Although many consumers would say that “flavor rules,” texture is close behind. When it comes to cultured dairy products, smooth and creamy is always the target, and textural attributes such as grainy, gel-like, shrunken, weak or ropy are typically considered defects.
Most product developers spend time on ingredients and/or processes to help prevent these defects. Understanding the basics of cultured dairy product processing for products such as yogurt, sour cream, kefir, crema and others is a good place to start in understanding how the process contributes to their texture.
Consider processing conditions
Most products start with raw milk, which is separated into skim milk and cream. It then is re-blended to the desired fat content and homogenized. Increasing fat in yogurts or other cultured dairy products automatically provides a smoother, creamier texture.
Whether you start with only the raw cream and milk mixture or also add other ingredients, the raw mix has to be pasteurized. The pasteurization step for cultured products such as yogurt typically involves much higher temperatures and holding times, (i.e., 185-200 degrees Fahrenheit for 5-10 minutes) than typical milk pasteurization (161 degrees Fahrenheit for 16 seconds).
These heating conditions denature (unfold) the whey protein (β-lactoglobulin) and form disulfide bonds with casein. This reaction provides a firmer gel structure in the yogurt with better water-binding ability and less syneresis compared to yogurt mixes pasteurized at lower temperatures. There are yogurts that rely on these pasteurization conditions to provide all of their textural attributes, without any added ingredients other than cultures.
One other processing condition that can change the texture of your yogurt is the breaking temperature. After fermentation is complete, the yogurt is cooled and the curd or gel is broken with agitators in the fermentation tank. Breaking the gel at a warmer temperature such as 60-70 degrees Fahrenheit will result in a firmer texture than cooling to 50 degrees Fahrenheit or lower before filling the container.
Consider added ingredients
Most yogurts also use added ingredients such as nonfat dry milk, whey protein concentrate, milk protein concentrate, starches, gelatin and/or hydrocolloids such as pectin to increase firmness and prevent syneresis. If clean label and clean flavor are your targets, then a dairy ingredient is your best choice.
Typically, the more protein you add, the firmer the texture, but casein-based ingredients will likely provide more firmness than whey protein ingredients. Starches also increase firmness, bind water well and are economical, but they often mute added flavors. Gelatin is economical but isn’t used as much anymore. It often can be the culprit for a product with a “gel-like” defect if used at too high a level.
Just remember, these ingredients need to be well hydrated in the yogurt mix prior to pasteurization to optimize their performance to avoid that grainy texture defect. Following these tips will help you to develop the desired texture in your next cultured product.
Kimberlee (K.J.) Burrington is director of training, education and technical development for the American Dairy Products Institute.