When should I add fresh fruits in homemade yogurt?

Question

I just bought an Instant Pot and want to use it to make yogurt. I found a recipe online for fresh fruit yoghurt that I want to try (https://recipes.instantpot.com/recipe/fresh-fruit-yogurt-in-the-instant-pot/). After scalding the milk, the recipe calls for the addition of fresh fruit, sugar, and skim milk powder to the milk BEFORE allowing the soon-to-be-yogurt to incubate.

Is this safe? Wouldn't the introduction of the ingredients before incubation (especially the fruit) potentially add unsafe bacteria to the yogurt? Or am I being overly cautious?

Answer 1

The Codex Alimentarius standard 243-2003 on fermented milk products, states in section 2.3 that:

The non-dairy ingredients can be mixed in prior to/or after fermentation.

So, yes the recipe is correct and you can even sell the product if you follow all the other WHO standards as well.

However, as you introduce additional microbial agents when using fresh fruit, the rule of thumb (to be analytically tested) is half of the minimum of both products separately:

• As you're probably doing this for home use, this means in plain English:
  Eat the yoghurt in half the time you would eat the fresh fruit.
• If this would be for professional use:
  You should not be asking random strangers on the Internet what to do and have your commercial product tested analytically. ;-)

Answer 2

While fruit are in fact covered in bacteria, they usually aren't pathogenic.(This is entirely dependant on farming practices used when growing that fruit) In addition, yogurt has antibacterial properties . I would still recommend cooking the fruit down before adding it to the yogurt, or at least washing it.

Answer 3

fruit has water, adding fruit to yogurt will make it harder for the proteins to create the gel structure, some whey might form around the fruit pieces.

The easiest way is to just add fruit after the incubation period, when you cool it, or just mix it in when you eat it.

If you want to add fruit prior to incubation so that the flavor is more prominent fruit should be washed of course (and cut if the type of fruit allows it without making a mess...) and then dried in the oven, you can try different temperatures (50C-90C) and periods of time (>10m). A full drying process can take from 6-12hours but it is not really needed in this case, usually 30m should be enough; drying the fruit will:

• help killing some unwanted bacteria
• sweeten the fruit so that more flavor is added to the yogurt
• possibly absorb part of the milk water content helping the gelification
• help stabilize the milk temperature (assuming you have finished drying right before starting jarring the milk for the incubation so that the fruit is still warm) which again will help the gelification