NEWSLETTER ARTICLES

Small Farms and Specialty Crops

One of the key evaluations performed in Dr. Cantwell’s lab was pyruvic acid development (PAD). The PAD analysis is a laboratory test, which has been inversely related to mildness or "sweetness" as evaluated by taste panels. In other words, a high PAD value is a sign of a more pungent onion and thus, less desirable as a sweet onion. Sweet onions produced in a range of environments are generally acceptable to consumers as "sweet" onions when the PAD is below 5.0. The lower the PAD, the "sweeter" or milder the onion. A standard, "storage type" onion, will typically have PAD levels in the 9-12 range. It is important to note that sugar content has not been consistently related to mildness or "sweetness" in taste panel evaluations.

All of the short day onion cultivars, which we have evaluated over the past two seasons, have shown PAD values in the range of acceptability for sale as sweet onions. There has been some variation between growing sites and factors, such as soil sulfur levels and weather conditions which have been shown to affect pungency. Growers in the famous Vidalia sweet onion production area of South Georgia have recently announced plans to develop a "certified" Vidalia Sweet Onion where they will actually test individual fields for PAD. Under this proposal, onions testing below 3.5 will be "Certified Super Sweet" and those testing 3.5 to 5.5 will be "Certified Vidalia Sweet Onions."

Storage allows growers to extend the marketing season, but there are limitations with storing short day sweet-type onions. Sweet short day onions typically are not stored for extended periods due to a relatively high moisture content. The best storage onions are long day, low moisture onions. In South Georgia, sweet onions are occasionally stored in controlled atmosphere (CA) storage for up to four months to extend the sales season.

During storage, pungency decreased in 16 of 22 samples analyzed. Pungency decreased an average of 12% after 12 weeks in storage at 5°C (41°F). Dry weight declined an average of 8.5% in storage. Total extracted sugars were also analyzed, but these results were not consistent (data not presented). As with 1996 analyses, onions with a range of pungency (PAD) values had both high and low sugar contents.

Visual characteristics and decay are two quality components of onions which decline over time in storage. Dr. Cantwell also evaluated the onions for visual quality features both before and after 8 weeks of storage in air at 5°C (41°F). That data is presented in Table 2.

Visual quality of the onions declined from an average score of 9 (excellent) to about 8 following 8 weeks of storage (12 weeks from harvest) at the two sites. Other factors, such as rooting, were also evaluated (data not presented), and some rooting was apparent in some cultivars after 12 weeks. Some of the rooting may be due, however, to the high relative humidity (~85%) in the storage room. With further management modifications, it may be possible to improve storage conditions for short day onions. It is clear from these trials that it may be possible to substantially extend the marketing season for sweet onions by careful harvest and curing of the onions followed by cold storage.

Several growers have inquired recently about growing fresh sprouts on a small scale for farmer’s markets, restaurants, and other types of direct marketing. Interest has been especially keen regarding broccoli sprouts after reports from Johns Hopkins Medical Center and elsewhere that broccoli sprouts contain fiftyfold more cancer- fighting compounds than broccoli. Many other growers are just interested in diversifying their product line into additional items with demand in the marketplace.

I use small scale production because fresh sprouts are grown on a massive scale on some farms as well as in metropolitan New York and other major cities. There are nearly 60,000 restaurants in New York City and the sprout consumption is huge. Enterprising "growers" have gone into old abandoned tenements and warehouses and completely renovated them for sophisticated large scale sprout production using computer assisted lighting and temperature control. Large stainless steel vats are used to produce sprouts in bin size lots which are trucked out daily to waiting buyers. For this discussion, we are interested in something smaller.

There are a wide range of seeds, which can be sprouted for use as a flavorful fresh dressing on salads and sandwiches or incorporated into a number of dishes. The finer seeded species such as alfalfa and the clovers are mainstays of the sprout market, but larger seeded species may be sprouted as well. Garbanzo bean sprouts are considerably larger and have their own following among shoppers and chefs. Mung beans and lentils are intermediate between the two size extremes. Wheat sprouts have also become popular as so-called "wheatgrass" juice drinks and other foods.

The key elements in successful sprout growing are managing water and temperature while maintaining cleanliness to avoid contamination. Light is also important in some instances to develop the appealing green color when growing out longer term seedling sprouts. The rapidly growing sprout tissues are an ideal environment for many bacteria and fungal pathogens. Hence, cleanliness and sanitation are especially critical at all phases of sprout production and marketing. The seeds/sprouts produce heat during the germination process. Regular wetting is used to supply water, cool the sprouts and keep them clean.

The production of high quality mung bean sprouts requires that a weight be placed on top of the sprouting seed. The pressure on the germinating seed lot causes the seeds to produce ethylene, which in turn is a powerful plant growth regulator which causes the root, stem and seed to thicken. This contributes to the distinctive texture and flavor of mung bean sprouts.

In growing sprouts there are general guidelines and specific techniques depending upon the species. Beginning growers should start with one or two species until they get the details of their production system worked out. Alfalfa and radishes are good beginning species. For continual supplies it is important to develop a system, which permits managing regular seeding and harvest with thorough cleanup between batches.

Equipment needs will vary with the size of the operation and the volume of sprouts desired. The seeds may be sprouted in any type of container or tray with drainage. Plastic or metal containers will enable easier cleaning between lots. Metal or plastic screen or cheese cloth may be used to cover the container to allow frequent washing without loosing the seed. Or the seed may be dumped out of the container onto a mesh screen for rinsing. Alternatively, holes may be punched in the bottom of the container to permit drainage. You may wish to experiment with a variety of container types until you find the best type for your production “system.” You want to be able to wash the seed frequently or set up some type of automatic misting or watering system which then drains quickly. Containers and work surfaces should allow for easy cleaning and sanitizing once the sprouts are harvested.

Seed-type sprouts will be ready in about 5-7 days, depending on temperature. Temperatures between 55°F and 75°F are ideal. Seed-type sprouts may be germinated in the dark or in dim light.

Seedling-type sprouts are grown on some type of water-holding medium in trays and will require bright light for best results. These seedling sprouts are grown out for a longer period of time to young seedlings, 3-5 inches tall. They are usually harvested by cutting at the surface of the growing media in contrast to seed sprouts which are harvested whole. Seedling sprouts may be grown in sand or soil or on top of a thin sponge or foam rubber. Use 1-2 layers of paper towels on top of the foam. An artificial medium, such as foam, may be disinfected between batches whereas sanitation is more of a problem with the sand or soil.

An 8-inch tray Auto-Sprouter sprout production unit is available from Johnny's Selected Seeds (207) 437-4395 voice or (800) 437-4290 fax. Johnny's also offers additional information on sprout cropping in a leaflet entitled "Continuous Cropping with Sprouts."

General Guidelines

Use clean, pathogen-free potable water.

Use clean, untreated seed. Don’t be afraid to surface sterilize the seed in a dilute chlorox solution (1/2 Tbsp. of household bleach per gallon of water) for five minutes, then wash thoroughly with clean water. Pick out any trash in the seed lot.

Soak the seed overnight in a container to allow the seed to imbibe water. The volume will typically increase 7-10 times.

Pour off the water and rinse thoroughly. Transfer the seed to a rearing container with good drainage.

Rinse the seed frequently with cool water. The seed needs constant moisture to develop and the seed lot heats up and needs to be cooled frequently by rinsing.

Rinse every 12 hours. In unusually warm conditions,more frequent rinsing may be necessary.

Once the sprouts are harvested, pack in clean containers and store in a cooler until sold. Keep out of direct sunlight during storage or marketing.