Research Methods on how to measure Proximate and Heavy metal Contents in Papaw fruits

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Hello teachers, students, and researchers, I am here again today, Thursday, 7th May, 2020, to share a guide on the methods to follow in determining the Heavy metal Contents in Papaw fruits during research.

It is fairly well established that there is a close relationship between diet and health; more people are aware that a balanced diet can benefit their health and are becoming very concerned about the chemistry of what they eat. Also, the food industry is interested in maintaining a high standard of quality of their food products which could meet the demands of an increasing sophisticated consumer. This makes the determination of food composition which aids in the establishment of analytical control a relevant research adventure. To measure the heavy metal composition of fruits, let's take Pawpaw as an example, you will be required to do the following.

Sample Collection

Collect fresh unripe and mature fruits of Carica papaya from their trees at say, three sampling sites.

Sterilization of Glass Wares

All glass ware used in this research work must be washed with detergent, rinsed with distilled water and air dried. They must also
be sterilized on a hot air oven and each material should be wrapped with aluminium foil before sterilization.

Sample preparation

1. Peel the fruits, remove the seeds, slice the flesh into pieces and finally homogenize using blender.
2. Poor the homogenate into a test tube and centrifuged at 300 rpm for 10 minutes.
3. Use the supernatants for glucose and protein estimation (Wurochekke, Eze and Declan, 2013).
4. Carry out the Proximate analysis (discussed below), vitamin A and C determination and total acidity on the fruits

Determination of Proximate Analyses

1. For proximate analysis, standard techniques of Association of Official Analytical Chemists (AOAC) (1990) can be followed.
2. The proximate analyses (moisture, fibre, ash, fats, proteins and carbohydrates) of all the samples should be determined in three replications.
3. Determine the moisture and ash using weight difference method.
4. Estimate Fibre content from the loss in weight of the crucible and its content on ignition.
5. The nitrogen value, which is the precursor for protein of a substance, should be determined by micro Kjeldahl method, involving digestions, distillation and finally titration of the sample (Pearson, 1976).
6. Convert the nitrogen value to protein by multiplying a factor of 6.25.
7. Determine the Ether extract (crude fat) by the Soxhlet apparatus. Extraction should be done in petroleum ether having boiling point 40⁰C- 60⁰C.
8. Present your proximate values in percentage (AOAC, 1990; American Oil Chemist Society (AOCS), 2006).
9. The sum of total crude protein, ether extract, crude fibre and total ash should be subtracted from 100.
10. Total ash content should be determined by heating the ground material in a dry crucible on a low flame and then it should be heated in muffle furnace at 600⁰C for 3- 4 hours Calcium and Phosphorus contents would be determined from the ash samples.

Determination of Heavy Metal Contents

1. Homogenized pawpaw fruit samples using a heavy duty blender with deionized water.
2. Ten grams (10g) of each sample should be weighed using an analytical balance and dissolved in 100 ml of deionized water.
3. Record the pH of the samples using Corning pH meter by introducing the meter probe into the prepared samples.
4. Measure the Salinity by introducing the probe of the HACH CO 150 conductivity meter.
5. Determine the concentrations of the heavy metals using the Jenway 3340 ION selective meter.

You need to access a standard laboratory to use the apparatus.

References

• American Oil Chemist Society (A.O.C.S) (2006). Official Methods of Analysis 5th ed. Association of Official Analytical Chemists Washington, DC, USA.
• Association of Official Analytical Chemists (A.O.A.C.); Journal of Official Method of Analysis, 1990; 8(1): 551-573.
• Wurochekke, A.U., Eze, H.T. and B. Declan (2013). Comparative Study on the Nutritional Content of Carica Papaya at Different Ripening Stages. International Journal of Pure and Applied Sciences and Technology 14(2): 80-83

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I am your Research Assistant @Uyobong. We hope to meet again tomorrow for some helpful educational research tips. Feel free to use the comment section of this post to ask questions so we can interact the more.