Research at the Midwest Grape and Wine Industry Institute

Industry Problem

Low participation in the Iowa Wine Growers Association’s Iowa Quality Wine Consortium (IQWC) program, which aimed to increase consumer awareness and confidence in choosing high quality Iowa wines in the marketplace.

Research Idea

MGWII proposed to design and conduct a project to provide data and context to the state of the quality of wine produced in Iowa. This study provides a snapshot of the quality of the wines produced in Iowa 10 years after the development of the IQWC program. Additionally, results will assist in directing the future efforts of a revamped program that is both beneficial to the industry and helps continually raise the quality level of wines produced.

The MGWII randomly purchased 74 wines produced by Iowa wineries of varying size. Chemical analyses were conducted at the MGWII wine lab and sensory fault screening panels identified the presence or absence of common visual and aroma and flavor wine faults. The MGWII staff analyzed the results and used statistical methods to look for relationships among the data.

Findings: The study pointed out several areas where wine quality can be improved, including extra attention to sulfur dioxide (SO2) management, minimizing oxygen exposure, frequent screening for volatile acidity, and thorough cleaning and sanitation. A complementary approach of lab testing and sensory screening is recommended throughout the winemaking process to prevent or address quality issues as they arise.

Industry Problem  

Iowa does not currently have a signature wine style. There is little to no data to support what consumers like based on what is grown and produced in Iowa.

Research Idea

A Specialty Crop Block Grant was secured from the Iowa Department of Agriculture and Land Stewardship in the 2019 cycle. We surveyed industry members (both grape and wine) as to their grape production (cultivars and acres) and what wines they produce and which sell very well. We also collected comments on the idea of an Iowa Signature Wine.  The MGWII staff purchased 75 wines based on the varieties that were reported in the survey. Four wines of each variety (Brianna, Edelweiss, La Crescent, Marquette and Frontenac) were selected to present to consumers. These wines also went through a thorough chemical analysis. Consumers were used to collect preference scores. Results are currently being evaluated to investigate correlations between chemical analysis variables and consumer preference.

Findings:

Industry Problem

Wines made from Interspecific Red Hybrid grape cultivars are low in tannin, leading to wines that have little mouthfeel and “structure” compared to red wines made from Vitis vinifera. The low tannin concentration in wines is related to low concentrations in the grapes and to poor tannin extraction during fermentation. This low extraction phenomenon has been previously correlated to a higher concentration of proteins in hybrid grapes.

Research Idea 1

In this experiment, Marquette (low-tannin, high-protein) was blended in different ratios with California-grown Cabernet Sauvignon (high-tannin, low-protein). The blending was done in two different ways, pre-fermentation blending to give a co-fermented wine, and post-fermentation blending where the monovarietal wines were blended. The experiment was repeated for the 2016 and 2017 season. Tannin concentration was measured in wines using the methylcellulose precipitation assay and protein concentration was measured in wines by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). Tannin and protein concentrations were compared between blend types (co-ferment vs. post-ferment blending) as well as to a predicted value based on the mathematical combination of the unblended mono-varietal wines. Statistically, there was no difference between the blend types for either tannin or protein concentrations during either year. In terms of tannin concentration, there were several co-fermented blends that differed significantly from the predicted, however none of the post-ferment blended wines showed a difference.

Findings: Blending (post-fermentation) can increase tannin concentrations of wines, however at low blending amounts (in order to follow labelling rules), do not give a large enough increase in tannin to detect during tasting.

Read the Study: Nonlinear Behavior of Protein and Tannin in Wine Produced by Cofermentation of an Interspecific Hybrid (Vitis spp.) and Vinifera Cultivar

Research Idea 2

An investigation into the poor tannin extraction and retention using juice and mesocarp (flesh) from Marquette will help researchers understand what types of interactions are occurring and necessary to overcome. Tannin extracted from V. vinifera is added to juice/mesocarp and incubated. Both protein and tannin are quantified post-incubation. Several pre-incubation steps are being evaluated to disrupt any tannin-cellular material interactions. We hope to understand better the mechanism of tannin interactions and how to disrupt them for maximum extraction/retention in final wines.

Findings: This work is currently in progress.This work is in collaboration with Dr. Gavin Sacks at Cornell University and Dr. Keren Bindon at the Australian Wine Research Institute.

Industry Problem  

The Midwest Grape and Wine Industry is composed of vineyards and wineries with a large size range with most growers and producers having small operations (less than 5 acres, less than 5,000 gallons). The purchase of equipment for making high quality wines can be burdensome on small wineries.

Research Idea  

Flash détente is a technology originally invented in France where grape must is heated to high temperatures and then subjected to a low-vacuum pressure environment. This can improve color and tannin extraction from the skins of red grapes without extracting bitter phenolic compounds from the seeds. These machines have a market price of around $500,000 for a five ton per hour machine. A Techno-Economic Assessment and Life Cycle Assessment of Flash Détente machines were performed by an Agricultural and Biosystems Engineering class in Fall 2019. This analysis examined the environmental impacts (since the Flash Détente machine requires high energy inputs) and cost input/outputs of these systems. A report is being prepared to highlight the findings.

Findings: The Flash Détente technology is of interest for Midwest wine producers, however the high upfront costs, and utility costs, may make the machine out of reach for individual winery owners. A co-operative model may be more feasible.

This work is in collaboration with Dr. Kurt Rosentrater of the Department of Agricultural and Biosystems Engineering at Iowa State University.

Industry Problem  

As the wine and grape industry in Iowa evolves, so do wineries’ needs and capabilities when it comes to chemical lab analysis. Not everyone is measuring the same things in the same ways, and it can be hard to know how your methods and measurements compare to those of others.

Research Idea  

The MGWII will distribute a sample of the same wine to each of the wineries who volunteer to participate, and will collect anonymously-submitted lab results for a range of common chemical parameters. Participating wineries will then receive a report of all the collected results, and will be able to see where their readings fall compared to others for various methods.

The collected results will also help inform MGWII planning to better serve the industry through educational programming and lab services.

Findings: This project is in the data collection stage. Stay tuned!

Industry problem

The yeast Hanseniaspora uvarum is the predominant yeast on grapes and in early fermentation, but there is little understanding of the factors that influence its growth and spread on grapes before harvest.

Research Idea

The goal of this project is to understand more about the environmental biology of H. uvarum, because it is a major component of the microbial community on grapes before and after harvest. However, it has been neglected because it is neither a vineyard pathogen (like Botrytis cinerea) nor a major fermentative yeast (like Saccharomyces cerevisiae). A lot of recent research has focused on a “zoomed-out” picture of microbial communities in the vineyard, and very little work has been done on characterizing individual vineyard yeasts like H. uvarum.

This project will involve both lab work in controlled environmental conditions, as well as field work with samples of La Crescent and Marquette grapes from the ISU Horticulture Research Station.

Findings: This project is entering year two in Fall 2022. Work-in-progress will be presented at Plant Health 2022. Stay tuned!

This work is in collaboration Dr. Mark Gleason of the Department of Plant Pathology and Microbiology at Iowa State University 

Industry problem

Many cold-hardy hybrid white wine varieties contain a large amount of haze-forming proteins, which can either cause a visible haze or require high rates of bentonite treatment to remove.

Research Idea

Barrel fermentation has potential to reduce protein haze and the need for high rates of bentonite treatment in cold-hardy hybrid white wine varieties. Bringing the concentration of haze-forming proteins into a narrower range would also allow for better predictions of the effective rate of bentonite treatment required. The cost, time, labor, and product losses involved in bentonite fining could be reduced, while product quality could be protected from the effects of over-fining.

This project uses a neutral-oak barrel to ferment La Crescent and evaluates the protein stability of the resulting wine compared to fermentation of the same juice in a glass carboy or steel tank.

Findings: Preliminary results indicate that fermenting La Crescent in a neutral oak barrel significantly reduces protein instability in the wine. Further evaluation on a larger scale will be required for higher confidence and more generalizable conclusions.

Industry Problem  

Cold-hardy hybrid wine grapes are typically high in acid, and the tart flavor of the wines often needs to be balanced with sweetness; however, residual sugar in the wines can contribute to microbial instability.

Description

Glycerol is a sweet-tasting alcohol produced in small quantities by wine yeasts during fermentation. Some types of yeast naturally produce more glycerol than others. High glycerol concentrations in wine could potentially give the perception of sweetness without the need for residual sugar in the wine.

Findings: There was not enough difference in the glycerol concentration produced by the yeasts in this study to make a sensory impact.

This work will be presented at the 2022 International Cool Climate Wine Symposium.

Industry Problem

Emerging cold climate grape and wine industries in the Midwest and Northeast US face challenges to production, processing, and marketing. 

Description

The Northern Grapes Project, a USDA NIFA Specialty Crops Research Initiative project, was conducted across 12 states between 2011 and 2016. The project’s objectives focused on varietal performance, viticultural and winemaking practices, and consumer preferences and marketing strategies. The goal was to increase the profitability and sustainability of cold climate grape and wine industries in the Midwest and Northeast wine regions. 

Findings: 

Among the project’s findings were cultivar performance evaluation, cultivar aroma and flavor analysis, comparison of vine trellis systems, insight into the effect of sun exposure on acidity, commercial yeast strain trials, evaluation of deacidification methods, assessment of tannin addition impact, and evaluation of the impact of tasting room attributes and wine branding on sales. For more detail on specific objectives and results, please visit http://northerngrapesproject.org/