Combine all the ingredients and mix well. Chill in the refrigerator.
To drink, dilute it with water, soda water or milk etc. by 4-5 times the amount of liquid to concentrate, and enjoy.
Yu-a used this in her "Calpis Milk Jelly" (Recipe ID: 818411). This has yogurt whey in it and is packed with minerals, so I recommend it.
Yumi's Cafe used this with "Preservative-Free and Safe Strawberry Syrup" (Recipe ID: 566568). What a pretty pink color. The syrup is delicious!
I tried adding 2 slices of canned mango to the concentrate, and diluted it with clear soda. The fruit flavor was delicious. It may be better than commercial mango-flavored soda.
Citric acid is available at pharmacies. I bought 22 g for 260 yen. It keeps for a long time so it's handy to have on hand when you don't have any lemons.
You can keep the concentrate in the refrigerator for 10 days. I think you could even keep it longer. Please make it with fresh yogurt.
You can make the concentrate in no time, so I recommend making an amount that you can use up within a week.
Story Behind this Recipe
I make this copycat Calpis (Calpico) drink base a lot in the summer. Storebought Calpis is getting expensive, plus I can make this as quickly as my kids ask for it when I keep a supply in the fridge.
Please dilute by 4-5 times the amount of liquid or to taste. I adjusted the sourness so that kids can drink it easily. If you prefer it more sour, add a bit more of the ● ingredients. You can make a jelly using this concentrate, the same as you would with storebought Calpis.