Material and Methods

Tomato and juice preparation

Tomatoes fruits (Licopersicon esculentum) were purchased fromsanad farm, Damietta Governorate, Egypt during the month ofAugust 2013. Only ripe and fresh tomatoes were used in this study.The tomato juice was prepared according to the method of [11].Tomato fruits were washed in water manually, chopped, squeezedin a blender (BRAUN 4184, Czech), cold extracted and sieved (0.8mm holes) to remove seeds and peels. The extract was concentratedto 9% T.S.S (juice) by using a rotary evaporator at 18 °C for 2h undervacuum and packaged in glass cans of 350g net weight. The cans weresterilized at 100 °C for 30 min. and were analyzed after (zero, 6, 12and 18 month) at room temperature.

Chemical composition

Chemical composition (moisture, proteins, fat, carbohydratesand ash) using the AOAC procedures (AOAC [12],). The crudeprotein content (N × 6.25) of the samples was estimated by themacro- Kjeldahl method; the crude fat was determined by extractinga known weight of powdered sample with petroleum ether, using aSoxhlet apparatus; the ash content was determined by incineration at600±15 °C. Total carbohydrates were calculated by difference.

Physical properties

PH value: PH value was determined according to the methoddescribed by A.O.A.C [12], as follows: A known weight of tomatoesand tomato products (juice, puree and ketchup) (10ml) were blendedwith (100ml) distilled water and PH of the slurry was then measuredusing (CRISON GLP 21) PH meter.

Total acidity

Total acidity was measured by titrating (10g) of tomatoes andtomato product (juice, puree and ketchup) with NaoH o.1N solutionusing (phph) as indicator. The results were expressed as % Citric acid,as described by A.O.A.C [12].

Color measurements

The Color measurement in tomato products was determined byMert [13]. The samples were filled into a clear glass Petri dish and color Parameters (a*and b*) were determined using a Minolta colorimeter(laboscientificas.r.l. - parma; Italy model: LS 2000). The Petri dishwas placed on the colorimeter sensor during measurements. Threemeasurements were taken for each sample and average values werereported.

Taste index and the maturity

A taste index and the maturity were calculated using the equationproposed by Navez, et al., [14] and Nielsen [15] starting from the Brixdegree and acidity values which were determined in a previous paper[16].

Determination of phytochemical compounds

Total phenolic compounds: Total polyphenolic compoundsin the crude extract of raw tomato and tomato products weredetermined by the folin - ciocalteu method according to Meda et al.[17] as follows:

0.1gm lyophilized powder of tomato samples was dissolved inl ml deionized water. This solution (0.1ml) was mixed with 208mlof deionized water, 2ml of 2% Na₂Co₃ and 0.1ml of 50% folinciocalteaureagent. After incubation at room temperature for 30 min.The reaction mixture absorbance was measured at 750 nm against adeionized water blank on a spectrophotometer (JENWAY 6315 madein England). The concentration was calculated using gallic acid (GA)as standard and results were expressed as mg gallic acid equivalents(GAE)/gm lyophilized powder. Finally, the results were converted tomg GAE / 100gm fresh matter of tomato.

Total flavonoid

The total flavonoid content was determined according as thealuminum chloride colorimetric method described by Chang etal. [18]. Briefly, aliquots of 0.1 g of tomato and tomato productssamples were, respectively, dissolved in 1 ml deionized water. Thissolution (0.5 ml) was mixed with 1.5 ml of 95% alcohol, 0.1 ml of 10%aluminum chloride hexahydrate (AlCl3), 0.1 ml of 1 M potassiumacetate (CH3COOK), and 2.8 ml of deionized water. After incubationat room temperature for 40 min, the reaction mixture absorbancewas measured at 415 nm against a deionized water blank on aspectrophotometer (JENWAY 6315 made in England). Quercetinwas chosen as a standard using a seven point standard curve (0-50mg/l).

Antioxidant activities

Determination of Total ascorbic acid: Total ascorbic acid (vit.C) was estimated according Kapur et al., [19]. Samples of tomatoproducts and raw tomato were first chopped and homogenized ina laboratory homogenizer. Approximately 0.23mL of 3% brominewater were added into4 mL of centrifuged sample solution to oxidizethe ascorbic acid to dehydroascorbic acid and after that 0.13 mLof 10 %thiourea to remove the excess of bromine. Then 1 ml of 2,4 dinitrophenylhydrazine solution was added to form osazone. Allstandards, samples and blank solution were kept at 37 °C temperaturefor 3 hours in a thermostatic bath. After it all were cooled in icebath for 30 minutes and treated with 5 mL chilled 85% H₂SO₄, withconstant stirring. As a result, a colored solution’s absorbance wastaken at 521 nm on a spectrophotometer (JENWAY 6315 made inEngland).

Determination of lycopene

Extraction method was performed according to Fish et al., [20].Samples of tomato products and raw tomato were first chopped and homogenized in a laboratory homogenizer. Approximately 0.3 to 0.6g samples were weighed and 5 mL of 0.05% (w/v) BHT in acetone, 5mL of ethanol and 10 mL of hexane were added. The recipient wasintroduced in ice and stirred on a magnetic stirring plate for 15 min.After shaking, 3 mL of deionized water were added to each vial andthe samples were shaken for 5 min on ice. Samples were then left atroom temperature for 5 min to allow the separation of both phases.The absorbance of the hexane layer (upper layer) was measured in a1-cm-path-length quartz cuvette at 503 nm blanked with hexaneon aspectrophotometer (JENWAY 6315 made in England).

Statistical analyses

All results were performed in three replicates and the results werestatistically analysed. Significant statistical differences of observedchemical parameters means of tomato juices were determined by theFisher´s least significant differences (LSD) test, after the analysis ofvariance (ANOVA) for trials set up according to the RCB design.

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Results

Chemical composition

Proximate chemical composition of fresh juice and processedjuice are presented in Table 1. Moisture 95 and 91%, protein 0.78and 1.50%, fat 0.49and 0.90% , fiber 1.13 and 1.58% , ash 0.90 and1.20%, carbohydrate 1.70 and 3.28% , total soluble solid (T.S.S) 5and9% and total energy 14.33and 27.22% respectively. From Table 1 alldifferences between fresh juice and processed juice were significantexcept ash there was no difference significant among there. Theresults were in agreement with that reported by Kamil et al. [21].

Table 1: Chemical composition of raw juice and processed juice.

Chemical composition of processed juices were determinedduring the storage period and presented in Table 2. From that table it was found that the moisture content is slightly reduced after 18month storage period comparing other storage periods.

Table 2: Effect of storage period on gross chemical of processed juice.

Table 5: Effect of Thermal treatment on phytochemicals in fresh juice andprocessed juice.