18 Applications of Xanthan G u m in Foods and Related Products
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THOMAS R. ANDREW Kelco, Division of Merck & Co., Inc., 8225 Aero Drive, San Diego, CA 92123
Xanthan gum was approved for use as a food additive on March 19, 1969, by the Food and Drug Administration in accordance with 21 CFR 121.1224. Since then it has been used in a wide variety of foods for a number of important reasons including emulsion stabilization, temperature s t a b i l i t y , com p a t i b i l i t y with food ingredients, and its unique pseudoplastic rheological properties. It has been proposed that xanthan gum, which is produced by the microorganism Xanthomonas campestris, is in fact a survival device for the organism generating it and it has, through millions of years of evolution, been perfected for this purpose (1). Thus, i t is not surprising that a substance generated for the protection of a microorganism should possess such unusual properties and be so resistant to thermal, chemical, and biological degradation. A great deal of progress has been made toward understanding the chemistry of xanthan gum. Figure 1 shows the structure of xanthan gum as i n i t i a l l y postulated. It was shown that i t consisted of a sixteen-residue repeating unit composed of D-glucose, D-mannose, and D-glucuronic acid as shown (2, 3). In a paper published in 1975 Jansson and co-workers proposed the somewhat more simplified structure shown in Figure 2. This structure is composed of a back bone of 1 - 4 linked β-D-glucose units with side chains which consist of two mannose and (4) a glucuronic acid unit on every other glucose unit. Every other side chain carries a pyruvic acid group. In 1972 Rees proposed a double helix solution conformation (Figure 3) for xanthan gum which went a long way toward explaining the yield point phenomenon and the flat temperature-viscosity curve, unique among polysaccharides (5,6). A further extension of Rees's study (Figure 4) provided an 231
Sandford and Laskin; Extracellular Microbial Polysaccharides ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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e x c e l l e n t e x p l a n a t i o n o f why xanthan gum r e a c t s t o form e l a s t i c g e l s w i t h l o c u s t bean gum but not guar gum. The u n i f o r m l y d i s t r i b u t e d g a l a c t o s e s i d e c h a i n s a l o n g t h e mannose backbone o f guar gum p r e v e n t the c l o s e a s s o c i a t i o n o f the m o l e c u l e w i t h the xanthan gum h e l i x w h i l e the e x i s t e n c e o f "smooth" zones ( F i g u r e 5) i n the l o c u s t bean gum m o l e c u l e a l l o w s a s s o c i a t i o n and, t h e r e f o r e , g e l a t i o n ( 7 ) . As i s u s u a l l y t h e case w i t h the use o f gums, t h e o r y and p r a c t i c e have run on almost p a r a l l e l paths b u t the t w a i n have n o t y e t met. Theory h e l p s us u n d e r s t a n d t h e r e s u l t s b u t has not l e d us t o them. When xanthan gum e n t e r e d the food m a r k e t p l a c e i n 1969, i t s b a s i c p h y s i c a l p r o p e r t i e s were a c t i v e l y promoted, f o l l o w e d by a number o f suggested f o r m u l a t i o n s , a l l o f which were examples o f advances o v e r p r e v i o u s systems s t a b i l i z e d w i t h o t h e r gums. S a l a d d r e s s i n g w i t h e m u l s i o n s t a b i l i t y extended t o a y e a r o r more and s a l a d d r e s s i n g s t h a t c o u l d be r e t o r t e d o r r e p e a t e d l y f r o z e n were d e v e l o p e d . An i n s t a n t pudding which was almost the same as the cooked starch v e r s i o n was f o r m u l a t e d , and i n d u s t r y d e v e l o p e d a number o f o t h e r improved p r o d u c t s . P a s t e u r i z e d P r o c e s s e d Cheese
Spread
More r e c e n t work has been completed which demonstrates the u t i l i t y o f xanthan gum i n p a s t e u r i z e d p r o c e s s cheese s p r e a d ( 8 ) . U s i n g a s t a n d a r d f o r m u l a f o r p a s t e u r i z e d p r o c e s s cheese, samples were p r e p a r e d under d u p l i c a t e c o n d i t i o n s i n a cooker commonly used f o r t h i s purpose. As T a b l e I i n d i c a t e s , a number o f combinations o f xanthan gum, l o c u s t bean gum, and guar gum were e v a l u a t e d t o determine t h e optimum r a t i o f o r good meltdown, f i r m n e s s , s l i c e a b i l i t y , and f l a v o r r e l e a s e . I t i s i n t e r e s t i n g t o note t h a t o n l y one c o m b i n a t i o n g i v e s good r e s u l t s i n e v e r y c a t e g o r y , T r i a l No. 17A. These r e s u l t s n o t o n l y demonstrate the u t i l i t y o f xanthan gum b u t a l s o the n e c e s s i t y f o r u s i n g b l e n d s a t times t o o b t a i n f u n c t i o n a l advantages n o t o b t a i n a b l e w i t h s i n g l e t h i c k e n e r s . Each gum cont r i b u t e s a d e s i r a b l e c h a r a c t e r i s t i c t o the f i n a l p r o d u c t , b u t t h e s y n e r g i s t i c b l e n d i s b e t t e r than t h e sum o f i t s p a r t s . C o t t a g e Cheese D r e s s i n g Table I I again i l l u s t r a t e s the f u n c t i o n a l s u p e r i o r i t y o f the s y n e r g i s t i c b l e n d . C o t t a g e cheese
Sandford and Laskin; Extracellular Microbial Polysaccharides ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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EXTRACELLULAR MICROBIAL POLYSACCHARIDES
DOUBLE HELIX RANDOM COIL Predominant in the sol; Provide cross-linking can exist as "connectingjunctions in the gel. lengths" in gel structure and impart elasticity when they do so. Sol ;j=i Incipient g e l ^ Clear elastic gel ^
Figure 3.
Stiff gel ^
Turbid rigid gel
AGGREGATE Add cross-linking to consolidate the gel structure, thus acting as "super-junctions'." Phase separation syneresed gel
States of polysaccharide molecules and their role in gel prop erties
Figure 4. Schematic of galactomannan conformation. Each line represents a sugar unit consisting of the backbone composed of β-Ό-mannopyranose units and the side chains composed of a-O-gahctopyranose units.
Figure 5. Possible model for the inter action between xan than gum and locust bean galactomannan, resulting in gel for mation
Sandford and Laskin; Extracellular Microbial Polysaccharides ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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cream d r e s s i n g , which i s n o r m a l l y about 10 p e r c e n t b u t t e r f a t w i t h s a l t added, i s f o r m u l a t e d t o p o s s e s s enough v i s c o s i t y t o make i t c r e a m i e r and t o g i v e good c l i n g t o t h e c u r d . I f the v i s c o s i t y o f the cream i s t o o h i g h , t h e r e s u l t i n g c o t t a g e cheese w i l l be t o o " d r y " and t h e e a t i n g q u a l i t i e s w i l l s u f f e r . A n o t h e r p o t e n t i a l problem a r i s e s because o f t h e i n h e r e n t gummy m o u t h f e e l e x h i b i t e d by many gums a t a c o n c e n t r a t i o n o f 0.2 t o 0.3 p e r c e n t , t h e normal use l e v e l o f gums i n c o t t a g e cheese cream. As T a b l e I I i l l u s t r a t e s , a b l e n d o f xanthan gum, l o c u s t bean gum, and guar gum c a n be used t o d e v e l o p t h e v i s c o s i t y n e c e s s a r y f o r good c l i n g , b u t t h e a c t i v e gum conc e n t r a t i o n i s low enough so t h a t m o u t h f e e l and t e x t u r e do n o t s u f f e r ( 9 ) . The cream remains homogeneous and u n i f o r m l y mixed w i t h c u r d and does not separate w i t h time. L i q u i d C a t t l e Feed
Supplements
L i q u i d f e e d supplements, a l t h o u g h n o t f o o d i n t h e sense t h a t t h e y a r e consumed d i r e c t l y by humans, a r e n o n e t h e l e s s an i m p o r t a n t f a c t o r i n t h e f o o d supply. L i q u i d f e e d supplements a r e b a s i c a l l y one o r more n u t r i e n t m a t e r i a l s s u p p l i e d i n a l i q u i d v e h i c l e such as water o r m o l a s s e s . The g r e a t m a j o r i t y a r e added t o t h e d r y f e e d o f f e e d l o t c a t t l e and a r e s h i p p e d and s t o r e d i n l a r g e t a n k s where, because o f the formation o f p r e c i p i t a t e s o r f l o c c u l a n t s o r t h e addition o f insoluble material, maintaining uniformity is difficult. I t i s e s p e c i a l l y important t o maintain u n i f o r m i t y because v i t a m i n s and t r a c e m i n e r a l s which a r e added t o t h e r a t i o n t e n d t o adsorb on t h e s o l i d f l o c c u l a n t s t h a t form and w i l l n o t s t a y u n i f o r m l y d i s t r i b u t e d u n l e s s s e d i m e n t a t i o n i s p r e v e n t e d by t h e use o f a s u s p e n d i n g agent o r c o n t i n u o u s a g i t a t i o n . F i g u r e 6 i s a t y p i c a l l i q u i d f e e d supplement formul a t i o n o f the high-molasses, phosphoric-acid type. Note t h e s i m i l a r i t y t o f e r t i l i z e r . Figure 7 i l l u s t r a t e s t h e f u n c t i o n a l i t y o f xanthan gum as a s u s p e n d i n g agent a t room t e m p e r a t u r e , and F i g u r e 8 i l l u s t r a t e s i t s s t a b i l i t y a t 95°F (10). These f i g u r e s i l l u s t r a t e two p o i n t s : (1) xanthan gum i s an e x c e l l e n t s u s p e n d i n g agent because i t p o s s e s s e s a y i e l d p o i n t , and (2) s u s p e n d i n g q u a l i t i e s o f xanthan gum a r e n o t s i g n i f i c a n t l y d i m i n i s h e d by e l e v a t e d t e m p e r a t u r e s as o c c u r s w i t h l i q u i d f e e d supplements i n warm weather. I n a d d i t i o n , because o f i t s p s e u d o p l a s t i c i t y , xanthan gum f a c i l i t a t e s pumping.
Sandford and Laskin; Extracellular Microbial Polysaccharides ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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Table
I
POLYSACCHARIDES
F O R M U L A S AND RESULTS
OF EXPERIMENTAL PASTEURIZED PROCESSED CHEESE SPREADS % GUM CONTENT TRIAL NUMBER
XANTHAN GUM
GUAR GUM
LBG
BODY RESILIENCY
SLICING PROPERTIES
MOUTH FEEL
FLAVOR RELEASE
SANDWICH MELT
1A
0.2
Fair
Tacky
Lumpy
Fair
Excellent
2A
0.5
Fair
Tacky
Lumpy
Fair
Good
3A
0.8
Fair
Tacky
Lumpy
Fair
Good
4A
— —
Good
Good
Lumpy
Fair
Good
Excellent
Excellent
Lumpy
Fair
Excellent
Excellent
Excellent
Lumpy
Fair
Excellent
5A 6A
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ORGANOLEPTIC EVALUATIONS
0.2 0.5 0.8
— —
—
7A
0.2
Poor
Tacky
Smooth
Excellent
Good
8A
0.5
Poor
Tacky
Smooth
Excellent
Excellent
9A
0.8
Fair
Tacky
Smooth
Excellent
Excellent
— — — — —
0.14
Fair
Tacky
Lumpy
Fair
Good
0.45
Fair
Tacky
Lumpy
Fair
Good
0.35
Good
Tacky
Smooth
Good
Excellent
0.25
Fair
Tacky
Lumpy
Fair
Good
10A
0.06
11A
0.05
12A
0.15
13A
0.25
14A
0.24
0.56
Good
Tacky
Smooth
Good
Excellent
15A
0.06
0.04
0.10
Good
Tacky
Smooth
Good
Good
16A
0.15
0.10
0.25
Good
Good
Smooth
Good
Excellent
17A
0.24
0.16
0.40
Excellent
Excellent
Smooth
Excellent
Excellent
18A*
0.15
0.10
0.25
Good
Good
Smooth
Good
Good
'Trial 1SA contained 0.2 percent pimento solids or 12.50 pounds of drained pimentos per batch.
T^.Ul^
'Cible
Τ Τ
11
Dressing Viscosities (cps) (| itial/24hr.) n
Percent Stabilizer:
0.05
0.10
0.15
Xanthan gum/ galactomannan blend Xanthan gum Guar gum Blend 1 Blend 2 Blend 3 Blend 4 Locust bean gum
27/41 10/10 6/4 7/8 6/5 4/12 7/13 11/16
118/115 40/60 15/31 9/21 8/11 7/19 10/24 23/35
260/245 107/133 33/60 16/42 13/19 18/41 21/49 52/69
0.20
0.30
Not evaluated 373/480 160/250 45/71 27/58 62/105 66/135 175/95
155/225 51/86 23/47 18/35 36/67 51/95 105/130
Cane Molasses, 79.5 Brix
67.5
Urea Liquor, 50%
20.9
Salt
5.0
Trace Minerals
0.2
Phosphoric Acid, 75%
6.4 100.0
%
Figure 6. Liquid supplement for mulation high molasses, range type
Protein Equivalent
32
Phosphorus
1.5
Solids, Calculated
60
Sandford and Laskin; Extracellular Microbial Polysaccharides ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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238
EXTRACELLULAR
Calf Milk
MICROBIAL
POLYSACCHARIDES
Replacers
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A r e l a t e d a p p l i c a t i o n i s t h e use o f xanthan gum f o r s t a b i l i z i n g c a l f m i l k r e p l a c e r s . C a l f milk r e p l a c e r s may c o n s i s t o f d r i e d whey and h e a t p r o c e s s e d soy beans o r s i n g l e - c e l l p r o t e i n . A dry mix i s added t o water, s t i r r e d t o d i s p e r s e t h e s o l i d s , and f e d t o c a l v e s . I f t h e f e e d i s n o t s t a b i l i z e d , t h e i n s o l u b l e s o l i d s w i l l q u i c k l y s i n k and t h e s h o r t term u n i f o r m i t y which i s r e q u i r e d w i l l be l o s t . As l i t t l e as 0.032 p e r c e n t xanthan gum can p r o v i d e enough s t a b i l i t y t o m a i n t a i n u n i f o r m i t y , as F i g u r e s 9, 10, and 11 show ( 1 1 ) . Thermal P r o c e s s i n g Recent work by Cheng and Kovacs has e x p l o r e d t h e r h e o l o g i c a l p r o p e r t i e s o f xanthan gum under h i g h temperature and moderate shear found i n most a g i t a t e d commercial c a n n i n g systems (12). A Fann 50C v i s cometer, an i n s t r u m e n t which p e r m i t s t h e measurement o f v i s c o s i t y a t shear r a t e s from 1.7 - 1075 sec"" , temperatures t o 500°F, and p r e s s u r e s t o 1000 p s i , was used. F i g u r e 12 d e p i c t s t h e v i s c o s i t y drop t h a t xanthan gum undergoes a t two a r b i t r a r i l y s e l e c t e d shear r a t e s , 170 sec"" and 511 s e c " , w i t h and w i t h o u t NaCl. The well-known " f l a t " v i s c o s i t y v e r s u s temperature c u r v e i s seen from ambient temperature t o about 190°F w i t h a l l s o l u t i o n s . The s t a b i l i t y t o t h e r m a l d e g r a d a t i o n imparted by an e l e c t r o l y t e can a l s o be seen. Furthermore, F i g u r e 9 i l l u s t r a t e s that the e l e c t r o l y t e - s t a b i l i z e d solut i o n s l o s e 98 p e r c e n t o f t h e i r v i s c o s i t y a t r e t o r t temperature (250°F) and r e c o v e r about 80 p e r c e n t o f t h e i r o r i g i n a l v i s c o s i t y on c o o l i n g . Obviously, a t h i c k e n e r t h a t i s t h i n a t r e t o r t temperature w i l l f a c i l i t a t e heat t r a n s f e r , thereby shortening the p r o c e s s time. T h i s r e d u c t i o n i n p r o c e s s time i s i m p o r t a n t f o r i n c r e a s i n g p r o d u c t i v i t y and i n t h e t h e r m a l p r o c e s s i n g o f foods which a r e a d v e r s e l y a f f e c t e d by " o v e r c o o k i n g " . 1
1
Other
1
Advances
Xanthan gum has a l s o been used t o s t a b i l i z e f r o z e n d e s s e r t s and t o s t a b i l i z e t o o t h p a s t e , where i t s r h e o l o g i c a l p r o p e r t i e s can be used t o f o r m u l a t e a p r o d u c t t h a t t h i n s when squeezed from t h e tube but has t h e o r i g i n a l c o n s i s t e n c y on t h e b r u s h . A s y n e r g i s m w i t h d e x t r i n has a l s o been used i n d e n t u r e
Sandford and Laskin; Extracellular Microbial Polysaccharides ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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Products
Figure 9
Figure 10
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EXTRACELLULAR MICROBIAL POLYSACCHARIDES
Figure 11
Figure 12. The effect of retorting at shear rates of 170 sec' and 511 sec' on the viscosities xanthan gum with and without electrolyte 1
1
Sandford and Laskin; Extracellular Microbial Polysaccharides ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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a d h e s i v e s and i n a number o f f o o d s . Xanthan gum a l o n e and i n c o m b i n a t i o n w i t h galactomannans shows e x c e l l e n t promise i n canned, g r a v y - t y p e p e t f o o d s . I t has a l s o been r e p o r t e d t h a t xanthan gum shows good p o t e n t i a l as a g l u t e n s u b s t i t u t e i n b r e a d (13, 1 4 ) . A l t h o u g h t h i s p o t e n t i a l use i s i m p o r t a n t t o t h e segment o f t h e p o p u l a t i o n who a r e a l l e r g i c t o g l u t e n , i t has much b r o a d e r i m p l i c a t i o n s as a p o s s i b l e a d j u n c t t o l o w - q u a l i t y wheat f l o u r o r grains that are not s u i t a b l e f o r baking. We have reviewed today some o f t h e more r e c e n t developments i n xanthan gum usage. I n view o f t h e unique p r o p e r t i e s i t p o s s e s s e s as a r e s u l t o f i t s f u n c t i o n i n n a t u r e , we can undoubtedly e x p e c t even w i d e r usage i n t h e f u t u r e .
Literature Cited 1. "Xanthan Gum/KELTROL/KELZAN, A Natural Polysac charide for Scientific Water Control," Kelco Co., Second Edition. 2. Sloneker, J . Η., James Α . , Am. J. Chem. (1962) 40, 2066-71. 3. Siddiqni, Carbohyd. Res. (1967)4 (4), 284-91. 4. Jansson, P. Ε . , Keen, L., and Lindberg, Β . , Carbohyd. Res. (1976) 45 (1), 275-82. 5. Rees, D. Α . , Biophysical Society Winter Meeting, London, England (1973). 6. Rees, D. Α . , Biochem. J . (1972) 126, 257-73. 7. Dea, I. C. Μ., McKinnon, A. A. and Reese, D. A. (1972) J . Mol. B i o l . 68 (1), 153-72. 8. Kovacs, P . , and Igoe, R. S. (1976) Food Product Development, in press. 9. Kovacs, P. and Titlow, B. D. (1976) American Dairy Review 38 (4) 34J-34N. 10. Jackman, K. R., Randel, J . H. and Wintersdorff, P. (1976) A Unique Suspending Agent, National Feed Ingredients Association Meeting, Kansas City, Missouri (April 15). 11. Ibid. 12. Kovacs, P. and Cheng, H. (1976) Effects of High Temperatures and Shear Rates on Hydrocolloid Viscosities During Simulated Canning and HTST Processing Conditions. Unpublished report. 13. Kulp, K . , Hepburn, F. Ν . , and Lehmann, T. A. (1974) The Baker's Digest 48 (3), 34-37. 14. Christianson, D. D. Gardner, H. W., Warner, Κ., Boundy, Β. K. and Inglett, G. E. (1974) Food Technology 28 (6), 23-29.
Sandford and Laskin; Extracellular Microbial Polysaccharides ACS Symposium Series; American Chemical Society: Washington, DC, 1977.