Editing to add, 04/18/2012:

Please note that I haven’t experimented with this recipe in a couple of years. The last one was 2010 and I didn’t bother documenting because it was a busy time in our lives. My routine when making puto these days is soak rice overnight, and then refrigerate for up to 3 days or until I have time to make it — I switched to this technique because my life is so unpredictable sometimes and I had an instance when I forgot the mixture for over a week and as you can imagine, I ended up with a really icky vomit-inducing mess. I wish I could experiment on this recipe again and answer all the questions here, but as it is, I don’t have time right now. Please feel free to keep on commenting and sharing your experiences via the comment section. I’ll join in when I can. Thanks for your understanding and good luck with your puto experiments!

Judging from the requests I get here, by e-mail, from friends, etc., making Philippine puto is one of the biggest mysteries of our cuisine. Traditional recipes aren’t easy to find, and even people who used to make puto the old way seem to have resorted these days to the use of wheat flour. Even my aunt whom I was counting on to provide me with a reliable, old-fashioned recipe, recently sent me her “tried-and-true” wheat puto recipe. She said they simply don’t make it “that way” anymore. So it’s left largely up to us culinary enthusiasts to discover the secrets behind traditional puto making. My goal was not to duplicate any specific puto — the objective is simply to find a puto recipe that will work where I am with what I’ve got. After this, I’ll leave it up to you, dear readers, to try out and experiment and figure out other specifics to hopefully achieve puto that will make you and your loved ones happy.

My very first clue as to how puto was made in the old days was provided by Lewing Mendoza, a friend in St. Louis who makes wonderful puto from scratch. Her recipe which she gave to me back in 1995 became the basis of many experiments. It was a good recipe, and produces a serviceable puto, but I think that experience taught her a few tricks she didn’t reveal, because try as I might I couldn’t copy hers exactly. As with my many kitchen adventures though, the experimentation couldn’t be done consistently or regularly — family commitments, travel, etc. If you’re a regular reader you’ve read that here before, I’m sure. My most extensive trials were carried out in 2001, when I attempted several batches, utilizing a rice starter that was fed repeatedly — after several good to very good results, I let it die the 4th day after a refreshment. After that, everything was put on hold, except for an occasional trial.

Until November 2007 when my Cebuana friend Cynthia passed along a recipe in one of her cookbooks and asked that I make the puto to go with her dinuguan. It was definitely the right time to try again, as we were entering into Advent and I had planned a leisurely month of almost no school for the kids, and lots of reading and kitchen fun instead for all of us. Cynthia’s recipe is different from Lewing’s recipe in that it includes fermentation periods, albeit shorter than the fermentation periods I had gone up to in
past experiments. Luckily, I still had my notes from 2001 so I did some combining here, some tweaking there, and just went puto-crazy the whole month of December.

Fermented Foods

Fermented foods intended for consumption have been around for centuries. Most likely rice fermentation was a product of necessity — the lack of refrigeration in the old days. People needed to do something with their food to make it keep for longer periods of time. Fermentation allows ingredients or the dishes themselves to develop microorganisms that aid in preserving the food and keep it from spoiling.

Rice starters are the result of fermentation. They are not just used for making puto , however. Many other countries use fermented cake-like preparations (some using rice, others different grains): the Korean jeungpyon and kichudok, the Indonesian tape, the Sri Lankan hopper (appa), the Ethiopian injera and the Sudanese kisra are some examples. Another similar product is the Indian idli, the main difference between that and our puto being the legumes and spices, and sometimes buttermilk, added to idli. (1, 2)

These products have been developed empirically over generations to suit local conditions and the majority involve primarily a lactic acid fermentation, but a detailed understanding of their microbiology is still in its early stages. (2)

Fermented rice is an integral component of soy sauce and wine making. Moldy rice starters called qu in China have also been used to improve the flavor of meat or fish sauces.

The purpose of the preparation of the starter is to grow mold on the rice and/or wheat grains to produce various kinds of enzymes useful in the production of shao-hsing wine. The difference between rice starter and wheat starter is that there is more saccharifying amylase in the former and more protease in the latter. – Rice by Bor Shiun Luh

(Rice starters are also becoming more popular as the number of people that suffer from wheat and other allergies increase. On a celiac board I visited there was talk about a brown rice starter which is on my list of must-try’s, as brown rice is more nutritious than the white with which we grew up.)

[Disclaimer before we continue: Chemistry is not one of my strongest subjects. I am just summarizing here what I've read and trying to convey how *I* understood it. If you see any errors, please feel free to correct and clarify. My main goal is to get a general picture of how the science behind puto -making works.]

puto is basically a steamed cake, prepared from rice ground with water and allowed to ferment. It is this fermentation that causes the production of natural acids and gases and leavens the puto. This becomes the starter, which then is used either to make a first batch of puto , or to inoculate subsequent batches.

Studies of microorganism content after fermentation revealed the presence of the following: Lactic acid bacteria, the most predominant being the heterofermentative Leuconostoc mesenteroides, plus to a lesser degree, Saccharomyces cerevisiae, or baker’s yeast. These are the organisms responsible for the fermentation and leavening that produce the unique characteristics of puto. L. mesenteroides initiates the fermentation process. S. cerevisiae is a minor component until the final stage of the fermentation in which it can reach as much as 18% of the total population, resulting in a small amount of ethanol. The yeast together with L. mesenteroides may play an important role in leavening the batter. (4, 5)

[One chart also listed Streptococcus faecalis as one of the microorganisms, but a discussion of its presence and possible deleterious effects (it's already present in our bodies, but can also cause disease) -- would be difficult to cover in this post, so I won't go there -- but do note that I am duly concerned and will write about this again at a later date if I find out anything else. The research simply stated that it was only significant in acid development, although the following quote may explain why we don't get sick from eating puto.]

Lactic acid bacteria are used in the food industry for several reasons. Their growth lowers both the carbohydrate content of the foods that they ferment, and the pH due to lactic acid production. It is this acidification process which is one of the most desirable side-effects of their growth. The pH may drop to as low as 4.0, low enough to inhibit the growth of most other microorganisms including the most common human pathogens, thus allowing these foods prolonged shelf life. The acidity also changes the texture of the foods due to precipitation of some proteins, and the biochemical conversions involved in growth enhance the flavor. The fermentation (and growth of the bacteria) is self-limiting due to the sensitivity of lactic acid bacteria to such acidic pH. (6)

The specific qualities of different kinds of puto are dependent on microflora that are already present in the milled rice, and the kind of rice used. Microorganisms can either be aerobic or anaerobic. That is, they either need oxygen to do what they’re going to do, or not. Lactic acid bacteria are mostly anaerobic. It was found that aerobic bacteria present at the beginning of the fermentations disappeared.

A thorough discussion of fermentation and beneficial yeasts can be found here.

References:

1. Arora, Dilip K. et al. Handbook of Applied Mycology.
2. Lund, Barbara et al. The Microbiological Safety and Quality of Food. 2000
3. Beuchat, Larry R. Food and Beverage Mycology.
4. Rosario, 1987. Cited in Fungal Biotechnology in Agricultural, Food, and Environmental Applications
5. Steinkraus, Keith. Handbook of Indigenous Fermented Foods.
6. http://waksmanfoundation.org/labs/mbl/lactic.html

The recipe, after the jump!

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