Yogurt Recipes From Dr. Bootsie's Test Kitchen

These are the recipes I've worked out for my own personal yogurt making, to go along with the tips and advice in yesterday's post.

Instant Powdered Milk Yogurt
1 1/2 cup powdered milk
Water to make 3 3/4 cups milk
1/4 to 1/3 cup yogurt with active culture

Measure powdered milk into quart jar. Add water and mix until you have 3 3/4 cups milk in jar. Heat jar, uncovered, in microwave, to 110 degrees F. That's about 1 1/2 minutes in my microwave--your milage will vary. Add 1/4 cup to 1/3 cup "live" yogurt--either from storebought yogurt with the label "active cultures" or from your previous batch of yogurt (my favored starter.) Incubate yogurt at 110 degrees F until it thickens. This may take 14 hours with grocery store starter, or as little as six hours with fresh, home-grown yogurt. Refrigerate when it reaches the desired texture and degree of sourness. This slows down, but does not stop yogurt culture growth.

Pasteurized Fresh Milk Yogurt
3 1/2 cups milk
1/3 to 1/2 cup instant powdered milk (to thicken finished yogurt)
1/4 to 1/3 cup yogurt with active culture

First, scald the milk, as described in yesterday's post. Disolve the powdered milk in the hot milk. Allow mixture to cool to 110 degrees F. (You can speed the process by placing your hot milk in your quart jar, and setting the quart jar in a pan of cold water.) Once the yogurt cools, add the live cultures. (Don't put it in too soon, or you'll cook your microbes, and no yogurt will appear.) Incubate yogurt at 110 degrees F until it thickens. This may take 14 hours with grocery store starter, or as little as six hours with fresh, home-grown yogurt. Refrigerate when it reaches the desired texture and degree of sourness. This slows down, but does not stop yogurt culture growth.

Yogurt Thickened and Flavored With Jell-o

If you have developed a taste for grocery store yogurt, especially the fat-free, sugar-free, artificially sweetened and colored types, you can duplicate them at home. Make a package of Jell-o according to directions on box, but leave out 1/4 cup water. Add 1 cup yogurt to partially-set Jello. To duplicate the total grocery store experience, you can pour the mixture into cup-sized containers for individual servings.

Here are a few food science links about factors that affect yogurt texture, and some miscellaneous cool stuff.

• A sample test for high school science teachers from Southern Illinois University at Carbondale

  What process is responsible for the gel-like texture of yogurt?...Curdling is caused by proteolytic enzymes, heat, lactic acid, and other means. Each milk gel consists of a protein matrix, which is modified by lactic acid to produce a smooth yogurt product....Lactic acid bacteria produce polysaccharides that decrease the flowability of the yogurt.

• A taste of culture - culture polysaccharides, flavors, stabilizers and sweeteners

  Next to taste, texture is the most important sensory attribute in dairy foods. Dairy cultures, with the assistance of stabilizers, are responsible for imparting desirable textures. Yogurt cultures produce exopolysaccharides in two forms, as a non-ropy capsule surrounding the cell and as mucoid material that freely moves away from the cell causing ropiness...capsular polysaccharides play an important role in the development of yogurt microstructure and texture. Yogurt made using such cultures has increased viscosity, a more stable structure and a softer texture.

• Foods Under the Microscope

  by Miloslav (Milos) Kaláb, Ph.D., a full-time Principal Research Scientist at the Centre for Food and Animal Research, Agriculture and Agri-Food Canada in Ottawa until August 1995. Then, he continued - part time - in electron microscopy studies of foods and foodborne microorganisms at the Food Research Program in Guelph, Ontario, Canada.