Acacia Gums - American Chemical Society

Chapter 5

Acacia

Gums

Stabilizers for Flavor Encapsulation

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on December 20, 2016 | http://pubs.acs.org Publication Date: May 31, 1988 | doi: 10.1021/bk-1988-0370.ch005

F. Thevenet Iranex, S. A. 4, rue Frédéric Passay, 92205 Neuilly-sur-Seine, France Acacia gum's unique structure makes it an excellent c a r r i e r for flavor encapsulation. A natural product - t r a d i t i o n a l l y c o l l e c t e d in the bush by nomads - it is now possible to r a t i o n a l i z e , through many plantations, the harvest and q u a l i t y of the gum. Starting from t i s s u e s , i n - v i t r o c u l t i v a t i o n has already begun in our laboratories preparing the Third Generation Acacia gums. A few examples will underline how far t h i s research has advanced. This paper will also cover the association of acacia gums which are now filling i n for t r a d i t i o n a l gum arabic i n the aromatic industry. Different formulations will be studied for making flavors i n powder form using acacia gums as protective c o l l o i d s . Organoleptic character and shelf-life will be v e r i f i e d according to the type and concentration of the gum.

A c a c i a gums, commonly c a l l e d gum a r a b i c , a r e n a t u r a l v e g e t a b l e c o l l o i d s o b t a i n e d by e x u d a t i o n s from the t r u n k and branches o f leguminous p l a n t s o f t h e f a m i l y o f A c a c i a . There a r e s e v e r a l hundred s p e c i e s o f A c a c i a ; o n l y a few o f which a r e a b l e t o produce gum and these are m a i n l y c o n c e n t r a t e d i n t h e s u b - d e s e r t r e g i o n o f t h e A f r i c a n c o n t i n e n t : t h e SAHEL. The main p r o d u c i n g c o u n t r i e s o f gum a r a b i c a r e t h e Sudan, S e n e g a l , M a l i and N i g e r i a . The w o r l d market f o r t h i s gum, which i s used as an i n g r e d i e n t and a d d i t i v e , i s around 6 0 , 0 0 0 metric tons. K o r d o f a n , a Sudanese r e g i o n p r o d u c i n g gum a r a b i c , has g i v e n i t s name as a tradename t o the gum which comes from the A c a c i a Senegal. The A c a c i a Senegal has been used on o c c a s i o n s as a r e f e r e n c e f o r pharmacopoeias and d i f f e r e n t s t a n d a r d s r e g u l a t i n g gum a r a b i c b u t i n c r e a s i n g l y t h e r e l a t e d s p e c i e s o f A c a c i a are b e i n g s o l d i n t h e market. The gum a r a b i c i s c o l l e c t e d d u r i n g t h e d r y season which runs from November t o May. The t r e e s a r e f i r s t tapped by the v i l l a g e r s and then the e x u d a t i o n b e g i n s . A f t e r e x u d a t i o n and d r y i n g t h e gum forms nodules which are then c o l l e c t e d by hand and l a t e r s o l d i n 0097-6156/88/0370-0037$06.00/0 • 1988 American Chemical Society

Risch and Reineccius; Flavor Encapsulation ACS Symposium Series; American Chemical Society: Washington, DC, 1988.


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markets where they a r e bought by w h o l e s a l e r s . The gum i s then s o r t e d by hand t o s t a n d a r d i z e t h e p r o d u c t , baged and e x p o r t e d . D e s p i t e two h a r v e s t s p e r y e a r (December and A p r i l ) , t h e q u a n t i t y o f gum o b t a i n e d from each t r e e g e n e r a l l y does n o t exceed 300 g. Even though t h e q u e s t i o n i s s t i l l b e i n g s t u d i e d , t h e p r o d u c t i o n o f gum seems t o be a response t o some type o f a g r e s s i o n upon t h e A c a c i a t r e e : i n j u r y o f t i s s u e s o r i n f e c t i o n by micro-organisms. Encouraging r e s e a r c h i s now b e i n g conducted on e x p e r i m e n t a l p l a n t a t i o n s t o study t h e i n f l u e n c e s t h a t v a r i o u s t r e a t m e n t s ( s p r a y i n g , f e r t i l i z e r s ) e x e r t on gum p r o d u c t i o n . Some p r o d u c t i o n comes from " w i l d " t r e e s but i n c r e a s i n g l y t h e gum i s h a r v e s t e d i n o r g a n i z e d gum t r e e p l a n t a t i o n s . A t r a d i t i o n a l method o f c u l t i v a t i o n i s b e i n g used. F i r s t the seeds a r e s e l e c t e d and a r e p l a c e d i n a hothouse and watered r e g u l a r l y t o a s s i s t g e r m i n a t i o n . The young s e e d l i n g i s then t r a n s p l a n t e d i n a c a r e f u l l y p r e p a r e d p l o t o f l a n d a t t h e s t a r t o f t h e r a i n y season. Four y e a r s l a t e r t h e A c a c i a t r e e can be tapped t o produce gum. A c a c i a gum t r e e p l a n t a t i o n programs i n v o l v i n g thousands o f h e c t a r e s are b e i n g c a r r i e d o u t i n d i f f e r e n t A f r i c a n c o u n t r i e s w i t h t h e t e c h n i c a l a s s i s t a n c e o f s p e c i f i c gum development a s s o c i a t i o n s . I t must be n o t e d t h a t i n a d d i t i o n t o p r o v i d i n g gum, A c a c i a p l a n t a t i o n s c a r r y numerous advantages i n these d e s e r t r e g i o n s . They a r e an e f f i c i e n t means o f combatting d e s e r t i f i c a t i o n by f i x i n g s o i l s , i m p r o v i n g f e r t i l i z a t i o n o f t h e crop growing l a n d ( n i t r o g e n , enrichment ( a legume)) and a permanent source o f income which s e t t l e s nomadic p e o p l e s . I n a d d i t i o n t o these v i l l a g e p l a n t a t i o n s , we a t o u r M a r s e i l l e s Research C e n t e r a r e d e v e l o p i n g a g e n e r a t i o n o f A c a c i a p l a n t s by i n v i t r o c u l t i v a t i o n . P r o d u c t i o n o f A c a c i a p l a n t s by seed g e r m i n a t i o n does n o t a l l o w a l l t h e p r o p e r t i e s o f t h e donor t o be g e n e t i c a l l y reproduced. On t h e c o n t r a r y , b i o t e c h n o l o g y a l l o w s us through m i c r o - p r o p a g a t i o n t o m u l t i p l y and c l o n e specimens which a r e a l l g e n e t i c a l l y i d e n t i c a l t o t h e i n i t i a l specimen. The advantages o f t h i s method a p p l i e d t o A c a c i a c u l t i v a t i o n a r e i m m e d i a t e l y apparent: p e r f e c t s e l e c t i o n o f s p e c i e s , c o n s i s t e n t gum y i e l d s , i n c r e a s e d gum o u t p u t , improved s t a n d a r d i z a t i o n o f exudates. For t h i s t e c h n i q u e , a c u t t i n g i s taken from a r i c h gum p r o d u c i n g a d u l t specimen. T h i s c u t t i n g w i l l be decontaminated and then i n s e r t e d i n t o a m u l t i p l i c a t i o n medium c o n t a i n i n g hormones needed t o form new buds. Some o f t h e d e s i r a b l e specimens t h a t r e s u l t from t h i s budding are i n s e r t e d i n t o an inducement medium t o r o o t . From one bud, f o u r buds take r o o t each month. The i n c u b a t i o n stage i n p h y t o t r o n l a s t s 15 days and i s f o l l o w e d by a f u r t h e r 15 days o f r o o t i n g i n a tube i n t h e presence o f hormones m a i n t a i n e d a t a c o n t r o l l e d temperature and h u m i d i t y . A f t e r two weeks o f t r a n s p l a n t i n g and growth i n a hothouse, t h e growth i s then completed by 2 months i n a c o n v e n t i o n a l n u r s e r y . We l a c k t h e e x p e r i e n c e t o a c c u r a t e l y e v a l u a t e t h e output g a i n o b t a i n e d from m i c r o - p r o p a g a t i o n , b u t compared t o t h e development o f r o s e bushes, 800,000 new r o s e bush p l a n t s a r e o b t a i n e d i n 11 months from 3 donors; t h e t r a d i t i o n a l s e e d l i n g method r e q u i r e d 3 y e a r s from 10,000 donors. I n crude form ( e x p o r t e d from A f r i c a ) A c a c i a gum c o n t a i n s a percentage o f i m p u r i t i e s c o m p r i s i n g m i n e r a l and v e g e t a b l e m a t t e r



5.

THEVENET

Acacia Gums: Stabilizers for Flavor Encapsulation

39

i n h e r e n t i n the system o f c o l l e c t i o n . To e l i m i n a t e these i m p u r i t i e s , the o l d method t r e a t e d the p r o d u c t by a dry p r o c e s s u s i n g d i f f e r e n t s t a g e s : c r u s h i n g , p u l v e r i z a t i o n , s e l e c t i o n and s i f t i n g . Increasingly A c a c i a gums are s o l d i n spray d r i e d form. Before spray d r y i n g , the gum i s p l a c e d i n a water s o l u t i o n and i s then f i l t e r e d and c e n t r i fuged. T h i s ensures l e v e l s o f i m p u r i t i e s l e s s than 0.04%. I n a d d i t i o n b a c t e r i o l o g i c a l q u a l i t y i s improved s i n c e the s o l u t i o n undergoes p a s t e u r i z a t i o n and the p r o d u c t i o n batches are s t a n d a r d i z e d t o be p e r f e c t l y u n i f o r m . A l l t h e s e A c a c i a gums and/or s y n e r g i s t i c c o m b i n a t i o n s o f A c a c i a are s o l d w i t h guarantees o f c o l o r , v i s c o s i t y and l e v e l s o f i m p u r i t i e s . F u r t h e r t r e a t m e n t such as s t e r i l i z a t i o n by gamma o r beta r a d i a t i o n are a p p l i c a b l e t o A c a c i a gums w i t h o u t a l t e r a t i n g the products f u n c t i o n a l p r o p e r t i e s . A c a c i a gums belong t o the group o f complex a c i d p o l y s a c c h a r i d e s o f p r i m a r i l y u r o n i c a c i d type and o c c u r i n g as a mixed s a l t (sodium, c a l c i u m , magnesium and p o t a s s i u m ) . Owing t o the complex c h a r a c t e r o f t h i s polymer, the s t e r o c h e m i c a l o r g a n i z a t i o n o f the m o l e c u l e i s not c o m p l e t e l y known even though the q u a l i t a t i v e and q u a n t i t a t i v e a n a l y s i s o f the sugars i s . N e v e r t h e l e s s , h y d r o l y s i s o f a gum a r a b i c s o l u t i o n i n an a c i d medium and a n a l y s i s o f the sugars by paper chromatography r e v e a l s the presence o f the f o l l o w i n g s u g a r s : D G a l a c t o s e , L A r a b i n o s e , L Rhamnose, D p a r t i a l l y m e t h y l a t e d glucuronic acids. C e r t a i n authors a l s o f i n d traces of glucose. I n the case o f A c a c i a Senegal exudate, the percentage o f the c o n s t i t u e n t sugars are q u a n t i t a t i v e l y 40% f o r g a l a c t o s e , 24% f o r a r a b i n o s e , 13% f o r rhamnose and 23% f o r g l u c u r o n i c a c i d s . The m o l e c u l a r s t r u c t u r e may be r e p r e s e n t e d by the F i g u r e 1; i t i s i m p o r t a n t t o note t h a t the main s k e l e t o n comprises g a l a c t u p u r a n o s e u n i t s w i t h 1-3 bonds w i t h the o t h e r sugars connected by 1-6 bonds. I t i s a l s o w o r t h n o t i n g t h a t the a c i d p a t t e r n s are a t the p e r i p h e r y o f the m o l e c u l e and are t h e r e f o r e v e r y a c t i v e i n c r e a t i n g an a n i o n i c environment. The m o l e c u l a r weight i s not v e r y h i g h : 500,000 d a l t o n s . However by g e l e x c l u s i o n chromatography i t i s easy t o h i g h l i g h t the presence o f h i g h m o l e c u l a r weight polymers as w e l l as polymers w i t h l o w e r m o l e c u l a r weight and the same sugar c o m p o s i t i o n . Only the degree o f p o l y m e r i z a t i o n i s d i f f e r e n t ; d i f f e r e n c e s i n p r o p e r t i e s may r e s u l t . T h i s g l o b u l a r and h i g h l y branched s t r u c t u r e o f gum a r a b i c i s r e s p o n s i b l e f o r the v i r t u a l absence o f the development o f h i g h v i s c o s i t y when compared w i t h o t h e r c o l l o i d s c o n t a i n i n g s i m i l a r sugars i n t h e i r m o l e c u l a r s t r u c t u r e s and comparable m o l e c u l a r w e i g h t s . The major d i f f e r e n c e between c o l l o i d s such as Guar, T r a g a c a n t h and Carrageens i s the l i n e a r m o l e c u l a r o r g a n i z a t i o n which w i l l form more r i g i d s t r u c t u r e s w i t h h i g h v i s c o s i t y ( o r g e l i f i e d s t r u c t u r e s ) t h r o u g h b r i d g e s o f hydrogen bonds between the d i f f e r e n t l i n e a r c h a i n s and water. (See Table I ) The ash c o n t e n t , p r o t e i n c o n c e n t r a t i o n , maximum i n t r i n s i c v i s c o s i t y , e q u i v a l e n t weight and r o t a t o r y c a p a c i t y are some o f the f e a t u r e s s p e c i f i c t o each s p e c i e s o f A c a c i a exudate. The p h y s i c a l p r o p e r t i e s o f gum a r a b i c are due t o i t s h i g h s o l u b i l i t y i n water (up t o 5 0 % ) , s t a b i l i t y i n an a c i d medium (up t o ph3), b i n d i n g and a d h e s i v e p r o p e r t i e s , a f f e c t s upon c r y s t a l growth, f i l m forming and s u r f a c e a c t i v e f e a t u r e s . The l a s t two f u n c t i o n a l


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Table I .

COMPARATIVE VISCOSITIES BETWEEN VARIOUS COLLOIDS S o l u t i o n a t 1% c o n c e n t r a t i o n i n w a t e r B r o o k f i e l d RVT 20 rpm 3500 3000 700 500 5

Guar gum L o c u s t Bean Gum Tragacanth Carrageens (Lambda) Gum A r a b i c Downloaded by UNIV OF CALIFORNIA SAN DIEGO on December 20, 2016 | http://pubs.acs.org Publication Date: May 31, 1988 | doi: 10.1021/bk-1988-0370.ch005

ENCAPSULATION

cps cps cps cps cps

p r o p e r t i e s w i l l now be d i s c u s s e d s i n c e they are the prime reasons f o r the a p p l i c a t i o n o f gum a r a b i c i n the f l a v o r i n d u s t r y . In the a r o m a t i c i n d u s t r y A c a c i a gums are used as s t a b i l i z e r s and e m u l s i f i e r s t o prepare c o n c e n t r a t e s f o r beverages and as an e n c a p s u l a t i n g agent t o produce aromas i n powder form. More g e n e r a l l y they r e n d e r a l l l i p o s o l u b l e substances ( v i t a m i n s , f a t s , c o l o r i n g a g e n t s ) h y d r o d i s p e r s a b l e and ensure t h e i r e f f e c t i v e p r o t e c t i o n a g a i n s t o x i d a t i o n , h y d r o l i s i s and o t h e r more s u b t l e c h e m i c a l r e a c t i o n s i n d u c e d by temperature, pH, e t c . The p r e p a r a t i o n o f c o n c e n t r a t e s f o r beverages e n t a i l s the f o l l o w i n g s t a n d a r d s t a g e s : - manufacture o f the aqueous phase by d i s s o l v i n g A c a c i a gums i n water ( s t a b i l i z i n g - e m u l s i f y i n g agents^ w i t h o t h e r a d d i t i v e s (preservatives, coloring agents), - p r e p a r a t i o n o f the o i l phase by d i s s o l v i n g the w e i g h t i n g c l o u d i n g agent i n the a r o m a t i c c o m p o s i t i o n ( p u r i f i e d and d e s o d o r i z e d Damar gum, e s t e r i f i e d colophany, SAIB, brominated oils). The n e x t s t e p i s t o mix the o i l phase w i t h the aqueous phase and succeed i n r e d u c i n g the o i l phase i n t o g l o b u l e s w i t h a diameter o f 1 micron. E x p e r i e n c e shows t h a t the n a r r o w e r the d i s t r i b u t i o n around 1 m i c r o n , the g r e a t e r the s t a b i l i t y . The o i l g l o b u l e s w i l l then remain p e r f e c t l y s t a b l e i n the c o n c e n t r a t e and i n the beverage. F o l l o w i n g poor s t a b i l i z a t i o n , c o a l e s c e n c e o f the p o o r l y d i s p e r s e d o i l phase w i l l o c c u r and t h i s w i l l produce a w h i t e o r c o l o r e d r i n g a t the top o f the b o t t l e o r a l o s s o f t u r b i d i t y a t the bottom o f the b o t t l e . To a c h i e v e t h i s r e d u c t i o n i n s i z e , the a q u e o u s / o i l phase m i x t u r e i s s u b j e c t e d t o pre-homogenization u s i n g a h i g h s h e a r i n g mixer t o reduce the s i z e o f o i l g l o b u l e s t o 5 microns f o l l o w e d by homogenization a t s e v e r a l s t a g e s up t o 250 kg/cm . The s i z e o f the g l o b u l e s under m i c r o s c o p i c e x a m i n a t i o n must be 1 micron. For the purpose o f f i n e a n a l y s i s i t i s p o s s i b l e t o s t u d y the weighted d i s t r i b u t i o n o f the p a r t i c l e s i z e by use o f the C o u l t e r Counter method ( F i g u r e 2). The t r a d i t i o n a l c o n c e n t r a t e f o r m u l a f o r beverages ( t y p e 1%) i s as f o l l o w s : 2

Aromatic composition R e s i n ( w e i g h t i n g agent) Spray d r i e d A c a c i a gum Water

6 t o 8% 3 t o 8% 15 t o 20% q.s. 100%

S y n e r g i s t i c combinations o f A c a c i a gums (Emulgum type R) e x i s t on the market w h i c h are s p e c i a l l y f o r m u l a t e d t o develop e m u l s i f y i n g



5.

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Acacia

Gums: Stabilizers for Flavor Encapsulation

GAL AÇA GAL ARA 4-MeGlcA—GAI GAL G £ L GAL ARA ARA G £ L — G Â L — GIcA ARA ARA — GAL ARA ARA GAL GAL — GAL GAL — GAL GAL ARA—GAL GAL — ARAf — G*L — ARA GIcA GIcA RHA GAL- -GAL- -ARA ARA GAL R

Figure 1.

Diameters

orange o i l

3,5 %

Emulgum (Acacia gums)

6,0 %

E s t e r i f i e d colophany

Weights

0.50 0.63 0.79 1.00 .26 .59 .00 -52 .17 4.00 5.04 6.35 8.00 10.08 12.70 16.00

1Q0% water D i f f e r e n t i a l Weights ("

D i f f . Weights 1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

(Stephen 1982).

6,5 %

q.s. Percentage i n D i f f e r e n t i a l

RHA AÇA — GAL GAL— ARA

A

Proposed structure f o r gum arabic

Formulation :

Range

H

41

25.7 18.9 12.2 8.1 6.7 5.8 4.2 3.2 2.6 2.8 1.7 2.2 1.3 1.4 1.0 1.9

25

20

15

10

51 π -

ON

OJ

-

o ο

- - Ο ui v_n o O J vo r v j o o i o oc

0> ο ο

Diameters Figure 2. T y p i c a l d i s t r i b u t i o n of o i l phase i n an oil/water emulsion f o r soft drinks (Coulter Counter).



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ENCAPSULATION

c a p a c i t y 4 t o 5 times g r e a t e r than t h a t o f t r a d i t i o n a l A c a c i a gum, a mere 3 t o 5% o f these blended c o n t r o l l e d A c a c i a gums are used. T h i s f o r m u l a t e d c o n c e n t r a t e i s d i l u t e d w i t h 1% sugar syrup a t 65 B r i x i n the presence o f c i t r i c a c i d t o o b t a i n the s y r u p . T h i s syrup w i l l then be d i l u t e d 5 t i m e s w i t h c a r b o n a t e d water t o o b t a i n the f i n a l d r i n k a t 10 B r i x . Because o f the n a t u r a l d i f f e r e n c e s i n o i l s , the g e n e r a l f o r m u l a must be a d j u s t e d f o r each o i l c o m p o s i t i o n and each type o f r e s i n employed. V a r i o u s parameters must be c o n t r o l l e d t o ensure good e m u l s i o n stability: - the o i l phase must have a d e n s i t y as c l o s e as p o s s i b l e t o t h a t of the aqueous phase (d-1.03). The l e v e l o f w e i g h t i n g agent w i l l be c a l c u l a t e d a c c o r d i n g t o d e n s i t y o f the r e s i n used (from 1.04 f o r Damar r e s i n t o 1.33 f o r the brominated o i l s ) . - Owing t o i t s f i l m f o r m i n g p r o p e r t i e s A c a c i a gum must c o v e r p e r f e c t l y each o i l g l o b u l e w i t h a c o l l o i d a l f i l m . As A c a c i a gum e m i t s n e g a t i v e charges around the c i r c u m f e r e n c e of i t s m o l e c u l e , e l e c t r i c r e p u l s i o n w i l l o c c u r between each o i l g l o b u l e so t h a t c o a l e s c e n c e i s p r e v e n t e d . The o i l g l o b u l e must be n e i t h e r too s m a l l as t h i s would cause the g l o b u l e s t o agglomerate nor too l a r g e (immediate r i s e ) . - F i n a l l y the v i s c o s i t y o f the aqueous phase i n d u c e d by the A c a c i a gum slows i n t e r n a l a g i t a t i o n and s t a b i l i z e s the system. The use o f A c a c i a gum as an e n c a p s u l a t i o n agent i s governed by the same p r i n c i p l e s as the p r e p a r a t i o n o f a s t a b l e l i q u i d e m u l s i o n . In the aqueous phase the c o l l o i d a l agents are made s o l u b l e . These agents are atomized c a r r i e r s which when d i s s o l v e d i n water p r o v i d e a u n i f o r m and f l e x i b l e f i l m around each f a t g l o b u l e . T h i s c o a t i n g w i l l ensure the s t a b i l i t y o f the aroma i n powder. The f i l m must p r o t e c t the aroma a g a i n s t o x i d a t i o n by the a i r o r l i g h t and prevent evaporation of v o l a t i l e matter. The most e f f i c i e n t c o l l o i d s are pure A c a c i a gums. For reasons of economy, m i x t u r e s o f A c a c i a gums and d e x t r i n may be used. As i n the p r e p a r a t i o n o f c o n c e n t r a t e s f o r beverages, the o i l phase t o be p r o t e c t e d w i l l be added t o the aqueous phase and the c o a t i n g w i l l be formed d u r i n g h o m o g e n i z a t i o n . The e m u l s i o n w i l l then be d r i e d by a t o m i z a t i o n w i t h a i r temperature a t the i n l e t o f 160 o r 180°C and a powder temperature a t the o u t l e t o f 85 t o 90°C. A t y p i c a l e m u l s i o n f o r m u l a f o r e n c a p s u l a t i o n on pure gum may be e x p r e s s e d as f o l l o w s : Aromatic composition Spray d r i e d A c a c i a gum Water

7% 28% q.s.

100%

The d r y substance c o n t e n t i s 35% and the f l a v o r c o n t e n t on the powder 20%. When m i x i n g a medium as w i t h gums and m a l t o - d e x t r i n s , the f o r m u l a becomes: Aromatic composition Spray d r i e d A c a c i a gums Malto-dextrins Water

10% 15% 25% q.s.

100%



5. T H E V E N E T

Acacia Gums: Stabilizers for Flavor Encapsulation

43

The s o l i d c o n t e n t o f the emulsion i s then 50% and the f i n a l d r i e d powder w i l l c o n t a i n 20% o f aroma. Once t h e aroma i s o b t a i n e d as a powder a t the o u t l e t o f the tower, i t i s n e c e s s a r y t o determine the q u a n t i t y o f aroma e f f e c t i v e l y f i x e d on the s u p p o r t . T h i s i s done by steam d i s t i l l a t i o n o f t h e powder. I n the case o f e n c a p s u l a t i o n on pure A c a c i a gum, t h e a t o m i z a t i o n e f f i c i e n c y ( r a t i o between the q u a n t i t y o f o i l r e c o v e r e d a f t e r w a r d s by steam d i s t i l l a t i o n and the t h e o r e t i c a l f i x e d q u a n t i t y ) i s 98%. The q u a n t i t y o f s u r f a c e o i l must a l s o be t e s t e d . I f the o i l i s n o t p r o p e r l y e n c a p s u l a t e d , i t w i l l be q u i c k l y o x i d i s e d . The q u a n t i t y o f s u r f a c e o i l may be determined by c o l d washing the powder w i t h hexane. S t a b i l i t y d u r i n g s t o r a g e may be t e s t e d by chromatographic a n a l y s i s o f a powder s u b j e c t e d t o a c c e l e r a t e d ageing i n an oven. The most p r a c t i c a l method remains t a s t e e v a l u a t i o n o f the atomized product by a p a n e l (Table I I ) . Table I I . ENCAPSULATION OF ORANGE OIL USING ACACIA GUMS Comparative c o m p o s i t i o n o f o i l b e f o r e and a f t e r spray d r y i n g n

Components A l p h a Pinène Sabinène Beta Pinène Myrène Octanal Limonène Linalcol Monanal Decanal Neral Géranial Valencène

~ ., Orange o i l

Spray d r i e d orange ^

0,31 0,347 0,055 1,488 0,129 97,77 1,059 0,062 0,216 0,139 0,252 0,174

0,30 0,333 0,10 1,469 0,129 94,05 1,039 0,061 0,517 0,139 0,22 0,162

I f the l i p o s o l u b l e c o l o r i n g agents a r e e n c a p s u l a t e d ( c a r o t e n e e t c . ) , t h e a b s o r p t i o n spectrum, i . e . c o l o r e v o l u t i o n must be f o l l o w e d by spectrophotometry. I f the q u a n t i t y o f o i l t o be f i x e d i n a d r i e d powder i s a parameter dependent on the end u s e , t h e f o r m u l a t o r can choose between d i f f e r e n t A c a c i a gums. With a t r a d i t i o n a l A c a c i a gum (exudate o f A c a c i a S e n e g a l ) , a d r y substance v a l u e o f 35% r e p r e s e n t s a maximum v a l u e b e f o r e spray d r y i n g . Beyond t h i s v a l u e the emulsion v i s c o s i t y i s t o o h i g h and d r y i n g i n s i d e t h e a t o m i z a t i o n tower does not take p l a c e s a t i s f a c t o r i l y . On the o t h e r hand, u s i n g a s y n e r g i s t i c c o m b i n a t i o n o f A c a c i a gums w i t h a h i g h e m u l s i f y i n g c a p a c i t y (Emulgum BV) and low v i s c o s i t y i n m i x t u r e w i t h m a l t o - d e x t r i n s , a d r y substance o f 50% and q u i t e a c c e p t a b l e a t o m i z a t i o n may be o b t a i n e d . By t h i s p r o c e s s t h e spray d r y i n g c o s t i s g r e a t l y reduced. A 4 month s t o r a g e s t u d y o f a powder c o n t a i n i n g 20% o f orange aroma shows, u s i n g chromatography i n t h e steam phase, t h a t e n c a p s u l a t i o n on a m i x t u r e o f Emulgum BV and m a l t o d e x t r i n w i t h 50% s o l i d s i n t o t h e d r y e r i s as e f f i c i e n t as e n c a p s u l a t i o n as pure A c a c i a gum w i t h 35% o f d r y s o l i d s i n t o the d r y e r .



44

FLAVOR

ENCAPSULATION

A r e c e n t s t u d y has been performed on v a r i o u s s p r a y d r i e d orange f l a v o r s { 2 0 % o i l f i x e d i n t h e powder) e n c a p s u l a t e d on v a r i o u s A c a c i a gums and on m i x t u r e s o f A c a c i a gums and m a l t o - d e x t r i n s . The aromas i n powder were t e s t e d by chromatography and then examined by e l e c t r o n i c microscopy. T h i s c l e a r l y shows t h e r e g u l a r and u n i f o r m f i l m c o v e r i n g each p a r t i c l e 10 t o 40 m i c r o n s i n d i a m e t e r . Prints of broken p a r t i c l e s r e v e a l numerous o i l d r o p l e t s (1 m i c r o n i n d i a m e t e r ) spread i n a gum n u c l e u s . P r o t e c t i o n o f t h e o i l phase then becomes fully effective. These n a t u r a l v e g e t a b l e exudates o f A c a c i a t r e e s have been known and used i n t h e f o o d i n d u s t r y f o r many y e a r s . The g r e a t e r knowledge o f b o t a n i c a l s p e c i e s and i n - d e p t h s t u d y o f t h e exudates have made i t p o s s i b l e t o extend t h e range o f usage A c a c i a gums. Growing by m i c r o - p r o p a g a t i o n now p e r m i t s r e l i a b l e and o r g a n i z e d p r o d u c t i o n o f these s e l e c t e d s p e c i e s . I n t h e a r o m a t i c i n d u s t r y , t h e e m u l s i f y i n g , s t a b i l i z i n g and e n c a p s u l a t i n g p r o p e r t i e s o f A c a c i a gums make them t h e most e f f e c t i v e medium f o r t h e s t a b i l i z a t i o n o f l i q u i d emulsions o r t h e e n c a p s u l a t i o n by a t o m i z a t i o n o f l i p o s o l u b l e compounds s e n s i t i v e t o o x i d a t i o n . W i t h t h e p r e v i o u s l y mentioned developments i n f a r m i n g and knowledge o f s t r u c t u r e , i t i s now p o s s i b l e t o e l i m i n a t e problems o f p r i c i n g and a v a i l a b i l i t y . This i n turn allows the f l a v o r i s t t o prepare e n c a p s u l a t e d p r o d u c t s ( s p r a y d r i e d and e m u l s i o n s ) w h i c h a r e o f t h e h i g h e s t gum a r a b i c q u a l i t y and l e s s expensive than o t h e r chemically derivatized substitutes.

REFERENCES 1. Anderson, D.W.; Process Biochemistry, 1977, 12-24. 2. Ullmann, G.; Thesis, University of Grenoble, France, 1983: Etude de l a structure et de l a biosynthèse d'un exsudat naturel de plante d'importance industrielle. 3. Defaye, J.; WONG, C.C.; Acquisitions récentes dans les domaines des hydrocolloides végétaux naturels; Presses Universitaires d'Aix-Marseille, 1983, p. 171. 4. Fenyo, J . C . ; Acquisitions récentes dans les domaines des hydrocolloides végétaux naturels; Presses Universitaires d'AixMarseille, 1983, p. 47. 5. Davidson, R.; Handbook of water soluble gums and resins; McGraw-Hill Book Company, 1980, 8-1. 6. Iranex; Technical bulletins Q 113, Q 115, Q 214; 1986. 7. Marion, J . P . ; Information of flavours and dyestuffs into formulated food products; Congress Nice, 1987. RECEIVED

March

16, 1988


Acacia Gums - American Chemical Society

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