Another study just came out trying to determine the ideal ratio of grains to milk.
They looked at what happens to the growth rate, pH, CO2 (carbonation), texture and overall flavor (as determined by a panel of judges) with different ratios of grains to milk.
Milk kefir grains are slow to grow. It may be hard to visually see growth after one batch. But after about a week (if its doing well), you may see it double in size. The study looked to see if different quantities of milk kefir grains produced different growth rates. The smallest quantity they used is about .4 tablespoons per cup of milk, then they increased it to .8 tablespoons and then 1.2 tablespoons and then finally 1.6 tablespoons per cup.
The results were that the smallest quantity of grains .4 tablespoons has the highest growth rate. And the yield progressively got lower as the grains increased. The largest quantities of grains (1.6 tablespoons) had the lowest growth rate.
To me that makes perfect sense. That’s what we’ve noticed across all cultures. The least quantity of grains / cultures has the highest growth rate. A small healthy batch will usually double in size long before an overcrowded batch of grains.
As the milk kefir grains ferment the milk, the lactic acid bacteria convert the lactose into beneficial acids which in turn lowers the pH level. It’s what makes that delicious fermented sourness. Most people enjoy some level of acidity, but too much and its like drinking vinegar.
Adding more grains should theoretically speed up the ferment and make it more acidic much quicker. And yes, in the study that is exactly what happens.
They started with about .4 tablespoons per cup of milk. That lowered the pH to about 4.3. It progressively got lower with each increase of grains. The 1.6 tablespoons of grains managed to ferment the milk to about 4 pH.
Carbonation is the by-product of yeast activity within the grains. Yogurt generally does not have any carbonation as it is simply made from lab selected bacteria strains. However, kefir has a natural balance of both bacteria and yeast. For some people who have only had yogurt, it can be a little strange to taste that fizz. But most people do enjoy a little bit of carbonation in their kefir. Too much though is usually undesirable.
Add more grains means that there’s more yeast which should lead to more carbonation. The study confirmed that. The carbonation slowly increased with each progressive increase in milk kefir grains.
This is the category I was most curious about. Does the texture change with different amounts of grains?
Texture is defined by how thick it gets . There are many factors that contribute to the thickness of kefir. In this study, the texture or thickness did not significantly change with different quantities of grains. Or in other words, the quantity of grains does not matter when it comes to how thick you want your kefir.
However, I would disagree on a long-term basis. Some of the thickest kefir we’ve made is with small batches. We use just 1-2 teaspoons of grains per 2-3 cups of milk and you can a delicious bacteria rich thick kefir. However, it can take a couple or so batches to get that ideal ferment. As the grains adapt to all that nutrient rich milk (with less competition from overcrowding), it usually becomes more bacteria rich instead of yeasty. And that bacteria rich grains will usually make a nice thick kefir.
Overall flavor and aroma
Perhaps the most important factor in determining how good the kefir really is how does it taste and smell to you. The panelists in the study looked at taste, smell and texture to determine the best ratio.
The overall winner was the 2nd lowest amount - the .8 tablespoons per 1 cup of milk. Followed shortly by the lowest amount .4 tablespoons per cup. The worst of the group was the largest amount of grains - the 1.6 tablespoons per cup.
Although taste is a personal preference, most people generally prefer a less stronger fermentation with milk kefir. Milk kefir can be overwhelming when strongly fermented.
Health and Probiotics
The study did not talk about which is the most healthiest though. With stronger, warmer or longer ferments, there are more probiotics or CFU's. However, that does not necessarily mean its healthy. When the ferment is slower and cooler and when you use less grains, there is more probiotic diversity. Which is more important than overall count.
The new study tried to determine which is the ideal ratio of grains to milk. They tested 4 different amounts (.4, .8, 1.2, 1.6 tablespoons per cup of milk).
- The lowest amount of grains had the highest growth rate
- The highest amount of grains had the lowest growth rate
- The lowest amount of grains had the lowest pH
- The highest amount of grains had the highest pH
- The lowest amount of grains had the lowest carbonation
- The highest amount of grains had the highest carbonation
- The texture did not change for this study
- The overall favorite as determined by a panel of judges was the 2nd lowest amount
- A low ratio means more diversity but less overall CFU count.
Less grains mean less acidity and less carbonation. In the short term, the texture may not change, but long term, it may improve. Flavor is best at the lower amounts of kefir grains as well. The health of the drink is also ideal at lower amounts.