Observations and results
Was the yogurt in all of the jars firm and white? Did the yogurt cultures taste and smell like a very mild version of the original yogurts used?
The yogurt cultures in the jars will probably seem very similar in several ways, with some subtle differences based on the original type of yogurt used to make them. They should also be relatively firm, or firm enough so they do not slosh when tipped, and all have a similar texture. If the yogurt is not firm at all, but is actually fluid or runny, something may have gone wrong in the process and killed the bacteria—most likely the milk was too hot when added to the yogurt starters.
The yogurt cultures, however, may have small differences in taste and color based on the original yogurt used to make them. For example, if the original yogurt was really sweet, the yogurt culture should be only mildly sweet. Likewise, if the original yogurt was a bit sour (like Greek yogurt), the culture should also be a little sour. If you used one yogurt with artificial coloring (such as with Red 40) and one that was white, both resultant yogurt cultures should look white, just like the milk used to make them. If you put them side by side, however, you may notice that the culture whose original yogurt had artificial coloring is slightly off-white with a tinge of color. Overall, multiple factors affect the yogurt culture, including: the presence of some nonliving diluted ingredients from the original yogurt such as diluted Red 40 coloring, the exact process used to make the culture such as the amount of time in the cooler, and the types and amount of bacteria that were in the original yogurt.
If the yogurt cultures were made correctly, you should be able to enjoy your jars of yogurt as a tasty, healthy snack! You should also be able to refrigerate the sealed yogurt for one to two months. The acidity of yogurt (from lactic acid) helps preserve it and prevent potentially harmful bacteria from growing.
More to explore
Better Homemade Yogurt: 5 Ways to Make Thicker Yogurt from Emma Christensen at theKitchn
Live and Active Culture (LAC) Yogurt FAQ's from AboutYogurt.com
Yogurt Making Illustrated from David B. Fankhauser, PhD, University of Cincinnati Clermont College
Yogurt Cultures from Science Buddies
This activity brought to you in partnership with Science Buddies