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Engineering gone nuts: "chestnuts roasting on an open fire" and more.

The warm, sweet, edible subject of "The Christmas Song"--roasted chestnuts--makes for a delicious treat, a warm sole, and great lyrics. But the yuletide refrain, however catchy, isn't necessarily a strong basis upon which to build a potentially growing commodity industry.

After the devastation last century by American chestnut blight (Endothia parasitica), chestnuts are making a comeback in the United States with a project based at Michigan State University. A team of researchers across the disciplines of agricultural engineering, horticulture, plant pathology, food science, packaging, and agricultural economics have a goal: to develop a chestnut industry with a market-driven approach in contrast to one that is more traditional and production-driven. Given the opportunity for a relatively fresh, new, industry beginning, the project is reversing the cliche and developing the industry "from the table to the tree."


Much is involved in "scaling up" a commodity from a family tradition around the fire to a large-scale profitable industry providing diversification for orchard operations and other producers. Bringing forth a new (albeit traditional) commodity opportunity involves multiple facets of agricultural and biological engineering input. Engineering directly comes into play in harvesting, postharvest handling and storage, processing, and packaging. The objective is to determine and develop new products and evaluate markets for chestnuts (not to be confused with water or horse chestnuts), which will bring profitability to the industry, then match and develop production and processing technology to such opportunities. Some examples of value-added products include gluten-free flour, slices and crumbles for breading and toppings, puree, pesto, and delicious soups.


Peeling the peel appeal

A key factor in developing chestnut markets beyond fresh market sales is the ability to shell or peel the chestnut. The initial plan and approach to the shelling was to collect ideas from similar processes and commodities as well as from "home remedy" techniques and then design and scale a peeling system to fit the industry. Plans were significantly modified and simplified when unexpected funding and an investigative trip overseas to Italy yielded a commercial peeler.

Peeling, which is a continuous operation on this line, is based on two principles or processes. The first, the brulage process, is to rapidly heat the outer shell in a gas-fired oven to make the shell brittle, followed by a rather vigorous tumbling/threshing of the nut to break away the outer peel. The second process is to subsequently and slowly pass the nuts through a hot-water-and-steam-heated tunnel to loosen remaining shell or pellicle and then onto a cleaning table with counter rotating rollers to pull off any remaining covering from the chestnut. The peeling line was assembled and operated for one season, the autumn of 2003 being our second.




The peeling line serves two purposes: first, as a research tool and second, to provide peeled product for an establishing cooperative for commercial market development. Data from some initial studies has shown that weight losses of approximately 33 percent from postharvest handling and peeling can be expected. First year studies showed efficiency of peeling (completely peel- and pellicle-free product) ranged from 22 to 96 percent with the range caused by variables of nut variety, growing environment, maturity of nut, moisture and temperature management after harvest, and temperature of the nut entering peeler. Many engineering and integration challenges remain to refine the peeling line and identify postharvest handling that will produce effective and efficient peeling of varieties that are relatively unique to Michigan and the United States. Anticipated future engineering needs will surface in areas of further processing of the peeled nuts to produce specific products and in sorting and grading of both unpeeled and peeled product.

Bushels of peeling and appealing questions

Following this market-driven vs. production-driven approach to development of a new commodity industry is, truly, a case study in systems thinking. Multiple variables exist to optimize: whole peeled nuts, total yield, post-peeling product status for storage or processing needs, throughput, and others. Interfaces between physical and mechanical aspects of handling and processing must be considered against biological aspects of chestnut production. For example, the easiest nut to produce in the field may not be best suited for peeling or marketing.

The industry development and project--enhanced by outstanding cooperation, relationships, and support from producers, extension, the experiment station, and government agencies--has many questions and challenges for agricultural and biosystems engineers to solve now and in the future. Some of the questions the project must address are:

* How do we best get the commodity into consumers' hands ... or better yet ... their mouths?

* Do storage and treatment conditions affect the shelling process?

* How do storage conditions and treatments affect appearance and flavor?

* What storage conditions and treatments are optimal for storage of unshelled chestnuts (modified atmosphere, temperature, humidity, etc.)?

* What storage conditions, treatments, and packaging are optimal for storage/preservation of shelled chestnuts?

* What physical-damage thresholds exist for shelled and unshelled chestnuts?

* Do any official or unofficial quality or grade standards exist?

* What quality characteristics and physical properties are critical for fresh or processed product? Can these quality characteristics be measured (density, optics, etc.)?

* Can a system be modified or developed for mechanical or mechanically assisted harvest of chestnuts?

Many aspects of biosystems and agricultural engineering are already coming into play and will have a major role in the future of this emerging industry--if consumers are willing to look beyond the traditional yuletide fare, adding this nutritious and delicious food to their year-round plate.

Daniel Guyer is a professor in Michigan State University's Department of Agricultural Engineering, Farrall Hall, East Lansing, MI 48824 USA; 517-353-4517, fax 517-432-2892,
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Author:Guyer, Dan
Publication:Resource: Engineering & Technology for a Sustainable World
Article Type:Cover Story
Date:Dec 1, 2003
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