High-throughput, Microscale Protocol for the Analysis of Processing Parameters and Nutritional Qualities in Maize (Zea mays L.)

This method can help answer key questions, regarding how we can better select for maize varieties that produce more nutritional food products, and also, how different nutritional compounds react to current food processing parameters. The main advantage of this technique, is that it allows us to analyze multiple samples in the laboratory simultaneously. And it allows us to sample the beginning, intermediate, and final stages included in the production of cornflakes.

Visual demonstration of the method is critical, since many of the steps that increase the throughput of the protocol are not intuitive, and result in cross contamination of samples, if caution is not taken. To begin, place a 15 liter pressure cooker onto an electric hotplate. Add one liter of tap water to the pressure cooker, and heat the water to 100 degrees celsius.

While the water heats, add a sugar-salt solution and 100 grams of flaking grits, to four one-quart canning jars. Next, use a glass stirring rod to mix the solution, with the flaking grits. When the water in the pressure cooker begins to boil, add one liter of tap water to reduce the water temperature.

Then place the canning jars containing the sample flaking grits into the pressure cooker. After the water reaches a rolling boil, replace the lid of the pressure cooker. Cook the sample flaking grits at 15PSI for one hour.

The, allow the pressure cooker to cool, and completely de-pressurize. Carefully, use heat resisting gloves, to remove the lid from the pressure cooker. Next, use specialized tongs to remove the sample flaking grits from the pressure cooker.

Use a spatula to remove any non-endosperm material, from the flaking grits. Place 30 grams of the cooked grits into a weigh boat, and dry in an oven at 65 degrees celsius for 12 hours. The, use a coffee mill to grind the cooked grits sample into a fine powder.

First, bake the grit samples, on a foil lined baking sheet in a convection oven, at 107.2 degrees celsius for 50 minutes. Stir the samples after 25 minutes to ensure even baking. After the 50 minute baking period remove the baking sheet, and allow the samples to cool at room temperature for 30 minutes.

Then, remove 30 grams of the baked grits from the baking sheet, place the sample in a weigh boat, and dry in an oven at 65 degrees celsius for 12 hours. After drying, use a coffee mill, to grind the sample to a fine powder, and store for subsequent analysis. First, remove the remaining baked grits from the baking sheet and place them in a 1 meter length of parchment paper folded into a pouch.

Then carefully feed the baked grits in the pouch through a tortilla press. After rolling the baked grits through the press, use a pizza cutter to cut the rolled baked grits into two and a half by two and a half centimeter squares. Open the parchment paper pouch, and allow the rolled flake samples to dry at room temperature for 12 hours.

Next, place the flaked samples in a pre-heated convection oven, at 204.4 degrees celsius for 60 to 90 seconds. To ensure uniform toasting, spread the samples evenly. Allow the samples to cool at room temperature, for five minutes to yield the final toasted cornflake product.

Finally, use a coffee mill to grind the toasted cornflake sample into a fine powder. This protocol can be used in conjunction with many different nutritional analysis. Using this protocol the Ferulic acid, and p-Coumaric acid content of cornflakes throughout all stages of processing was analyzed.

Regardless of the specific hybrid cultivar, most of the insoluble bound Ferulic acid was removed during dry milling and cooking. Similarly, p-Coumaric acid was also removed during dry milling and cooking. Additionally, the initial ranking of the cultivars in terms of the insoluble bound Ferulic acid content, and p-Coumaric acid content was not indicative of their ranking at the final processing stage.

Once mastered, 16 samples can be analyzed daily using this technique, if performed properly. This is in comparison to the older protocols we used, that allowed for only three to four samples to be analyzed daily. After it’s development, this technique allowed us to explore not only what happens to the overall content of certain nutritional compounds throughout processing, but also whether the compounds are present in different forms with different bio-availabilities.

Don’t forget that when working with a pressure cooker, it can be extremely hazardous, and precautions, such as following and understanding all written materials provided with the equipment and safety protocols, should always be followed while performing this procedure.