forth across the field. What were these bacteria, and which one was responsible for all the gas?

I knew, from having made so many starters by now, that this pattern does turn into sourdough if given more time. So, I looked at cultures each day in the process, comparing them to my established starter which was yeasty and stable. Everything quiets down in there and yeast emerges a few to several days later. They don't appear to be coming from the air as many people believe, because it happens even in a covered container. But if they are already in the flour as the more reliable sources say, then why couldn't I find any? Obviously, there was more to this than just a symbiotic relationship between lactobacilli and yeast gradually increasing in number, good guys out-competing bad---the usual explanation. It was evident that there are many more bacterial and fungal species present in flour than just sourdough lactobacilli and yeast. But where were the good guys? Why weren't they growing? It was time to close the cookbooks and open the textbooks.

I turned to a large, newly updated food microbiology tome, and was disappointed to find only two brief paragraphs on sourdough, and not much more on yeasted breads. So it became a challenge to find the information, mostly borrowed from chapters on wine, beer, dairy, and other food fermentations that share something in common with sourdough. I was able to narrow down the gas producer to a Leuconostoc species. The tip-off was reading that almost 90% of spoiled doughs are caused by Leuconostoc mesenteroides or Leuconostoc dextranicum. When I started searching for more on the genus, I found Leuconostoc mesenteroides is considered the primary agent in the fermentation of an Indian steamed bread called idli. (Spoilage is a subjective thing from culture to culture.) After soaking grains for a day and then grinding them with water into a paste, there is a 15-24 hour fermentation during which the idli batter increases in volume by about one and one half to three times---the same as our wild day two growth.

Leuconostocs are also occasional spoilage bacteria in wine making, "but they undergo little or no growth during the alcoholic fermentation and tend to die off because of competition from yeasts. Nevertheless, these bacteria are capable of abundant growth in the juice and, if yeast growth is delayed, they could grow and spoil the juice or cause stuck alcoholic fermentation."[1] Many microorganisms produce characteristic aroma compounds, and so smell is also an important clue. I had previously described an unamended, all-white seed culture as smelling like sour milk with a hint of rotten cheese. Then I learned that some leuconostocs are added to dairy fermentations (such as cultured buttermilk, and cheeses like Gouda, Edam, blue cheese and havarti) for their carbon dioxide and aroma compounds. Together, these pieces all fit what we were seeing, and according to the chapter on fermented vegetables, leuconostocs are quite common in nature and found routinely on all kinds of produce and plant material. So, we can expect them to be present on grains and in flour.

Knowing how bland a flour-water mixture starts out, and seeing how the microscopic picture becomes more subdued as the sourness increases, it was apparent that the shift in populations and activity are tied to changes in acidity. pH is a fundamental factor in microbial growth. Some like it neutral while others need more acidity or alkalinity, but each species has its own pH range. The reason that the starters had become quiet on day three was because the pH had fallen and the gas-producing bacteria were no longer growing. Even though I still wasn't sure what these bacteria were, it was clear that whenever the gas-producing one or ones grew, the starter would subsequently become still and take longer to finish---sometimes by several days. I reasoned that the best solution might simply be to keep them from growing. And since they stop growing as the pH drops, why not add an acidic ingredient to the mixture to lower the pH and inhibit them from the outset?

It was May now and Evan Shack had entered the picture. Unaware that this was already a hot topic, he began posting to the message board seeking help after having just tried to make starter and getting the same result that we had. Evan was interested in learning the science behind it, and he and Pat were both eager to get to the bottom of the problem, so they volunteered to do some testing. Soon after we joined forces, Gary Wray contacted me and we invited him to join our little task team. With so many different recipes to choose from, it was clear that there are several approaches to making starter. But we needed to pick a direction to focus our problem-solving efforts. And because so many people on the message board were loyal fans of The Bread Baker's Apprentice, the group decided the goal would be to use that formula, altering it as little as possible, and make it proceed as described in the book. The fix should be simple, with ingredients readily available at home or in the average grocery store. Our choices for the acids were ascorbic (vitamin C), citric (sour salt), tartaric (cream of tartar), acetic (vinegar), lactic (yogurt), and mixed acids (fruit juices).

For our first trial we chose ascorbic acid, because it is readily available in the vitamin supplement section, known to be beneficial, and widely accepted in bread-making. Pat and I used vitamin C tablets that we had on hand. We crushed them and mixed the powder with the flour and water on day one. And much to our amazement... it worked! No gassy bacteria, and we were both growing yeast on or before day four, where it had been taking about seven days. But I discovered a little problem with supplement pills, which is that some are buffered without being labeled as such. I was not getting the pH to drop in mine even though I kept adding more and more vitamin C. When I took a closer look at the bottle, I found two ingredients listed which together, formed a buffer system that was keeping me from reaching the pH I was aiming for. Pat's vitamin C was not buffered and her starter took off in only three days.

Buffer problems aside, neither one of us enjoyed the task of crushing pills. And whirring them in a blender with the water only worked so-so. We also had no idea what the best dose would be. Gary and I both had ascorbic acid powder, so we did another experiment testing different doses ranging from 1/8 to over 1 teaspoon mixed with the 4.25 ounces of flour on day one. It was a fun experiment to do. With the jars lined up next to one another, they looked like perfect stair steps as the starters began to rise. It was easy to see which doses were most effective by how fast and how high the cultures rose. For me, the most active jars were the ones with 1/4 and 1/2 teaspoon of ascorbic acid powder. For Gary, the best results came from 1/2 and 3/4 teaspoon, and so we settled on 1/2 teaspoon as the recommended dose. While the ascorbic acid worked quite well, and may be the ingredient of choice for purists or professionals, the average person must go a little out of their way to find or mail-order it. So we decided to press on.

All of the acids that we tried, inhibited the gassy bacteria effectively, but sour salt (sometimes found with canning supplies) was so strong that it was hard to measure the tiny amounts accurately. Cream of tartar (found in the spice section) was too weak, and required an impractical amount to effectively lower the pH. We dismissed lactic acid because we didn't want to deal with dairy or go to the trouble of draining yogurt for the whey. And vinegar was so highly inhibitory to yeast in the doses required to lower the pH, that it was no solution at all. That left fruit juices. I tested the pH of various juices and made a list for the group to try---apple cider, orange, lemon, grapefruit and pineapple juices seemed like the most suitable candidates based on wide availability. But whenever trying a new juice or acid, I had the group run a negative control alongside---a duplicate to the test in every way, except using plain water. This would show whether changes in the result were due to the ingredients under evaluation, or to chance or variation in experimental conditions. Time after time though, the control jars followed the familiar pattern, while the test jars proceeded by the book.

While the trials were under way I went back to basics, monitoring the changes in acidity and examining seed cultures under the microscope every day. I recorded pH readings, growth measurements and observations at the beginning and end of each 24-hour feeding cycle. After a number of runs, I gathered my notes to compare and look for patterns. (My pH paper was only sensitive to the nearest 0.5 increment, so readings are approximate.) I found that when I acidified the day one mix to 4.5, it stayed at 4.5 until I fed it again on day two. If I didn't add more acid at that time, the freshly fed starter would read 5 and the gassy bacteria grew on day two and followed the oh-so-familiar pattern. If I acidified the day one mix to 4, it stayed at 4 until I fed it on day two, after which it read 4.5. The gassy bacteria did not grow and the culture started producing its own acid as other lactic acid bacteria were increasing in activity. During the second 24 hours, the pH dropped to 3.5 and the starter tasted really sour. Yeast usually appeared the day after. When I acidified the day one mix to 3.5, I actually got some yeast growth on day two. I'm not sure that this is the best way to go, though. I've only done it once with citric acid and yeast were not as vigorous the next day as I had hoped to see them. More testing could be done. But the key points here are that the gassy bacteria grew at or above pH 5, not at or below 4.5, and the cultures I was growing all failed to produce acid of their own in the first 24 hours. That is important because a day one flour-water paste measures about 6---quite inviting to leuconostocs. And even more importantly, in all my trials I have never seen yeast before a starter gets sour, but it usually follows very soon after.

I was hoping orange juice would perform well, since it is a good source of Vitamin C and a staple in many homes. But, it turned out not to be acidic enough to meet the group's objective, which was to use it only on the first day. However, Orange juice and apple cider do work well if they are used in place of the water for two or three days. Pat was the first to try pineapple juice, which has a lower pH than most other juices, and just happens to come in handy 6-oz cans (exactly the right measure for day one). She liked it so well that she stopped testing anything else and started recommending it to others. Almost everyone who tried it was thrilled with the results, and so pineapple juice became the solution that stuck. While the group's mission was accomplished, the story doesn't end here. But the rest will have to wait until next time, so please stay tuned...

Doyle, Michael P., Larry R. Beuchat, and Thomas J. Montville. 2001. Food Microbiology Fundamentals and Frontiers, 2nd ed. American Society for Microbiology Press, Wahington, DC.

This article was first published in Bread Lines, a publication of The Bread Bakers Guild of America.
Vol. 16, Issue 1, March 2008

The Pineapple Juice Solution, Part 2 | The Fresh Loaf


davidg618's picture

the answer got posted below.

David G

Doc.Dough's picture


Great graphic!  It really separates out the major variables.

Now let me see if I understand (or not) why each line stands alone. (Please excuse my inability to edit in HTML)

Yeast / Lift   <----->   Bacteria / Sourness 

Flour:                          100% White / low ash  <----->  100% Whole Grain / high ash

In this case, it is not so much that the yeast benefits from the low ash flour but that the total acidity (as measured by TTA) is increased by the buffering capacity of the high ash flour which allows the LAB to continue to churn out acid until the pH drops below 3.6 or so which happens later in a whole grain culture. The yeast is relatively insensitive to pH so the yeast growth is almost totally independent of the LAB population and the TTA that it yields.

Temperature:                                        Cool  <----->  Warm

This is clearly true if the threshold for "Warm" is above 24°C since between 2°C and 24°C the growth rates for yeast and LAB are very close to each other with LAB having a small but insignificant advantage everywhere. Between 28°C and 32*C the yeast growth rate is declining while the LAB growth rate is still going up and the acidity will peak well before the yeast population begins to plateau.  At this point the LAB just make acid  or go dormant depending on the specifics while the yeast make as much progress as the temperature will allow.

Hydration:                                            Drier  <----->  Wetter

This I don't understand. Is there something about the higher hydration starters that dilutes the acid enough to encourage additional LAB growth?  The pH certainly doesn't respond to an increase in H2O concentration. Or maybe the LAB being much smaller are not as mobile in a highly viscous/drier environment (that argument doesn't make any sense to me either).  Your insights and hypotheses about why this works will hopefully turn on the light.

Feeding:                 Smaller / More Frequent  <----->  Larger / Less Frequent

Again, while observation supports this conclusion, my explanation would be that smaller refreshments result in a lower post-refreshment pH and thus disables LAB growth sooner after the refreshment while the yeast just eats and multiplies when given more glucose, fructose, and compatible glucofructans. So the left extreme is not so much a benefit to the yeast as it is a detriment to the LAB while the larger/less frequent end of the spectrum is more of an equal opportunity case for both yeast and LAB.

Refreshment Point:                   Under-ripe  <----->  Over-ripe

The left end of this trade is an area where I have no data (so I will go there and observe) but if the process is being run at temperatures above 27°C it should not make any difference as the LAB will peak well before the yeast reaches maximum numerical density growth rate and under those conditions the yeast is always playing catch-up.

It seems that in general there is weak coupling between the yeast and LAB growth rates, and the stability of a culture depends mostly on the lack of competition for sugars, acid tolerance of the yeast(s), and net positive gains on a per-generation basis for the dominant species relative to all of the competitor constituents that come with the flour used for the refreshment (for reasons that may be unique to each culture).  So one result is that you can mistreat a culture for quite some time before it goes south on you (in fact it can go on for a long time before you even detect that there is something threatening the good guys - and by then it may be too late, though your magic methods seem able to recover some pretty badly mistreated cases).



Debra Wink's picture
Debra Wink


My advice is to not dwell on the absolute values of laboratory data collected under a controlled set of conditions. Those aren't going to help much here. It's never that simple with living things, because they interact with each other and their environment in dynamic ways, adjusting and readjusting to multiple factors as they go along. Shift your focus instead to the relationships---learn to think in relative terms instead of absolute.

Flour: 100% White / low ash <-----> 100% Whole Grain / high ash

The yeast is relatively insensitive to pH so the yeast growth is almost totally independent of the LAB population and the TTA that it yields.

Yeast are relatively insensitive to pH in the normal ranges encountered in sourdough, but their growth isn't unaffected by the LAB population.

Temperature: Cool <-----> Warm

between 2°C and 24°C the growth rates for yeast and LAB are very close to each other with LAB having a small but insignificant advantage everywhere.

This isn't about absolute growth rates. It's about relative growth rates, and how they affect the ratio of LAB to yeast over multiple refreshments (when consistently fed at "ripe").

Hydration: Drier <-----> Wetter

This I don't understand.

Yeasts have a lower minimum water activity than LAB (meaning they can grow in drier conditions). Again, it's about relative growth rates, and how they change with conditions.

Feeding: Smaller / More Frequent <-----> Larger / Less Frequent

So the left extreme is not so much a benefit to the yeast as it is a detriment to the LAB

This is about the influence that the number of generations has on growth kinetics. LAB have the longer lag phase which gives yeast a head start, but they reproduce faster than yeast once they take off. So extending the logarithmic phase gives them an advantage. And conversely, reducing log phase stops them short giving yeast a boost in the ratio.

Refreshment Point: Under-ripe <-----> Over-ripe

the LAB will peak well before the yeast reaches maximum numerical density growth rate and under those conditions the yeast is always playing catch-up.

It simply has to do with where each population is in its growth cycle at refreshment. Yeast enters stationary phase first, often when LAB are just hitting their stride.


davidg618's picture

I didn't check my notes, and doing it from memory I got the bread levain build mixed up with the biscuit build. What I've posted is wrong.

This time I checked my notes.

Bread levain build: 12g of seed starter refreshed 1:1:1 progressively, every 8 hours, 3x; (((12x3)x3)x3) = 324g. I needed 250g for the bread dough, which left 74g of ripe levain to replace my seed starter. I used 20g refreshed 1:1:1 and tucked it into the refrigerator last Saturday, replacing my seed starter. I just started doing this following Debra Winks guidance. This levain build was done last, Friday-Saturday, dough mixed and retarded Saturday-Sunday, and loaves baked Sunday.

Bicuit levain: Monday evening I took 89g from the discard bucket and refreshed it twice with a 6 hour interval between two, 2:1:1 feedings; ((89x2)x2) =356g. Tuesday I mixed and baked the biscuit. I'd been refreshing my new seed starter every 6 to 8 hours, at room temperature, and keeping the discard. Since the discard was a mix spanning ten to three days old, I built the levain warm, wet, fed lightly and often to favor yeast development, thinking the discard's sourness might be more than I wanted. Again, these are things I've learned only recently, guided by Ms. Wink.

Thanks for catching my senior moment. I glad I don't get that sloppy when I bake :-).

David G


Doc.Dough's picture

Thanks David.  Now I understand both tracks (to bread and to biscuits). And the biscuits look really interesting - I would have expected them to be more like sourdough pancakes where the acid in the starter serves to rapidly create CO2 when combined with a chemical levening agent such as baking soda.


davidg618's picture

Hi, Doc

It's by far not the main reason I bake bread, cook, brew and vint, but I have an interest in the history of all things food, and I've ocassionally tried to replicate antique kitchen, campfire or brewhouse lore. If you're interested read the two TFL links re Sourdough Biscuits I referred to in my post, A Summary of Successes, posted above. I had fun doing and writing about the doings, however, I started off with a serious curiosity in what trail cooks might have done baking with sourdough, before the introduction of baking powder.  Truth is, I believe cattle trail biscuits probably were akin to the hardtack sailors broke their teeth on in the same era. Nonetheless, I tried to produce a light, well risen biscuit relying only on the levaining power of sourdough.

I'm convinced the success I had here and earlier (described in the two posts) are as much influenced by the way I handled the integration of flour, fat and levain as it is the levain itself. Most (all?) baking powder biscuit recipes prescribe combining the the flour and fat with a pastry cutter, "until the mixture looks like coarse corn meal". What I do, by hand, is closer to frisage, and this time I made the fat/flour globules about the size of  hulled sunflower seeds.

Additionally, I've observed shortened, low-hydrations doughs levained with sourdough don't rise very much, but they get "puffy" with CO2 when proofed for at least a couple of hours, and exhibit good oven spring.  I've also found the flavor delightful.  A turkey sausage patty on a sourdough biscuit is my usual breakfast.

David G

Doc.Dough's picture


A question over on the other thread.


theluckyfox's picture

Thank you for this very informational and fastidious bit of writing.  I am doing my own starter trials now, and my results are, after 24 hours, following your findings, to the letter.  So many questions had gone unanswered in my sourdough trials, then I found your articles.  I am so very grateful, and appreciate your time, *very* much!


okinawa's picture

Finally someone who deals with the problem in a scientific way. Very interesting. I wanted to ask a few questions: do you know whether in the scientific literature there are cases of food poisoning by solid or liquid sourdough sourdough? He did make the analysis even at a stable sourdough to observe food safety? It is safe and the genius keep the dough cool reported in the home? Confirm the food security of sourdough 100% in a scientific way? She has never happened to find clostridia? His books are published also in Italian? For which the publisher? Sorry for the many questions and thanks for what he does. I apologize for my English I'm using a translator

Debra Wink's picture
Debra Wink

I'm not sure I understand all of your questions, but I do see a thread of concern for food safety running through them. First, understand that sourdough has been a part of human history and culture for more than 5000 years --- long enough to have proven itself as safe even without refrigeration. Like other food fermentations, sourdough actually contributes preservative properties. I know of no cases of food poisoning by clostridia in sourdough. They, and other pathogens, simply don't grow in a sourdough environment. I'm sorry I have no information about books published in Italian.

All best wishes,

XRangerD's picture

The scientific base for the art desperately needs a comprehensive book on the subject.  Your research into this is one of a kind.  Thank you!

I suspected there was a biological cascade, but didn't have the requisite knowledge.  Your work had helped dispel a lot of mythology.  I honestly think that your efforts could be expanded into a wonderful treatise on the subject. I know it would be a great help to beginners.  And I believe even experts would find it useful for developing unique flavors and cultures. Great work...


A n d thanks again!



XRangerD's picture
Debra Wink's picture
Debra Wink

I'll check it out

Herbgarden's picture