An improved method for the quantitative

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An improved method for the quantitative determination of carboxymethyl cellulose in food products Article in Food Hydrocolloids · January 1999 DOI: 10.1016/S0268-005X(98)00062-9

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Food Hydrocolloids 13 (1999) 73±76

Short note

An improved method for the quantitative determination of carboxymethyl cellulose in food products Murat Zorba*, GuÈlden Ova Food Engineering Department, Ege University Engineering Faculty, 35100 Bornova-Izmir, Turkey Received 18 July 1997; accepted 17 June 1998

Abstract Sodium carboxymethylcellulose, CMC, in ice-cream was determined quantitatively with 2,7-naphthalenediol method by making some modi®cations of the H. D. Graham's `clean-up' process of the method. CMC was used alone and in the presence of the other gums such as carrageenan, guar gum, sodium alginate and locust bean gum. The highest average recovery value of CMC was obtained as 94.64% when it was used alone at its dierent concentrations such as 0.010, 0.025, 0.050, 0.075 and 0.100%. The lowest average recovery of CMC was 91.26% when it was used together with locust bean gum at a ratio of 1:2. # 1998 Elsevier Science Ltd. All rights reserved.

1. Introduction Sodium carboxymethylcellulose (CMC) is a derivative of cellulose which is used widely to viscosify various food products such as dairy products, frozen desserts, jellies, cake mixes, salad dressings etc. Its chemical and physical properties have been studied a great deal (Klose & Glicksman, 1972; Arbuckle, 1977; Ganz, 1977; Zecher & Van Collie, 1992). The identi®cation and determination of CMC in foods seems to be a complex analytical problem and in most cases, the critical phase of the analysis lies in the separation of CMC from fats, carbohydrates, proteins, starches and other water soluble gums that may constitute interferences (Hercules Incorporated, 1963). For identi®cation of CMC, many methods have been developed and these are generally colorimetric or gravimetric, e.g. uranyl (Francis, 1953) and copper (Conner & Eyler, 1951) precipitation methods; uranyl (Hercules Incorporated, 1963), 2,7-Naphthalenediol (Graham, 1971), chromotropic (Graham, 1972) and anthrone (Black, 1951) colorimetric methods. Of the colorimetric methods available for the quantitative determination of CMC, the 2,7-naphthalenediol method (Szalkowski & Mader, as cited in Graham, 1971) is the most speci®c. In addition to this Graham (1971, 1977) developed a `clean-up' process in this * Corresponding author.

method for selective isolation from foods and speci®c determination of CMC, when used in conjunction with other food gums. In our study, some modi®cations on the `clean-up' process have been carried out for increasing the eciency of the 2,7-naphthalenediol method. 2. Materials and methods 2.1. Materials Papain was obtained from BDH, England, Hy¯o Super Cell was obtained from Aldrich, cetylpyridinium chloride, cysteine HCl and 2,7-naphthalenediol were obtained from Sigma. The Hydrocolloids were obtained from the following companies: sodium carboxymethylcellulose, Selkim A.S., Turkey, sodium alginate, Grindsted, Denmark, guar gum, Tic Gums, USA, k-carrageenan, Copenhagen Pectin, Denmark, locust bean gum, Sano®, France. Buer EDTA-cysteine HCl-papain mixture and 2,7naphthalenediol reagent were prepared as described in Graham (1971, 1977). For the standard CMC solution; 3±4 mg of CMC was weighed and it was dissolved in hot (80 C or higher) 30% H2SO4 solution, then the volume was made up to 50 ml with this solution; 0.2, 0.4, 0.6, 0.8 and 1 ml of the CMC solution were taken and their absorbances were

0268-005X/98/$Ðsee front matter # 1998 Elsevier Science Ltd. All rights reserved PII: S0268-005X(98)00062-9

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M. Zorba, G. Ova/Food Hydrocolloids 13 (1999) 73±76

measured as a result of their reaction with 2,7-naphthalenediol reagent. For every experiment the standard CMC solution was prepared just before the analysis. 2.2. Methods 2.2.1. Ice-cream production According to Turkish Food Regulations (TFR, 1990), CMC is permitted to be used at a maximum concentration of 500 mg/kg (0.05%) in ice-creams. In this study, therefore, two lower CMC concentrations such as 0.010% and 0.025% and two higher ones such as 0.075% and 0.100% other than the maximum concentration were chosen. CMC was used at each concentration; alone, with k-carrageenan, guar gum, Na-alginate, locust bean gum, and with k-carrageenan±locust bean gum at a total of 6 dierent combinations. CMC ratios in these combinations were 1:1 for CMC:k-carrageenan and 1:2 for CMC:other gums [Klose & Glicksman, 1972; Arbuckle, 1977; Dahle (as cited in Arbuckle, 1977); Glicksman (as cited in Arbuckle, 1977); Cottrell & Kovacs, 1977; Moirano, 1977; Meer, 1977]. In ice-cream production milk powder, the combinations of CMC and the other gums and sugar were mixed to homogenize and ®nally milk was added. Ice-cream was prepared according to the classical method and was stored in a deep freeze before analysis. 2.2.2. Procedure In this study, the 2,7-naphthalenediol method developed by Graham (1971, 1977) was used for the quantitative determination of CMC. This is described in Fig. 1. In the method, ®rstly proteins in the sample were digested with papain to release any CMC bound to proteins and the Na-alginate was removed by precipitation as an insoluble calcium salt. Carrageenan was removed by precipitation as its cetylpyridinium complex in the presence of 0.5 M NaCl. CMC was precipitated selectively with cetylpyridinium chloride (CPC) in the presence of 0.2 M NaCl. The isolated CMC was treated with 30% H2SO4 and reacted with 2,7-naphthalenediol reagent to measure the color development at 540 nm. 2.2.3. Modi®cations on the method A 25 g sample was taken instead of 10 g in order to obtain signi®cant color development at CMC concentrations as low as 0.01%. Glass wool was used at all ®ltration procedures instead of `Reeve Angel 202' ®lter paper. The volume on the third stage of the method was made up to 500 ml instead of 600 ml. In addition, the incubation for 15 min at 35 C was eliminated and this liquid was not ®ltered through the ®ltration column. Fifty millilitres of this solution was pipetted to another 250 ml-Erlenmayer Flask and 50 ml of

Fig. 1. Flow sheet for the separation and determination of CMC by 2,7-naphthalenediol method (Graham, 1971).

absolute ethanol and 100 ml of ethyl acetate were added. The liquid in this ¯ask was ®ltered through the column after incubation for 30 min at room temperature. The ®ltration agent in the ®ltration column (Graham, 1971) was not used and only a 2 cm plug of glass wool was placed on the bottom of the column. The volume of liquids used to wash the column on the fourth stage of the method were reduced by the ratio of 1 to 10. All the modi®cations are shown in Fig. 2 2.2.4. Statistical analysis `Split Plot Design' was selected for analysing the results statistically. In the design, there were two factors. They are CMC concentrations and CMC combinations with other gums and their replication number was three. `The Least Signi®cant Dierence', L.S.D., test was applied where there were statistically signi®cant dierences (Ac,ikgoÈz, 1990). 3. Results Average recovery values of CMC from ice-cream are given in Fig. 3. The highest recovery of CMC was


obtained as 96.73% when it was used alone at 0.1% concentration and the lowest value was obtained as 88.67% when it was used in the presence of locust bean gum (1:2) at 0.01% concentration. The dierences between recovery values of CMC of the six combinations were found signi®cant at the 1% level of signi®cance. This shows that quantitative determination of CMC is eected by these gums. Therefore, the LSD test was applied to create statistically homogeneous groups. It was found that CMC:k-carrageenan and CMC:k-carrageenan:locust bean gum combinations are on the same group, whereas the other combinations have dierent groups. Overall average recoveries of CMC of the six combinations are listed in Table 1. Another signi®cant dierence was found between CMC concentrations and recoveries of CMC at the 5% level of signi®cance. However, this dierence was not signi®cant at the 1% level of signi®cance. This declares that quantitative determination of CMC is aected by the CMC concentrations at the 5% level of signi®cance. It was also detected that there is a linear relationship between them. Through the all combinations, when CMC was used at its 0.1% concentration it was recovered back as 94.14% maximum (Table 2).

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Fig. 3. Average recovery values of CMC of six combinations at its dierent concentrations. A: CMC alone, B: CMC: k-carrageenan (1:1), C: CMC: guar gum (1:2), D: CMC: Na-alginate (1:2), E: CMC-locust beam gum (1:2), F: CMC: k-carrageenan: locust bean gum (1:2:1). Table 1 Overall average recoveries of CMC of the six combinations Gum combinations

Overall average recoveries of CMC (%)

Standard deviation

94.64 93.50 92.82 91.86 91.70

2.42 2.29 1.82 2.73 1.69

91.26

2.51

CMC: alone CMC: guar gam CMC: Na-alginate CMC: k-carrageenan CMC: k-carrageenan: locust bean gum CMC: locust bean gum

Table 2 Overall average recovery of CMC at its selected concentrations CMC concentration (%) 0.100 0.075 0.050 0.025 0.010

Recovery (%)

Standard deviation

94.14 92.58 92.39 92.08 91.96

1.65 0.92 1.93 2.93 3.70

Table 3 Recovery values of CMC obtained in Graham (1971) and in this study Other gums used together with CMC

Recovery values (%) A B (sample: milk) (sample: ice cream)

Alone 84 k-Carrageenan 84 Guar gum 83 Na-Alginate 84 Locust bean gum 83 k-Carrageenan+locust bean gum No experiment Fig. 2. Flow sheet for the separation and determination of CMC by 2,7-naphthalenediol method modi®ed in this study.

96.73 93.35 95.49 93.71 93.14 92.41

A: 2,7-Naphthalenediol method developed by Graham (1971). B: The modi®ed 2,7-naphthalenediol method used in this study.

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4. Discussion

References

The Graham`s `clean-up' process for isolation of CMC is necessary to determine CMC quantitatively in the presence of other food gums. Then it is also necessary to use a speci®c reagent for CMC. It is stated that the 2,7-naphthalenediol method is speci®c for CMC in the presence of other gums, since the `clean-up' process removes all other polysaccharides except Xanthan gum. It is also stated that the `2,7-naphthalenediol test' is highly speci®c for formaldehyde produced by CMC during the heating process (Graham, 1971). The recoveries of CMC obtained in this study by using the modi®cations are higher than the results obtained by Graham (1971). In his study, he used milk as a food sample and recovered CMC at a rate of 84% in the presence of various gums (Table 3). CMC is precipitated selectively with CPC on the third stage of the method developed by Graham (1971) and this is a particular precipitation. In our study, an absolute ethanol and ethyl acetate mixture was also added to precipitate CMC completely in a gel form in addition to the particular precipitation. Hansen and Chang (1968) determined that CMC could be prepiciated from this system by decreasing the polarity of the solution which was accomplished by the addition of a mixture of absolute ethanol and ethyl acetate in the ratio of 1 to 2.5. However, it was later found that a mixture ratio of 1 to 2 is sucient to precipitate CMC selectively. This selective precipitation of CMC increased the recovery of CMC. After the end of the experiment it was found that the method used was reproducible, because the dierences between replications were not found signi®cant at the 1% level of signi®cance. In this study, the eciency of the `clean-up' process and the eciency of the method were increased. However, further studies are needed for determination of CMC from various food products, quantitatively.

Ac,ikgoÈz, N. (1990). Research and experimental methods in agriculture. Ege University. Agriculture Faculty Publications. 2nd ed., _ Number 478, Izmir-Turkey. Arbuckle, W. S. (1977). Ice cream, (3rd ed.). Westport, CT: The AVI Publishing INC. (pp. 97±105). Black Jr, H. C. (1951). Determination of sodium carboxymethyl cellulose in detergent mixtures. Analytical Chemistry, 23(12) 1792±1795. Conner, A. Z., & Eyler, R. W. (1951). Analysis of sodium carboxymethyl cellulose. Analytical Chemistry, 22(9), 1129±1132. Cottrell, I. W., & Kovacs, P. (1977). Algin. In H. D. Graham (Ed.), Food colloids (Chapter 11, pp. 438±463). Westport, CT: The AVI Publishing INC. Francis, C. V. (1953). Sodium carboxymethyl cellulose. Determination of DS active agent. Analytical Chemistry, 25(6), 941±943. Ganz, A. J. (1977). Cellulose hydrocolloids. In H. D. Graham (Ed.), Food colloids, (Chapter 9, pp. 383±417). Westport, CT: The AVI Publishing INC. Graham, H. D. (1971). Determination of carboxymethyl cellulose in food products. Journal of Food Science, 36, 1052±1055. Graham, H. D. (1972). Determination of carboxymethyl cellulose with chromotropic acid. Journal of Dairy Science, 55(1), 42±50. Graham, H. D. (1977). Analytical methods for major plant hydrocolloids. In H. D. Graham (Ed.), Food colloids, (Chapter 14, pp. 540±579). Westport, CT: The AVI Publishing INC. Hansen, P. M. T., & Chang, J. C. (1968). Quantitative recovery of carboxymethyl cellulose from milk. Journal of Agricultural and Food Chemistry, 16(1), 77±79. Hercules Incorporated (1963). Analytical procedures for assay of CMC and its determination in formulations. Bulletin VC-472A Coating and Speciality Products Department. Hercules incorporated, Wilmington, Delaware. Klose, R. E., & Glicksman, M. (1972). Gums. In T. E. Furia (Ed.), Handbook of food additives, (Vol. 1, 2nd ed., Chapter 7, pp. 295±359). Boca Raton, Fla: CRC Press. Meer, W. A. (1977). Plant hydrocolloids. In H. D. Graham (Ed.), Food colloids, (Chapter 11, pp. 523±539), Westport, CT: The AVI Publishing INC. Moirano, A. L. (1977). Sulfated seaweed polysaccharides. In H. D. Graham (Ed.), Food colloids, (Chapter 8, pp. 347±381). Westport, CT: The AVI Publishing INC. TFR (1990). Turkish Food Additives Regulations. Republic of Turkey. Ocial Newspaper. Number: 20541. Zecher, D., & Van Coilie, R. (1992). Cellulose derivatives. In A. Imeson (Ed.), Thickening and gelling agents for food, (Chapter 3, pp. 40±66). Glasgow: Chapman & Hall.

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