Is UHT Milk Better for Homemade Yogurt Than Fresh Milk?
Did you know that the milk you use to make home-made yogurt can have an impact on the texture of your yogurt? Some types of milk will produce nice, thick yogurt, while others will yield a runny liquid that resembles more buttermilk than actual yogurt. Let's take a look at how UHT milk, pasteurized fresh milk, and unpasteurized raw milk fare against each other.
Can You Use UHT Milk for Home-Made Yogurt?
There's been a lot of confusion about whether UHT milk, also known as shelf stable milk, can be used to make yogurt in an automatic yogurt maker at home. The benefit of UHT milk in general is that compared with fresh milk, it has a long shelf life (usually several months). This means that you can easily buy it in bulk when it's on sale and store what you don't need (provided that the sterile packaging has not been damaged). The extraordinarily long shelf life of UHT milk is a result of a special sterilization process known as the ultra-heat treatment (UHT) process. During this process, the milk is first pressurized and then heated to extremely high temperatures for a few seconds.
As UHT milk is highly sterile, it can be used as a basis for home-made yogurt without heating it first. However, some people find that using UHT milk without heating it first results in rather runny yogurt. But what does research say?
A study published in the August 2004 issue of the Journal of Food Science compared the texture of UHT milk and conventionally-treated fresh milk. In this study, the UHT milk was not heated before it was turned it into yogurt, but the fresh milk was heated at 185°F (85°C) for 30 minutes. Although both types of milk fermented as expected, the yogurt made from UHT milk was runnier than the yogurt made using fresh milk. Unfortunately, however, this study did not test whether pre-heating of UHT milk could improve the quality of yogurt.
Pasteurized Fresh Milk is Best for Making Yogurt
Most of the fresh milk you find at the stores has been pasteurized using the High Temperature/Short Time (HTST) method. Milk sterilized in such a way typically has a refrigerated shelf life of two to three weeks. This type of milk is considered better for making yogurt than UHT milk, especially if you like your yogurt thick.
However, before using HTST-treated milk in a recipe for home-made yogurt, you will have to heat it to make sure it is completely free of all pathogenic bacteria. This is also thought to improve the texture of home-made yogurt as it helps destroy any remaining competing bacteria, thus allowing the probiotic cultures prosper and thicken the yogurt. Furthermore, high temperature heating alters the protein molecules in milk, making them more likely to coagulate and to produce nice, thick yogurt.
Stay Away from Unpasteurized Raw Milk
Raw milk has not been pasteurized or homogenized before delivery to the consumer. As a result, this type of milk contains its original microorganisms, and many agencies in the US and around the world state that pathogens in raw milk, including potentially bacteria that may cause tuberculosis, diphtheria, typhoid and streptococcal infections, make raw milk unsafe to consume.
Potential health problems aside, unpasteurized raw milk is also difficult to culture because the microorganisms it contains compete with the live cultures of probiotic bacteria used to make yogurt.