Emulsion-Stabilizing Starches - American Chemical Society

Chapter 6

Emulsion-Stabilizing

Starches

Use in Flavor Encapsulation

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P. C. Trubiano and N. L. Lacourse National Starch and Chemical Corporation, 10 Finderne Avenue, Bridgewater, NJ 08807 In recent years the importance and utilization of powdered or encapsulated flavors has grown tremendously. Large quantities of encapsulated flavors are used by the food industry in dry packaged goods such as beverages, puddings, cake mixes and other desert products where shelf-life and flavor stability are important. The key to optimum encapsulation of fats and flavors is the performance of the encapsulating agent (1). For an agent to perform at its optimum, it should provide the following functions (2): 1. Protect the active ingredient from oxidation, light, evaporation, humidity and other substance in the food system. 2. Mask taste, flavor or odors until needed. 3. Delay release of an active ingredient. 4. Provide the ability to put the active ingredient into a free flowing powder for ease of handling. In order to provide these functions the encapsulating agent should have the following properties: Emulsion Stabilization Good Film Forming Low Hygroscopicity Low Viscosity Bland Taste - No Odor Release Flavor On Hydration Low Cost Gum arabic has been the encapsulating agent of choice for many years. Gum arabic has all the properties mentioned above which has helped expand its use in the Food Industry.

c

0097-6156/88/0370-00045$06.00/0 1988 American Chemical Society

In Flavor Encapsulation; Risch, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

46

FLAVOR

ENCAPSULATION


In the e a r l y 1970's and mid 1980's gum a r a b i c has s u f f e r e d from s u p p l y s h o r t a g e s due to drought c o n d i t i o n s i n the major p r o d u c i n g r e g i o n s ( i . e . , Sudan). These s e v e r e s h o r t a g e s have reduced the a v a i l a b l e output of gum a r a b i c and caused the p r i c e to r e a c h $2.50 per pound ( 3 ) . To make up the d i f f e r e n c e s i n s u p p l i e s , due to crop l o s s , p o o r e r q u a l i t y gum a r a b i c has been used w i t h i n c r e a s e d r e g u l a r i t y . The p o o r e r q u a l i t y gum a r a b i c i s h i g h e r i n d i r t c o n t e n t and more s u s c e p t i b l e to heat d e g r a d a t i o n d u r i n g the p a s t e u r i z a t i o n p r o c e s s which reduces i t s e n c a p s u l a t i n g p e r f o r m a n c e . The s u p p l y s h o r t a g e s have f o r c e d many f l a v o r m a n u f a c t u r e r s t o l o o k f o r s u b s t i t u t e s f o r gum a r a b i c . I n i t i a l work began w i t h t e s t i n g v a r i o u s s t a r c h e s f o r e n c a p s u l a t i o n p r o p e r t i e s . Low v i s c o s i t y , s t a b l e s t a r c h d e x t r i n s were f i r s t e v a l u a t e d v e r s u s gum a r a b i c f o r encapsulation e f f i c i e n c i e s . D i s p e r s i o n s of c o r n and t a p i o c a d e x t r i n s were used t o e n c a p s u l a t e s i n g l e f o l d orange o i l . The s p r a y - d r i e d powders were e v a l u a t e d f o r s u r f a c e and encapsulated o i l . The data i s p r e s e n t e d i n T a b l e 1 ( 2 ) . TABLE 1 ENCAPSULATION PERFORMANCE OF GUM ARABIC v s . STANDARD STARCH DEXTRINS

Encapsul-

ating

Starting Oil Level

Agent Gum Arabic

20.0

Corn Dextrin

20.0

Tapioca Dextrin

20.0

Total O i l Retained After SpraySurface EncapsulDrying Oil ated % O i l , 7o % 18.1

16.9

17.9

1.4

16.7

Encapsulated Efficiency,7o 83.5

4.1

12.8

64.0

2.9

15.0

75.0

One sees from the d a t a , p r e s e n t e d i n TABLE 1, t h a t the s t a r c h d e x t r i n s have the a b i l i t y t o e n c a p s u l a t e the orange o i l , but does not e n c a p s u l a t e as much o i l as gum a r a b i c . The s t a r c h d e x t r i n s match the v i s c o s i t y and s t a b i l i t y of the gum a r a b i c when p l a c e d i n s o l u t i o n , however; o t h e r p r o p e r t i e s such as e m u l s i f y i n g and e m u l s i o n s t a b i l i z i n g p r o p e r t i e s are p o o r e r i n the d e x t r i n s . We b e l i e v e t h a t the e m u l s i f y i n g p r o p e r t i e s i n h e r e n t i n gum a r a b i c are p a r t i a l l y responsible for i t s encapsulating a b i l i t i e s .



TRUBIANO & LACOURSE

Starches


E m u l s i o n s made w i t h a f i n e o i l d r o p l e t p a r t i c l e s i z e , u s u a l l y l e s s than one m i c r o n , are more s t a b l e w i t h the o i l d r o p l e t s l e s s l i k e l y t o c o a l e s c e and s e p a r a t e . The e n c a p s u l a t i o n o f a good q u a l i t y e m u l s i o n i s g e n e r a l l y more e f f i c i e n t w i t h l e s s s u r f a c e o i l on the s p r a y - d r i e d powder. We wanted t o b u i l d s u r f a c t a n t p r o p e r t i e s i n t o the s t a r c h backbone t o improve e n c a p s u l a t i o n e f f i c i e n c i e s . Studies of the mechanism by which s u r f a c t a n t s s t a b i l i z e e m u l s i o n s were made i n o r d e r t o a c c o m p l i s h t h i s . C o n v e n t i o n a l s u r f a c e a c t i v e agents are c h a r a c t e r i z e d by the p r e s e n c e i n the m o l e c u l e o f a h y d r o p h i l i c group and a h y d r o p h o b i c group. These m o l e c u l e s o r i e n t themselves a t t h e o i l / w a t e r i n t e r f a c e when the o i l i s d i s p e r s e d i n water under high a g i t a t i o n . The h y d r o p h o b i c p o r t i o n o f the m o l e c u l e d i s s o l v e s i n the o i l phase and the h y d r o p h i l i c group d i s s o l v e s i n the water phase. A monolayer o f the s u r f a c t a n t m o l e c u l e s u r r o u n d s the o i l d r o p l e t and p r e v e n t s reagglomeration. These monolayer f i l m s are weak and c a n e a s i l y be d i s r u p t e d c a u s i n g the e m u l s i o n s t o b r e a k . I n the p a s t , s t a r c h e s have been used t o add v i s c o s i t y t o t h e e m u l s i o n s thus p r e v e n t i n g c o a l e s c i n g by the n a t u r e o f t h e i r hydrophilic chains. When s t a r c h e s are t r e a t e d w i t h l i p o p h i l i c r e a g e n t s so t h a t they c o n t a i n h y d r o p h o b i c and h y d r o p h i l i c groups, t h e s t a r c h m o l e c u l e s are a t t r a c t e d t o the i n t e r f a c e o f the water and o i l d r o p l e t s i n an e m u l s i o n . The r e s u l t i n g f i l m s u r r o u n d i n g the o i l d r o p l e t i s much s t r o n g e r and more c o n t i n u o u s making the e m u l s i o n more stable. The s t a r c h d e r i v a t i v e s w i t h b a l a n c e d h y d r o p h o b i c and h y d r o p h i l i c groups are s u p e r i o r t o u n m o d i f i e d s t a r c h e s i n s t a b i l i z i n g emulsions. A v e r y s u c c e s s f u l approach t o the p r e p a r a t i o n o f s t a r c h based e m u l s i o n s t a b i l i z e r s has been the development o f polysaccharide d e r i v a t i v e s of s u b s t i t u t e d d i c a r b o x y l i c acids by C a l d w e l l and Wurzburg ( 4 ) . The i n v e n t i o n i n v o l v e s the treatment o f s t a r c h w i t h s u b s t i t u t e d c y c l i c d i c a r b o x y l i c a c i d a n h y d r i d e s h a v i n g the f o l l o w i n g s t r u c t u r a l f o r m u l a :

0

II

it 0 wljiere R r e p r e s e n t s a d i m e t h y l e n e o r t r i m e t h y l e n e r a d i c a l and R i s t h e s u b s t i t u e n t group, o r d i n a r i l y a long h y d r o c a r b o n chain. An example o f these types o f r e a g e n t s are t h e

American Chemical Society Library 1155 16th St., N.W.

In Flavor Encapsulation; Risch, S., et al.; Washington, D.C. 20036 ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

48

FLAVOR

s u b s t i t u t e d s u c c i n i c a c i d a n h y d r i d e s i n which the s u b s t i t u e n t h y d r o p h o b i c c h a i n i s an a l k y l o r a l k e n y l c o n t a i n i n g from 5 t o 18 c a r b o n atoms.

ENCAPSULATION

group

The s t a r c h d e r i v a t i v e i s p r e p a r e d by a s t a n d a r d e s t e r i f i c a t i o n r e a c t i o n where t h e r e a g e n t and t h e s t a r c h suspended i n water a r e mixed under a l k a l i n e c o n d i t i o n s . The a c i d e s t e r may be r e p r e s e n t e d by the f o l l o w i n g s t r u c t u r a l formula :


0 Na

0 -C

s -o-c-L' T

II ο

w h e r e i n R i s the d i m e t h y l e n e o r t r i m e t h y l e n e r a d i c a l and R* i s the s u b s t i t u e n t h y d r o p h o b i c group. The most i m p o r t a n t d e r i v a t i v e c l e a r e d f o r food use by the FDA and h a v i n g a p p l i c a t i o n s i n the p h a r m a c e u t i c a l and i n d u s t r i a l a r e a s as w e l l , i s o c t e n y l s u c c i n i c a c i d anhydride ( 5 ) . The FDA has s e t a maximum l e v e l o f treatment f o r o c t e n y l s u c c i n i c a c i d a n h y d r i d e on the s t a r c h a t 3 7 o which c o r r e s p o n d s t o a degree of s u b s t i t u t i o n o f 0.02 ( 6 ) . T h i s t r e a t m e n t can be c o n d u c t e d on a wide v a r i e t y o f s t a r c h b a s e s , a c i d h y d r o l y z e d s t a r c h e s and d e x t r i n s . The s t r u c t u r e o f t h e s t a r c h o c t e n y l s u c c i n a t e i s shown below:

CH (CH ) CH=CHCH CH-C-0ST 3

2

4

2

0

II CH C-0 Na o

Materials

and Methods

Carrier Gum a r a b i c , s t a n d a r d s t a r c h d e x t r i n s and l a b o r a t o r y p r e p a r e d low v i s c o s i t y s t a r c h o c t e n y l s u c c i n a t e s were used f o r a l l e n c a p s u l a t i o n work. Flavor

Oils

Orange t e r p e n e s , lemon o i l and s i n g l e f o l d orange o i l o b t a i n e d from Naarden I n c . , were used f o r e n c a p s u l a t i o n studies.


».

TRUBIANO & LACOURSE

Emulsification


Starches

and S p r a y - D r y i n g

Two hundred grams o f c a r r i e r was d i s p e r s e d i n d i s t i l l e d water a t the d e s i r e d l e v e l s ( s o l u t i o n v i s c o s i t i e s s i m i l a r t o gum a r a b i c ) and f l a v o r o i l emulsions were made u s i n g a Waring b l e n d e r a t h i g h speed f o r two m i n u t e s . The e m u l s i o n was s p r a y - d r i e d u s i n g an i n l e t temperature o f 200 C and an o u t l e t temperature o f 90 C. A t o m i z a t i o n was a c h i e v e d u s i n g c e n t r i f u g a l wheel a t o m i z a t i o n .


Oil

Retentions

A 10 gram sample was p l a c e d i n a 200 ml round bottom f l a s k and 100 ml o f d i s t i l l e d water added. A Dean-Stark t r a p and condenser were used and the m i x t u r e was brought t o a b o i l . The steam d i s t i l l e d o i l was measured a f t e r f o u r hours v e r s u s control mixtures. In o r d e r t o measure s u r f a c e o i l on the s p r a y - d r i e d powders, the powder was f i r s t washed w i t h a s o l v e n t ( e t h y l e t h e r o r hexane) then o i l r e t e n t i o n s were r u n by the steam d i s t i l l a t i o n method i l l u s t r a t e d above. D i f f e r e n c e s i n o i l volume f o r s o l v e n t washed v e r s u s nonwashed were a t t r i b u t e d t o s u r f a c e o i l on t h e s p r a y - d r i e d powders.

GC A n a l y s i s t o Measure C a r r i e r ' s A b i l i t y Terpenes from O x i d a t i o n

to Protect

Orange

Orange t e r p e n e s were e m u l s i f i e d i n v a r i o u s c a r r i e r ' s and spray-dried. The s p r a y - d r i e d powders were aged f o r 3 days at 80 C i n a d r a f t oven. Beta-pinene i s an o x i d a t i o n p r o d u c t i n orange t e r p e n e s which can be measured by GC. The b e t a - p i n e n e l e v e l i s p r o p o r t i o n a l t o the degree o f o x i d a t i o n of the orange t e r p e n e s . High l e v e l s o f b e t a - p i n e n e c o n t e n t i n t h e s p r a y - d r i e d powders i n d i c a t e poor o x i d a t i o n r e s i s t a n c e imparted t o the e n c a p s u l a t e d t e r p e n e s by the carrier. A Beckman Model 4 GC was equipped w i t h a carbowax column, temperature 180 C ( i n l e t ) . A m i c r o l i t e r i n j e c t i o n was made and the o x i d i z e d b e t a - p i n e n e peak was measured. The r e t e n t i o n time f o r the o x i d i z e d b e t a - p i n e n e peak i s 5.5 minutes. The e n c a p s u l a t e d orange t e r p e n e s were f i r s t d i s s o l v e d i n water b e f o r e i n j e c t i o n . Emulsion P a r t i c l e

Size

P a r t i c l e s i z e o f the o i l d r o p l e t s a f t e r e m u l s i f i c a t i o n was determined by m i c r o s c o p y . T h i s was a c c o m p l i s h e d p r i o r t o spray-drying. A t y p i c a l good e m u l s i o n would have an o i l p a r t i c l e s i z e o f l e s s than 2 microns (urn).


50

FLAVOR

Overnight Emulsion

ENCAPSULATION

Stability

T h i s i s a s u b j e c t i v e t e s t to determine the s t o r a g e s t a b i l i t y of an e m u l s i o n . A sample of the l i q u i d e m u l s i o n b e f o r e s p r a y - d r y i n g i s used to f i l l a 16 oz. t a l l g l a s s j a r . The j a r i s capped and s t o r e d i n an oven f o r 16 hours at 50 C. When s t o r a g e i s complete, the j a r i s removed from the oven and e v a l u a t e d . S u r f a c e o i l l a y e r s on the e m u l s i o n i n d i c a t e poor e m u l s i o n s t a b i l i t y performance by the c a r r i e r .


Results

and

Discussion

An example of the improved e m u l s i o n s t a b i l i z i n g p r o p e r t i e s imparted by treatment of s t a r c h w i t h o c t e n y l s u c c i n i c a c i d a n h y d r i d e can be seen i n TABLE 2 ( 5 ) :

TABLE 2

EMULSION STABILITY OF GUM CARRIERS

% Encapsulating Agent

Percent Solids

Lemon Oil

30

30

Conventional Dextrin

40

30

Low V i s c o s i t y Starch Octenylsuccinate

40

30

Gum

Arabic

ARABIC v s .

STARCH

Emulsion Particle Size (urn)

Overnight Emulsion Stability 50°C

< 3

Some Surface O i l 10

< 2

Oil

Layer

Excellent

The o c t e n y l s u c c i n i c a c i d a n h y d r i d e t r e a t e d s t a r c h e s g i v e on the average s m a l l e r o i l d r o p l e t p a r t i c l e s i z e s and b e t t e r e m u l s i o n s t o r a g e s t a b i l i t y than b o t h gum a r a b i c and a s t a r c h dextrin. Emulsions of lemon o i l s t a b i l i z e d w i t h gum a r a b i c , a c o n v e n t i o n a l s t a r c h d e x t r i n and a low v i s c o s i t y s t a r c h o c t e n y l s u c c i n a t e were s p r a y - d r i e d and e v a l u a t e d f o r encapsulating e f f i c i e n c i e s . O i l r e t e n t i o n s and s u r f a c e o i l d e t e r m i n a t i o n s were made a c c o r d i n g to the M a t e r i a l s and Methods s e c t i o n . TABLE 3 demonstrates the s u p e r i o r i t y of the s t a r c h o c t e n y l s u c c i n a t e i n f l a v o r r e t e n t i o n and s u r f a c e o i l to gum a r a b i c and a s t a r c h d e x t r i n ( 5 ) :


6.

TRUBIANO & LACOURSE


Starches

TABLE 3 COMPARISON OF ENCAPSULATING EFFICIENCIES OF GUM ARABIC v s . STARCH CARRIERS


Flavor Amount of F l a v o r L o s t On Encapsulating In Powder Drying Agent (7o) (%) I n i t i a l Retained

Retained F l a v o r On Surface

Truly Encapsulated Flavor

(%)

(7o)

Gum A r a b i c

30.5

28.7

5.9

16.5

23.9

Conventional Dextrin

30.7

23.5

23.6

25.6

17.4


30.1

30.0

0.3

1.0

29.4

The data show t h a t when s p r a y - d r y i n g a 3 0 7 lemon o i l l e v e l on the weight of the c a r r i e r , the s t a r c h o c t e n y l s u c c i n a t e o n l y l o s e s 0 . 3 7 o f the o i l d u r i n g the s p r a y - d r y i n g p r o c e s s . S u r f a c e f l a v o r o i l was a l s o lower f o r the s t a r c h o c t e n y l s u c c i n a t e s which i n d i c a t e s e x c e l l e n t e n c a p s u l a t i o n ef f i c i e n c i e s . o

o

In o r d e r t o f u r t h e r demonstrate the s u p e r i o r e n c a p s u l a t i o n e f f i c i e n c i e s o f s t a r c h o c t e n y l s u c c i n a t e s , comparison s t u d i e s of s u r f a c e o i l v e r s u s o i l l e v e l were made a g a i n s t gum a r a b i c (2). The data i s p r e s e n t e d i n TABLE 4:

TABLE 4 SURFACE OIL COMPARISON OF GUM ARABIC v s . STARCH OCTENYLSUCCINATE O i l L e v e l On S p r a y - D r i e d Powders (7o)

% O i l On S u r f a c e o f Powders Low V i s c o s i t y S t a r c h Gum A r a b i c Octenylsuccinate

20

1

1

30

8

1

40

23

7

50

71

14


52

FLAVOR ENCAPSULATION


At lower o i l usage l e v e l s (20% - 30%) gum a r a b i c and s t a r c h o c t e n y l s u c c i n a t e s performed e q u a l l y . High o i l l e v e l s ( g r e a t e r than 40%) showed marked d i f f e r e n c e s i n s u r f a c e o i l c o n t e n t of the powders, w i t h the s t a r c h o c t e n y l s u c c i n a t e s out p e r f o r m i n g gum a r a b i c . Less f l a v o r o i l on the s u r f a c e of the powder w i l l h e l p improve o v e r a l l s h e l f - l i f e stability. Another important aspect of e n c a p s u l a t i o n e f f i c i e n c y i s the r e s i s t a n c e to o x i d a t i o n t h a t the c a r r i e r imparts to the flavor o i l s . The o x i d a t i o n r e s i s t a n c e p r o p e r t i e s are c r i t i c a l to s h e l f - l i f e s t a b i l i t y of the encapsulated product. O x i d a t i o n p r o p e r t i e s can be measured o r g a n o l e p t i c a l l y by a t a s t e p a n e l or by gas chromatograph of the r e c o v e r e d o i l . Peaks r e l a t e d to o x i d a t i o n p r o d u c t s of orange t e r p e n e s o b t a i n e d from GC a n a l y s i s can be m o n i t o r e d as the powders are aged f o r t h r e e days at 80 C. The GC was used to measure b e t a - p i n e n e , an o x i d a t i o n p r o d u c t of orange t e r p e n e s . The r e s u l t s are r e p o r t e d i n square i n c h e s . The g r e a t e r the area f o r the b e t a - p i n e n e peak, the p o o r e r the o x i d a t i o n r e s i s t a n c e of c a r r i e r towards the orange t e r p e n e s . The data i s p r e s e n t e d i n TABLE 5:

TABLE 5 OXIDATION RESISTANCE OF Encapsulation Agent Gum

Arabic

ORANGE TERPENES v s . CARRIER TYPE

Orange Terpene Level (%)

GC^ (in )

20

1.04

Dextrin

20

1.77


20

0.95

Tapioca

Taste Panel Excellent Good Excellent

As can be seen from the data i n TABLE 5 the low v i s c o s i t y s t a r c h o c t e n y l - s u c c i n a t e c l o s e l y matches the o x i d a t i o n r e s i s t a n c e of gum a r a b i c . T h i s p r o d u c t would o f f e r improved s h e l f - l i f e over a s t a n d a r d s t a r c h d e x t r i n and s i m i l a r s t a b i l i t y to a gum a r a b i c e n c a p s u l a t e d flavor. S p r a y - d r y i n g c o s t s are always a f a c t o r i n d e t e r m i n i n g the economics of an e n c a p s u l a t e d p r o d u c t . D r y i n g c o s t s are r e l a t e d to the amount of water t h a t must be removed i n the spray-drying process. I t i s t h e r e f o r e advantageous to e n t e r the d r i e r at the h i g h e s t p o s s i b l e s o l i d s t h a t s t i l l g i v e s


6. T R U B I A N O & L A C O U R S E

Emulsion-Stabilizing Starches

low enough v i s c o s i t y t o p r o v i d e f o r e f f i c i e n t a t o m i z a t i o n as w e l l as good o i l r e t e n t i o n . A comparison o f s o l i d s v e r s u s B r o o k f i e l d v i s c o s i t y f o r gum a r a b i c and a low v i s c o s i t y s t a r c h o c t e n y l s u c c i n a t e demonstrate the s t a r c h e s ' a b i l i t y t o be used a t h i g h e r s o l i d s (TABLE 6 ) . T h i s improves s p r a y d r y i n g r a t e s and lowers cost ( 8 ) .


TABLE 6 BROOKFIELD VISCOSITY OF GUM ARABIC v s . STARCH OCTENYLSUCCINATE AS A FUNCTION OF CONCENTRATION V i s c o s i t y RV B r o o k f i e l d cps % Solids

Gum A r a b i c

Starch

30

200

100

35

380

200

40

1,000

Octenylsuccinate

200

Conclusions Starch octenylsuccinates o f f e r excellent emulsifying p r o p e r t i e s , f l a v o r o i l r e t e n t i o n and good o x i d a t i o n r e s i s t a n c e v e r s u s gum a r a b i c . They can be made on a v a r i e t y of s t a r c h b a s e s , d e x t r i n s o r f l u i d i t i e s which p r o v i d e v e r s a t i l i t y and improved s p r a y - d r y i n g c o s t s . Starch o c t e n y l s u c c i n a t e a r e low i n c o s t , d o m e s t i c a l l y produced and are not s u b j e c t t o the market f l u c t u a t i o n s t h a t gum a r a b i c encounters.

References 1. Glicksman, M., Utilization of Natural Polysaccahride Gums in the Food Industry. Advances in Food Research, 11, 170, 1962. 2. King, W., Trubiano, P., and Perry, P., Modified Starch Encapsulating Agents Offer Superior Emulsification, Film Forming and Low Surface Oil, Food Prod. Dev., 10, 54, 1976. 3. Chemical Marketing Reporter, August 17, 1987.


FLAVOR ENCAPSULATION

54

4. Caldwell, C. G., and Wurzburg, O. Β., U.S. Patent #2,661,349, 1953. 5. Trubiano, P., Succinate and Substituted Succinate Derivatives of Starch in Modified Starches: Properties and Uses, Wurzburg, O. Β., Ed., CRC Press, Inc., Boca Raton, 1986, Chapter 9.


6. Code of Federal Regulations, Title 21, Chapter 1, Part 172, Food Additives Permitted in Food for Human Consumption, Section 172.892, Food Starch- Modified, U.S. Government Printing Office, Washington, D.C., 1981. 7. Trubiano, P.C., unpublished data, 1978. 8. Monteleone, M. G., unpublished data, 1981. RECEIVED February 23, 1988


Emulsion-Stabilizing Starches - American Chemical Society

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