Bean Sprout Production: An Overview

mung_bean_sprouts_by_sungarden_sproutsBean Sprout Production - An Overview

Bean sprouts have been produced in Asia for around 5000 years.  The traditional method involves sprouting green or black mung beans or soybeans in buckets in which a large stone was placed on top. The sprouts were watered a few times each day. As the bean sprouts were forced to push the stone up, the sprouts grew thicker and shorter and yielded a greater volume of sprouts with less roots. This process is called "stress". 

In 1981 ISS hired their first of several biochemists to determine what was involved in this process and how to improve upon it.  Engineers were hired to develop the equipment to take advantage of the advances made by the research department. We took into account the different needs of growers in various countries and growers with different economic realities. The process that follows applies to companies who produce small quantities of sprouts as well as those who produce 40 tons per day using only two workers.

Starting with the SeedMung Beans

There have been many pathogen outbreaks throughout the world involving sprouts.  Several people have died, and over 7,000 have been hospitalized from eating contaminated sprouts.  The main problem is that seed coming from a field may have come in contact with animal waste.  Animal waste can harbor the dangerous and sometimes lethal bacteria E.coli 0157:H7 and Salmonella, as well as other pathogens.  The prefect environment for sprouting is nearly ideal for the growth of pathogens.  Each Salmonella cell will grow to about 100,000 cells in 48 hours.

No reasonable method of decontaminating the seed is 100% safe, so there are several steps that need to be taken in order to insure you have safe sprouts.  The first being to buy seed in which precautions have been made to reduce the risk of contamination.

Your seed needs to be stored in a clean warehouse or area free from rodents, insects and moisture.  If you are going to store the seed for any length of time, the area should have a low humidity and maintain a low temperature.

Having purchased "safe" seed that is properly stored, you need to sanitize the seed before sprouting it.  This is in case a pathogen was missed by the supplier in the seed screening process.

The most effective way of sanitizing the seed is by dousing it in calcium hypochlorite for ten minutes and rinsing it off.  We have manual equipment for small growers and fully automated equipment for larger growers.  

The seed is then placed in growing bins and the bins are placed in a growing room precisely built to control the environment.   

Growing the SproutsMung bean sprout production

The things that effect bean sprouts are:

  • Seed quality.

  • Water quality, consistency, flow, duration, temperature and watering interval.

  • Gasses in the room.

  • Nutrients in the water.

  • Room temperature and humidity.

Some of these change during the growing cycle.  All are computer controlled by any of the ISS growing systems, with detailed records kept.

The bean sprouts are grown in the growing room for 4 to 6 days.  Each bin in the growing room may have sprouts at a different growing stage.  The computer remembers when each bin was started and caters to its' individual needs.

Removing the Seed Hullsmung bean sprout wash tank

When the sprouts are grown, the grower removes the bins from the growing room with a pallet jack or electric fork lift. The sprouts are removed from the bins either manually by a stainless steel pitch fork or automatically with a bin dumper.

The next stage is removing the green seed hull.  This can be done either wet or dry.  There are advantages and disadvantages to each.  Using the dry method, sprouts are conveyed along a vibrating table with a perforated top.  The seed hulls fall through the holes and if there are root hairs on the sprouts, many of them are removed as they pass over the perforations.  The ISS Vibrating Huller is favored in areas where labor is expensive and water is dear.  This equipment is generally less expensive and takes less space than the wet method.

The ISS Wash System is the preferred method for quality.  It uses a water bath to separate the seed hulls.  The ISS Wash System allows you to chill and sanitize your sprouts, which increases shelf life.  A dewatering system is needed with this system, whereas it is not needed with the ISS Vibrating Huller.   We make both types of hullers in a variety of sizes to handle any volume.

Mung bean sprout dehullerDe-Watering the Sprouts

If the ISS Wash System is used, the sprouts need have the water removed before packaging.  There are two good ways to do this.  The sprouts can either be placed in an ISS Cyclone Mung bean sprouts centrifugeCentrifuge or run over and ISS Air Knife System to remove the water.  The ISS Cyclone Centrifuge is less expensive in the initial investment.  You put about 22 kg (50 lbs) of wet sprouts in a perforated bucket, place the bucket in the Cyclone and in about 30 seconds the water is removed.  This is necessary equipment for smaller growers.

The ISS Air Knife System is an in-line system that removes water without production labor other than clean up.  The sprouts move along a vibrating table that is identical to the ISS Vibrating Huller.  Several "air knives", are placed above the table to blow the water off the sprouts.  The evaporation can help cool the sprouts as the sprouts move freely onto a packaging machine or packing table.  This is the equipment of choice for larger growers.

 

Packaging the Sprouts

Sprouts are packaged in a variety of packages and materials.  This is where a great deal of money and labor can be saved with careful planning.  Your ISS sales person can help you find a package and process that is best for your size and situation.

An Example of the Product Flow for Producing Bean Sprouts

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