Laboratory‎ > ‎ Tomato Paste

Mutlu

10 yıl önce

PURPOSE:

The aim of this experiment is determination of Black point, Sugar content, Color, Total soluble solids, Acidity, and Salt of tomato paste, and discussing our results.

MATERIALS:

Glasses, Refract meter, Funnel, Filter paper, Pipette, Burette, Beaker, Flask, Hunter lab, Bunsen burner,

THEORY:

The tomato is an extremely valuable raw material for a very wide range of processed foods and the demand by the food industries of the world for tomatoes continues at high level. The conversion of tomatoes into tomato paste will be examined in considerable details as this materials now forms an almost standard article of commerce and constitutes a most convenient means of shipping and storing tomato solids in a form which can be readily converted to finished product or food ingredient. In several countries and in international trade it was often referred to as tomato puree until a few years ego. During the transition stage of altering the name from tomato puree to tomato paste several canners and suppliers called the higher concentrations (say 28/32%) tomato paste and the lower concentrations (say up to 26%) tomato puree. This still continues in some circles and in several Regulations and Recommendations still in operation the expression tomato puree is used. The tomato (Lycopersicum esculentum) is, of course, a true fruit, but in view of its association with savory dishes it is seldom eaten as such. It finds major acceptance in the fresh state as a salad component, as a juice which may be consumed fresh or preserved by canning or freezing, it may be peeled and preserved either whole, peeled or even sliced, used as an ingredient in sauces and soups, or completely dehydrated to a powder which, like tomato paste, may be used as a convenient ingredient in a whole range of other food product.

The relative ease with which tomatoes could be crushed and concentrated to form a paste gave rise to some traditional methods of making this material on a domestic basis in those countries where the fruit could be grown as an outdoor crop. The simplest means of producing such tomato pastes consisted of spreading the crushed ripe tomatoes on stone slabs in the hot sunshine, and after concentration by evaporation; the product was mixed with salt and could be stored for use during the winter months. The qualities desired in a tomato to be used in the production of tomato paste may be summarized as follows:

1: It should have a high content of soluble solid.

2: It should posses an intensely red color, not only of the skin but of the entire flesh.

3: The flavor must be good and characteristic, free from scanted and other off-flavors.

During the last twenty years there has been considerable rationalization of methods and equipment employed in the preparation of tomato pulp and its concentration to form the tomato paste of commerce. At the present time the general sequence of operations in almost all factories is basically similar and consists of the following unit phases:

Reception of tomatoes from the fields, washing and sorting, breaking or crushing to form pulp, heating of the pulp, removal of skins and seeds, refining of the screened pulp, concentration of pulp to the desired solids content, filling of finished tomato paste into cans or other storage container.

PROCEDURE:

1: Testing for Black Points: First of all 1 gram of tomato paste was weighed. Then this tomato paste was placed between two pieces of glass. After, the glasses were pressed together and paste made to squash out into a thin film, which could be viewed through the glasses.

2: Determination of Sugar Content of Tomato Paste: 10 gram of sample was taken. Then the sample was diluted to 500 ml. Then 50 ml. sample was filtered from this solution and 50 ml. water was added to this filtered, final solution was completed to 100 ml. than this solution was filled into burette. After that 5 ml. of Fehling1 was placed into flask and 5 ml. of Fehling2 was placed into same flask. Than 10 ml. of solution was added from burette into flask. After, the liquid into flask was boiled. Then, 3 drops of Methylene blue was added as an indicator. And titration was made until the blue color converted to brick-red color. Finally, volume was recorded.

3: Determination of Color: This could be assessed by means of Hunter Lab. Red should be predominant over yellow. An excess of blue may indicate scorching.

4: Determination of Total Soluble Solids in Tomato Paste:

A: By oven drying:

3 gram of tomato paste placed into a dry and weighed dish. Then it was spreaded evenly over the bottom surface. Then the dish content was dried in a vacuum oven at 70°C until constant weight was attained.

B: By Refract meter:

I: Direct measurement: Undiluted tomato paste was put on a refractometer prism. Approximately total solids could be obtained by reference to the tables.

II: Measurement after dilution: One part by weight of the tomato paste was diluted with three parts of distilled water and mixed well. After filtration the refractive index was readed by one drop of filtrate. Finally, the actual solids of the sample could be calculated by multiplying the dilution factor i.e.4.

5: Determination of Acidity: Firstly a 1:3 dilution, by weight, of tomato paste, in which the solid content was known, was filtered. The first few drops may carry though some suspended matter, but this may be returned to the filter. So that, the filtrate for test was as clear as possible. Than 10 ml. of the filtrate was mixed with 50 ml. of water and using 1 ml. of 1 % phenolphthalein and 0.1 N NaOH the titration was made until a pink color persisted at least 30 seconds.

6: Determination of Salt: First 10 gram of puree was weighed and it was put into a beaker. Then about 90 ml. of water was added to beaker, with the rod, the mixture was warmed slightly and it was transferred carefully to a 500 ml. volumetric flask. Than it was cooled, it was made up to 500 ml. after it was mixed and filtered (A).To 50 ml. of A (=1g of sample), then 5% potassium chromate solution was added. And a piece of marble was added. And this solution was titrated with 0.05Nsilver nitrate solution. Finally, volume was recorded.

CALCULATIONS:

1) For sugar content; 34 ml. solutions was used.

34ml.→ 51.7 (invert sugar, No sucrose)

(51.7/ 34) * 100 = 152 mg sugar/100ml.

152*10=1520 mg. = 1.52 gr. For ,10 gr.

(1.52 /10) *100 = 15.20 %

Dry matter = 15.20/0.26 = 58 %

2) For total soluble solid = 6.5 Brix Dilution factor: 4

= 6.5 * 4 = 26 %

3) For determination of acidity = (56.8 * 0.0064) /10 * 100 = 3.64 %

4) For determination of salt = (23.3 * 0.00292)/1 * 100 = 6.81

RESULTS:

Black point: It was not found.

Invert sugar: 34 ml. solutions were used. And: 58 %

Color: a =25.67 Hunter a / b = 25.67 / 11 = 2.33

b = 11

L = 19.73

Y = 201.6

Brix: 26 %

Salt: 6.81 %, 23.3 ml. solutions were used.

Acidity: 3.64 % , 56.8 ml. solutions were used.

DISCUSSION:

In this experiment we made some tests. Those are determining the quality of tomato paste. In order to conform to certain quality standards the acidity should be fairly low. The NaOH solutions used in the routine examination of tomato products should be accurately standardized before use.

The texture, size of fibres, presence of black points can be seen and the quality of the paste thereby evaluated. Excessive black rot on tomatoes, indicative of poor sorting or trimming. Black points also occurs presence of foreign matter, burn –on in heat exchangers, damaged screen or cyclone fault.

The color of the raw tomato is an index of its maturity and this, in turn, is directly related to maximum flavor development. Tomatoes for processing are required at optimum maturity and color forms a useful means of assessment.

Salts are added to tomato paste to give flavor and for preservation.

The addition of sugar to tomato paste, as distributed in commerce, is not generally permitted but it may accosionally be required to determine if additional sugar is contained in the course of some manufacturing process, or if a sample has been adulterated.

Tomato should have a high content of soluble solids for desired quality of tomato paste.

According to TS; black point is maximum 2/g , we did not find black point, therefore our result convenient to TS. In color determination we found the ratio of a/b as a 2.33 and in TS; this value is minimum 1.8. So; our result convenient to TS. According to TS; reducing sugar is minimum 40 % we found sugar as a 58 %. In TS acidity is maximum 10% of total solid we found the acidity as a 3, 64%. In TS the salt content is 10% of total solid and we found as 6.81%. In TS the soluble solid for puree minimum 11% for double concentrated min. 28% for triple concentrated minimum 36% and we found this soluble solid content as 26%. As a result of the comparison of the values and the TS values; the data show that TAT tomato paste has a good quality and these data show us our experiment was good.

DATA