Evaluation of Storage Stability Leaf Curl Resistant Cultivars for Producing Dehydrated Tomato

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1 Journal of Agriculture and ood Sciences Discourse Journal of Agriculture and ood Sciences Vol. 1(1), pp. 1-7, January 2013 l. 1 Evaluation of Storage Stability Leaf Curl Resistant Cultivars for Producing Dehydrated Tomato Usha HR, Neena Joshi, Suvarna V Chavannavar, Surendra,HS, N Nagaraju University of Agricultural Sciences, GKVK, Bangalore for Correspondence: nj_pande@yahoo.com ABSTRACT Cut tomatoes of four disease resistant cultivars salted or unsalted were hot air or sun. Retention of vitamin C and lycopene was determined. Dried tomato samples were stored in PET jars for a period of 3 months. Retention of lycopene and moisture was determined in the stored samples. Safety of the samples was assessed by determining bacterial and mold population in the samples. Vitamin C and Lycopene contents were higher in the oven samples. Vitamin C ranged from to and to mg/100g and lycopene contents were respectively to and mg/100g in sun samples and oven samples. At the end of the storage period of 3 months the dehydrated tomato samples treated with salt had lower lycopene degradation 8 13 per cent as compared to the samples without salt per cent in both sun and oven samples. The bacteria and mold counts were slightly less in oven samples as compared to sun sample. Both oven drying as well as salting exerted a beneficial effect to storage of products. Key words: Dried tomato: retention of ascorbic acid and Lycopene, microbial load, storage of tomato. INTRODUCTION Tomatoes and tomato foods are important contributors of lycopene (Shi and Maguer, 2000) β-carotene, vitamin C and phenolics (Kaur et al., 2004) to the human diet. Tomato leaf curl virus (TOLCV) is one of the most devastating begomovirus diseases of tomatoes causing serious threat to tomato cultivation. Tomato is an important crop of Karnataka. Newer varieties which are resistant to leaf curl virus and tolerant to bacterial wilt have been developed at University of Agricultural Sciences, Bangalore (Muniyappa and Kulkarni, 2001). There is a growing consumer demand for safe products with zero pesticide residues. The disease resistant varieties can fulfill this demand. Dried tomatoes are gaining popularity globally. Dehydrated () tomatoes are usually rehydrated before use or simply added to recipes that include water and allowed to soften (May, 2004).Seasonal market gluts can be exploited for dehydrated products. Availability of abundant sunshine makes sun drying an attractive option. The marginal growers cannot invest on big processing plants. A study was undertaken to evaluate selected leaf curl resistant cultivars of tomato to obtain a safe and nutritious product. Materials and Methods irm vine ripened fruits of tomato TOLCV resistant varieties namely, Nandi, Sankranthi, Vybhav and Arkavikas were obtained from the experimental plots maintained by Virology laboratory, UAS, Bangalore. Nandi, Sankranthi and Vybhav. Variety Arkavikas which is sensitive to leaf curl viruses, served as control. The material required for processing tomato such as net material, trays, knife, utensils, plastic PET jars and ingredients for product development were purchased from local market.

2 2 Preparation of dehydrated tomato: Tomatoes were washed thoroughly with cold tap water to remove adhering extraneous matter. Tomatoes were blanched in boiling water for one minute. After that tomatoes were peeled manually. They were cut in to wedges of 1 cm thickness using stainless steel knife. The wedges of tomatoes were as such or after a salt pre-treatment. Salt (5g/Kg) was sprinkled uniformly on the top of the tomato pieces. Drying condition: Two types of drying conditions were employed (i) Sun drying (ii) Hot air oven drying. Sun drying : Unsalted and salted tomato pieces were spread on nylon netted trays and kept under sunlight between 9.00 am to 5.00 pm. Tomatoes were kept under a steam of cold air during rest of the period. This was continued till the equilibrium moisture levels were attained. Hot air oven drying: Unsalted and salted tomato pieces were spread on netted trays and were in hot air oven at 60 C till the equilibrium moisture levels were attained. Laboratory Hot Air Oven, Model DHO- 18s of Deen Instruments, Bangalore Storage: Dry tomato samples prepared from different tomato varieties namely Nandi, Sankranthi, Vybhav and Arkavikas were subjected for shelf life study. Both salted and unsalted samples were kept in separate plastic pet jars (triplicates) and were maintained at room temperature for a period of 3 month of storage. The dehydrated tomatoes were analyzed for moisture, lycopene, bacteria and mold count. Packaging : Samples were packed soon after completion of drying. Dried tomato pieces were packed in PET jars and stored at ambient temperature. or conducting storage study 50 g of sample was packed in PET jars. Each type of sample was worked in triplicates. Thus, in all 16 samples were considered in this study (Table 1). Table 1. Description of the tomato samples used in the study Salted Unsalted Sun Oven Dried Sun Oven Dried our varieties our varieties our varieties our varieties Ascorbic acid: Sample was macerated using a glass mortar and pestle and filtered. Sample was extracted using acetic acid - metaphosphoric acid mixture. Ascorbic acid was estimated by stoichiometric reduction of the dye 2,6- dichlorophenol indophenol (Ranganna, 1987). Lycopene: Lycopene was estimated by rapid method as described by Ranganna (1987). An aliquot (5 ml) was diluted to 50ml with petroleum ether and the colour was measured in a UV-vis spectrophotometer Shimazdu at 503 nm using petroleum ether as blank. Calculation: Optical density (OD) of 1.0 = µg 1lycopene/ ml Microbial counts: The microbial contamination was estimated by analyzing microbial load in dehydrated tomato slices by using Nutrient Agar(NA) for bacteria and Martins Rose Bengal Agar (MRBA) for mould count following the dilution pour plate method. 10-2, 10-3 and 10-4 were the three dilutions used for analyzing bacteria and mould respectively. Initial and final microbial counts were estimated. Statistical analysis: Mean and standard deviation was worked out for all the parameters in the study. Two-way analysis of variance was employed in ing the significant difference between varieties, between methods and storage periods Result and Discussion A perusal of table 2 reveals that values for both Lycopene (50.93mg mg/100g) and ascorbic acid ( mg / 100 g) were within a narrow range. However, within this narrow range we did see some interesting variations. Dried samples from variety Vybhav were found to be richer in lycopene. However the ascorbic content was slightly lower in the samples obtained from this cultivar when compared to varieties Nandi and Sankranthi. According to Joshi et al (2006) sun tomato sample from cultivar vybhav had a good flavor.

3 3 Table 2. Vitamin C and lycopene composition of different samples of dehydrated tomatoes per 100 g dry matter. Varieties (V)/ Method Vitamin C (mg) Lycopene (mg) Sun Oven Sun Oven Nandi Sankranthi Vybhav Arkavikas V M VXM V M VXM -value * * NS * * * SEm± CD at * Significant at level NS: Non-significant Effect of dehydration on the vitamin C and Lycopene: Vitamin C: In sun samples the ascorbic acid content (table2) ranged from to mg/100g and in the oven samples it was higher (68.04 to mg/100g). Samples were blanched. Blanching is considered as desirable before dehydration as it inactivates the enzymes. Gupta and Nath (1984) observed that drying time of blanched samples was much less than that of un-blanched sample. About 38.8 per cent of ascorbic acid was lost. The loss was higher in unblanched and sun sample. Blanching before slicing reduced the losses due to inactivation of ascorbic acid oxidase. In another study Tripathi and Nath (1989) observed that blanching reduced pectin methyl esterase activity by 31.6 per cent. They concluded that the tomato slices possessing good colour can be obtained by blanching them whole in boiling 2.5 per cent brine for 60 sec. Cutting in to 1.5 cm thick slices dipping in 2.5 per cent starch solution containing 5 per cent KMS and drying in a cabinet drier at 78 and 55 C. These slices were reported to retain their red colour well during 6 months of storage as observed visually. However, greater losses of nutrients were observed due to the pretreatments; ascorbic acid content decreased from to 28.0 mg/100g solids during drying. Lower values in their samples can be attributed to pretreatments. In this study the ascorbic acid content when expressed on moisture free basis of fresh fruit ranged between mg / 100g and it reduced to mg / 100g in sun and mg/100g in oven samples. Thus, the pretreatment used in the study was found to be conducive to a better retention of vitamin C. Lycopene: In the present study the sun sample lycopene content ranged from to mg/100g. In the oven samples the lycopene content show higher value ranging from mg/100g, which are comparable to what has been reported by others. Loss of Lycopene is dependent on the drying techniquie. Tripathi and Nath (1989) reported that the lycopene content of cabinet tomato was mg/100g solids. This effect was observed by Shi and Maguer (2000) who reported values of 755, 755, 731 and 726 µg lycopene / g dry basis in fresh tomato, osmotic treated vacuum and air samples. Destruction of Lycopene is also affected by blanching tomatoes prior to drying. Gupta and Nath, 1984 reported that the blanched samples had higher lycopene content than the unblanched samples. They observed that when tomatoes were blanched before air drying at 70 C it resulted in a higher Lycopene content (91.19 mg/100g total solids) while those that were not subjected to blanching before drying had a lower Lycopene content (71.31 mg/100g). At a slightly higher temperature of drying (80 C) the lycopene contents were and mg/100g total solids for blanched and unblanched respectively for the tray samples. In the sun samples blanched ones had mg/100g and in unblanched samples lycopene contents were mg/100g of dry matter. Keeping in view the results obtained by other workers in the present study Lycopene appears to be well retained. Effect of Storage Moisture: In the present study the moisture content had slightly increased at the 3rd month of storage study in all the 4 varieties of tomato (table 3). Dry tomato is a hygroscopic material. Packaging it properly is considered imperative to storage (Von Loesecke, 2009). In another study Akpan et al. (2004) observed that when dry tomato samples were stored in polyethylene bags moisture content of dry tomato samples examined decreased as the dry season approached in the month of October to November (11.4 to 10.) while during wet season of August September there was an increase in the moisture content of dry tomato (6.8 to 15.). Lycopene: Tomato is considered a single most important source of Lycopene (Lumpkin, 2005) therefore retention of this

4 4 Table 3. Lycopene content of different samples of dehydrated tomatoes stored for a period of 3 months Treatment Nandi Sankranthi Vybhav Arkavikas Duration Sun Oven Sun Oven Sun Oven Sun Oven Without salt 1 st month rd month With salt 1 st month rd month Treatment (T) * * * * Duration (D) * * * * Method (M) * * * * T X D * * * * T X M * * * * D X M * * * * T X D X M * * * * Method (M): Sun, Oven * Significant at level Table 4. Bacterial counts (10 2 cfu/g) of different samples of dehydrated tomatoes stored for a period of 3 months Treatment Nandi Sankranthi Vybhav Arkavikas Duration Sun Oven Sun Oven Sun Oven Sun Oven Without salt 1 st month rd month With salt 1 st month rd month Treatment (T) * * NS * Duration (D) * NS * * Method (M) * * * * T X D NS NS NS NS T X M NS NS NS NS D X M NS NS NS NS T X D X M NS NS NS NS Method (M): Sun, Oven * Significant at level, NS: Non-significant

5 5 Table 5. Mould counts (10-2 cfu/g) of different samples of dehydrated tomatoes stored for a period of 3 months Treatment Nandi Sankranthi Vybhav Arkavikas Duration Sun Oven Sun Oven Sun Oven Sun Oven Without salt 1 st month rd month With salt 1 st month rd month Treatment (T) * * * NS Duration (D) * NS * * Method (M) * * * * T X D * NS NS NS T X M NS NS NS NS D X M NS NS NS NS T X D X M NS NS NS NS Method (M): Sun, Oven * Significant at level, NS: Non-significant constituent was studied. In the present study the dehydrated tomato samples were stored for a period of 3 months, at the 3rd month of storage the degradation of lycopene was observed (table 4). The dehydrated tomato samples treated with salt had lesser lycopene degradation 8 13 per cent as compared to the samples without salt per cent in both sun and oven samples. The chemical stability of lycopene in two commercial tomato powders was evaluated during storage by Anguelova and Warthesen, (2000). Tomato powder was stored at 6 and 45 C for up to 6 week. About 60 and 30 per cent of the lycopene was degraded at 45 C and 6 C after 6 week. Several lycopene degradation products were tentatively identified in the initial and stored powder. Mechanisms of losses were attributed both to isomerization as well as oxidation. Microbial count: Method of drying; that is whether the tomatoes were sun or oven influenced the microbial loads of the all the four varieties of tomatoes. Oven drying resulted in lower bacterial population. Generally higher population was seen at three months storage compared to freshly samples; and in salted rather than unsalted samples (table 5). The bacterial load was within safe limits even after storage ( It is well known that salt exerts a preservative action (Anon., 2000). No statistically significant interactions between the variables were observed. Higher values of microbial load have been reported by Akpan et al. (2004). They reported that aerobic plate counts of dry tomato sold in Nigerian markets ranged from to 27.15cfu/g, staphylococci ranged between and 34.13cfu/g, coliform count ranged between 10.0 and 37.86cfu/g and yeast and mould counts ranged between 10.0 and 24.67cfu/g. The high microbial load was attributed to poor environmental and unhygienic handling and processing condition of dry tomatoes. It should be remembered that our samples were produced in laboratory conditions which were presumably cleaner. Mold counts: Similar to the observations for bacterial load oven drying and salting exerted a protective action. These values were expectedly lower than those reported by Akpan et al. (2004). They reported yeast and mold counts between 10.0 and 24.6cfu/g (table 6).

6 6 irm, healthy, red coloured tomatoes Washed in cold tap water Blanched for 1 minute Peeled manually Cut in to 1 cm thick wedges Salted (5g/kg) Unsalted Spread on nylon net Sun Packed (PET jar) Oven Packed (PET jar) CONCLUSION The results of this experiment allow the conclusion that the all the four cultivars of tomato were quite similar. The sun samples exhibited a good retention of Lycopene and ascorbic acid. Even after three months of storage the samples did not have unsafe levels of microbial load. Thus, it may be said that the leaf curl resistant varieties of tomato cultivars can be used to produce sun tomatoes which are nutritious. REERENCES Akpan I, Olusegun O, Ogunfowokan, OA (2004). Microbiological quality and nutrient composition of dry tomato. J. ood. Sci. Technol., 41(4): Anguelova K, Warthesen J (2000). Lycopene stability in tomato powders. J. ood Sci., 65(1): Anonymous (2000). Akalank s the Prevention of food adulteration act 1954 and rules 1955, Akalanks publications, Delhi, p. 78 Gupta RG, Nath N (1984). Drying of tomatoes. J. ood Sci. Technol. 21: accessed on Joshi N, Nagaraju, N, Muniyappa V, Raghavan GSV, John C (2006) Evaluation of virus resistant tomato varieties for sun

7 7 drying. In Abstracts of CIST/AAC Joint conference, Montreal May 28 30, p Kaur C, George B, Deepa N, Singh B, Kapoor HC (2004), Antioxidant status of fresh and processed tomato A rev. J. ood Sci. Technol. 41(5): Lumpkin H (2005). A comparison of lycopene and other phytochemicals in tomatoes grown under conventional and organic management systems. Technical Bulletin No. 34. AVRDC publication number Shanhua, Taiwan: AVRDC The World Vegetable Center. p. 48. May B (2004). Dehdyrated tomatoes in hand book of vegetable preservation and processing, eds. Hui YH, Ghazala G, Murrel DM, Nid KD, WK, Marcel/ Dekker, Inc. USA, pp Muniyappa V, Kulkarni RS (2001). Release proposals of tomato varieties sankranthi (TLB-111), Nandi (TLB-130) and Vybhav (TLB-182), UAS, Bangalore and NRI University of greenwich, UK and VRDC, Taiwan, UAS, Bangalore, pp Ranganna S (2002). Handbook of analysis and quality control for fruits and vegetable products. Tata McGraw Hill Pub. Co. Ltd., New Delhi. Shi J, Maguer ML (2000). Lycopene in tomato: chemical and physical properties affected by food processing. Crit. Rev. ood Sci. Nutr. 40(1): Tripathi RN, Nath N (1989). Effect of starch dipping on quality of dehydrated tomato slices. J. ood. Sci. Technol., 26(3): Von L (2009). Drying and dehydration of foods, Agrobios (India), Jodhpur, pp