Commercialization of Hazelnuts for Growers in the Upper Midwest

Commercialization of Hazelnuts for Growers in the Upper Midwest

Summary

Our project is off to a great start.  We have completed work analyzing the phenolic and antioxidant content of the leaves, involucres, and nuts of American and Hybrid hazelnuts and have published the results in the American Journal of Essential Oils and Natural Products.  We have begun exploratory work identifying anti-quality flavor compounds in hazelnut kernels.  We have completed the 2016 harvest and data analysis and have identified the top 20 plants for micropropagation.  The top five plants to emerge will then be used to populate the on-farm performance trials scheduled for 2017 and 2018.  We have completed development of EMC (Equilibrium Moisture Content) curves in order to optimize cracking and dry-down procedures.  Implementation of the dry-down and storage trials will occur in the fall of 2017 with publication of optimized post-harvest handling procedures scheduled for 2018.

Objectives/Performance Targets

Outcome/Objective 1: On-Farm Evaluation of Select Hazelnut Genotypes

Achieving Objective 1 of this project will take all three years. The first year will finalize selection of the top genotypes and put those genotypes through micro-propagation.  Years 2 and 3 will focus on establishment of the replicated performance trials.

Outcome/Objective 2: Optimizing Post-Harvest Handling for Processing

The first step in this objective is to develop EMC curves for the hazelnuts in order to identify optimal cracking moisture and dry down procedures.

Outcome/Objective 3: Optimizing Post-Harvest Handling for Flavor

The next step is to implement the dry-down and storage trials to determine optimal procedures for protecting hazelnut flavor.

Outcome/Objective 4: Screening Hazelnuts for Phenolic Content and Novel Compounds

The purpose of this objective is to screen hazelnut kernel, shell, and involucre for phenolic content for possible identification of novel phenolics with commercial potential.

Accomplishments/Milestones

Outcome/Objective 1: On-Farm Evaluation of Select Hazelnut Genotypes

The 2016 harvest and sample processing is complete and we are now in the process of finalizing our list of top genotypes. We currently have 20 genotypes in micropropagation based on the 2015 results and it looks like we’ll be adding 4-5 new genotypes.  Micropropagation is proceeding at Knight Hollow Nursery, but it is going slowly as the isolations take time and the shoot growth is slow.  As such we appear to be on track for a fall 2017 and spring 2018 planting schedule.

Outcome/Objective 2: Optimizing Post-Harvest Handling for Processing

Work has been completed on developing the EMC curves for the in-shell and in-husk nuts and we are working on a publication for this work. We have also begun working to developing specialized drying equipment in order to run the dry-down experiments in the fall of 2017.  Our work to optimize cracking will proceed with the conditioned nuts starting this winter.

Outcome/Objective 3: Optimizing Post-Harvest Handling for Flavor

Analysis of the negative flavor attribute, bitterness is currently on-going. A hybrid of C. Americian and C. Avellana obtained from Gibs 6-10 hazelnuts (Montevideo, Western Minnesota), analyzed.  As a first step, the sample preparation was optimized,  involving solvent extraction, ultrafiltration and solid phase extraction to obtain representative bitter isolate. Taste-guided first dimension fractionation was then performed by a liquid chromatography system coupled with a preparative RP C18 LC column (21.2 × 250 mm, 5 µm, Varian, USA). Fractions were collected and after solvent removal and freeze drying, they were submitted for sensory evaluation by a trained panel of four judges in order to identify the fractions with the highest bitter intensity. Bitterness intensity was rated on a designated categorical scale (not present, threshold, weak, moderate and strong) and caffeine references were provided to panelists. Two fractions with the highest reported bitterness intensity, were selected for further separation and taste-guided fractionation in order to reduce sample complexity and facilitate with bitter compound identification (by MS and NMR). Second dimension fractionation and sensory evaluation is currently underway.

A similar work-flow was optimized and applied to C. Americana hazelnuts (Cedar Creek Natural History Area). Taste- guided first dimension fractionation was completed and revealed multiple bitter fractions with intensities ranging from threshold to strong taste. One fraction had the highest bitter intensity and was thus selected for further investigation and sensory guided fractionation analysis. Second-dimension LC fractionation was carried out using an alternative column chemistry (RP Bonus column, 5 µm, Agilent, Santa Clara CA, USA) an optimized gradient elution with acidified (pH 2.5) methanol and water. Sensory evaluation of second dimension fractions revealed two fractions present with moderate bitterness intensity. In order to characterize the compounds responsible for bitterness, further separation and purification is needed and currently on-going. Structural elucidation of bitter compounds will then be performed via MS and NMR analysis.

Outcome/Objective 4: Screening Hazelnuts for Phenolic Content and Novel Compounds

This work has been completed and the results published:

Demchik. M.C., Fischbach, J., and J. Hall.   2016.  Phenolics and antioxidant Activity of American and hybrid hazelnuts.  American Journal of Essential Oils and Natural Products.  4(1):50-52

Hazelnut leaves, involucres, shells and nutmeats all have quite high levels of phenolics and antioxidant activity.  The level of phenolics was highest in the leaves and lowest in the nuts.  This would be expected, as high phenolic levels are often associated with bitter flavors and bitter nuts would not be a preferred food.  When corrected to the same levels, phenolics from the leaves and involucres provided the strongest antioxidant activity.  Overall, the potential of hazelnut co-products, like involucres and leaves, to provide another product is exciting and deserving of additional research.

Impacts and Contributions/Outcomes

Our primary impact at this point is publication of our work on the phenolic and antioxidant activity of hazelnuts. The primary impact of this project will occur in the last two years.  This first year has been primarily the foundational work in preparation of the field trials, dry-down experiments, and storage conditioning work that will provide real-world post-harvest handling recommendations to growers.

Collaborators: