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Guar and Locust Bean Gums

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Guar and Locust Bean Gums
                                   O




Guar gum (guaran)
   Source
    S
    –   Cyamopsis tetragonolobus, a plant not unlike
           b      Grown in India, Pakistan, and the
        soybeans. G      i I di P ki t         d th
        U.S. Guar gum is from the seed endosperm
    –                          l t b
        Sometimes also called cluster bean
   Structure
    –   Mannose:Galactose = 2:1 (best data 1.8:1)
    –   MW = 1-2 x 106 daltons
                    O




Guar gum


           A guar plant,
           Cyamopsis tetragonolobus
                                 O




 Guar gum harvesting




In the US, this is done by machine, much like the
harvesting of soybeans
                              O




Guar gum--Structure


               Alpha-1,6 linkage




           Beta-1,4
           Beta-1 4 linkage
                            O




Commercial guar gum
 73-87%
  73 87% guaran
 8-14% moisture
 3-6% protein
  1 4%
 1-4% fiber
 0.8-2.0% ash
  0.5-1.0% li id
 0 5 1 0% lipid
 Available in a variety of grades and mesh
  sizes
                                   O




Guar gum
   Hydrates rapidly in cold water to give
    hi hl viscous pseudoplastic di
    highly i           d l i dispersionsi
    –   A 1% dispersion has a viscosity of 4000 to
        7500 mPa.sec (
              P                       10 000
                     (very pure up to 10,000
        mPa.sec)
           i   f h              h     h
    A new view of the structure shows that
    the mannan backbone is not uniformly
      b tit t d
    substituted
G       G G GG G G         GG      G G G G       G
MMMMMMMMMMMMMMMMMMMMMMMMMM
                             O




Guar gum hydration
 Guar dispersions obtain about one-half of
  G     di      i     bt i b t         h lf f
  their ultimate viscosity in 10-15 minutes
    ith    heating
  with no h ti
 About 1 hour is required for full viscosity
  development
     g
 Higher ultimate viscosities will result
  from first heating, then cooling a
  dispersion of g
      p               gum
                 guar g
 Provides a non-slimy texture
                              O




Interactions with other gums
   Guar interacts with
    G    i t    t ith
    –   Starches
    –   Cellulose
    –   Agar
    –   -Carrageenan
    –   Xanthan
   Interaction may cause an increase in the
    viscosity of guaran dispersions
            y g            p
                                       O




    Guar-xanthan interaction
        Max viscosity depends on ionic strength
        b normally about 70 30
        but       ll b     70:30              Observed




                               Predicted



Xanthan 0         25         50            75        100
Guar 100          75         50             25         0
                                          O




Guar gum
   Uses
    U
    –   Processed cheese
          Minimizes   syneresis
    –   Ice cream
          Prevents
         P          i         l      h
                     ice crystal growth
    –   Meat
    –   Dressings and sauces
        D    i      d
    –   Beverages
   Use levels: 0.35-2.0%
                                   O




Guar gum uses
   Baked    d
    B k d goods
    –   Improves mixing
    –   Improves shelf life through moisture
        retention
    –   Prevents syneresis in pie fillings
    –   Controls spreadability in icings
                                      O




Locust bean gum
   Source
    S
    –   The carob tree (Ceratonia siliqua). Grows in
        the      East d Mediterranean. Also
        th near E t and M dit              Al
        known as St. John’s bread
    –            by early          ho sed
        Planted b earl traders who used the
        uniformly sized seeds for measurement of
        weight (originally one karat was the weight
        of one carob seed)
          Seeds                 g           p y pods are
                are used to make gum and empty p
          used to make carob (chocolate extender)
                                        O




Locust bean gum
   Structure
    St t
    –   A galactomannan (Man:Gal = 4:1; best data
        3.9:1)
        3 9 1)
    –   MW 300,000 to 360,000
          Contains
         C t i      long stretches of b
                     l     t t h     f bare mannose
           backbone (up to 80 D-mannose units long) which
                 p             y g
           is responsible for synergism
          These sections alternate with sections of up to 25
           mannose units where each mannose is substituted
           with a galactose
                           O




Locust bean gum


            Alpha-1,6 linkage




        Beta-1,4
        Beta-1 4 linkage
                             O




LBG properties
 Slightly l bl i          t        t
  Sli htl soluble in room temperature
  water
 For good dissolution, heat to 85oC
       g         gels alone, but does gel
 No significant g         ,          g
  when mixed with
    –    g
        agar
    –   -carrageenan
    –   xanthan
                                 O




         LBG-xanthan gels
           ngth
   Gel stren
   units
   G
   u




Xanthan 0         20   40   60       80   100
LBG     100       80   60   40       20    0
                                O




LBG--Structure and uses




Uses
   Ice cream, cheese products, meat products
                            O




LBG-carrageenan
 Addition f       ll      t f
  Additi of a small amount of LBG
  makes -carrageenan gels less brittle and
  l prone to syneresis
  less      t         i
 Replaces stronger carrageenan-
  carrageenan junction zones with weaker
  carrageenan-LBG junction zones
                             O




LBG-xanthan
 When hot l ti         f   th (non-
  Wh a h t solution of xanthan (
  gelling) and LBG (non-gelling) is cooled,
       li f     d
  a gel is formed
 Due to junction zone formation between
  the two polysaccharides
                                O




   Synthetic LBG

Guar



                        Alpha-galactosidase




         Synthetic LBG: Man;Gal = 6.7:1
                  O


Carrageenan- or
xanthan-LBG interaction



                      Carrageenan or
     LBG              xanthan
                                   O




LBG uses
   Dairy  d t     d frozen d
    D i products and f            t
                            desserts
    –   85% of LBG is used in these applications
    –   Rarely used alone; more often in
        combination with CMC, carrageenan,
         anthan g ar g m
        xanthan or guar gum
   Cheese
    –   Speeds coagulation and increases curd yield
    –   Enhances body and prevents syneresis
   Use levels: 0.15-0.8%
                                   O




LBG uses
   Ground meat products (
    G    d    t                 )
                   d t (sausages)
    –   Binder and stabilizer
    –   Aids extrusion
    –   Increases water binding and yield
    –   Improves shelf life
                  g gravies
    Sauces, dressings, g
    –   Provides mouthfeel and controls water
        absorption
   For more uses see BeMiller, p. 252
                                O




Galactomannan labeling
   Guar
    G
    –   Guar gum
   LBG
    –   Locust bean gum or carob gum
                             O




Tara gum
 From seeds of t
  F                   h b (S. America)
           d f tara shrub (S A      i )
 Man:Gal ratio is intermediate between
  guar and locust bean gum
 Gels with
    –   Kappa-carrageenan
    –   Xanthan
   But gels are weaker than those produced
    with LBG
                            O




Tara gum
 Viscosities are higher after heating
  Vi    iti       hi h    ft h ti
  dispersions
 1% solution: viscosity will be 3500-5000
  mPa.s
 Used in dairy products, mainly ice cream,
         y g
  frozen yogurt and cream cheese (it(
  prevents syneresis)
 Not used very much due to cost

				
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