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Academia Journal of Agricultural Research 3(8): 127-131, August 2015 DOI: 10.15413/ajar.2015.0131 ISSN: 2315-7739 ©2015 Academia Publishing

Research Paper

Effect of sonication and blanching postharvest treatments on physicochemical characteristics and antioxidant compounds of tomatoes: Fresh and refrigerated

Accepted 2rd June, 2015

ABSTRACT The effect of blanching and ultrasound treatments on pH, total soluble solids (TSS), color, firmness, lycopene, and antioxidant capacity (IC50) in tomatoes was studied during 5 days of storage (4-5°C). TSS decreased in blanched tomatoes at 90°C/45 s conditions. The sonicated tomatoes show a lower change in color parameters; therefore, the total color change (ΔE) was lower, after 5 days of storage. The firmness of fruits decreased in all treatments, being more notable in blanching process. Lycopene content was not significantly affected (p>0.05) by the treatments (35-41 mg/kg FW); however, during the storage it was observed an increase, being greater in sonicated and blanching (low temperature) tomatoes, with values of 75±6 and 83±7 mg/kg FW, respectively. The IC50 varied in 9.1, 37.9, and 25.5% in sonicated, blanching at high temperature, and blanching low temperature tomatoes, respectively, which indicate a low reduction of the antioxidant capacity in sonicated tomatoes. Keywords: Tomato, sonication, blanching, quality, antioxidant activity.

INTRODUCTION Tomato (Solanum lycopersicum L.) is one of the most popular vegetable worldwide, it is typically consumed in fresh form, although a large amount of products are obtained from tomato, such as ketchup, sauces, and soups (Santos-Sánchez et al., 2013). Mexico is one of the main producers of tomatoes worldwide. In 2013, the tomato production in Mexico reached 2, 694, 358.19 tons, with a national yield of 57.21 ton/ha (SIAP, 2013).

The researches on the bioactive compounds and antioxidant activity of the fruits and vegetable have been increased, because these compounds have an important role in the prevention of several human chronic diseases (Willcox et al., 2003; Luna-Guevara et al., 2014). The tomato contains a high amount of bioactive compounds such as lycopene, phenolic compounds, flavonoids, and vitamins (C and E), with high antioxidant capacity (Toor and Savage, 2005; Juroszek et al., 2009). Moreover, the consumer

prefers tomato fruits with a good color and firmness, associated to the lycopene content and the activity of some enzymes such as pectinesterase, respectively (Satyan and Patwardhan, 1983; Kader et al., 1997).

In order to extend the shelf life of fruits and vegetables, the blanching is used to inactivate enzymes and reduced the microbial load; although some undesirable changes may occur, such as sensorial attributes and the reduction of the bioavailability of some nutrients (López et al., 1994). In this sense, there have been developments emerging or non-thermal technologies, such as ultrasound (US), that promote the extraction, freezing, and filtration process, reducing the processing time thereby increasing the efficiency (Vilkhu et al., 2008). Moreover, the US is capable of modifying the plant cell material by increasing the bioavailability of micronutrients, retaining the quality of the products (Vilkhu et al., 2008). Therefore, the aim of

M L Luna-Guevara1, P Hernández-Carranza1, J J Luna-Guevara1, R Flores-Sánchez1 and C E Ochoa-Velasco2*

1Ingeniería en Alimentos. Facultad de Ingeniería Química. Benemérita Universidad Autónoma de Puebla, Puebla, México. 2 Departamento de Bioquímica-Alimentos. Facultad de Ciencias Químicas. Benemérita Universidad Autónoma de Puebla, Puebla, México. *Corresponding author email: carlosenriqueov@hotmail.com Tel: (+52)222295500; Ext: 7251

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Academia Journal of Agricultural Research; Luna-Guevara et al. 128 this study was to compare the effects of the sonication and blanching treatments on the physicochemical and antioxidant characteristics of tomatoes Roma VF variety during the storage at refrigeration conditions. MATERIALS AND METHODS Tomato sample Tomatoes Roma VF variety were grown in a fertirrigation greenhouse located at north of Puebla state, Mexico. The fruits were harvested at mature stage 5 (pink color) according to color chart of USDA (1997). The tomatoes were randomly divided in 4 batches. Treatments and storage Two batches were blanched at two different conditions, one of them at 90°C in 45 s (HT) and the other batch was treated at 55°C for 20 min (LT). The sonication processes were done at 45°C for 10 min with frequency of 37 kHz in an ultrasonic bath (Elmasonic S30H, Elma, Singen, Germany). All treatments were carried out in triplicate. An untreated batch of tomatoes was selected as control. Treated and untreated tomatoes were stored at 4-5°C (90% RH) for 5 days (when tomatoes are consumed in Mexico after buying). Physicochemical characteristics

The pH and total soluble solids (TSS) were estimated according to the 981.12 and 932.12, AOAC (2000) methods, respectively. Firmness was evaluated by puncturing the equatorial zone of each tomato using a texture analyzer TA, XT plus, 10917 (Massachusetts, USA). The color parameters were evaluated in the Hunter scale, using a colorimeter colorflex M 6405 (Virginia, USA) in the reflectance mode. Lycopene

Lycopene from tomato fruit was extracted using a solution of hexane/acetone/ethanol (2:1:1) (JT Baker, PA, USA) and evaluated according to Sadler et al. (1990). The lycopene content of samples was measured spectrophotometrically at 472 nm using hexane as blank and extinct coefficient of 31.2. The results were expressed as mg/kg FW. Antioxidant capacity

The radical scavenging capacity (antioxidant activity) of

methalonic extracts was measured by the DPPH radical (1, 1-diphenyl-2-picrylhydrazyl) using the method of Mongkolsilp et al. (2004). To obtain the tomato extract, 6 g of tomato pulp (fresh weight) was mixed with 30 mL of aqueous methanol solution (80% v/v) and incubated at 40°C for 12 h. Two (2) mL of DPPH radical (0.1 mM) (Sigma-Aldrich, MO, USA) were mixed with 500 μL of extract and was stored for 30 min in darkness. The absorbance was read at 517 nm and the inhibition percentage was calculated as:

(1)

Where I is the inhibition (%), Absfis the absorbance of

blank, and Absiis the absorbance of the methanol extract.. The concentration to reach an inhibition of 50% (IC50) of the antioxidant capacity was calculated.

Statistical analysis All results were evaluated by analysis of variance (ANOVA). A p value of 0.05 was used for deciding significant differences among averages (Tukey’s test). RESULTS AND DISCUSSION Physicochemical characteristics The total soluble solids were affected by the treatments applied, the total soluble solids significantly decreased (p<0.05) in blanching at high temperature (HT). This is probably due to the high temperature which causes the increase of permeability and the cell wall alteration that generate the loss of total soluble solids (Aguilar et al., 1999). The sonication and blanching at low temperature, slightly affected the total soluble solids and the results are similar to those reported by Tigist et al. (2013). The pH was not significantly (p<0.05) affected by the treatments applied. During the storage, the total soluble solids and pH did not significantly change. Color Table 1 presents the color parameters of tomatoes treated and stored for 5 days. The L, a, and b color parameters were not affected by the treatments. During the storage, the tomatoes untreated and treated with blanching (LT) present a significantly decreased in the luminosity (L) parameters, which indicate a slightly darkening. Brown (1979) stated that the prolonged blanching of fruits causes

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Table 1. Effect of the treatments on color parameters of tomatoes during the storage.

Time (d) L a b Hue Chroma ΔE

Control

0 33.9a 25.7a 21.3b 39.6c 33.4a 0.0b

5 30.2b 23.7ab 21.0b 41.6bc 31.6a 4.3a

Sonicated

0 34.3a 24.8ab 21.5b 40.9bc 32.8a 0.0b

5 32.4ab 25.5a 22.7ab 41.6bc 34.2a 2.9a

Blanched (HT)

0 34.4a 23.5ab 22.8ab 44.1b 32.8a 0.0b

5 33.5ab 22.0b 26.2a 50.3a 34.2a 3.9a

Blanched (LT)

0 34.9a 22.8ab 21.8b 43.7b 31.5a 0.0b

5 30.9b 22.0b 24.5a 48.1a 33.0a 4.9a

Letter different (a, b, and c) in the same column indicate significantly difference (p < 0.05).

the filtration of micronutrient by solubilization, thereby affecting the color. The great change in the color parameters was observed in the hue angle, which indicates the degree of similarity of the product color to the primary color (red, green, yellow, and blue). This color parameter was significantly increased (p<0.05) by the blanching process. During the storage, the tomatoes untreated and treated with sonication did not change in the hue parameters, while, the tomatoes blanching shows a significant increased that indicate a slight change to the yellow color (color chart space). The total color change was lower in sonicated tomatoes after 5 days of storage. The color of tomatoes is one of the most important parameter of quality that consumers evaluate during the buying and consuming. Firmness The firmness is one of the most important characteristics of fruits and vegetables. During the storage, the firmness of the fruit was reduced due to different factors such as enzymes, pretreatments, and storage conditions (Luna-Guevara et al., 2014). Figure 1 shows the firmness of tomatoes with different treatments. The firmness of sonicated tomatoes was similar to the control tomatoes. In tomatoes blanching, the firmness was reduced significantly (p<0.05). All treatments have in common the use of water as a medium of process; therefore, the water could affect the firmness of tomatoes (Luh, 1997). Moreover, the combination of high temperature and longtime of

processing could inactivate the pectinesterase and polygalacturonase enzymes; thereby reducing the firmness of tomato fruits (Shook et al., 2001). During the storage, the firmness of tomatoes was slightly increased, although it was not significant (p<0.05).

Lycopene Table 2 shows the lycopene content (mg/kg) of tomatoes treated with different processes. Blanching at low temperature increased the lycopene contents, although no significant change was observed (p>0.05). Similar values of lycopene contents were reported by Ajlouni et al. (2001). They obtained values of 36-115 mg of lycopene/kg of fresh tomatoes during the storage at different temperatures. During the storage, a significant increase (p<0.05) of lycopene was observed in all tomatoes, due to the maturity and senescence process. Toor and Savage (2005) reported that lycopene contents during the storage depend on the temperature of storage. Moreover, Grierson and Kader (1986) pointed out that lycopene accumulation is a function of internal membrane system. Treatments of sonication and blanching (LT) greatly affected the membrane system, therefore, an increase of lycopene was observed. The lycopene is the main content responsible for the red color of tomatoes, the increase of lycopene during the storage was corroborate by the hue and chroma values, which indicate the side in the color side chart (red) and the intensity of the red color, respectively.

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Figure 1. Firmness of tomatoes treated with different technologies and stored during five days at 4-5°C.

Table 2. Lycopene contents and IC50 values in fresh tomatoes and stored.

Lycopene (mg/kg FW) IC50 (Kg FW/kg DPPH)

Treatments 0 (d) 5 0 (d) 5

Control 35±3a,x 52±7b,y 1230±11a,x 1024±47a,x

Sonicated 36±2a,x 75±6b,z 1396±146a,x 1524.±58a,y

Blanching (HT) 34±4a,x 40±4b,y 1219±88a,x 1681±47b,z

Blanching (LT) 41±2a,x 83±7b,z 1404±27a,x 1763±53b,z

Letter different (a, b, and c) in the same line indicate significantly difference (p < 0.05). Letter different (x, y, and z) in the same column indicate significantly difference (p < 0.05).

Antioxidant capacity (IC50) Table 2 shows the IC50 of tomatoes pre-treated during the storage. The values of IC50 of fresh tomatoes were similar to those values reported by other researchers. It was observed that the value of IC50 slightly (not significant) increase in tomatoes treated with sonication and blanching (LT), which indicate a reduction in the antioxidant capacity of the tomatoes. Sánchez-Moreno et al. (2006) reported similar trends in the results obtained in this study. During the storage, there was a significantly increase (p<0.05) in the IC50 in all processed tomatoes, this indicate that blanching and sonication affected other important bioactive

compounds (not lycopene contents) presents in tomatoes. Similar results were reported by Sánchez- Moreno et al. (2006) in tomato purée treated with heat and high pressure. They reported that vitamin C (potential antioxidant compounds) decrease with the treatments, and suggest that protect the lipophilic compounds during the processing. CONCLUSIONS Blanching is a typical treatment used for the conservation of tomatoes; however, blanching significantly affects (p <

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Academia Journal of Agricultural Research; Luna-Guevara et al. 131 0.05) the color and firmness of tomatoes. Moreover, the sonication as a non-thermal treatment slightly affected these important quality parameters. The sonication treatment produce an increase in the lycopene during the storage (similar results were observed in blanching at low temperature), although it did not promote a reduction in the antioxidant activity during the storage. The use of sonication as treatments for tomatoes provides an alternative to the increase of some bioactive compounds, maintaining the quality parameters desired by the consumers. ACKNOWLEDGEMENTS The authors would like to thank the Program for the Improvement of Teaching, PROMEP (Project: 103.5/12/4310) for the financial support of this research. REFERENCES Aguilar CN, Reyes ML, De la Garza H, Contreras JC (1999). Aspectos

bioquímicos de la relación entre el escaldado TB-TL y la textura de vegetales procesados, J. Mex. Chem. Soc. 43:54-62.

Ajlouni SS, Kremer S, Masih L (2001). Lycopene content in hydroponic and non-hydroponic tomatoes during postharvest storage, Food Aust. 53:195-196.

AOAC. Association of Official Analytical Chemists, The Official Methods of Analysis. 2000, Washington, DC.

Brown MS (1979). Frozen fruits and vegetables: their chemistry, physics, and cryobiology, Adv. Food Res. 25:181-237.

Grierson D, Kader AA (1986). Fruit ripening and quality. pp.241-280. In: The tomato crop: A scientific basis for improvement Atherton JG, Rudich J (ed). Chapman, Hall, Lond, UK.

Juroszek P, Lumpkin HM, Yang RY, Ledesma DR, Ma CH (2009). Fruit quality and bioactive compounds with antioxidant activity of tomatoes grown on-farm: comparison of organic and conventional management systems. J. Agric. Food Chem. 57: 1188–1194.

Kader AA, Stevens MA, Albrightholton M, Morris LL, Algazi M (1997). Effect of fruit ripeness when picked on flavor and composition in fresh market tomatoes. J. Am. Soc. Hort. Sci. 102:724-731.

López P, Sala FJ, De la Fuente JL, Condon S, Raso J, Burgos J (1994). Inactivation of peroxidase, lipoxygenase, and polyphenol oxidase by manothermosonication. J. Agric. Food Chem. 42:252−256.

Luh BS (1997). Principles and Applications of vegetable processing. In: Processing vegetables Science and technology. Smith DS, Cash JN, Nip WK, Hui YH (ed). Technomic Pushing Company, PA, USA. pp.3-46.

Luna-Guevara ML, Jiménez-González O, Luna-Guevara JJ, Hernández-Carranza P, Ochoa-Velasco CE (2014). Quality Parameters and Bioactive Compounds of Red Tomatoes (Solanum Lycopersicum L.) cv Roma VF at Different Postharvest Conditions. J. Food Res. 3:1-11.

Mongkolsilp S, Pongbupakit I, Sae-Lee N, Sitthithaworn W (2004). Radical scavenging activity and total phenolics content of medicinal plants used in primary health care. J. Pharm. Sci. 9:32-35.

Sadler G, Davis J, Dezman D (1990). Rapid extraction of lycopene and β-carotene from reconstituted tomato paste and pink grapefruit homogenates, J. Food Sci. 55:1460-1461.

Sánchez-Moreno C, Plaza L, De Ancos B, Cano MP (2006). Impact of high-

pressure and traditional thermal processing of tomato purée on carotenoids, vitamin C and antioxidant activity. J. Sci. Food Agric. 86:171–179.

Santos-Sánchez NF, Valadez-Blanco R, Salas-Coronado R (2013). Factors affecting the antioxidant content of fresh tomatoes and their processed products. In: Tomatoes: Cultivation, Varieties and Nutrition. Higashide T. (ed) pp.191-212. Nova Science Publishers, Hauppauge NY, USA.

Satyan SH, Patwardhan MV, (1983). Organic acid metabolism during ripening of fruits, Indian J. Biochem. Biophys. 20: 311-314.

Shook CM, Shellhammer TH, Schwartz SJ (2001). Polygalacturonase, pectinesterase, and lipoxygenase activities in high-pressure-processed diced tomatoes. J. Agric. Food Chem. 49:664-668.

SIAP (Servicio de Información Agroalimentaria y Pesquera). (2013). Cierre de la producción agrícola por cultivo. http://www.siap.gob.mx/cierre-de-la-produccion-agricola-por-cultivo/.

Tigist M, Workneh TS, Woldetsadik K (2013). Effects of variety on the quality of tomato stored under ambient conditions. J. Food Sci. Technol. 50:477-486.

Toor RK, Savage GP (2005). Antioxidant activity in different fractions of tomatoes, Food Res. Int. 38:487-494.

United States Department of Agriculture. United States Standards for Grades of Fresh Tomatoes. http://www.ams.usda.gov.

Vilkhu K, Mawson R, Simons L, Bates D (2008). Applications and opportunities for ultrasound assisted extraction in the food industry, A review. J. Innov. Food Sci. Emerg. 9:161-169.

Willcox JK, Catignani GL, Lazarus S (2003). Tomatoes and cardiovascular health. Crit. Rev. Food Sci. Nutr. 43:(1)1-18.

Cite this article as: Luna-Guevara ML, Hernández-Carranza P, Luna-Guevara JJ, Flores-Sánchez R, Ochoa-Velasco CE (2015). Effect of sonication and blanching postharvest treatments on physicochemical characteristics and antioxidant compounds of tomatoes: Fresh and refrigerated. Acad. J. Agric. Res. 3(8): 127-131. Submit your manuscript at http://www.academiapublishing.org/journals/ajar