Freshly vs. Commercially Prepared Orange Juice

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Introduction

Oranges is a fruit that is characterized by a sweet scent and a bright orange color. The fruit is believed to have its origin in the tropical and sub-tropical parts of Asia particularly China. For many years, extract from orange fruits has been used by human beings as a kind of drink that supplements his diet. Recent years have seen development in the manner in which the juice is prepared and with technological advancement, the extract from the fruit has been able to be processed into commercial juice.

The focus of this research is to compare commercially prepared juice with an extract from an orange fruit in terms of its chemical content. The initial assumption is that there exists a difference in various chemical aspects and the quality of a natural orange extract and commercially prepared orange juice.

Literature review

Although orange juice has come to symbolize purity in glasses, the content of juice may be heated up, watered down, and having a lot of sugars. The flavor that characterizes the juice might be one that has been artificially engineered and is worse when the juice has been in store for a long period of time (Ashurst, 2009) Orange juice that is stored particularly in an aseptic pack is normally stripped of its oxygen through a process known as de- aeration.

There is a need for people to prefer orange fruits than the juice itself because of the nature of chemicals that are used to add flavor to it and its preservation method (Alissa, 2009). There are several chemicals that make commercial juice which is in one way or the other harmful to human beings. An orange consists of 88% water, 10% sugars, and 1% citric acid and vitamin C (Gregory, 2009).

Objectives

The main objective of this experiment is to:

1. To investigate orange juice yield and processing.
2. To compare chemical and physical properties of freshly prepared orange juice and commercially prepared orange through experimental techniques.
3. To evaluate the quality of freshly prepared orange juice and commercial heat-treated juice.

Requirements

The following are the requirements for the experiment

1. Freshly prepared orange juice.
2. Commercial heat-treated orange juice.
3. Refractometer.
4. pH meter.
5. Phenolphthalein indicator.

Methodology

Aspects of the two types of juices that will be assessed include the brix (which is the refractive index of the liquid measured by use of refractometer), the pH level by use of a pH meter, titrable acidity. In addition, other physical properties of these juices will be assessed with the aim of comparing them.

Yield and mass balance

The initial measurements taken for the orange are as follows

Table 1: Initial measurement of the orange.

Oranges will then be cut into half and the juice then squeezed from them. The juice was then collected in the jug and the peel in the bowl.

Table 2: Lost weight of the orange juice.

Loss in percentage = Loss weight X 100%/Orange Wt

Loss is therefore = 0.93%

Orange juice yield % = Loss weight X 100%/Orange Wt

Orange juice yield % = 39%

Experiment Procedure

Brix Measurement

The refractive indices of the two juices were assessed by the use of a refractometer through the following procedure.

1. A few drops of the test liquid were placed on the glass prism of the refractometer
2. The temperatures should be maintained between 5 to 40 degrees since the refractive index is affected the level of temperature.
3. The pad labeled READ was pressed and the measurement was reflected on the screen.
4. The brix is then recorded.
5. The prism was then cleared thoroughly for the test of the other liquid.

pH Meter

The acidity or alkalinity of the two juices was measured using the following procedure. The primary instrument that was applied is the pH meter.

1. The pH meter was set up correctly and then turned on.
2. Electrodes of the meter were then immersed into the sample of the two juices
3. 30 seconds were allowed for equilibration before the pH reading of the juice was recorded.
4. On completion, the electrodes of the meter were rinsed in distilled water before the same procedure was carried out for the second type of orange juice.

Titratable acidity

This is the measure of the amount of standard alkali that is needed to neutralize the acid in any given food sample to the level of the color change of an indicator. Phenolphthalein indicator with an endpoint of about 8.1 is the indicator that is recommended for use when dealing with food and drink samples. The following is the procedure that was applied in the experiment

1. A burette was filled with 0.1 M NaOH.
2. 5ml of orange juice measured by the use of a pipette was added to the content above together with distilled water.
3. A small amount of phenolphthalein indicator was then added to the mixture.
4. The level of the burette was taken to make the first reading in the experiment.
5. The mixture was then titrated with 0.1M NaOH up to a permanent rose color.
6. The final reading was undertaken and the first reading subtracted from it to come up with the volume of NaOH used.
7. The same experiment was repeated three times to ensure that the results are accurate.

Calculation of titratable acidity

Tritable acidity = MLS NaOH x Mwt of the acid x Molarity of NaOH x 100/(1000 x sample g Weight (or ml Volume) x valency)

Sensory analysis of the two juices was also carried out and the results record.

Sensory analysis

The following are some of the physical aspects of the two types of orange juice that were tested by the use of senses. 16 tasters participated in the experiment by marking their opinion appropriately as shown below.

The intensity of orange color

The level is marked by a red X.

Table 3: Intensity of the orange color.

Intensity of sweetness

The level is marked by a red X.

Table 4: Intensity of sweetness.

Intensity of sourness

The level is marked by a red X.

Table 5: Intensity of sourness.

Preference of each juice

The level is marked by a red X.

Table 6: Preference of each juice.

Findings

The following are the findings of the experiment

Brix

The refractive index for the two types of juices was found out to be as follows

Table 7: Refractive index of the two juices.

pH level

Table 8: pH level of the two juice types.

Titratable acidity (Citric acid)

Table 9: Titratable acidity.

Sensory testing

The results of the sensory were recorded and summarized as shown below.

Table 10: Sensory taste results.

Discussion

The results of this experiment indicate a lot about the difference between freshly extracted juice and commercially prepared juice that is heated. The results displayed in table number 7 imply that there is a difference in refractive indices of freshly prepared juice and commercially heated juice. The refractive index of commercially prepared juice happens to be lower because of all the chemical processes that it has undergone.

The pH level of commercially prepared juice is higher than that of freshly prepared juice to mean that freshly prepared orange juice has more citric acid than commercially prepared juice. The basic nature of commercially prepared juice can be attributed to the fact that additional chemicals and especially those used to preserve it tend to lower the acidity. This fact can be backed up by the results in table 9 that show that commercially prepared orange juice has a lower percentage of titratable acid than freshly prepared juice.

A sensory test that involved about 16 students indicates that the orange color intensity is high in commercially prepared juice than freshly prepared juice. In addition, the sourness of the two juices differs and this serves to impact the preference of the two juices by students who participated in the experiment.

Conclusion

In summary, it can be noted that the quality of freshly prepared orange juice heavily differs from that which has been commercially prepared and heated. The chemicals that are utilized in the preservation of commercially prepared juice can be said to affect the quality of this juice. There is a need therefore for complimentary research to establish how chemical materials added to commercial orange juice affect consumers since they tend to affect its quality as compared to freshly prepared.

References

Ashurst, P, R., 2009. soft drink and juice problems solved. Woodhead: Cambridge.

Alissa, H., 2009. Squeezed: What you dont know about orange juice. London: Yale University Press.

Gregory, K., 2009. Advanced pH measurement and control. NC: Research Triangle Park.

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