Wednesday, April 15, 2015

Two Frozen Natto Starters Compared

  I have been using packaged frozen natto as the starter for a long time. I did this by saving a portion of the freshly made natto and freezing it. When this became low, I saved a portion again and successfully did it until the third generation when it suddenly became unstringy. This was probably due to contamination or due to prolonged freezing killing the natto. I will never know the reason and for many batches after that, I tried to use the third generation starter to see if I could change the fermentation conditions to make stringy natto again.

After a while, I got tired of eating unstringy natto and gave up using my third generation starter. This was hard to do as I initially thought that I would be able to keep a starter culture indefinitely. To start over, I went to the Japanese market and got 3 packaged natto. The first two that I tried were, Tokyo Natto and Okame Natto. I forget what the third was... So I fermemted two batches side by side to see how the natto would turn out.

On the left is Tokyo Natto. I randomly picked this so there is no logical reason for this choice. On the right, Okame natto. A widely distributed long seller that is one of the most common natto brands.

These packages are kept in the freezer at all times. When frozen, I cut them into 12 small frozen pieces per package. So a 3 pack will yield 36 frozen natto starter cubes. I plop a cube into the steamed soybeans and mix it in. For full instructions refer to the Homemade Natto Recipe.

Might be hard to see, but Tokyo natto is a little bit weak visible by the shinnier appearance and thinner natto growth on the bean. Also when the cling wrap was pulled, stringyness was not too visible. As for the Okame natto, the natto growth was much stronger and stringyness was seen when the cling wrap was pulled back.

This to me is the moment of truth when the natto is stirred with chopsticks. Here, the difference in natto is obvious. Tokyo natto on the left is very loose compared to Okame natto which is thick and almost gummy in texture.

Adding liquid seasoning such as shoyu or mentsuyu is the ultimate stringiness test as the weaker natto will decrease in stringiness when seasoning is added (left). Okame natto is going strong with the liquid seasoning added and becomes almost frothy when stirred vigorously.

On the pull test, the weaker Tokyo natto has a loose appearance and the strings do not hold the beans. In comparison, the Okame natto has strong thick strings which hold the beans.

Okame natto is the winner!

Concluding thoughts:
After running this side-by-side fermemtation, it is apparent that the natto starter used will have a big impact on the finished natto. Furthermore, the existence of "Niowa Natto", or low smelling natto tells me that there are different strains of natto used by the natto manufacturers. My assumption would be that older strains would be more stinky and may be linked to more stringiness. Okame Natto, which has been around for decades may be using an older, more traditional strain of natto that is more stringy and more stinky. This being based on my assumptions concocted by my perceptions are more for discussion than to inform you.

The other possible explanation is that the Okame natto package that I happen to pick up was fresher thus had a stronger livelier population of natto-kin.

The take home message to fellow natto makers is to weigh-in more on the natto starter if you have perfected the cooking conditions and are still getting poor results. As of now, my working hierarchy of making good natto in descending order of importance is:

1) Proper soaking of soybeans: At least 12 hours in the summer with a preference towards 16 hours, up to 22 hours in the winter. 
There are two test that can be done to check full hydration. First, split the soybean in half. The two halves should not have a gap in the middle. When fully hydrated, the two halves will touch in the middle. Second, foam will start to appear on the surface of the water. Probably due to respiration of the soybean getting ready to germinate.
When not properly soaked, the natto will turn hard when finished fermemting.

2) Proper steaming of soybeans: The soybeans should be steamed under pressure with a pressure cooker for 40 minutes. You can steam them in a regular pot, but expect up to 6 hours of steaming to achieve what can be done in 40 minutes steamed under pressure. By cutting corners here, the natto will turn hard when finished fermenting. The natto-kin might also have a hard time getting nutrients. I do not recommend boiling soybeans as the flavors will leach out into the water and the natto will lack flavor.

3) Fermenting Temperature: The standard is to ferment at 40C or 104F at least for the first 6-8 hours, when the natto start growing vigorously. You can tell that they are starting to grow by the pleasant nutty fermenting aroma. After this critical period, the natto will start to generate heat by its metabolism and you can be more relaxed about temperature on the last 10-12 hours of fermentation.

4) Natto starter: If you have the top three conditions under control and you are still not getting good results, this will more than likely be the culprit. I have used Mitoku Natto Starter in the powder form, but I have never made a stringy batch using it. Use frozen packaged natto, and try different brands if available as the results will vary as shown above.

5) More trivial, non-crucial matters: 
-Moisture and aeration. I usually use enough water from the bottom of the pressure cooker to wet cooked soybeans so water does not pool in the fermenting vat (about 3 spoonfuls). Having said that, I have forgotten to put the water and it still comes out fine. I have read online that natto needs lots of air, but I have found that this is not true. When the fermenting natto is exposed to air, the surface will start to dry out and harden and will look dark brown. I recommend the poked double cling method explained on the Homemade Natto Recipe.
-Adding sugar and/or salt: I have also seen this where sugar is added to make the natto happy. I have never used sugar and I get consistently good results. Same is true with salt.

I went a little longer than intended, but if this helps a fellow natto maker out there, my mission is accomplished.

Happy natto making and cheers to you for improving your well-being by eating natto!

Natto Dad

Wednesday, May 14, 2014

Natto: Essential fermenting conditions

We will look at the natto fermentation from the perspective of our main character, Bacillus subtilis natto. It is a bacteria commonly found in nature and for this reason is also referred to as hay bacillus or grass bacillus. The relation to hay goes back to 1086 AD in Japan when soybeans spontaneously fermented when wrapped in hay (Natto, wikipedia). Due to this spontaneous nature, I am sure that the origin of natto fermetation goes back even further.

Natto is unique in its fermentation as it does not produce acids when fermenting with lactobacillus ie. yogurt and pickles. It also does not produce alcohol as is the case with yeast fermentation. Natto produces stringyness, which comes from long-chain polysaccharides. The stringiness is very unique to fermented products and is what makes natto so cool!

The essential conditions to produce this wonderful stringiness are as follows,
-Properly soaked and cooked beans.
Soybeans have a really tough skin and take a long time to cook. The natto-kin (natto bacteria) has to penetrate to skin in order to get to the nutrients inside. I do not know if the natto-kin actually grow into the soybean or if they absorb the nutrients and grow on the surface, but the result is the same. The nutrients have to be available for the natto-kin and in order to do this, the soybeans have to be soaked long enough for full hydration. I soak the beans for 10-12 hours in the summer and 20-24 hours in the winter time. A good way to tell is to split the soybean in half to see if the two halves touch in the middle. If there is a gap, they need to be soaked longer for full hydration. 
Boiling the soybeans is usually the first method people try for its ease. The disadvantage is that the flavors leach out of the bean and the amount of time it takes, 4-6 hours. The next solution is to steam the beans over boiling water. This will make tastier natto, but it also takes hours to cook. Then there is boiling the soybeans under pressure. This will take 40 minutes, but again one runs into the problem of leaching flavors out of the bean. The best method and the only method I use now is to steam to soybeans under pressure. This solves both problems of time and flavor. Steaming under pressure will retain the flavors and take 40 minutes. From the natto-kin perspective, this is important because more flavor equals more food for them and softness of the beans means that nutrients will be easier to access from within the bean.

-Optimum Temperature
Natto-kin is interesting that although it is tolerant to extreme conditions, it grows slowly and is vulnerable to other bacteria in the initial stages of growth. I have not experienced this personally, but there are anecdotes of contamination in the fermentation. To favor ideal growth conditions, natto should be fermented at a higher temperature when compared to a lactic fermentation. I usually shoot for 95F-108F (34C-42C). It is important to keep this temperature the initial 6 hours of fermentation to establish a strong natto-kin population. After 12 hours, the natto-kin start to generate heat and so one can be more relaxed about maintaining temperature. 

-Moisture and Air
This relationship was really difficult to maintain as there is an inverse relationship. Many natto makers stress the importance of having good ventilation so the natto-kin can breath. This makes absolute sense, as B. subtilis is classified as an obligate aerobe, meaning it needs air to grow. Unfortunately, moisture is impossible to maintain if you keep the fermentation container open. The surface of the natto would become dehydrated and brown and the growth of the natto-kin would decrease. I took a hint from packaged natto which is packaged in a styrofoam container. On top of that, the natto is covered directly with a plastic sheet with small holes. This is how I came up with the double cling-wrap method. I put a cling-wrap with small holes, poked with a tooth pick, directly over the soybeans and another with holes on the baking sheet. Having a cling-wrap directly over the soybeans really helps to prevent drying of the surface. The air gap formed between the sheets also helps slow down evaporation.

The intial 6 hours as mentioned above are very crucial to establish a healthy population of natto-kin. Not much is visible, but the natto-kin is busy getting settled in, absorbing nutrients and later starting to multiply. Then in the 6-12 hours of fermentation, the bacteria go through a population explosion and you can start smelling the aromas coming from the fermentation. After 12 hours of so, the natto start to generate heat from metabolism and will continue fermenting until they start to slow down due to overcrowding and depletion of nutrients at around 18-20 hours. From experience, I have found that under ideal conditions, the fermentation will be done in 18 hours.

Not mentioned here is about the starter used and this deserves a post of its own. 

Tuesday, July 2, 2013

The Perfect Fermentation Baking Dish

This was a good find for me. Amazon has a plethora of good baking dishes. They come in all shapes and sizes and the prices vary too. Being frugal and curious to find what else was out there, I stumbled upon this perfect baking dish for natto making.

MIXTUR Oven/Serving Dish (14" x 10")

I found it at IKEA for $6.99. It is a generic baking dish and that is all there is to it, but for $6.99 it is a steal!

One thing I like about glass dishes is that it is non-reactive and plastic wrap sticks to it very well. I had used a plastic container but I always wondered about chemicals fumes coming out of the plastic when exposed to long warm conditions. Also, plastic wrap did not stick to it.

One advantage that I later found about using a glass container was that it retains heat well and also evenly disperses the heat rising from the coil heater which I use to warm up the oven.

Tuesday, June 4, 2013

Troublesshooting Guide for Homemade Natto

I have made many bad batches of natto. Hopefully this troubleshooting guide will help homemade natto makers out there make better natto. If you have any questions that are not listed here, please send me a comment and I will try to post the answer here.

Q: My natto is not stringy, what's up?
A: This one is the hardest question and probably deserves its own post. From past experiences, the best short answer might be that the starter is not doing its job. I have used Mitoku natto spore starter and it is very fussy. I have not isolated what the problem is and would love to hear from a fellow natto maker. I have switched to using frozen packaged natto which produces stringy natto every time. I keep it in the freezer cut up into cubes ready to use.
A: Another possibility noted on some natto blogs is that the fermentation temperature is too high. I have not experienced this personally but it sounds reasonable.
A: I used to think that overcooking the soybeans somehow destroyed a nutrient to make the silky threads, but this is not the case. Overcooking should not be a concern from what I have seen. As a note, I have noticed that boiling soybeans will make the natto have a non-stringy rubbery growth on the beans.

Q: My natto looks leathery and dry.
A: This is related to the question above. When the natto is not stringy, it usually turns out leathery and white. One working theory is that the initial concentration when using natto spore starter is too high. Having said that I have used one tiny spoonful, the one that comes with the Mitoku starter, diluted in about 100 mls of water. Then I use 5 soup spoon fulls of diluted starter and it still turned out white and leathery. Another theory is that the natto spore starter is old, has gone evil and/or is contaminated. The band-aid solution is to use frozen packaged natto.

Q: My natto stinks of ammonia.
A: I associate this with temperature problems. One of my earlier batches smelled strongly of ammonia and the natto was not stringy. If I remember correctly this was because the temperature was too low and I left the natto batch fermenting for 24 hours waiting for the stringyness to appear.

Q: My natto does not have flavor.
A: Boiling the soybeans is the reason why natto turns out flavorless. Boiling them in a regular pot or boiling them under pressure will do this. Curiously the skin of the soybean will come off when boiled. To resolve this, you must cook the soybeans in a steamer basket or strainer above the boiling water. I use a small glass bowl to suspend the steamer basket over the boiling water.

Q: My boiled soybeans are soft, but the natto is hard.
A: The reason is that the soybeans were not cooked long enough. This is hard to accept when you spend 4-6 hours of your valuable time to steam the soybeans. I have done this and there is that transitional stage when they are almost soft enough, but not quite. The soybeans should be a dark beige color and not yellow. Also, when eaten, it should have an almost creamy texture. I recommend steaming them under pressure which only takes 40 minutes.

Q: My natto is dry.
A: I initially thought that natto needed a lot of ventilation for the natto to breathe and to blow off the ammonia produced in the fermentation. So I covered the natto with paper towels and newspaper and then put it in a paperbag. This was a very long path to a dead end which led to not so tasty dry natto. Turns out that natto does not need that much air. So now I use the Double Cling Wrap Method (scroll down to the middle of the post). I poke holes on the cling wrap with a tooth pick so there is a hole every 1-2 cm (1/2" to 1") apart. This is tedious, but I enjoy this mindless repetitive work.

Q: My natto tastes like boiled soybeans and not natto.
A: The temperature of the fermentation was too low.
A: I do not have a vendetta against the Mitoku Natto Spore Starter, but the spore starter has given me this result. So for now with the Mitoku Natto Spore Starter, I either make leathery white natto or unfermented natto that tastes like cooked beans. Use packaged natto as the starter.

Q: How much packaged natto starter should I add?
A: When I use the frozen packaged natto, I chop up the package into 9 cubes. For Okame Natto, one package is 50gr, so one cube is 5-6gr. One cube will easily ferment 400 grams of dry soybeans (a little less than 1 lb). So a 3-pack of 150 grams will yield 27 cubes, or 27 batches of natto!

Q: What is the conversion rate of Dry soybeans to fully hydrated soybeans (after 18 hours). 
A: For soybens, I use x2 as the conversion factor. So 400 grams of dry soybeans will become 800 grams of fully hydrated soybeans.

Monday, May 27, 2013

Batch # 40: Back on track

After the last batch which turned out okay, I made a really good batch of natto. Mainly it is due to the new frozen natto pack that I used to ferment this batch. I did note the brand: Shukuba Nattou by Murakami. I bought it a few weeks ago probably because it was on sale.

Batch #40 looked slightly wet but had good sticking power. With shoyu, it formed thick long threads.

The freshly made natto almost had a pleasant apricot smell

One thing I like about making natto in the summer is that the fermentation seems to go smoother. I have come to associate this with temperature. This is especially true when I was making natto with only a yutanpo as the heat source. I have not seen many homemade natto makers mention this, but natto fermentation is truly a metabolic marvel. Each individual natto bacteria is going about its life eating and multiplying. This in itself is an insignificant event that is too small in scale to matter but in large numbers, it takes a whole new dimension.

I mention this in relation to natto making in the summer time because I have noticed that when the ambient temperature is high enough, the natto fermentation can continue with its own generated heat. I did not notice this at the beginning and was baffled why the natto fermentations in the summer seemed to go better than the winter fermemtations when using a yutanpo. After a while, I bought a thermometer to keep track of the fermentation temperature and I discovered something truly amazing. Seven hours into the fermentation to somewhere around the fifteenth hour of fermentation, the natto superorganism consisting of billions of individual natto bacteria metabolize the food in soybeans and generate enough heat to keep it at its ideal growth temperature without requiring an external heat source. This is evident when making large quantities of natto, in my case 400 grams of dry soybeans (~1 lb), when the ambient temperature is somewhere around 23C/75F or higher. The glass baking dish which has insulating qualities in addition to the double cling wrap to cover the top helps to retain the heat.

So in essence, it is possible to make natto if it is possible to maintain an ideal temperature in the first 6 hours of the fermentation using a low tech, cheap method such as warming the oven for a few seconds every hour or by using a yutanpo. Using a small cooler or styrofoam box, which I have not tried, would probably suffice to make good natto if ideal temperatures can be kept for the first 6 hours until the natto kick in to generate its own heat. After the natto slows down, the natto could be kept in the cooler for another few hours to let it ferment with the latent heat.

Saturday, May 25, 2013

Fail: Homemade Natto Using Packaged Natto -Batch #39

A timely failure to keep me humble. After a few successful runs which can be seen on Batch #37, Batch #39 fails on me. I guess I am a little bit harsh on myself because it was not a complete fail. I had mentioned previously that one important criteria for good natto was its silky long strings. I love to make a batch that has strong threads that hold the beans within the string even when lifted.

On Batch #39, the fermentation looked fine and I was looking forward to eating natto. One quick test is to take out a small portion of the freshly fermented natto and do the wet seasoning test. You can use shoyu or mentsuyu. 

On a successful batch, the freshly made natto looks almost gummy and will stick to each other. When mentsuyu is added, it will still be gummy and sticky.

On the other hand, unsuccessful batches will almost have flaky natto growth with thin strings. When this is mixed with mentsuyu, the strings will have a wet look and will not have sticking power. You can see how the natto has not clumped together in the bowl after mixing.

I always thought this was due to a problem with the fermentation, but on this batch I used the same method as the successful batch #37. The only thing that I did different this time was to use a different starter. I had ran out of the old frozen natto so I used a new package. Unfortunately, I did not keep the outer label so I have no idea what the brand was. So assuming that I used a different brand of frozen natto starter, the outcome of the fermentation could be strongly linked to the strain of natto used for the fermentation. I am sure different brands use different strains of natto to establish their style. 

I will start noting what brands I use as the starter to see if there are strains that are more stringy than others. I have heard that in Japan, there is a trend towards less stinky natto. There could be a correlation to natto that turns out less stringy when this less stinky natto is used. 

This is a good remainder to me not to be discouraged by a bad batch. It is very possible that your natto did not turn stringy because of the starter used. If possible, try to use a different brand to see how the natto turns out.

Wednesday, May 15, 2013

Discovering Lauras Natto Soybeans (Kotsubu Soybean)

For the majority of my natto making year, I bought the organic soybeans found in the bulk section of Whole Foods. They taste great and are of very good quality. Initially, I made the natto with this and enjoyed it. After a few months my wife pointed out that they were too large and texturally were not ideal. So we settled on making "hikiwari natto" which is the chopped up version. Usually, hikiwari natto is said to be chopped before fermenting it. This was too hard at home so I chopped it right before we ate it.

The only thought that was nagging me was that they were not the "kotsubu" (small bean) variety. The natto that is store bought is made of this kotsubu variety and it was impossible to find in the US. On one of my deep googling expeditions late at night, I hit upon the gem I was looking for. Finally, I found kotsubu soybeans at Lauras Soybeans!