How does the ability of turmeric to act as a preservative for tomatoes (solanum lycopersicum), measured in terms of mass loss, pH and lycopene content depends on the percentage concentration (mass by volume) of the turmeric solution used and the type of tomato used-green tomato and red tomato ?
Use of turmeric as a preservative is a common practice in Indian kitchen. Turmeric has always been a common ingredient in almost all Indian recipes. As claimed by chefs and nutritionists, it is so because of the antibiotic and antiallergic therapeutic effects of turmeric. Being an inquisitive learner, the observation that made my interest about this more innate was the fact that I have seen applying turmeric and salt on fish and meats before they are refrigerated. I was more surprised to know that it is done to preserve the meat and fish for a longer time. I went through some research papers and came to know more about it and the biology behind it which will be explored further in the next section. However, the question that striked me was, will turmeric act as a potential preservative for vegetables as well ? Does the efficacy of a preservative depends on the type of the food substance preserved? In the current scenario of e-commerce, selling of packaged and processed foods contributes largely to the economy. To ensure health and safety, use of safe preservatives and their shelf life has become a major issue in food technology and preservation science genre. This finally brought me to the research question stated above.
Turmeric is a common tropical crop in Asia and Sub-Saharan regions(Shelef et al.). It has various medicinal as well as nutritional benefits. It belongs to the genus- “Curcuma longa” (Yarru et al.). The main ingredient of turmeric is curcumin which can acts as anti-oxidant. Moreover, it also shows abilities to produce vitamins through reductive degradation mechanism and can also acts as a precursor or co-factor of various other enzymes that are involved in the biological reactions happening during ripening of fruits and vegetables(Buch et al.). Curcumin can also degrades to form proteins and polyphenolic compounds which finally converts them to long chain fatty acids and can inhibit various diseases in plants due to deficiency of micro and macro nutrients (Almeida-Doria and Regitano-D’Arce).
Tomatoes of “solanum lycopersicum” is generally claimed to be a perennially grown vegetable albeit botanically it belongs to the class of berry fruit (Singh et al.). It is one of the most popular crop consumed worldwide which started it journey from South America and was then exported to Europe around the 15th century(OECD ). The main constituent of tomato is lycopene which has immense nutritional and medicinal benefits and is a pigment that offers the red colour to the fruit. Apart from this, tomato is also a major source of vitamins like – Vitamin B1 and Vitamin B3(Solanum Lycopersicum, Tomato: Life Cycle, Flower and Fruit Anatomy at GeoChemBio). The major part of tomato is carbohydrate and because of that it is a good source of calorie without unwanted fats for the dieticians (Stevens et al.)
Food preservation is a technique which is used to inhibit or delay the biochemical reactions in a fruit which may lead to the loss of nutritional benefits of the fruit accompanied by loss of texture, colour, aroma and turning rancid which eventually makes the fruit unsuitable for usage either in raw form or for cooking. There are multiple methods approved by the USDA (United States Department of Agriculture) for food preservation(“The Science Behind Food Preservation”). All of these or most of these methods aims to stop the growth of microorganisms and harmful bacteria in the fruits either by interfering with the conditions that are required for their growth or by adding chemicals or foreign substances named as preservatives which may kill the bacteria grown or inhibit their growth. The most popular methods of preservations are(“Science behind Food Preservation Methods”) - adding preservatives (chemical or natural), dehydrating (making the fruit stored in a moisture free condition), atmospheric canning (storing the fruit in a chamber or closed space filled with liquid nitrogen under high pressure), adding salts, adding acids to lower down the pH level that inhibits bacterial growth. In this investigation, use of turmeric a natural and homely method of preserving fruits will be discussed and its efficacy will be investigated.
There are various analytical methods to monitor and assess the quality of tomatoes:
Null hypotheses (Ho): There is no correlation between the percentage concentration of the turmeric solution used and it’s efficacy as a preservative for tomatoes – green and red. Any correlation, if identified is an outcome of a methodological or a systematic error.
Alternate hypotheses (H1): There is a positive or negative correlation between the percentage concentration of the turmeric solution used and it’s efficacy as a preservative for tomatoes – green and red. Any correlation, if identified is an outcome of a methodological or a systematic error.
There are two independent variable in the investigation –
The percentage concentration has been chosen to understand if using more amount of turmeric increases the efficacy or not and thus determining the optimum concentration of turmeric solution that can be used. The percentage concentration was varied from 0.00% (control), 5.00%, 10.00%, 15.00%, 20.00% and 25.00%. The values of concentration are expressed as mass by volume. For example, a 5.00% solution of turmeric means 5.00 ± 0.01 g of turmeric was added to 100 cm3 of water. To understand if the effect of turmeric as a preservative depends on the genus or biological variety of the sample or not, two different types of tomatoes-green and red were chosen.
The dependent variable of this investigation is the efficacy of the turmeric solution as an indicator.
The efficacy of the indicator will be measured in terms of three quantitative aspects – pH, dry mass loss and lycopene content. Refer to the background information for more details. A pH probe will be used to measure the pH, a digital mass balance will be used to record the mass and a colorimeter will be used to record the absorbance while measuring the amount of lycopene colorimetricaly.
Variable | Why was it controlled? | How was it controlled? |
---|---|---|
Storage time | More the contact time of the tomatoes with the turmeric solution, more the amount of curcumin that enters the cells of the tomatoes and performs the biological functions. | In all cases, the tomatoes were stored in the turmeric solution for 3 days. |
Temperature | Both preservation and rancidification involves multiple biochemical reactions and uses enzymes. The rate of these reactions and the functioning of the enzymes will depend on the temperature the sample is exposed to. | All trials were conducted at room temperature. All samples were stored for the same period of time so that the fluctuations of temperature, if any is same for all of them. |
Genetic variety of the turmeric | Turmeric belongs to the botanical group-“curcuma longa” and thus the curcumin content of turmeric will vary along with the genetic origin and variety of it. | The turmeric powder used were made from the same pieces of turmeric from the same plant as procured from a local organic farm. |
Volume of the turmeric solution used | More the volume of the turmeric solution used, more the curcumin content available to the tomatoes. | In all cases, the tomatoes were exposed to a 50 cm3 solution of the turmeric. |
Apparatus | Quantity | Least count | Absolute uncertainty |
---|---|---|---|
Digital mass balance | 1 | 0.01 g | ± 0.01 g |
Digital colorimeter | 1 | 0.001 AU | ± 0.001 AU |
Glass beaker-50 cm3 | 35 | --- | --- |
Glass beaker-500 cm3 | 5 | ||
Glass rod | 1 | --- | --- |
Mixer grinder | 1 | --- | --- |
Spatula | 1 | --- | --- |
Watch glass | 1 | --- | --- |
Thermometer | 1 | 1.0 o C | ±0.5o C |
Graduated measuring cylinder | 1 | 1.0 cm3 | ±0.5 cm3 |
Graduated pipette | 1 | 0.10 cm3 | ± 0.05 cm3 |
Cuvette | 1 | --- | --- |
Soft tissue | 1 roll | --- | --- |
pH probe | 1 | 0.01 | ± 0.01 |
Buffer solution of pH 10 | 1 | --- | --- |
Funnel | 1 | --- | --- |
Filter paper | 1 box | --- | --- |
Conical flask | 1 | --- | --- |
Bunsen burner | 1 | --- | --- |
• A laboratory coat and safety gloves were used.
• Social distancing protocols were maintained.
• The solutions were made under the supervision of an expert technician.
• The instruments were handled with care.
• The work station was kept clean and organized.
All unused and waste materials were thrown into the disposal bin and disposed using standard safe procedures.
None of the materials were wasted and minimum possible amount of materials were used. Any toxic or prohibited materials were not used.
The experimental procedure has been self- procured by the experimenter in conjunction with references from laboratory manuals for “measuring pH using pH meters” (What Is a PH Meter? Introduction to Digital PH Meters), “making lycopene extract” (Chiu et al.) and “Using colorimeter in food industry” (Huang et al.)
Stage-1 - Preparing the turmeric solution
500.00 ± 0.01 g of turmeric was kept on a watch glass on a top pan digital mass balance and weighed using a spatula. The weighed turmeric was transferred into a clean and dry mixer grinder. The grinder was operated to obtain a fine powder of the turmeric. The powdered turmeric was kept in a 100 cm3 glass beaker.
For a 5.00% solution, 5.00 g of turmeric should be added to 100 cm3 of water.
Mass of turmeric powder for 500 cm3 of 5.00% solution = \(\frac{5.00}{100} × 500 = 25.00 \, \,g\)
25.00 ± 0.01 g of the turmeric powder was weighed on a top pan digital mass balance and using a watch glass and a spatula. The weighed turmeric was completely transferred to a 500 cm3 glass beaker. The beaker was filled with drinking water till the mark of 500 cm3 . A glass rod was used to stir the solution and dissolve the turmeric. Thus, a 5.00 % solution of turmeric powder was made.
The other solutions – 10.00%, 15.00%, 20.00% and 25.00% were made in the same way. For the control – 0.00%, drinking water was used and no turmeric was added.
Stage-2: Preserving the tomatoes in the turmeric solution and measuring pH and lycopene absorbance:
The same process was repeated for all other % concentration of turmeric solutions – 0.00%, 5.00%, 10.00%, 15.00%, 20.00% and 25.00%. The same process was repeated for samples of green tomatoes.
Key
Sample calculation
For Row-1: (0.00% turmeric solution)
For Trial-1, Change in mass (m) = Initial mass (m1) – Final mass (m2)
= 95.30 ± 0.01 g – 91.65 ± 0.01 g = (95.30-91.65) ± (0.01 + 0.01) g = 3.65 ± 0.02 g
Average change in mass (m) =\(\frac{(3.65±0.01)+(5.48±0.01)+(4.34±0.01)}{3}= 4.49 ± 0.01 \, \,g\)
Standard deviation (SD) = \(\frac{(4.49-3.65)^2+(4.49-5.48)^2+(4.49-4.34)^2}{3} = 0.92\)
Key
For 0.00% turmeric solution (control)
Change in mass (m) = 4.49 ± 0.01 g
Percentage error in change in mass = \(\frac{0.01}{4.49} × 100 = 0.22\)
pH = 4.13 ± 0.01
Percentage error in pH = \(\frac{0.01}{4.13} × 100 = 0.03\)
Absorbance of lycopene at 667 nm = 0.663 ± 0.001 AU
Percentage error in absorbance of lycopene at 667 nm \(=\frac{0.001}{0.663}× 100 = 0.15\)
Total percentage error for efficacy of turmeric as a preservative at 0.00 % (control) = 0.22 + 0.03 + 0.15 = 0.40
As the magnitude of percentage error is really less significant, it can be claimed that the results are accurate and precise enough.
The scatter graph above indicates the patterns in the decrease of mass for the red and the green tomato against the various values of percentage concentration of turmeric solution used.
As shown in Graph-2, the pH values of both red and green tomato ranges from 4.20 to 4.60 which is the ideal range of pH for all values of percentage concentration of turmeric solution. In both cases, the value for the control (0.00 %) is lower than the ideal range, 4.10 for red tomato and 4.13 for green tomato. Thus, it can be claimed that turmeric can act as a preservative and helps tomato to maintain the pH in the ideal range. However, the maximum value of pH is obtained for the percentage concentration of turmeric at 11.00% as indicated in the peak of the curve shown in the graph above. The maximum value of pH is around 4.63 which is slightly more than the ideal value.
The above graph depicts the variation of the lycopene content in red and green tomato against the percentage concentration of turmeric solution.
• For green tomato, the absorbance increases from 0.336 ± 0.001 AU to 0.714 ± 0.001 AU and for red tomato, it increases from 0.663 ± 0.001 AU to 0.995 ± 0.001 AU. This confirms that with the increase in the percentage concentration of turmeric solution, the lycopene content of both the red and green tomato increases resulting in increase in the absorbance of lycopene at 667 nm. Thus, it can be claimed that turmeric or preferably curcumin favours the production of lycopene in tomatoes.
• For both red and green tomatoes, the values at 5.00% turmeric solution and more concentrated solution is higher than the control (0.00%). This again confirms that turmeric helps in the bio-synthesis of lycopene pigment in tomatoes.
• The linear equation of trend line has been displayed in the graph and in both cases the gradient are positive (0.0129 for red tomato and 0.0156 for green tomato). This shows that the turmeric is favourable for the increase in the enzymatic pathway leading to the synthesis of lycopene.
The analysis above clearly shows that with the increase in the percentage concentration of turmeric, the loss in mass of tomatoes decreases, the content of lycopene increases and the pH of the tomatoes lies within the ideal range of 4.2 to 4.6 mostly barring few slight or insignificant variations. This can be justified by two scientific facts:
Turmeric contains curcumin. Curcumin from the turmeric solutions can penetrate into the cells of the tomato through diffusion. Lycopene is produced in a melavonate pathway which involves six stages of enzymatic pathway (Cabral). Curcumin acts as a precursor and maximizes the synthesis of Acetyl-CoA which is involved in this enzymatic pathway of biosynthesis of lycopene (Schwartz et al.). Thus, the addition of curcumin enhances the production of lycopene. This is in accordance with the data displayed in Table-4, as the percentage concentration of turmeric increases, the amount of curcumin penetrating into the cells of tomato is more, more co-factors is released and thus more lycopene is produced which finally increases the absorbance value.
Curcumin also shows anti-carcinogenic activities by killing pathogens and microbes. As indicated in a research based on antibacterial action of curcumin against S.aureus, “ Curcumin may bind into FtsZ proteins, thereby inhibiting the assembly of FtsZ protofilaments. This, in turn, suppresses the formation of Z-ring leading to inhibition of cytokinesis and bacterial proliferation” (Teow et al.). This shows how curcumin can delay the pathways through which the biological content of tomato can decompose and thus make it loss it’s biomass. This fact supports the data collected in Table-1 and Table-2, where it is clearly evident that the values of decrease in mass is reducing as the percentage concentration of turmeric increases.
From Graph-1, the value of regression coefficient is 0.95 for red tomato and 0.99 for green tomato which indicates that there is a strong negative correlation (negative as the value of gradient is negative) between the change in mass of tomato and the percentage concentration of turmeric solution used as a preservative. From Graph-3, the values of regression coefficient is 0.97 for both the red and green tomato confirming a strong positive correlation (positive as the magnitude of gradient is positive) between the absorbance of lycopene at 667 nm (an indicator of the lycopene content) and the percentage concentration of the turmeric solution as a preservative. Both of these factors allow us to confirm that there is a correlation between the percentage concentration of turmeric solution and it’s efficacy as a preservative for tomato. However, in the case of pH any such correlation is not significant. Considering that a correlation is observed in two cases – absorbance and mass loss and not in one-pH, the null hypotheses is rejected and the alternate hypotheses has been accepted.
This section aims to explore if there is any significant difference between the efficacy of turmeric as a preservative for red tomato and green tomato. As here the data has been collected for two different categories – red and green and the categories are mutually independent of each other, a T-test of independence will be done.
Though three different variables- mass loss, pH and absorbance of lycopene has been chosen to measure the efficacy of turmeric as a preservative, the T-test (“T Test (Student’s T-Test)”) will be conducted on data for change of mass and absorbance of lycopene at 667 nm as in case of pH any significant correlation between the percentage concentration of turmeric and the pH was not observed (refer to Graph-2).
Null hypotheses(Ho) The change in mass against % concentration of turmeric in red and green tomato are independent of each other.
Alternate hypotheses(H1) The change in mass against % concentration of turmeric in red and green tomato are not independent of each other.
Significance level (∝) = 0.05
Degrees of freedom (N) = 6 - 1 =5
Calculated t value \(\)\(\frac{\frac{\sum(X-Y)}{N}}{\sqrt{\frac{\sum(X-Y)^2-\frac{(\sum(X-Y))^2}{N}}{(N-1)N}}} = −1.09\)
According to the T-Table, the value of t at degrees of freedom = 5 is 2.015 (“T Test (Student’s T-Test)”) As the calculated value (- 1.09, negative sign being ignored) is less than the calculated value, the null hypotheses is accepted and the alternate hypotheses is rejected. This means that the efficacy of turmeric as a preservative for tomatoes when measured in terms of mass loss does not depend on the genetic variety of the tomato used.
Null hypotheses(Ho) The absorbance of lycopene at 667 nm against % concentration of turmeric in red and green tomato are independent of each other.
Alternate hypotheses(H1): The absorbance of lycopene at 667 nm agaisnt % concentration of turmeric in red and green tomato are not independent of each other.
Significance level (∝) = 0.05
Degrees of freedom (N) = 6 - 1 =5
Calculated t value = \(\frac{\frac{\sum(X-Y)}{N}}{\sqrt{\frac{\sum(X-Y)^2-\frac{(\sum(X-Y))^2}{N}}{(N-1)N}}} = 2.763\)
According to the T-Table, the value of t at degrees of freedom = 5 is 2.015 (“T Test (Student’s T-Test)”) As the calculated value (2.763, negative sign being ignored) is less than the calculated value, the null hypotheses is rejected and the alternate hypotheses is accepted. This means that the efficacy of turmeric as a preservative for tomatoes when measured in terms of absorbance of lycopene or lycopene content depends on the genetic variety of the tomato used.
How does the ability of turmeric to act as a preservative for tomatoes (solanum lycopersicum), measured in terms of mass loss, pH and lycopene content depends on the percentage concentration (mass by volume) of the turmeric solution used and the type of tomato used-green tomato and red tomato ?
Source of error | How does it impact? | How to improve? |
---|---|---|
The pH meter is a digital device and an instrumental error is associated with it. | The readings of pH will be inaccurate. | The pH meter must be calibrated using a buffer solution of pH 10.00 or 4.00. |
The digital photo colorimeter can also record the absorbance of the solvent which is ethanol-water mixture in this case along with the sample lycopene. | The values of absorbance recorded for lycopene at 667 nm would be higher than the actual value. | The colorimeter was calibrated using the solvent and setting the absorbance at 0.000 AU for the solvent to nullify the effect of solvent in the absorbance of lycopene. |
The digital mass balance can have random errors associated with it. | The values of mass recorded would not be precise. | Data was collected in triplicates and average values are considered. |
Lycopene is a aromatic hydrocarbon and is insoluble in water. Thus, the entire amount of lycopene from the tomatoes may not be extracted. | The absorbance of lycopene at 667 nm recorded would be lower than the actual value. | Ethanol was used in the extraction process. Lycopene being an organic compound can be extracted using ethanol as a solvent. |
Like turmeric various other substances like neem leaves, tulsi (Indian herb) leaves also has antibacterial effect. I would like to compare the antibacterial effect of these substances with the chemical anti-bacterial alternatives like laevocetrizine, allegra and Doxycycline. To do this, an extract of the natural substances and a solution of the chemical antibacterial drugs can be prepared. These can be applied on a petri dish where E.coli is grown in a agar agar medium and the zone of inhibition can be measured. A colony count method can also be used. Larger the zone of inhibition, better the antibacterial effect of the substance used. This investigation would allow us to compare and contrast the antibacterial effect of various natural and chemical substances that are claimed to have antibacterial effect.
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