Interpretive Summary: To improve the nutritional profile of crunchy snack foods, whey protein isolate was modified and extruded with corn meal. Most crunchy snack foods are made from corn meal in a machine called an extruder. The extruder consists of a long, heated barrel with two mixing screws inside. The corn meal is cooked as the screws mix and push it through the extruder to form the snack food. The crunchiness of the extruded snack is an essential quality, but earlier research has shown that adding unmodified proteins to corn meal reduces crunchiness. In this study, it was determined that it is better to modify the whey protein isolates, before adding them to the corn meal and extruding. This method modifies the structure of the proteins making them crunchier in the final product and creates a form of whey protein isolate that is more compatible with corn meal. This knowledge allows the creation of nutritious high-protein expanded crunchy snacks, and utilizes whey protein, a surplus byproduct of the cheesemaking process.
Technical Abstract: Adding whey protein concentrates or isolates to expanded snack foods would boost their nutritional content; however, adding non-textured whey proteins in amounts larger than 5% interferes with expansion, making the products less crunchy. To counter this effect, whey protein isolate was first extruded (texturized) at either 50 deg C (WPI-50) or 90 deg C (WPI-100) before adding to corn meal at 25% (WPI) level, and extruding again to make the puffed product. Corn meal, corn meal with non-texturized WPI (25%), corn meal with WPI-50, or corn meal with WPI-100 were extruded at high shear conditions (300 rpm) and die exit temperatures of 125 deg C. Corn meal extruded with the two texturized WPI blends, WPI-50 or WPI-100 expanded more than the corn meal or the corn meal with non-texturized WPI. WPI-50 was significantly (p<0.05) more expanded than the rest. All extrudates containing texturized WPI were firmer, crispier and easier-to-break than corn meal or corn meal with non-texturized WPI. Adding non-texturized WPI in expanded corn meal decreased color lightness L values, but using texturized WPI enhanced expansion and textural attributes, improving crunchiness. Pre-texturizing whey proteins and using them in extruded snacks improves textural properties making it possible to add large amounts of whey proteins into directly expanded snacks to fortify them.