Kefir culture preparation 5/5/2012 (14:00)

I have received the traditional milk fermenting kefir grains thankfully from Becca so at least for last several months if not years they were used for fermentation in South Korea.

The grains are of quite a big size ranging from 30-40 mm in diameter for the round ones and up to 70 mm length for the prolonged ones. They have traditional milky white colour and usual “rubbery” quality, they are quite resistant to disintegration. The ferment has a nice spark and sour flavour composing of various levels, which I consider typical for kefirs and superior to yoghurt in it’s complexity.

This experiment is to reactivate the culture which I have received and to test it’s coagulation capacities and flavour of the final product. I do not have the possibility to measure the temperature and it’s oscillations which are crucial for the fermentation, therefore the data resulting from this experiment are limited. In the near future I plan to measure the temperature and the changes in the weight of the grains during their growth.

Please note that kefir is comprising of many various microorganisms, in majority various strains of bacteria and also yeast, therefore to allow yeast to reproduce properly, at least sporadic access to air/oxygen so they can use their aerobic respiration capabilities is important. I plan to investigate the differences in aeration of the culture as opposed to the anaerobic fermentation in the future.

Ingredients

Culture 1
Vc 1 = 620 ml of culture/brew volume
4x kefir grains (see pictures)
+- 620 ml of cow milk (#1)(whole milk, homogenised, pasteurised, producer – Seoul Milk, The First Grade A milk)

Culture 2
Vc 2 = 220 ml of culture/brew volume
1x kefir grain (smaller)
+- 220 ml of cow milk (whole milk, homogenised, pasteurised, producer – Seoul Milk, The First Grade A milk)

Procedure

– prepare the 650 ml (250 ml respectively) culture container
– take out the kefir grains from the previous culture and wash them carefully with a lukewarm milk (catch the milk in a bowl)
– transfer the washed grains into the container (four grains in to the 650 ml, one smaller grain into the 250 ml) and add the milk which you used for washing in an appropriate ratio (1:4)
– add up to 620 ml (220 ml respectively) of lukewarm whole milk and mix a bit
– seal the container by a lid and let to ferment anaerobically for most of the time at 20-30°C for 1-2 days (out of direct sun)
– check after 6-12 hours for separation of liquid phase and coagulate (#2)
– once in 6-12 hours open the jar to allow fresh air in, close it and mix the culture by turning the jar few times (not too abruptly)
– once the phases are starting to separate start the tasting, once in 6-12 hours or so (if the temperature is above 25°C the fermentation and consequently the acidifying process will go very fast)
– when the taste is to your liking (12-36 hours) take out the kefir grains and transfer them to the next batch following the procedure above or switching for the simple 900 ml of milk and all grains added version (remember less grains, slower fermentation, the same applies to the temperature lower = slower!)
– prepare the pot or bowl and fix the strainer on the top
– lay out the cheesecloth into the strainer
– transfer both 620 and 220 ml of cultured milk into the strainer and let to strain covering the top by cheesecloth against the flies
– stop straining once the texture of the coagulate – kefir yoghurt (1-6 h) or yoghurt cheese (12-24 h) is to your liking
– mix the kefir yoghurt properly to allow aeration and transfer to the sealable container and close properly (#3)
– keep at room temperature for another few hours (2-4 hours) to allow for secondary fermentations and for the spark to develop
– transfer the container into the fridge and let to cool down before consumed or used otherwise
– transfer the whey to the sealable container and keep at cold before consumed or used for other purposes (preparation of Larry’s cooler, or high energy and protein drinks for example)
– both whey and kefir yoghurt may be used for probiotic culture preparation (#4)  and they can be stored at cold easily for 1 month or so just getting a bit more sour
– if you do not intend to continue immediately with further fermentation using the kefir grains “hibernate” them at low temperature (#5),

NOTES

#1 – For kefir based culture raw milk can be used because the culture is very stable and very resistant to any contamination unlike the commercial yoghurt cultures.

#2 – The traditional kefir culture is suppose to be shake/mixed during the process of fermentation. This is probably to improve the flow of the milk and the microbes in it so they can access undigested lactose and other nutritious substances more readily. The other reason is probably the distribution of oxygen which is important for aerobic respiration of the yeast in order to multiply properly which will secure keeping their ratios in the culture and therefore it’s stability.

3# – The oxygen in the air is supporting the aerobic respiration of the yeast, which end product among the others is a carbon dioxide, resulting in a nice sparkling sensation in the kefir yogurt, however the container has to be sealed properly!

4# – Culture originating just from kefir whey or yogurt (or both) is still very complex and resistant to contamination however changes in ratios various strains of bacteria and yeast will occur. For more read an article from Spasov and collective 2002 : Simonova E., Beshkova D., Angelov A., Hristozova Ts., Frengova G. and Spasov Z. (2002) Lactic acid bacteria and yeasts in kefir grains and kefir made from them. Journal of Industrial Microbiology&Biotechnology 28, 1-6.

5# – Hibernation (slowing down the microbial metabolism) –  Take the kefir grains and wash them in a cold milk properly. Transfer them into the sealable container (glass preferred) and add fresh cold whole milk. Close the container and move it to the fridge (low temperature as 4°C) preferred. Wait for 3-5 days for the microbes to slow down their metabolism. Prepare cold fresh milk and move the container out of the fridge and quickly repeat the procedure of washing and transferring keeping everything cold. Move to the fridge as quickly as possible. You will notice that the milk which you removed from the kefir grains is quite acidic turning into the kefir yoghurt. This is due to the fact that it takes some time for the microbes to slow down their metabolism. Please do note that the microbes are still active therefore repeated feeding by milk once per month or so is necessary. I do not recommend to keep the culture at cold for longer than 2-3 months at time because it can result in profound changes in ratios of various strains of bacteria and yeast. If you need to do that, try to restart the culture after 2-3 months for at least two weeks or so, letting it to ferment at 20-30°C again. It is likely that the kefir yoghurt and whey produced during this time will be not tasty, they may smell quite bad and is so they should not be consumed. The culture should get back to equilibrium within these two weeks and once it does it can be hibernated again.

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~ by algoldor on May 7, 2012.

2 Responses to “Kefir culture preparation 5/5/2012 (14:00)”

  1. […] second half of the meeting was more practical we have harvested batch of kefir prepared on 5th of May separating it by draining into the liquid kefir whey and firm kefir yogurt, following the manual […]

  2. […] have harvested a batch of kefir which was started on 13/52012 (more info here). The liquid whey was distinctly separated from the firm “kefir yogurt” part. It’s flavour was […]

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