Suitability of Some Tomato (Lycopersicon esculentum Mill.) genotypes for Paste Production

Transcription

1 Journal of Science and Technology 12 (02) December 2011 ISSN X Sudan University of Science and Technology Suitability of Some Tomato (Lycopersicon esculentum Mill.) genotypes for Paste Production Abdel Moneim E. Sulieman 1, Khalid M. A. Awn 1 and Mohammed T. Yousif 2 1 Department of Food Science and Technology, Faculty of Engineering and Technology, University of Gezira, Wad-Medani, Sudan 2 National Institute for Promotion of Horticultural Exports, University of Gezira, Wad-Medan ABSTRACT: The objective of this study was to evaluate the quality of some newlybred Sudanese tomato genotypes at the National Institute for Promotion of Horticultural Exports- Gezira University, to identify their suitability for paste production, these genotypes included: Juvenile, Top -1, Line -4, and Line -2. Line 4 scored the highest paste yield (17.5 ton/ha) followed by Juvenile (14.35 ton/ha), Top -1 (11.3 ton/ha) and Peto 86 (7.92 ton/ha). The proximate chemical analysis revealed that the moisture content of the different fresh tomato samples ranged between 92% and 94%, and notable differences were found in protein and ash contents. The paste samples differed significantly in ph, acidity, total soluble solids and vitamin C contents. Moreover, all paste samples contained appreciable amounts of calcium, phosphorous, potassium and sodium. The microbiological analyses revealed absence of yeast and moulds in all paste samples, while the paste prepared from Juvenile tomato genotype contained high total viable microbial cells. The sensory evaluation of various paste samples showed significant differences in their texture and overall quality. KEY WORDS: tomato, paste, physical characteristics, ascorbic acid, minerals. INTRODUCTION: The cultivated tomato ( Lycopersicon esculentum Mill) is a member of the according to Mohamed (1995) tomato was first introduced to Sudan through Egypt in 1821 and recently, it becomes as a night shade family Solanaceae. The genus popular vegetable crop ranking the Lycopersicon, coraprises of nine species second after onion in terms of cultivated (Wikipedia, 2006). Tomato is a warm areas. The main production areas are season vegetable crop and is Gezira, south Blue Nile, Kassala, and considered one of the most important Khartoum States. The annual production vegetable crops worldwide. In recent of Tomato in Sudan is tonnes years, tomato has received a considerable ( increment in its horizontal and vertical tries_by_tomato_production). Africa total annual production ( FAO, 1999). (specifically South and North) is a net World production area of tomatoes was consumer of tomato paste and is estimated to be 2-4 million hectares. importing more than 140,000 tones of Europe is the greater producer of tomato followed by North and South America and Asia. The highest tomato productivity per hectare was found to be in North and Central America (45 ton/ha) which is more than two folds increase as compared to that of Africa (20 ton/ha) as reported by the FAO (1999). The exact introduction of tomato to Sudan tomato paste from mainly European suppliers. Depending on world prices, this represents annual sales in Africa of $50-60 million. This is the market to be targeted by Uganda, which is set to increase as regional eating and culinary habits change in Africa generally and with increased demand for tomato related fast foods. has not been recorded. However, 45

2 In recent years demand for tomato paste in the Sudan; has increased considerably. The local annual demand for tomato paste was estimated to be about 6000 tons which is imported annually from European countries such as Greece with hard currency. In fact Sudan is rich n its natural resources and the conditions are quite suitable for tomato production and processing. Therefore, in order to save hard currency, it is advisable to grow tomato cultivars that are adaptable to the different local growing conditions in Sudan and suitable for processing. Accordingly, the objective of this research was to evaluate some newlybred tomato genotypes for paste production. MATERIAL AND METHODS Materials used Four inbred lines of tomato namely Top - 1, Juvenile, Line 2 and Line 4 developed at the National Institute for Promotion of Horticultural Exports, were used in this study. The commercial variety Peto 86 from Pop Vriend Seeds Company was used as a control. The seeds and the different tomato samples were grown in a Randomized Complete Block Design (RCBD), with three replications, at the Faculty of Agricultural Sciences of the University of Gezira. The sowing date was the 1st of July All recommended cultural practices used for growing tomatoes in central Sudan were followed (Mohamed, 1992). After cultivation, tomato fruits of the different entries were subjected to physical, physico-chemical, biochemical and microbial analysis at the Department of Food Science and Technology, Faculty of Engineering and Technology, University of Gezira, Sudan. The paste of different tomato genotypes was prepared following the procedure described by Fagir (2002). T omato fruits were sorted, washed, cut into halves and then placed in an open jacketed kettle and heated for 15 minutes at 68 C to inactivate enzymes, then poured into a juicer ( pulper) with the reject set at 2/3 rds. The extracted juice was concentrated in a vacuum evaporator (forced circulation type) at a temperature range of 52 C to 60 C. Then, the juice was concentrated till the amount of total soluble solids reached 24%. The resulted paste was packed into cans (400 g), sterilized at 100 C for 20 minutes and cooled. The canned paste samples were autoclaved at 121 C (15Lb) for 20 min., cooled for over-night at room temperature and then subjected to various analyses. Methods Physical and physicochemical methods Fruit physical characteristics included fruit length, fruit width and length / width ratio and fruit volume were measured using a Varnier caliper, while the total soluble solids and ph of tomato samples were determined. The total soluble solids using a hand refractometer, while, ph values were determined by a three digital ph meter, and the total titrable acidity was determined according to the AOAC (2000) procedure. Chemical methods The titrable acidity and ascorbic acid (vitamin C) contents were determined according to the AOAC (20 00) procedures. Moisture, protein and ash contents in the different samples were determined according to the methods of the Association of Official Analytical Chemists (AOAC 1990). Potassium (K), sodium (Na) and calcium (Ca) concentrations in different tomato genotypes and the paste were determined using a flame photometer (model Coring 400) according to the AOAC (2000) method. Microbiolgical analysis Total viable count One gram sample of paste was transferred in 99 ml of distilled water and the mixture was homogenized with continuous shaking for several minutes. Then, one ml of the sample solution was diluted in another tube with 9 ml distilled water. The total 46

3 viable count per gram of paste was carried out following the method of American Public Health Association (APHA 1967). Yeast and mould count The yeast and mould strains in the different samples were cultured on Potato Dextrose Agar (PDA) medium, and incubated at 25 C for 72 hours, then the yeasts and moulds were counted. Plates containing between 30 and 3000 colonies were counted as colony forming units (c.f.u.) per g of sample. Sensory evaluation Samples of the different tomato paste products were coded and subjected to sensory evaluation by using 10 panelists in a complete randomize design ( CRD). The panelists were asked to assess each sample for its texture, flavour, appearance and colour, in a comfortable room with sufficient light and fresh air. The results obtained from the panelists were converted to scores ranging from: like extremely (9) to dislike extremely (1). Yield, physical, physico-chemical and sensory evaluation data were statistically analysed according to the software packages of MSTAT (1985). RESULTS AND DISCUSSION Table 1 shows the total tomato fruits and their paste yield (ton/ha) of the different genotypes. Highly significant differences were found among the different genotypes for both fresh and paste yield. Line - 4 gave the highest fresh tomato yield (74 ton/ha) followed by Juvenile (69 ton/ha) and Top -1 (64 ton/ha) while, the commercial variety Peto 86 gave the lowest fresh tomato yield (39 ton/ha). This might be attributed to the high sensitivity of this variety to the rainfall growing conditions. The fruit yield of Line -4, Juvenile and Top-1 were higher than that obtained by Fagir (2002) for the variety Omdurman (53 ton/ha), whereas the fruit yield of Peto-86 was comparable to the fruit yield of the same variety (40 ton/ha) reported by Fagir (2002). Results of paste yield were in the same trend of that of fresh tomato yield, with Line 4 gave the highest paste yield of ton/ha followed by Juvenile (14.3 ton/ha), Top-1 (11.3 ton/ha) and Peto -86 (7.9 ton/ha). The paste yield of Pet-86 was comparable to that reported by Fagir (2002), which was 7.5 ton/ha. Physical characteristics of tomato fruits Table 2 presents different physical characteristics of different tomato fruits. Highly significant differences were found in fruit volume among different genotypes, with Line 4 gave the highest fruit volume (86.33 cm 3 ) followed by Juvenile (78.2 cm 3 ), Top 1 (73 cm 3 ), Line 2 (72.8 cm 3 ) and Peto 86 (65 cm 3 ). Fruit volume is considered to be a character of economic importance as large volume fruits are much easier to handle and transport. Moreover, regular fruit shape is necessary for paste production, because the fruits are directly subjected to the extractor (pulper) and therefore irregular fruits usually cause some difficulties in juice extraction. Insignificant differences were found in radius and total surface area among the different tomato genotypes, while significant differences were found among their length. 47

4 Table 1. Productivity and paste yields of the different tomato genotypes Tomato genotype Tomato productivity (ton/ha) Tomato paste yield (ton/ha) Paste Percentage Juvenile 69 b 14.3 a 20.8 Top 1 64 c 11.3 c 17.6 Line 4 74 a 17.5 a 23.7 Peto d 7.9 d 16.1 Significance level ** ** Where: *, ** and NS indicate significant difference at level 5%, 1% and insignificant difference, respectively. Table 2. Physical characteristics of different tomato genotypes fruits Tomato genotype Volume (Cm 3 ) Length (mm) Radius (mm) Surface area (Cm 2 ) Juvenile 78.2 b 40 b Top bc 39 b Line a 41 b Line c 31 b Peto d 55 a F value ** * NS NS Where: **,* and NS indicate significant difference at level 5%, 1% and insignificant difference, respectively. Chemical composition of fresh tomato fruits Proximate chemical composition of fruits of different tomato genotypes are presented in table 3. Moisture content of Juvenile, Line-2, Line -4. Top - 1 and Peto- 86 were 94.2%, 94%, 94%, 92 % and 92%, respectively. These values were in close agreement with the Sudanese Standards which is equivalent to 93%. Line -4 gave the highest value of protein (1.4%), followed by Juvenile (0.87%) and Line -2 (0.87%), Peto -86 (0.7%), and Top- 1 (0.53%). The protein content in Line 4 exceeded the Sudanese Standard which is 1.1%. Table 3 also shows that Juvenile and Line- 2 gave similar ash value of 0.8% followed by Peto -86 (0.6%), and Top -1(0.24%). The Sudanese Standard value for tomato ash is 0.6%. These results emphasized the importance of these genotypes as table fruit and for paste production. The highest phosphorus content was found in Juvenile and Line - 2 (1.6 mg/l00 g ) followed by Line-4 (1.4 mg/l00 g ), Top - 1 (1.2 mg/l00 g ), whereas Peto - 86 gave the lowest phosphorus content of 0.5 mg/l00g. The Calcium content of the different genotypes were found to be 86, 82, 80 and 64 for Line -2, Line -4, Peto -86, and Juvenile, respectively. The Ca content of the genotype Top-1 was less than the Sudanese standard value of 120 mg/l00g. Juvenile displasyed the highest K content (1.9 mg/l00g), followed by Line -4 (0.67 g/l00g), Line -2 (0.66 gm/l00gm), and Peto 86 (0.65 gm/l00g). Top -1 gave the lowest K content (0.15 g/10g), which was 13 times lower than that of Juvenile. The K content of Juvenile was three times higher than that of the commercial variety Peto 86. Line -4 gave the highest level of sodium (Na) content (340 mg/l00g) which was approximately four times higher than that of Peto 86 (96 mg/l00g). Physico-chemical characteristics of tomato paste Table 4 shows the physio-chemical characteristics of pastes of the different tomato genotypes. Significant differences were found among the different tomato pastes ph and titrable acidity. On the other hand, insignificant differences were found 48

5 among their TSS%. The ph values of the various samples ranged between 4.26 and 4.50, which lies within the optimum range (3.7 -o 4.5) reported by Saeed and El mubarak (1970). The optimum range of ph ( ) is considered as a limiting factor for storage of tomato paste. The TSS% of the paste of the different tomato genotypes were lower than those reported by Fagir (2002) for Omdurman genotype (28%), that was developed at the National Institute for Promotion of Horticultural Exports, University of Gezira in Significant differences were also found in the ascorbic acid (vitamin- C) content in the different paste samples. The paste prepared from Line-2 was recorded the highest value (22%), while the lowest value was recorded by Juvenile genotype (11 mg/100g). Table 3. Chemical composition of fresh tomato fruits Genotype Moisture Protein Ash P Ca K Na Juvenile Top Line Line Peto Table 4. Physico-chemical characteristics of tomato pastes and vitamin-c conten Genotype ph Titrable acidity % TSS % Vitamin C % Juvenile 4.36 ab 1.68 a c Top ab 1.15 b b Line b 0.95 b a Line b 1.18 b a Peto a 1.00 b b Significance level * * NS ** *,** indicate significant difference at 5% and 1% levels, respectively. NS indicate in significant difference. Microbiological analysis Table 5 shows the microbial analysis of tomato pastes prepared from the different tomato genotype. All samples were found to be free from mould and yeast. The paste prepared from Juvenile gave the highest value of total viable count (5x10 2 c.f.u/g), followed by the paste prepared from Peto -86 (4 x l0 2 c.f.u/ml), Top -1 (3 xl0 2 c.f.u/ml), while the paste prepared from Line -4 and Line-2 genotypes both gave the lowest value of total viable count (2 x 10 2 c.f.u/ml). The absence of mould and yeast cells in tomato paste samples indicated that the paste was produced under highly hygienic conditions as the standard mould count in tomato paste is 40 c.f.u/ml (http: tomato paste html 2002). Sensory analysis Table 6 shows the sensory evaluation of tomato pastes obtained from different genotypes. Insignificant differences were found between the paste samples prepared from the different tomato genotypes with regard to colour and flavour. In contrast, significant differences were observed in their texture and overall quality. 49

6 Table 5: Microbiology analysis of tomato paste after processing Genotype Total viable count (c.f.u/ml) Mould and Yeast (c.f.u/ml) Juvenile 5xl0 2 Ni Top- 1 3xl0 2 Ni Line -4 2x10 2 Ni Line -2 2x10 2 Nil Peto -86 4xl0 2 Ni Table 6. Sensory analysis of different paste samples Genotypes Color Flavor Texture Overall quality Juvenile s C b Top bc b Line C b Beto ab a Line b b ALBustan a a Significant level NS NS ** * *, ** and NS indicate significance level at 5% and non-significance 1%, respectively. CONCLUSIONS From the results obtained in this study we concluded that the genotype Line 4 and Juvenile are more suitable for paste production as they produced the highest fresh tomato and paste yields and the highest percentage of paste production (20.8%) (23.7%) (93.1). Moreover, the paste from Line 4 scored the highest TSS value (25% ) and considerable amount of ascorbic acid content (21 mg/100g). Nevertheless, the titrable acidity of Line 4 paste was not significantly different from the other tomato genotypes. Line 4 and Juvenile were also found rich in K (0.67 and 1.94 mg /100g). The microbiological evaluation revealed that all tested tomato genotype pastes were free from mould and yeast cells, although some samples contain high levels of total viable count of bacteria. ACKNOWLEDGEMENTS Our sincere regard to the members of the Department of Food Science and Technology, Faculty of Engineering and Technology, University of Gezira for their help during this study. REFERENCES: 1. AOAC. (1991). Association of Official Analytical Chemists. Official Methods of Analysis (14th Ed.).Washington, DC. 2. AOAC. (2000). Association Of Official Analytical Chemists, Official Methods of Analysis (17th Ed.). Arlington, VA. USA. 3. APHA. (1967). Compendium of Methods for the Microbiological Examination of Foods. American. Public Health Association, Washington. DC. USA. 4. Fagir, G. A. (2002). Evaluation of Some Newly- Bred Cultivars For Paste Manufacture. M.Sc. Thesis, University of Gezira, Wad-Medani, FAO(1999).Year book of Production. 35: Rome, Italy. 5. Leonard, G. S. and Nathan, R. (2003). Plant Biotechnology: Potential Impact for Improving Pest Management in European AgricultureTomato - Virus- Resistant Case Study, The National Center for Food and 50

7 Agricultural Policy 1616 P Street, Washington, DC. 6. Mohammed, M. B. (1995). Vegetable production in Central Sudan. Integrated Pest Management (IPM) Publication, Wad-Medani, Sudan. 7. MSTAT (1985). Michigan State University. East Lansing, M1, USA. 8. Saeed, A. M and Elmubarak, A. A. (1970). Processing quality of ten cultivars of tomato for paste manufacture. Sudan Journal of Science and Technology 3: WWW. Tomato - Wikipedia, the free encyclopedia.htm., tomato paste html t_of_countries_by_tomato_pro duction dmin/docs/fruit%20tomato%2 0paste%20processing-final.pdf. 51