Americans may associate Greece with mythology, weddings (if they remember the movie) and now protein-rich yogurt. Like other yogurts, such as organic varieties and those with fruit inclusions, Greek yogurts require specific attention when it comes to texture.
U.S. food industry interest in Greek yogurt grew in 2010. For example, the Hain Celestial Group acquired the assets and business of 3 Greek Gods L.L.C., including its Greek Gods brand of all-natural Greek-style yogurt. Also in 2010, Yoplait Greek was introduced in the four flavors of strawberry, blueberry, honey vanilla and plain.
Companies wanting to invest in Greek yogurt should know its protein content is no myth, and neither is its effect on texture.
“Greek yogurts have a wide range of textures due to several process variables, including the straining method utilized, the final protein content, the final fat content, the temperature and hold time utilized to pasteurize the yogurt mix and finally if and how the strained yogurt is mixed or sheared before packaging,” said Mike Molitor, pilot plant project manager for the Wisconsin Center for Dairy Research in Madison, Wis. “It’s more challenging to produce Greek yogurt with smooth texture than (regular) yogurt with smooth texture because the majority of Greek yogurts are much higher in protein than yogurt.”
A marriage of smooth texture with cost efficiency, while it may be a goal, is not easy to achieve.
Mr. Molitor said some variation of “straining” is implied if the word Greek is added to describe the yogurt. Straining concentrates the protein and butterfat, too, if it is a version made with some butterfat. Several straining methods exist, ranging from traditional to more efficient mechanized processes.
The most traditional Greek yogurt process would be whole milk yogurt strained to less than half of the original yogurt volume. The butterfat and protein in the yogurt are concentrated by removing whey.
The milk may be ultrafiltered at the beginning of the process sequence to strain or concentrate the protein and butterfat. Next the concentrated milk is pasteurized and cooled to the ideal incubation temperature. Then yogurt cultures are added.
“Concentrating before making the yogurt is the most cost-effective process although it’s the one that’s the most challenging to achieve smooth texture Greek yogurt with high protein content,” Mr. Molitor said.
Specialized types of ultrafiltration may be used to concentrate the yogurt after it is made. Ultrafiltration is the only concentration method that may be utilized before or after making the yogurt.
“Yogurt has higher viscosity than milk and for that reason, yogurt is more difficult to strain with ultrafiltration,” he said.
Donna Klockeman, a dairy food scientist for TIC Gums, White Marsh, Md., said the manufacturing of Greek yogurts may be divided into two groups: strained and non-strained.
“In strained products, a portion of the moisture is removed from the product following culture to deliver a very high protein finished product that is smooth and spreadable,” she said. “In non-strained products, the high protein content is added to the product up front, and the processing, culture and ingredients may be different. The finished product texture is also very different than products that are strained.”
National Starch Food Innovation, Bridgewater, N.J., recently extended the use of its texture knowledge and Dial-In texture technology approach to the Greek yogurt category, said Suzanne Mutz-Darwell, senior market development manager for texture for National Starch Food Innovation.
“We can now offer dairy processors solutions to create a thick, rich, creamy set Greek yogurt style texture, containing 0% fat and 10%-plus protein, that can be made on typical stirred or blended yogurt processing equipment, avoiding the capital investment of straining equipment,” she said. “This represents a tremendous cost savings to the processors and also eliminates the need to treat the waste effluent stream resulting from straining.”
Texture is a key determinant of consumer liking and acceptability in all yogurt products, Ms. Mutz-Darwell said. National Starch conducted a yogurt category appraisal that involved 200 consumers in four different U.S. cities evaluating 12 different samples of vanilla yogurts of varying textures, Ms. Mutz-Darwell said. They ranked each sample on a nine-point scale for overall liking as well as texture liking.
“Additionally we characterized these same 12 samples by an expert descriptive sensory panel, so we could compare the profile and intensity of each of the key textural attributes with those products that scored high in overall liking and texture liking,” she said.
Besides the Greek yogurt category, organic is another yogurt category demanding specific care.
TIC Gums now offers TICOrganic YG Cup Set, an organic stabilizer for cup set yogurt products, and TICOrganic YG Vat Set, a blend of organic ingredients ideal for stirred yogurt.
The product uses 100% organic agar, a gum, Dr. Klockeman said.
“A high gel strength fine mesh extract from red seaweed, TICOrganic Cup Set improves gel structure of yogurt with increased control of syneresis for improved product quality throughout shelf life,” the company said. “TICOrganic YG Vat Set offers the same benefits of YG Cup Set, but was specially developed to stabilize stirred style yogurts. These specialized blends of 100% certified organic ingredients deliver a smooth, thick, pudding style yogurt with increased control of syneresis.”
For organic yogurt or simple/clean label yogurt, National Starch may assist with the Novation line of starches, Ms. Mutz-Darwell said. They offer the functionality and process stability required to withstand the typical high heat and shear conditions associated with HTST or UHT processing, she said.
For yogurt fruit preparations, Danisco offers Grindsted pectin YF, which creates a gel with a yield value to suspend fruit pieces. Grindsted pectin B, which works in cultured dairy and yogurt, replaces texture and reduces costs in reduced-milk solids formulations.
Depending on the yogurt category and process involved, other texture issues may arise.
“Like many food products, how you manage the finished product texture of yogurt is influenced by the product formulation and how the ingredients are processed,” Dr. Klockeman of TIC Gums said. “The heat treatments used to pasteurize the milk prior to culturing have an effect on the protein components of the formulation. The total protein in the product and the source influence the product texture.
“You must also consider if the product will be cultured in a small container (cup set) or in a large container (vat set or stirred). The culture organisms can also have an effect on texture. The total texturizing system selected (formula, culture, processing, hydrocolloids) influences the texture profile of the finished product.”