Gas Chromatographic Determination of Propionic Acid and Sodium and Calcium Propionate in Bread and Cake 1

284

2 3 3 YASUHIDE TONOGAI ., AMARA KINGKATE3 , WANTHANEE THANISSORN and UDOMKIAT PUNTHANAPRATED

National Institute of Hygienic Sciences, Osaka Branch, 1-1-43, Hoenzaka, Higashi-ku, Osaka, Japan, and Downloaded from http://meridian.allenpress.com/jfp/article-pdf/46/4/284/1655588/0362-028x-46_4_284.pdf by guest on 28 September 2021 Division of Food Analysis, Department of Medical Sciences, Yod-se, Bangkok I, Thailand

(Received for publication October 1, 1982)

ABSTRACT mg/kg in other foods except meat products. Therefore, in this report, the authors intend to simultaneously determine A simple and accurate method for determination of propionic propionic acid and sodium and calcium propionate by a gas acid and sodium and calcium propionate was developed. These chromatographic method after extracting them from bread compounds were simultaneously extracted with ethyl acetate and cake. made acidic with phosphoric acid. The extract was injected di rectly into the gas chromatograph. Calibration curves of the three MATERIALS AND METHODS compounds ranged from 25-1251J.glml. The detection limit of these compounds were 25 ppm by this method. Commercial bis Materials cuits, breads and cakes were analyzed by this method and all of All of the samples were obtained from the market in Thailand. them contained less than the limit permitted by Thai regulations. Apparatus Gas liquid chromatograph equipped with FID, Yanaco G-2800 Propionic acid and propionates have been widely used in (Yanagimoto Co .. Ltd.). Blendor Model HD. Nihon Seiki Co .. Tokyo. Japan. breads and cakes to prevent development of mold and bac teria. Moreover, similar low molecular weight carboxylic Reagants acids are frequently contained in food products because Propionic acid, sodium propionate and calcium propionate were ob they are present in the raw materials or are formed in the tained from BDH chemical Ltd. (Poole, England). Standard Propionic course of manufacturing the products. Therefore, a simple, acid and sodium and calcium propionate (1 mg/ml) standards: 1 g of each was dissolved in 1 L of water. accurate method for determination of propionic acid and propionates would be useful. Conditions of gas chromatograph Until recently steam distillation, ion-exchange and then Column was 3 mm LD. x 2.0 m glass and packed with 5% PEG-20M/ a gas-liquid chromatographic method (3) were used for de gas chrom Q (80-100 mesh). Temperature of injection port was 200a C a termination of propionic acid. This procedure is cumber and that of column was 120 C. some and time-consuming. Graveland (I) developed a di Procedure rect extraction procedure with ether and then used a gas Place 5 g of sample into a 200-ml blender cup, add J ml of phosphoric liquid chromatographic method to determine propionic acid, lag of anhydrous sodium sulfate and 50 ml of ethyl acetate. Blend acid, sorbic acid and benzoic acid in rye bread and mar this mixture for 5 min in a blender and remove and save the upper layer. garine. Issiki et al. (2) improved this method by extracting Add 50 ml of ethyl acetate to the residue and blend again. Combine the two upper layers, filter the layers and fill to 100 mt Inject 5 fJ-I of the sol propionic acid with a mixture of dichloromethane and for ution into the gas chromatograph and calculate the content of propionic mic acid. However, they did not try to extract any propion acid or propionate via the calibration curve. ates. RESULTS AND DISCUSSION In Thailand, propionic acid and sodium and calcium propionate are regulated as follows: they should be not Conditions of gas liquid chromatography and calibration more than 3,000 mg/kg in cheese, and not more than 2,000 curve A glass column packed with 5% PEG-20M/gas chrom Q IThis study was supported partly by the Japan International Cooperation was used under isothermal conditions. A typical Agency's fund under the Japan-Thai/and Cooperative Project "Promo tion of the Provincial Health Services" . chromatogram of carboxylic acids is shown in Fig. I. The 2Nationaiinstitute of Hygienic Sciences, Japan. peak of propionic acid was very clear; moreover, separa 3Department of Medical Sciences, Thailand. tion of acetic acid, propionic acid and butyric acid was suf-

JOURNAL OF FOOD PROTECTION, VOL 46. APRIL 1983 DETERMINING PROPIONATES AND PROPIONIC ACID 285

ficient by this procedure. Calibration curves of propionic acid and sodium and calcium propionate were prepared for standard solutions, and that of propionic acid is shown in Fig. 2. There was a linear relationship between peak height "0 and concentrations with concentrations of 25 to 125 JLglmI. '0 ttl Reproducibility of this curve was within 5%. (.) 'E "0 0 '0 '5. ttl TABLE 1. Comparison of solvents for extracting propionic acid. a 0 (.) 'j;; "0 ct ;>. Solvent '0 .E ttl ciS- Methanol 70.0 OJ (.) 'Q.i '';::; Dichloromethane 39.5 .s:::. (I) (.) Ethyl acetate 73.4 .::L «

ttl Downloaded from http://meridian.allenpress.com/jfp/article-pdf/46/4/284/1655588/0362-028x-46_4_284.pdf by guest on 28 September 2021 (I) Ether 41.2 a.. Hexane 25.0 a5 g of sample, 10 mg of propionic acid, 10 g of sodium sulfate and 50 ml of solvent used to extract thc propionic acid.

Condition of extraction Solvent. A comparison was made of the extractability of propionic acid by five solvents (see Table 1). Since ethyl o 5 10 15 acetate gave the highest recovery, it was chosen as the ex Retention time (min) tracting solvent. Figure 1. Gas chromatogram of low molecular weight carboxylic Medium. Phosphoric acid, formic acid and neutral media acids: acetic acid. propionic acid and butyric acid. were compared as extraction media. Results are shown in Table 2. Highest recoveries were obtained from phosphoric acid-treated samples. Consequently, it was used for the ex traction medium.

TABLE 2. Comparison of media for extracting propionic acid and sodium and calcium propionate. a

(%) Compound Phosphoric Neutral Formic acid acid 10 Propionic 58.4 86.7 98.7 acid E s Sodium 16.0 74.1 97.2 .r: propionate -Ol '0) Calcium 12.7 71.5 95.6 .r::. .:.:

Recovery test Bread was used to test recovery of propionic acid and sodium and calcium propionate, which were added to sam ple at 200 and 2,000 ppm. These results are shown in Table 3. The value of reproducibility were very small, o 25 50 75 100 125 which means that this method is precise. Detection limits Concentration of propionic acid (pg/mO (SIN = 2) of propionic acid and sodium and calcium prop ionate were 25 ppm by this method.

Figure 2. Calibration curve of propionic acid determined by gas Actual survey chromatography. Commercial biscuits, breads and cakes were analyzed by

JOURNAL OF FOOD PROTECTION, VOL. 46, APRIL 1983 286 TONOGAI ET AL.

a TABLE 3. IIp,OFl\t.,,,.,, nrI1ni.nnJ!£' acid and sodium and calcium Added Found (%) :t C.V. (%) o 80 Propionic acid 200 274 97.0± 6.7 98.7± 4.9 o 80 Sodium propionate 200 271 95.5± 8.2 97.2± 5.6 o 80 Calcium propionate 200 268 94.0± 10.4 95.6± 9.1

"5 g of bread used as sample. Downloaded from http://meridian.allenpress.com/jfp/article-pdf/46/4/284/1655588/0362-028x-46_4_284.pdf by guest on 28 September 2021

TABLE 4. Survey of commercial foods for propionic acid and this method and the results are shown in Table 4. The total sodium and calcium propionate. Results are expressed as prop amount of propionic acid and sodium and calcium propion ionic acid. ate are shown as the amount of propionic acid, and these Found values were not corrected for recovery. All of them were No. under the legal limit permitted by Thai regulations. 1. Biscuit A 78 ± 4.0 2. Biscuit B 84 ± 5.3 REFERENCES 3. Biscuit C 150 ± 4.8 I. Graveland, A. 1972. Gas chromatographic determination of propionic, 4. Bread A 965 ± 6.7 sorbic, and benzoic acids in rye bread and margarine. J. Assoc. Off. 5. Bread B 1,200 ± 5.5 Anal. Chem. 55:1024-1026. 6. Bread C 1,620 ± 7.1 2. Isshiki K., S. Tsumura, and T. Watanabe. 1981. Gas chromatographic 7. Bread D 1,870 ± 6.0 determination of propionic acid in bread and cake. J. Assoc. Off. Anal. Chern. 64:280-281. Cake A 8. 740 ± 9.7 3. Pharmaceutical Society of Japan. 1973. Standard methods of analysis 9. CakeB 825 ± 9.2 for hygienic chemists. Kanehara Publishing Co. Ltd., Tokyo, Japan. 10. CakeC 960 ± 10.8 p.215-218.

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