Expanding Local Markets through Evaluating Sensory Characteristics and Agronomic Performance of Flint Corn Varieties

The overall objective of our project is to use flint corn field trials and a sensory directed product development approach to expand the flint corn market in the Northeast, while sharing the approach and results to the benefit of other grain growers in the United States.

Which flint corn varieties are best suited for growing in the Northeast?

Flint Corn Variety Screening Trial

The availability of high-quality flint corn varieties in the northeast region is variable and relatively low compared to dent corns. After several years of trialing as many varieties as we could find, it became clear that many of the varieties that are available on the market are either poorly adapted to our region’s growing season, do not possess the agronomic characteristics needed in commercial production, or are too expensive for a commercially viable business. Therefore, we decided to broaden the scope of our varietal evaluations to screen flint corn germplasm for basic agronomic traits. Sixty flint corn accessions were obtained from the USDA National Plant Germplasm System. Approximately 100 seeds of each accession were seeded in three rows planted 30” apart in Alburgh, VT on 21-May 2021. Each accession was therefore planted at approximately 26,000 seeds ac^-1. Each plot was evaluated for plant population, number of barren plants, plant height, ear height, lodging severity, ear disease severity, corn yield, and corn test weight when the corn reached black layer. For accessions for which there is sufficient material, samples will be processed in order to evaluate the sensory characteristics of the corn. This will help us to understand the potential culinary value of these accessions in hopes to identify those that have both agronomic and culinary potential.

Are the production practices (i.e. populations) for flint corn different than dent corn?

Impact of Seeding Rate on Heirloom Corn Yield

In 2021, two grain corn varieties, one flint and one heirloom dent, were each seeded at six different seeding rates at Borderview Research Farm in Alburgh, Vermont (Table 1). The trial design was a randomized complete block with split plots and four replications. Main plots were the varieties while sub-plots were seeding rates ranging from 20,000 to 30,000 seeds ac^-1. Plots were evaluated for populations, lodging, grain yield, grain moisture, and grain test weight. The soil type at the Alburgh location is a Covington silty clay loam. The seedbed was prepared with a Pottinger TerraDisc. The previous crop was corn silage. Prior to planting, plots were fertilized with 19-19-19 at a rate 300 lbs ac^-1 on 6-Apr. Plots were planted on 24-May with a 4-row cone planter with John Deere row units fitted with Almaco seed distribution units (Nevada, IA). Liquid starter fertilizer (9-18-9) was applied at planting at a rate of 5 gal ac^-1. Plots were 20’ long and consisted of four rows of corn 30” apart. Populations were counted in each plot after emergence at prior to harvest. An application of Acuron was made on 4-Jun at a rate of 3 qt ac^-1 to control weeds. On 7-Jul plots were top-dressed with 400 lbs ac^-1 24-12-18.

Table 1.  Treatment and trial management information.

On 8-Oct and 5-Nov the Cascade Ruby Gold and Wapsie Valley plots were harvested respectively. Corn populations and the number of barren plants, plants that did not form an ear, were counted. Plots were also visually assessed for lodging severity on a scale from 0 (no lodging) to 5 (completely lodged). Corn was picked by hand and fed through an Almaco SPC50 plot combine. The corn from each plot was weighed and the moisture and test weight measured using a Dickey John Mini-GAC Plus moisture and test weight meter. Yield data and stand characteristics were analyzed using mixed model analysis using the mixed procedure of SAS (SAS Institute, 1999).  Replications within trials were treated as random effects, and hybrids were treated as fixed. Hybrid mean comparisons were made using the Least Significant Difference (LSD) procedure when the F-test was considered significant (p<0.10).  

What consumer food products are each flint corn variety suitable for producing?

Which flint corn varieties result in food products that best meet consumer aroma and flavor preferences?

Fall 2020:                                Preparation for the 2021 growing season

In addition to the identification of the corn varieties to be used in this project, the descriptive sensory analysis piece was kicked-off and cornmeal sample preparation and sensory method development for its evaluation was initiated. One of the aims of this project is to develop new and effective ways to prepare cornmeal samples on which objective descriptive sensory analysis can be conducted to generate data that can be successfully correlated with both practices at the farms and sensory performance of final products such as corn tortillas and chips. We plan to adapt the standard approach used by many large international food companies to conduct sensory screening on grains such as corn. Typically, a 10% aqueous solution of each cornmeal sample is produced and submitted for objective descriptive sensory analysis.

The timeline and task updates are as follows:

August 2020:                          Project kick-off and logistics planning

A virtual meeting was held with the UVM Extension Northwest Crops and Soils Program team and staff from the All Souls Tortilleria to discuss the award and review overall project activities and timing, including the fall 2020 and winter 2021 preparations for the 2021 growing season.

January - March 2021:                 Sensory Orientation and Training

Early in January 2021, we collected corn tortilla chip samples produced by All Souls Tortilleria in Burlington, Vermont, to use in a sensory orientation of the trained descriptive sensory analysis panel at the University of Vermont Extension. Due to Covid-19 restrictions, individual samples were distributed to the UVM Extension trained tasters, and representatives from All Souls Tortilleria, and a virtual sensory orientation taste session was facilitated by Roy Desrochers on January 8, 2021. Participants used standard sensory methods to assess the headspace aroma of each sample bag and then record both flavor and texture data.

A modification of the Flavor Profile Method (FPM) of Sensory Analysis called Total Intensity of Aroma (TIA) was used for the bag headspace aroma analysis. FPM and TIA are standard sensory methods well defined and accepted through the American Society for Testing and Materials (ASTM), specifically committee ASTM E-18 which develops standard sensory methods.   (Reference: ASTM ML 13)

The flavor and texture of the samples was assessed using another modification of FPM call Profile Attribute Analysis (PAA) which is another standard ASTM method. These sensory methods will be used by the UVM Extension descriptive sensory analysis panel in the fall of 2021 to evaluate flint corn meal samples at the farm level, as well as flint corn tortillas and tortilla chips produced by All Souls Tortilleria using the trial flint corn samples.

In addition,  a virtual hands-on flint and dent corn sensory demonstration was included as a component of the 2021 Northern Grain Growers Association Annual Conference. 

November - December 2021:              Harvest, Physical Testing, and Sensory Directed Product Development

The flint corn trials will be harvested in the fourth quarter of 2021. Prior to harvest, plots will be assessed for populations, number of ears fully formed, number of plants forming ears, lodging presence and severity, ear orientation and husk cover. Plots will be hand harvested and yield, average ear length and number of kernel rows will be recorded. A subsample of ears will be shelled, and harvest grain moisture and test weight measured using a Dickey-John Mini-GAC Plus meter. Ears from each variety were fully dried in a grain bin, shelled, and a subsample submitted to the UVM Cereal Grain Testing Lab for a basic corn nutrient analysis via NIR (Near Infrared Reflectance) procedures and Deoxynivalenol (DON) content.

In 2022, cornmeal samples will be prepared for each of the 3 flint corn varieties and assessed by the UVM Extension descriptive sensory analysis panel using the sample preparation and analysis methods developed in the first quarter of 2021. We will then select samples of flint corn from the variety trials, based on agronomic performance and DON concentrations, and deliver them to All Souls Tortilleria for processing into food products. The samples will be nixtamalized, a process of cooking in a hot water bath with culinary lime to remove the pericarp and alter the proteins to create a malleable dough. The trained panel will conduct descriptive sensory analysis on a small portion the whole kernel, nixtamalized corn, known as hominy. Remaining hominy will be wet milled into a masa dough and rolled into tortillas.  The tortillas will be both baked into whole tortillas and cut and fried into tortilla chips. Objective descriptive sensory analysis will be conducted on both tortilla and tortilla chips samples. The trained sensory panel will also generate texture profiles for all the finished corn product samples. Aroma, flavor, and texture results for the end-products will be correlated with all other farming, flint corn variety, and flint corn sensory data, to connect these variables to end-product performance, which will be interpreted using the Flavor Leadership Criteria. (FLC) The FLC are a powerful set of sensory criteria, developed by ADL, to identify products with market leading potential. These criteria include early identifiable flavor, amplitude, mouthfeel, off-notes, and aftertaste.