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The chemical constituents of tomato seeds
FoodChemistry9 (1982) 315-318
Technical Note The Chemical Constituents of Tomato Seeds
INTRODUCTION
Tomato seeds are a waste product from the food canning industry and find use for animal feeding. Gad et al. (1968) determined the chemical constituents of tomato seeds; they found seventeen amino acids in their proteins. Tsatsaronis & Boskou (1975) stated that the amino acid content and the nutritive value of tomato seed proteins were similar to those of soybean and sunflower proteins. Amelotti et al. (1967) and Gad et al. (1968) studied the fatty acid constituents of tomato seeds. The present study was carried out to determine the nutritional value of tomato seeds for food and feed.
MATERIALS AND METHODS
Samples of tomato seeds were taken from fifteen kilogrammes of Roma variety tomatoes (Lycopersicum esculentum) at canning ripeness from the University Farm, Pisa, Italy. After juice extraction, the pomace was partially dried and the seeds were removed manually and dried by lyophilisation. Moisture, ether extract, ash, crude fibre, sugars and nitrogen were determined according to the methods of the Association of Official Analytical Chemists (1965) and nitrogen-free extract was obtained by difference. All determinations were made in triplicate. Amino acid analysis was carried out by using the Aminolyzer automatic amino acids analyser (Optica, Milan, Italy). Tryptophane was determined colorimetrically in the seeds according to Sodek et al. (1975). The following method was used for preparing the mineral solution. A dry ashing procedure was used for atomic absorption and spectrophotometric analyses of all elements. Triplicate 1.00 + 0.05g dried samples were weighed into clean, dry platinum crucibles. Each sample was pre-ashed and ashing completed by placing the sample in an electric muffle furnace at 500 °C for 4 h. The ash was dissolved in 5 ml 315 Food Chemistry 0308-8146/82/0009-0315/$02.75 ~ Applied Science Publishers Ltd, England, 1982 Printed in Great Britain
grammes per lOOg of dry sample 5.5 20.1 3.1
Constituents
Ash Crude fibre Total sugars (glucose) Protein (N × 6.25) Ether extract Nitrogen free extract 30.4 14.7
26.2
TABLE 1
Calcium Copper Iron Magnesium Manganese Nickel Potassium Sodium Zinc
Elements 166 2.22 17.5 289 5.12 4.16 778 111 4.64
milligrammes per lOOg of dry sample
T H E C H E M I C A L C O N S T I T U E N T S OF T O M A T O SEEDS
grammes per 100g of protein 4.91 2.26 8.81 9.68 3.10 4.88 18.5 15.4 4.62 3.70 0.81 3.81 0.80 3.56 5.81 3.40 3-61 1.01
Amino acids Lysine Histidine Arginine Aspartic acid Threonine Serine Glutamic acid Proline Glycine Alanine Half cystine Valine Methionine Isoleucine Leucine Tyrosine Phenylalanine Tryptophane
~o
~> Z
m > ~7 en ,r" ~>
Z~
>
O~
317
THE CHEMICAL CONSTITUENTS OF TOMATO SEEDS
of 20 ~ HCI. The solutions were warmed to effect complete solution and filtered through acid washed filter paper (Whatman No. 42) into 100 ml volumetric flasks. After diluting to volume, the solutions were ready for analysis by atomic absorption spectrophotometry. An Atomspek HI 170 (Hilger & Watts, 1971), atomic absorption spectrophotometer (AAS) was used for mineral analysis. The instrument setting and other experimental conditions were in accordance with the manufacturer's specifications. A Hewlett-Packard F & M 5750 gas chromatograph with a dual flame ionisation detector and (6 ft x 3 mm inside diameter) stainless steel columns packed with 10 ~o diethylene glycol succinate on 80-100 mesh Chromosorb W AW-DMCS were used for the determination of fatty acid methyl esters. Fatty acid methyl esters were prepared with methanol containing 3 ~o concentrated sulphuric acid (AOCS, 1966). Peak areas and retention times were determined by a Hewlett-Packard Model 3370 A integrator.
RESULTS AND DISCUSSION
The results in Table 1 show the constituent percentages of the tomato seeds as follows: 5-5 ash; 20.1 crude fibre; 3.1 glucose; 26.2 protein; 30.4 ether extract and 14.7 nitrogen free extract. All results are expressed on a dry weight basis. Tsatsaronis & Boskou (1975), in their study on tomato seed constituents, reported slightly lower constituents than this finding. They also found lower amounts of minerals in tomato seeds grown in Greece. There are eighteen amino acids in the tomato seed protein (Table 1). Gad et al. (1968) found seventeen amino acids in the tomato seed protein grown in Egypt, and Tsatsaronis & Bosku (1975) found eighteen amino acids but in different amounts. The fatty acid composition of the tomato seed oil is shown in Table 2. There are four saturated fatty acids and three unsaturated fatty acids. Gad et al. (1968) found two saturated fatty acids, palmitic (21.9 ~o) and stearic (3.2 ~o) and two unsaturated fatty acids, oleic (35.8 ~o) and linoleic (39.1 ~o). In addition, Amelotti et al. (1967) TABLE 2 THE FATTY ACID CONSTITUENTS OF TOMATO SEED OIL (AREA PER CENT OF TOTAL METHYL ESTERS)
Saturated fatty acids M yristic Palmitic Stearic Arachidic
o/ /o
Unsaturated fatty acids
%
0.5 16. l 5.5 0.5
Oleic Linoleic Linolenic
25- 5 50.5 1.4
318
ABDEL-HAMIDYOUSSEFABDEL-RAHMAN
found that tomato seed oil was composed of three major saturated fatty acids-palmitic (14.8 9/0), stearic (4.7 ~o) and arachidic (2 ~o)--and three major unsaturated fatty acids--oleic (20.3 ~o), linoleic (54.3 ~o) and linolenic (2.9 ~). The differences in results between the present investigation and the previous studies may be attributed to the varietal differences, region of cultivation and environmental factors. The data show that tomato seeds are rich in nutrients. The fatty acid constituents of the tomato seed oil are similar to those of cottonseed oil (Abdel-Rahman and Youssef, 1978). The oil contains more than 75 ~/o unsaturated fatty acids and is consequently a good salad oil. Its meal is a potentially useful animal feedstuff.
REFERENCES ABDEL-RAHMAN,A. Y. & YOUSSEF,S. A. M. (1978). Compositional study on some Egyptian cottonseed varieties. Grasas Y Aceites, 29, 91-6. AMELOTTI,G., GAROIA,V. & GOLDBERG,F. (1967). La Comparizione acidica di alcuni Oli Vegetali. La Rivista ltaliana delle Sostanze Grasse, 44, 372-8. AOCS (1966). Report of the Instrumental Techniques Committee. J. Amer. Oil Chem.]Soc.,43, 10A. ASSOCIATION OF OFFICIAL ANALYTICALCHEMISTS (AOAC) (1965). Official methods of analysis, Washington, DC. GAD, A. M., EL-KHALAFY,H. M., HASSAN,M. M. & SHOEB,Z. E. (1968). Chemical investigation on Egyptian vegetable fats and oils. Grasas Y Aceites, 19, 139-45. HILGER& WATTS(1971). Instruction manual for atomic absorption 'A tomspek" HI 170. Rank Precision Industrial Ltd., London. SODEK,L., VECCHIA,T. D. & LIMA,G. P. (1975). Rapid determination of tryptophan in beans by the acid ninhydrin method. J. Agric. Food Chem., 23, 1147-9. TSATSAROSlS,G. C. & BOSKU,D. G. (1975). Amino acid and mineral salt content of tomato seed and skin waste. J. Sci. Fd Agric., 26, 421-3. ABDEL-HAMID YOUSSEF ABDEL-RAHMAN
Food Science and Technology Department, Faculty of Agriculture, Alexandria University, Alexandria, Egypt (Received: 12 May, 1982)
Technical Note The Chemical Constituents of Tomato Seeds
INTRODUCTION
Tomato seeds are a waste product from the food canning industry and find use for animal feeding. Gad et al. (1968) determined the chemical constituents of tomato seeds; they found seventeen amino acids in their proteins. Tsatsaronis & Boskou (1975) stated that the amino acid content and the nutritive value of tomato seed proteins were similar to those of soybean and sunflower proteins. Amelotti et al. (1967) and Gad et al. (1968) studied the fatty acid constituents of tomato seeds. The present study was carried out to determine the nutritional value of tomato seeds for food and feed.
MATERIALS AND METHODS
Samples of tomato seeds were taken from fifteen kilogrammes of Roma variety tomatoes (Lycopersicum esculentum) at canning ripeness from the University Farm, Pisa, Italy. After juice extraction, the pomace was partially dried and the seeds were removed manually and dried by lyophilisation. Moisture, ether extract, ash, crude fibre, sugars and nitrogen were determined according to the methods of the Association of Official Analytical Chemists (1965) and nitrogen-free extract was obtained by difference. All determinations were made in triplicate. Amino acid analysis was carried out by using the Aminolyzer automatic amino acids analyser (Optica, Milan, Italy). Tryptophane was determined colorimetrically in the seeds according to Sodek et al. (1975). The following method was used for preparing the mineral solution. A dry ashing procedure was used for atomic absorption and spectrophotometric analyses of all elements. Triplicate 1.00 + 0.05g dried samples were weighed into clean, dry platinum crucibles. Each sample was pre-ashed and ashing completed by placing the sample in an electric muffle furnace at 500 °C for 4 h. The ash was dissolved in 5 ml 315 Food Chemistry 0308-8146/82/0009-0315/$02.75 ~ Applied Science Publishers Ltd, England, 1982 Printed in Great Britain
grammes per lOOg of dry sample 5.5 20.1 3.1
Constituents
Ash Crude fibre Total sugars (glucose) Protein (N × 6.25) Ether extract Nitrogen free extract 30.4 14.7
26.2
TABLE 1
Calcium Copper Iron Magnesium Manganese Nickel Potassium Sodium Zinc
Elements 166 2.22 17.5 289 5.12 4.16 778 111 4.64
milligrammes per lOOg of dry sample
T H E C H E M I C A L C O N S T I T U E N T S OF T O M A T O SEEDS
grammes per 100g of protein 4.91 2.26 8.81 9.68 3.10 4.88 18.5 15.4 4.62 3.70 0.81 3.81 0.80 3.56 5.81 3.40 3-61 1.01
Amino acids Lysine Histidine Arginine Aspartic acid Threonine Serine Glutamic acid Proline Glycine Alanine Half cystine Valine Methionine Isoleucine Leucine Tyrosine Phenylalanine Tryptophane
~o
~> Z
m > ~7 en ,r" ~>
Z~
>
O~
317
THE CHEMICAL CONSTITUENTS OF TOMATO SEEDS
of 20 ~ HCI. The solutions were warmed to effect complete solution and filtered through acid washed filter paper (Whatman No. 42) into 100 ml volumetric flasks. After diluting to volume, the solutions were ready for analysis by atomic absorption spectrophotometry. An Atomspek HI 170 (Hilger & Watts, 1971), atomic absorption spectrophotometer (AAS) was used for mineral analysis. The instrument setting and other experimental conditions were in accordance with the manufacturer's specifications. A Hewlett-Packard F & M 5750 gas chromatograph with a dual flame ionisation detector and (6 ft x 3 mm inside diameter) stainless steel columns packed with 10 ~o diethylene glycol succinate on 80-100 mesh Chromosorb W AW-DMCS were used for the determination of fatty acid methyl esters. Fatty acid methyl esters were prepared with methanol containing 3 ~o concentrated sulphuric acid (AOCS, 1966). Peak areas and retention times were determined by a Hewlett-Packard Model 3370 A integrator.
RESULTS AND DISCUSSION
The results in Table 1 show the constituent percentages of the tomato seeds as follows: 5-5 ash; 20.1 crude fibre; 3.1 glucose; 26.2 protein; 30.4 ether extract and 14.7 nitrogen free extract. All results are expressed on a dry weight basis. Tsatsaronis & Boskou (1975), in their study on tomato seed constituents, reported slightly lower constituents than this finding. They also found lower amounts of minerals in tomato seeds grown in Greece. There are eighteen amino acids in the tomato seed protein (Table 1). Gad et al. (1968) found seventeen amino acids in the tomato seed protein grown in Egypt, and Tsatsaronis & Bosku (1975) found eighteen amino acids but in different amounts. The fatty acid composition of the tomato seed oil is shown in Table 2. There are four saturated fatty acids and three unsaturated fatty acids. Gad et al. (1968) found two saturated fatty acids, palmitic (21.9 ~o) and stearic (3.2 ~o) and two unsaturated fatty acids, oleic (35.8 ~o) and linoleic (39.1 ~o). In addition, Amelotti et al. (1967) TABLE 2 THE FATTY ACID CONSTITUENTS OF TOMATO SEED OIL (AREA PER CENT OF TOTAL METHYL ESTERS)
Saturated fatty acids M yristic Palmitic Stearic Arachidic
o/ /o
Unsaturated fatty acids
%
0.5 16. l 5.5 0.5
Oleic Linoleic Linolenic
25- 5 50.5 1.4
318
ABDEL-HAMIDYOUSSEFABDEL-RAHMAN
found that tomato seed oil was composed of three major saturated fatty acids-palmitic (14.8 9/0), stearic (4.7 ~o) and arachidic (2 ~o)--and three major unsaturated fatty acids--oleic (20.3 ~o), linoleic (54.3 ~o) and linolenic (2.9 ~). The differences in results between the present investigation and the previous studies may be attributed to the varietal differences, region of cultivation and environmental factors. The data show that tomato seeds are rich in nutrients. The fatty acid constituents of the tomato seed oil are similar to those of cottonseed oil (Abdel-Rahman and Youssef, 1978). The oil contains more than 75 ~/o unsaturated fatty acids and is consequently a good salad oil. Its meal is a potentially useful animal feedstuff.
REFERENCES ABDEL-RAHMAN,A. Y. & YOUSSEF,S. A. M. (1978). Compositional study on some Egyptian cottonseed varieties. Grasas Y Aceites, 29, 91-6. AMELOTTI,G., GAROIA,V. & GOLDBERG,F. (1967). La Comparizione acidica di alcuni Oli Vegetali. La Rivista ltaliana delle Sostanze Grasse, 44, 372-8. AOCS (1966). Report of the Instrumental Techniques Committee. J. Amer. Oil Chem.]Soc.,43, 10A. ASSOCIATION OF OFFICIAL ANALYTICALCHEMISTS (AOAC) (1965). Official methods of analysis, Washington, DC. GAD, A. M., EL-KHALAFY,H. M., HASSAN,M. M. & SHOEB,Z. E. (1968). Chemical investigation on Egyptian vegetable fats and oils. Grasas Y Aceites, 19, 139-45. HILGER& WATTS(1971). Instruction manual for atomic absorption 'A tomspek" HI 170. Rank Precision Industrial Ltd., London. SODEK,L., VECCHIA,T. D. & LIMA,G. P. (1975). Rapid determination of tryptophan in beans by the acid ninhydrin method. J. Agric. Food Chem., 23, 1147-9. TSATSAROSlS,G. C. & BOSKU,D. G. (1975). Amino acid and mineral salt content of tomato seed and skin waste. J. Sci. Fd Agric., 26, 421-3. ABDEL-HAMID YOUSSEF ABDEL-RAHMAN
Food Science and Technology Department, Faculty of Agriculture, Alexandria University, Alexandria, Egypt (Received: 12 May, 1982)