614 J. Jpn. Oil Chem. Soc. Fatty Acid Composition and Total Trans Fatty Acid. Content of Lipids in Processed Foods. I.

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1 614 J. Jpn. Oil Chem. Soc. OR IGINAL Fatty Acid Composition and Total Trans Fatty Acid Content of Lipids in Processed Foods. I. Lipids in Biscuits and Crackers Nobuko KAWAI and Yukuho NAKAYAMA Osaka City Institute of Public Health and Environmental Science (8-34 Tojo-cho, Tennoji-ku, Osaka) The fatty acid composition and trans fatty acid content of lipids in biscuits or crackers were determined. The lipids contained greater amounts of saturated or trans fatty acids, but only small amounts of poly unsaturated fatty acide. The lipids were classified into two groups on the basis of fatty acid composition: a highly saturated acid group (total saturated acid 55%), and a low saturated acid group (total satuated fatty acid 55%). The lipids of the highly unsaturated acid group were found to contain greater amounts of 12:0 fatty acid (source assumed to be coconut oil), while those of the low saturated acid group greater amounts of trans acid (possibly from hydrogenated vegetable oil). Roughly estimating, the lipids of biscuits or crackers were found to consist of palm oil and hydrogenated vegetable oil (low saturated acid group). 1 Introduction The same species of natural foods generally have a characteristic fatty acid composition, though it differs somewhat in terms of the growth environment or season. Hence, the fatty acid composition is used as one of the method for distinguishing foods. However, the same species of processed foods do not have the characteristic fatty acid composition, because they contain various species of lipids. More() over, the hydrogenated oils which contain a considerable amount of trans unsaturated fatty acids (trans acid) are often used to make pro() cessed foods. Compared with cis unsatuarted fatty acids, the structure, physical properties (e.g., high melting point) or chemical stability of trans acids resemble those of the saturated fatty acids, and the physiological effects of trans acids are considered to be closer to those of saturated fatty acids than to cis unsaturated fatty acids1). Therefore, the measurement of the trans acid content of lipid is significant in considering the fatty acid composition of pro() cessed foods. The fatty acid composition and total trans acid content of the lipids of commercially available biscuits and crackers were measured in this study. The fatty acid composition (chain length 4 `24) was measured by the method des() crived in the previous report2), and total trans acids content by infrared (IR) spectrometry mo() difying the Standard Methods for Oil Analysis3) (Jap. Oil Chem. Soc.). The results of this study showed that the lipids of biscuits and crackers contained large amounts of saturated fatty acids or trans acids, and were classified into two groups based on their fatty acid com() position. 2 Methods 2 E1 Materials Thirty-eight samples of biscuits and 14 sam() ples of crackers were obtained from super() markets or department stores in Osaka. The biscuits samples were classified by their lipid content as soft biscuits samples (lipids 20%) and hard biscuits samples (lipids<20%). 2 E2 Reagents Pure (99%+) methyl trans-9-octadecenoate (t-18:1, methyl elaidate; Sigma Co. Ltd.), methyl octadecenoate (18:0, methyl stearate; Sigma Co. Ltd.) and methyl pentadecanoate (as internal standard for GLC; Sigma Co. Ltd.) were used for the measurement of trans acid content. Diazomethane ethyl ethes solution (from N-methyl-N-nitorosourea), Na-methylate methanol solution (from small pieces of sodium 34

2 Vol.35, No.8 (1986) 615 metal and methanol) and sulfuric acid-benzenemethanol (2:58:172) solution were used as methylation reagents. 2 E3 Apparatus Gas liquid chromatography (GLC) was car() ried out with a Shimadzu 4BM type gas liquid chromatograph equipped with FID detector and on a glass column (i.d. 3mm ~2m) packed with 20% DEGS on 60/80 mesh Celite 545, 10% FFAP on 100/120 mesh Gaschrom Q, or 15% OV-275 on 80/100 mesh Chromosorb P. The measurements of peak areas were made with an automatic integrator (C-RIA) attached to the GLC. IR spectra were measured by JASCO (Nihon Bunko) A-3 type IR spectrometer KRS-5 cell (10mm). The statistical treatment of data was performed with IBM Series-1 computer. 2 E4 Experimental Methods 2 E4 E1 Treatment of Sample Samples (about 50g) were chopped up with the multi-blender mill (Nihon Seiki) and about 2g of the sample was used for the measure() ment of water content (drying at 105 Ž, 3 h). The lipid of the sample (about 2g) was ex() tracted by refluxing with CHCl3-methanol (2: 1) according to the Standard Methods of Anal() ysis for Hygienic Chemists, Supple4)., the ob() tained liquid phase was passed through No.5 A filter paper (Toyo) into the round bottomed flask, and the organic solvents were removed by rotary evaporator (Tokyo Rika, 60 Ž, in vacuo). The lipid in the flask was dissolved in 25ml CHCl3. The lipid solution was dehydrated by anhydrous Na2SO4, and passed through No.5 C filter paper (Toyo). The crude lipid content (removing the solvent and drying at 100 Ž, 30min), fatty acid composition and total trans acid content were measured for a portion of the lipid solu() tion obtained by the aforementioned treatment. 2 E4 E2 Measurement of Fatty Acid Com() position According to the previous report2), the lipid (50 `100mg) obtained from a portion of the lipid extract was methylated by diazomethane and Na-methylate, and the fatty acid composi() tion (chain length 4 `24) was measured by GLC on 20% DEGS column (column temp. 200 Ž, detector temp. 230 Ž, N2 flow 50ml/min), on 15% OV-275 column (column temp. 80 ` 230 Ž, program rate 10 Ž/min, detector temp. 250 Ž, N2 flow 50ml/min; for the measurement of short chain fatty acid methyl esters) and on 10% FFAP column (column temp. 230 Ž, detec() tor temp. 250 Ž, N2 flow 50ml/min; for the measurement of fatty acid methyl esters which could not be separated on 20% DEGS column). 2 E4 E3 Measurement of Trans Acid Con() tent The lipid (about 25mg) obtained from a por() tion of the lipid extract was methylated by re() fluxing with sulfuric acid-benzene-methanol solu() t ion, and the fatty acid methyl esters were ex() tracted into petroleum ether, according to the Standard Method for the Analysis of Oil5). The solvent was completely removed, and the residual fatty acid methyl esters were dissolved in 25ml of CS2 (sample solution). The IR spectra of the sample solution were measured against CS2, and the absorbance of trans bond at 965cm-1 (ASamp) was obtained by the base line method (base line 1,050 `940cm-1). The methyl palmitate (16:0) content of the sample solution was measured by GLC under the con() dition of 2 E4 E2, using methyl pentadecanoate (15 : 0) as an internal standard. The total fatty acid methyl ester content of the sample solution (CSamp) was calculated from the methyl hexa() decanoate content and the fatty acid composition. The IR absorbance (AEl, ASt) and fatty acid methyl ester content (CEl, CSt) of the standard solution (about 1mg/ml CS2) of methyl elaidate or methyl stearate were also measured in the same manner. The total trans acid content (as methyl elaidate amount) of the sample lipid was calculated by the following equation, using methyl stearate as blank. Trans acid (%) ~ = ASamp/CSamp-ASt/CSt/AEl/CEl-ASt/CSt Results and Discussion 3 E1 Analytical Method of Trans Acids In the trans acid analysis of Standard of the Analytical Method3) the 200mg refined fatty acid methyl esters of sample lipids must be precisely weighed, and the IR spectra of their CS2 solution are measured. However, a consi() derable amount of short chain fatty acids (chain length 4 `12) have been lost during the 35

3 616 J. Jpn. Oil Chem. Soc. refining of fatty acid methyl esters. Therefore, in the present study, the total trans bond con() tent and the total amount of fatty acid of the samples were separately measured, so the loss of the short chain fatty acid methyl esters dur() ing refining was corrected. The good relation() ship between total trans acid content (by present method) and blending ratio of lipid was con() firmed as to natural lipid (soybean oil, palm oil or coconut oil) and hydrogenated oil (hydro() genated soybean oil or hydrogenated fish oil), or methyl stearate and methyl elaidate mixture. Since the process of refining, separation of fatty acid methyl esters and precise measurement for the weight of the methyl esters are unnecessary, the present method for trans acid analysis is considerably simple, when the fatty acid com() position is known. According to Ottenstein's method6), the spe() cies of trans acids were analysed by GLC on 15% OV-275 (coated on 80/100 mesh Chromo() sorb P) column (i.d. 3mm ~6m) for the sam() ple lipids, showing the high content total trans acid in the lipids. There was a small amount of t-16:1 fatty acid, t-20:1 fatty acid, t-20:2 fatty acid, t-22:1 fatty acid or t-22:2 fatty acid which may be derived from blended hydro() Fig,-1 Distribution frequency of fatty acid content (as methyl ester) of lipids in biscuits and crackers. Table-1 Correlation coefficient between total saturated acid and each fatty acid content of lipids in biscuits and crackers. genated fish oil, in the sample lipids However, most of the sample lipids contained only t-18 :1 fatty acid (elaidic acid) as a trans acid. 3 E2 Fatty Acid Composition and Total Trans Acids Content of Lipids in Biscuits and Crackers Plasticity and chemical stability are required for lipids used to make biscuits or crackers. Therefore, such lipids are considered to contain large amounts of saturated acids or trans acids which have a high melting point and show chemical stability. In Fig.-1, the histograms of total saturated fatty acids, total trans acids and their total content are shown. The total saturated fatty acid and the total trans acid content are distributed over a wide concentra() tion range, and the samples were divided into two groups in terms of saturated fatty acid content (boundary at 55%); few samples show() ed an intermediate concentration between two groups. The samples were also divided by trans acid content (boundary at 15%). How() ever, the total content of saturated fatty acids * HS: Highly saturated acid group ** LS: Low saturated acid group *** TTA: Total trans acids and trans acids showed a nearly normal distri() bution (average, 70 `75%, as much as milk fat). Hence, in the present study, the samples containing saturated acid more than 55% of total fatty acid were treated as a highly saturated acid group, and those less than this as a low saturated acid group. The relationships between total saturated acid content and major fatty acid contents were ex() amined. The correlation coefficients (r) were shown in Table-1 and the characteristic rela() 36

4 Vol.35, No.8 (1986) 617 vegetable oil (major fatty acids; 18:1 and traps acids) are seemed to be blended for the low saturated fatty acid group. By increasing the ratio of palm oil, 16:0 acid and total saturated fatty acid content were increased, but trans acid content decreased. On the other hand, palm oil and coconut oil (major fatty acids; 12:0 and 14:0 fatty acids) are seemed to be blended for the high saturated fatty acid group. By increasing the ratio of coconut oil, 12:0 fatty acid, 14:0 fatty acid and total saturated acid content were increased, but 16:0 fatty acid content was decreased. 12:0 FA ( ksfa l>55%): ksfa l=0.40 k12:0 FA l+59.4(%) 16:0 FA ( ksfa l>55%): ksfa l=-0.69 k16:0 FA l+82.3(%) 16:0 FA ( ksfa l<55%): ksfa l=0.98 k16:0 FA l+13.8(%) 18:1 FA: ksfa l=-1.02 k18:1 FA l+85.0(%) trans FA ( ksfa l<55%): ksfa l=-0.31 ktrans FA l+45.7(%) Fig.-2 Correlation between each fatty acid content and saturated fatty acid content (as methyl ester) of lipids in biscuits and crackers. tionships in Fig.-2. The contents of total saturated acids and 18:1 fatty acid were con() sidered to have a compensational relationship, because they showed quite a negative correla() tion (slope-1) for all samples. The rela() tionship between total saturated acid and 12:0 fatty acid, 16:0 fatty acid or trans acid con() tent was different for the samples from highly and low saturated group. A positive correla() tion was shown between total saturated acids and 12:0 fatty acid (samples of highly saturated group) or 16:0 fatty acid content (samples of low saturated group). A negative correlation was shown between total saturated acids and 16:0 fatty acid (samples of highly saturated group) or traps acids content (samples of low saturated group). The relationship between total saturated acids and 12:0 fatty acid (sam() ples of low saturated group) or trans acids (samples of highly saturated group) showed a low correlation. Hence, the source lipids used to make biscuits or crackers were presumed to be different for the two groups. 3 E3 Presume Source Lipids in Biscuits and Crackers The following inferences were made from the present fatty acid composition data of bis() cuits and crackers. Palm oil (major fatty acids; 16:0 and 18:1 fatty acids) and hydrogenated Kohno et al7). reported that shortening con() taining a large amount of saturated acid was presumed to be completely hydrogented oil. However, the completely hydrogenated oil was not thought to be much used for biscuits or crackers in the present investigation, because 18:0 fatty acid (major fatty acid of completely hydrogenated vegetable oil), 20:0 fatty acid (major fatty acid of completely hydrogenated fish oil) or 22:0 fatty acid (same as 20:0) content was low and showed a low correlation with total saturated fatty acid content. Some samples were presumed to contain hy() drogenated fish oil or milk fat from the con() centration of long chain fatty acid (carbon chain 20 `22) or 4:0 fatty acid, respectively. But because of the few samples, the latter were classified in to two groups according to their total saturated fatty acid content in lipid. In Table-2, the average lipid content, water content, fatty acid composition and total trans acid content of soft biscuits, hard biscuits and crackers were shown; those for the two lipid groups were also shown in this table. These results show that the lipid of biscuits or crackers contained large amounts of saturated acids or trans acids amounting to 70%, being comparable to milk fat. On the contrary, poly unsaturated fatty acids were few, so the ratio of poly unsaturated fatty acid to saturated fatty acid (P/S ratio) was low. Thus, such lipids show the type of plasticity and chemical sta() bility which are desired for the lipid of a bis() cuit or cracker. In addition, these lipids were classified into two groups owing to their fatty acid composition, which were approximately in() dicated in Fig.-3. The twenty samples be() 37

5 618 J. Jpn. Oil Chem. Soc. 38

6 Vol.35, No.8 (1985) 619 5) Ed. Japan Oil Chem. Soc., gstandard of the Analytical Method h, , 20-71, Jap. Oil Chem. Soc (1971) (in Japanese). 6) D.M. Ottenstein, L.A. Witting, G. Walker, V. Mahadlvan, and N. Pelick, J. Am. Oil Chem. Soc., 54, 207 (1977). 7) M. Kohno, Y. Cho, and M. Sugano, Eiyo-to-Shokuryo, 35, 217 (1982) (in Japanese). Fig.-3 Typical fatty acid composition of lipids in biscuits and crackers. longed to the highly saturated group (12 soft biscuit, 4 hard biscuit, 4 cracker) and the thirtytwo samples to the low saturated group (15 soft biscuit, 7 hard biscuit, 10 cracker) in the present study. We are indebted to Katsushige Kodera (student of Kinki Univ.) for his technical assistance and to Keiko Masumoto (our institute) for the data processing. (Received Jan. 16, 1986) References 1) B. Aaes-Jorgensen and H. Dam, Br. J. Nutr., 8, 281 (1954). 2) N. Kawai, Y. Nakayama, and K. Sasaki, Yukagaku, 34, 921 (1985). 3) Ed. Japan Oil Chem. Soc., gstandard of the Analyti() cal Method h , Japan Oil Chem. Soc. (1981) (in Japanese). 4) Ed. Pharm. Soc. Jap., gstandard Methods of Analysis for Hygienic Chemists with Commentary 1980 (Suppl. 1983) h p. 1285, Kanehara Shuppan (Tokyo) (1983) (in Japanese).