Soybean processing

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					                        FACT SHEET

Soybean Processing
     DR. LAWRENCE JOHNSON
     CENTER FOR CROPS UTILIZATION RESEARCH
     IOWA STATE UNIVERSITY
     AMES, IOWA 50010

     DR. KEITH SMITH
     KEITH SMITH AND ASSOCIATES
     15 WINCHESTER ROAD
     FARMINGTON, MO 6340
Soybeans are a relatively new crop    oil crop. The protein fraction of       value of soybeans based on their
in the United States; first commer-   soybeans finds its way into soy-        composition and current prices
cially grown in the 1920Õs as a       bean meal as a livestock feed           of soybean meal and oil. This
forage crop and for Ògreen            ingredient, as soy protein ingredi-     program demonstrates the direct
manureÓ fertilizer, and then as a     ents for the food industry and for      relationship between the composi-
source of vegetable oil for food      industrial uses (paper coatings,        tion of the soybean and the value
and protein for livestock feeding.    adhesives, etc.).                       of the products that can be
In the 1950Õs and 1960Õs, soybeans                                            produced. The program also
were referred to as Ò The             Soy oil has found many food uses        documents the added pounds of
Cinderella Crop,Ó and later in the    due to its excellent nutritional        product and the value of soybeans
1970s and 1980s as ÒThe Gold that     qualities, widespread availability,     containing higher amounts of oil
Grows.Ó Soybeans are extremely        economic value and wide-use func-       and protein. In general, the
important to the U.S. farm econo-     tionality. Soy oil is also an           processor will obtain from each
my, valued at about $15 billion       important ingredient for industrial     bushel of soybeans (60 pounds)
dollars, annually. Soybeans have      products such as paints, plastics,      about 10.5 pounds of oil and 48
changed U.S. agriculture in           lubricants and biofuels. Other by-      pounds of meal, and the remainder
many ways.                            products of soybean                     is shrinkage and moisture loss.
                                      processing include soybean hulls -      (A copy of the computer program
Soybeans have value due to their      mainly used in animal feeds and         is available at
high quality oil and protein.         as a source of soy fiber, and soy       http://www.stratsoy.uiuc.edu/epv/).
Historically, soy protein products    lecithin phospholipids - a nutrition-
account for about two-thirds of the   al supplement and functional            Soybean Processing
value of soybeans with the balance    emulsifying food ingredient.            Description
coming from the oil fraction. For                                             In the 1930Õs, soybeans were
this reason, many refer to soybeans   Researchers at Iowa State               mechanically processed using
as a protein crop as opposed to an    University developed a computer         hydraulic or screw presses (often
                                      program that estimates the process      known in the industry as
                                                                              expellers), which squeezed out the
                                                                              oil of the heated or cooked soy-
                                                                              beans. In the late 1940Õs and early
                                                                              1950Õs, most of the industry con-
                                                                              verted to the solvent-extraction
                                                                              process, which removes more oil
                                                                              from the soybean. Today, more
                                                                              than 99 percent of the U.S. pro-
                                                                              cessing capacity is using the
                                                                              solvent extraction process. U.S.
                                                                              soybean meal is produced in large
                                                                              crushing facilities that produce
                                                                              meals of consistent high quality.
                                                                              Several of these plants process
                                                                              more than 3,000 tons per day.

                                                                              The solvent extraction process is
                                                                              shown in Figure 1. The first step
Screwpress.                                                                   in the solvent-extraction process
                                                                              involves cleaning the soybeans to
                                                            loosen the hull, which     as meats. Often times, the hull
                                                            improves dehulling.        fractions from the aspirators are
                                                            The beans are cracked      passed over a gravity table to
                                                            into 8 to16 pieces by      salvage small pieces of meats that
                                                            passing them through       are aspirated along with the hulls.
                                                            corrugated rolls of        There are several advantages for
                                                            rollermills. A consis-     removing the hull: less total
                                                            tent bean size is          volume to process, which means
                                                            important to assure that   greater extraction output per day
Modern solvent-extraction soybean plant.                    the small beans will be    and improved protein content of
                                                            cracked properly.          the meal.
           remove the foreign material and
           drying the soybeans to approxmate-     The soybean hulls, which account     The cracked soybean meats are
           ly 9.5 percent moisture. The beans     for about 8 percent of the soy-      heated to about 165¡ F to soften
           are tempered where the moisture        bean, are removed by aspiration.     them prior to flaking. If the
           content is allowed to equilibrate to   The dehulled soybeans are known      soybean meals are not properly
                                                                                       cracked and conditioned, the
                                Solvent Extraction                                     flaking may not achieve the
                                                                                       desired cell rupture or distortion
                                                                                       necessary for efficient extraction
                                                                                       and/or produce excessive fine
                                  CLEANING
                                                                                       material that interferes with
                                                                                       efficient extraction. Highly
                                 CRACKING                                              distorted cells extract more easily.
                                                  ASPIRATING      GRAVITY
                                                                  TABLING              The heated and cracked meats are
                                                                                       passed through a roller mill
                                                                                       equipped with smooth surfaced
                                                                                       rolls to produce flakes about 10-
                               CONDITIONING
                                                                                       12 thousandths of an inch in
                                  FLAKING                                              thickness.

                                                                                       The flakes are then conveyed
            EVAPORATING                             EXPANDING
                                                                                       either directly to the extractor or
                                                                                       alternatively to an expander.
                                                                                       However, in recent years, the
   STRIPPING                      SOLVENT
                                EXTRACTING                                             industry has adopted a practice
                                                                                       first used in Brazil, where
                                                                                       soybean flakes are passed though
                                                                                       an extruder-like device known as
                                   MEAL
                              DESOLVENTIZING
                                                                                       an expander. Expanders produce
                                 TOASTING                                              a porous pellet with increased cell
                                                                                       rupture and greater density. The
                                  COOLING                                              advantages of using expander
                                 GRINDING                                              equipment are the ease of
                                                                                       extracting oil from flakes, the
                                                                                       solvent drains more completely,
                                                                                       thus reducing the amount of

Figure 1
solvent that must be evaporated from       The finished meal from dehulled           able than other oilseed meals. These
the meal, and the through-put capacity     soybeans will contain less than 1.5       meals find great use in dairy rations
of the extractor is increased. Plants      percent crude fat and about 48            to balance the amino acids supplied
vary in the amount of flakes being         percent protein, and is referred to as    by alfalfa forage, or corn-based by-
expanded from one-third to all flakes      high protein meal. In some soybean        products.
produced. Some plants have problems        processing operations, soybean hulls,
with excessive solvent drainage and        or soybean mill-run, are added back       Recently a third process, known as
reduced extraction when expanding          to the meal to adjust the protein         extruding-expelling, has been
more than one-third of the flake stream.   levels of the meal prior to grinding.     developed in which a dry extruder
                                           This allows the soybean processor to      replaces other steam-heating devices
There are several different types of       produce soybean meals that meet the       ahead of the screw presses and
extractors (chain and basket types), but   end-user specifications for protein       eliminates the need for generating
they all operate in a similar              and fiber.                                steam (Figure 3). These plants are
manner, involving percolation of the                                                 relatively small, typically processing
solvent through a bed of flakes and/or     Soybean meal can also be produced         5 to 25 tons of soybeans per day.
expanded material. The flakes are          by mechanically extracting the oil        Approximately 70 extruding-
washed in a countercurrent manner          from soybeans (Figure 2). The             expelling plants have been built for
with hexane, a petroleum distillate.       screw-press process involves heating      soybeans in the United States.
This solvent solubilizes the soybean       whole soybeans and the oil is             Usually they are farmer owned and
lipid material, and through a series of    mechanically squeezed out of the          provide meal to nearby livestock
steps, the hexane-oil mixture is           beans. The heat generated by fric-        feeders. These plants are also ideally
separated. The oil-rich extract called     tion of the screw presses destroys the    suited for identity-preserved process-
miscella is evaporated and the solvent     anti-nutritional factors in raw soy-      ing and for marketing certified
is recycled to the extractor.              beans. These specialized meals have       organic or non-genetically modified
                                           higher levels of residual oil (energy),   products or, in some cases, soybean
The soybean flakes, with the oil           lower protein contents, greater rumen     meals and oils with specific
removed, are called Òspent flakes.Ó        by-pass values and are more palat-        enhanced traits achieved by
From the extractor, the spent flakes are
conveyed to a desolventizer-toaster for                                          Screw Pressing
removing undrained hexane. The
process involves heating the spent
flakes to evaporate the hexane and
sparging steam to carry away hexane
                                                                CLEANING
vapors. This process also provides for
toasting of the meal to inactivate                                                       CRACKING           ASPIRATING

enzymes like urease and trypsin
inhibitors that may reduce the                                   DRYING
digestibility and nutritional value of                         OR COOKING
the meal.
                                                             SCREW PRESSING                        MEAL GRINDING
From the desolventizer-toaster, the
meal will go to a dryer-cooler where
                                                                 SETTLING                          MEAL COOLING
the meal is dried to about 13-14
percent moisture and cooled for safe                        POLISH FILTERING
storage. The meal is then screened and
ground with a hammer mill to produce
a uniform particle size prior to
shipment to the end user.

                                           Figure 2
                                                                                and/or the precision-fed cecec-
                                                                                tomized rooster assay to determine
                                                                                the digestibility of the protein in
                                                                                soybean meal. These methods use
                                                                                surgically modified animals to
                                                                                reduce the effects of intestinal
                                                                                microflora on amino acid excretion.
                                                                                The methods are known to detect
                                                                                differences in protein quality and
                                                                                amino acid digestibility between
                                                                                protein sources and meals processed
                                                                                using different heat treatments.


Inside a modern extruding/expelling soybean plant.                              There are numerous references in
                                                                                the literature showing the digestibil-
traditional breeding or genetic          Soybean Meal Quality                   ities of the amino acids in soybean
engineering. The characteristics of      Assays                                 meal are near 90 percent and signifi-
extruded-expelled meal are substan-      Even though soybean meal is one of     cantly greater than other oilseed
tially similar to screw-pressed meal.    the most consistent and high-quality   protein sources available to the feed
                                         protein sources available to the       formulator. Using these assays to
Composition of                           professional nutritionists, several    formulate diets on the basis of
Soybean Products                         animal and laboratory assays have      available amino acids can more
Soybean meal is a concentrated           been developed to monitor the          accurately target the speciesÕ amino
source of protein and energy, and        quality of soybean meal. In recent     acid requirements, reduce feed
is lower in fiber than most other        years, several research groups have    levels of supplemental protein and
oilseed meals available to the feed      used the illeal-cannulated pig assay   reduce nitrogen in animal waste.
manufacturer. The higher protein,
energy and lower fiber content of
soybean meal allow nutritionists to                                Extrudeing/Expelling Process
formulate higher-energy diets that
are more efficient in the conversion
of feed to meat. The table on page
7 provides the typical compositions
                                                             CLEANING
of several soybean products that are
available to the feed manufacturer.                                                CRACKING            ASPIRATING


Over the years, the soybean
processor has developed processes
                                                            EXTRUDING
that produce soybean meals
of consistent quality. The heat                              EXPELLING                       MEAL GRINDING
generated during processing and/or                         (screw pressing)
desolventizing/toasting assures the
                                                             SETTLING                        MEAL COOLING
protease inhibitors present in raw
soybeans are denatured, and the                          POLISH FILTERING
digestibilities of the protein are
maximized. Soybean meal can be
included in animal diets at relatively
high levels without affecting
performance.
                                         Figure 3
The nutritionists have long sought a      variation is between soybean            nutrient characteristics favor
rapid chemical assay that could relate    processors located in various           soybean meal use by swine and
to protein quality. Simple crude pro-     countries. Monitoring quality and       poultry. The highly digestible
tein or amino acid assays provide         modifying the feed formulation          protein in soybean meal provides
information on the protein, but do        accordingly reduces concern over        high levels of available amino acids
not provide useful information on the     minor variation. Studies have shown     that can complement amino acids in
quality of the protein. Chemists          that soybean meal is one of the most    cereal grain for least-cost rations for
have used trypsin inhibitor analyses,     consistent protein ingredients          swine and poultry. It has often
urease activity, protein solubility in    available to the feed formulator.       been stated that efficient swine and
potassium hydroxide, protein solubil-                                             poultry rations are dependent on
ity in water and dye binding methods      Soybean Meal Use                        soybean meal and cereal grain.
to assay for protein quality (heat        The United Soybean Board has
damage). While urease activity has        estimated that about 46 percent of      In ruminant rations, soybean meal
merit in detecting under heating of       the soybean meal produced in the        has long been competitive with other
the meal and KOH protein solubility       United States is used by broilers,      protein ingredients, while
is related to over-processing; the        layers and turkeys (Figure 4). Swine    soybean growers see great growth
search goes on for a simple, quick,       uses another 25 percent of soy meal     in the use of soybean meal in
cheap and accurate method of meas-        production. Ruminants, beef cattle,     aquaculture. Soybean meal is
uring protein quality.                    dairy and sheep account for about 21    replacing fishmeal in aquaculture
                                          percent and the remaining 8 percent     feeds due to price, wide availability
The variation in compositional            finds its way into a large variety of   and nutritional properties.
values for soybean meal is small:         uses (petfoods, aquaculture, minor
some variation is seen between            feed uses, food and industrial uses).
processing plants, and the greatest       The combination of price and



                 Soybean Meal Use (20002/03)


                Food & Industrial          2.5
                        Other Feed         2.0

                      Aquaculture         .06
                          Petfoods          2.5
                              Dairy                8.5
                               Beef                    13
                             Swine                                    25
                            Poultry                                                              46

                                      0           10         20             30         40             50
                                                                  Percent (%)


             Figure 4
  Composition of Soybean Feed Ingredient Products


                          Soybean Meal                                 Soybeans    Soybean   Soybean
                             Solvent     Dehulled-Solvent   Expeller    Full-fat    Hulls     Millrun
Proximate Analyses
Dry Matter                %       90            88            89           90        91.0      88.0
Crude Protein             %       44.0          47.8          42.0         38.0      12.1      13.6
Ether Extract             %       0.5           1.0           3.5          18.0      2.1       1.4
Crude Fiber               %       7.0           3.0           6.5          5.0       40.1      40.7
Ash                       %       6.0           6.0           6.0          4.6       5.1       5.1
Ruminant Values
Ruminant Dig. Protein     %       37.5          46.6          35.5         34.1
Ruminant TDN              %       78            79            78           85        77        44.0
Energy Values
Poultry ME              Kcal/lb   1020          1125          1100         1520
                        Kcal/lb   1405          1425          1360         1610
Amino acids
Methionine                %       0.65          0.70          0.6          0.54
Cystine                   %       0.67          0.71          0.62         0.55
Lysine                    %       2.9           3.02          2.7          2.4
Tryptophan                %       0.60          0.70          0.58         0.52
Threonine                 %       1.7           2.0           1.7          1.69
Isoluecine                %       2.5           2.6           2.8          2.18
Histidine                 %       1.1           1.3           1.1          1.01
Valine                    %       2.4           2.7           2.2          2.02
Leucine                   %       3.4           3.8           3.8          2.8
Arginine                  %       3.4           3.6           3.2          2.8
Phenylalanine             %       2.2           2.7           2.1          2.1


Minerals
Calcium                   %       0.25          0.20          0.20         0.3       0.69      0.42
Total Phosphorus          %       0.60          0.65          0.60         0.6       0.21      0.21
Available Phosphorus      %       0.20          0.21          0.20         0.2
Sodium                    %       0.04          0.04          0.04         0.04
Potassium                 %       1.97          1.90          1.71         1.70      1.27
Chloride                  %       0.02          0.02          0.02         0.03
Magnesium                 %       0.27          0.27          0.25         0.21
Sulfur                    %       0.43          0.43          0.33         0.30
Manganese                 ppm     27.5          27.5          32.3         30.0
Iron                      ppm     120           120           160          75
Copper                    ppm     28            28            18           15
Zinc                      ppm     60            60            59           35
Selenium                  ppm     0.1           0.1           0.1          0.1


Reference: Feedstuffs, 75(38):16. (September 17, 2003).
Summary Comments
  Soybeans have greatly changed U.S. agriculture.                 has been tested so thoroughly over the past 75 years
  The soybean processing industry has grown over                  as soybean meal. Soybean-meal based diets set the
  the years and is producing a high-quality protein               performance standards to evaluate other protein
  ingredient that has the respect of professional                 ingredients and to establish prices for alternative
  nutritionists. Probably no other feed ingredient                protein ingredients.




  For more information, please contact:
  Dr. Lawerence Johnson
  Crops Utilization Research Center
  Iowa State University
  Ames, IA 50010 or

  Dr. Keith Smith
  Keith Smith and Associates
  15 Winchester Road
  Farmington, MO 63640




The SOYBEAN MEAL INFORMATION CENTER is sponsored by the Soybean Checkoff:
Including the checkoff boards from, Iowa, Kansas, Michigan, Minnesota, Nebraska,
North Dakota, Ohio, and the United Soybean Board

				
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