Most dairy processing companies strive to make high-quality cultured dairy products that have a consistent day-to-day flavor, texture, and appearance. Despite good manufacturing practices, product defects can develop, which gives research and development people some job security and the ability to practice problem-solving skills.

Whether you are making yogurt, sour cream, cream cheese, or other types of cultured dairy products, they can develop similar product defects. Being aware of the potential sources of some common defects in a cultured dairy product might help to prevent them in the future.

Flavor 

Flavor defects can come from many different sources. One of the primary sources are from the ingredients used to make the cultured products. For instance, the freshness and the quality of milk, cream, and/or dried dairy ingredients can contribute to flavor defects such as oxidized, stale, rancid, and even bitter flavors.  

Cultures typically produce acidity and characteristic flavors, but over acidification can result from too high a fermentation temperature, improper cooling, wrong culture usage level, or low protein levels. Products that are too low in acid could be the result of low fermentation temperature, wrong culture usage level, excess sweetener, or presence of sanitizers, phage, or preservatives that might inhibit culture growth. Psychotrophic or thermoduric (bacillus) bacterial contamination can also lead to bitter off flavors.

Texture and appearance

Appearance and texture defects are interrelated. A ropy (or stringy) appearance of a product when you put your spoon in it might mean a texture with a slimy mouthfeel. Ropiness can be caused by a culture that produces too much EPS (exopolysaccharides), wrong level or type of protein or stabilizer, too low a fermentation temperature, or presence of a bacteriophage.

A grainy or lumpy appearance often means the texture will be grainy or lumpy as well. Graininess that is soft in texture can result from too fast an acidification or improper mechanical treatment of the curd/gel.  

A sandy texture or hard grains can be caused by lack of hydration time for added dairy protein ingredients, wrong usage level of stabilizers, low-homogenization pressures, too-high pasteurization temperatures, and/or too-high fermentation temperature.

Syneresis, or wheying off, is another common appearance defect with many possible causes. Poor milk quality such as microbial and somatic cell counts or protein level could be the issue. Poor quality and/or inadequate hydration of dairy powders, too-high or too-low pasteurization temperatures, low-homogenization pressures, and incorrect fermentation temperature are also considerations.

Whether you are a product grader for your dairy company or just a consumer, product defects aren’t good for anyone. Minimizing defects is always the goal.