BTW, to get back to the OP's question, the reason particle size is important is that many recipes do NOT call for dissolving the powder, and therefore the powder size is really, really important. The following recipe will absolutely fail if you use normal "large granule" powdered milk, right out of the box. I have highlighted, near the end of the recipe, the instructions that show how the powdered milk is being used. I have actually cooked this recipe, and it failed because I didn't use "spray process" milk. I used to get spray process milk at health food stores, back in the 1970s. I haven't seen it for a long time, but I'm sure it is still available.
Putting the powdered milk in a blender, prior to using it, would probably work, but it is an extra step, and the stuff might get all over the place. A PIA, for sure.
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Grilled Glazed Boneless, Skinless Chicken Breasts
Serves 4
Glaze
2 tablespoons rice vinegar
1 teaspoon cornstarch
⅓ cup hoisin sauce
2 tablespoons light corn syrup
1-2 tablespoons Sriracha sauce (Chili peppers & vinegar)
1 teaspoon grated fresh ginger
¼ teaspoon five-spice powder
Whisk vinegar and cornstarch together in small saucepan until cornstarch has dissolved. Whisk in hoisin, corn syrup, Sriracha, ginger, and five-spice powder. Bring mixture to boil over high heat. Cook, stirring constantly, until thickened, about 1 minute. Transfer glaze to bowl.
Chicken
¼ cup salt
¼ cup sugar
4 (6- to 8-ounce) boneless, skinless chicken breasts, trimmed
2 teaspoons nonfat dry milk powder
¼ teaspoon pepper
Dissolve salt and sugar in 1½ quarts cold water. Submerge chicken in brine, cover, and refrigerate for at least 30 minutes or up to 1 hour. Remove chicken from brine and pat dry with paper towels. Combine milk powder and pepper in bowl.
Turn all burners to high, cover, and heat grill until hot, about 15 minutes. Leave primary burner on high and turn other burner(s) to medium-high.
Clean and oil cooking grate. Sprinkle half of milk powder mixture over 1 side of chicken. Lightly spray coated side of chicken with oil spray until milk powder is moistened. Repeat on second side.
Place chicken, skinned side down, over hotter part of grill and cook until browned on first side, 2 to 2½ minutes. Flip chicken, brush with 2 tablespoons glaze, and cook until browned on second side, 2 to 2½ minutes. Flip chicken, move to cooler side of grill, brush with 2 tablespoons glaze, and cook for 2 minutes. Repeat flipping and brushing 2 more times, cooking for 2 minutes on each side. Flip chicken, brush with remaining glaze, and cook until chicken registers 160 degrees, 1 to 3 minutes. Transfer chicken to plate and let rest for 5 minutes before serving.