Lab Report Experiment Determination of ash PDF

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Lab report experiment chemical analysis of food...

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FST556 EXPERIMENT 6 DETERMINATION OF ASH

NAME: STUDENT ID: GROUP: DATE OF EXPERIMENT IS DONE: 08th DECEMBER 2020 DATE OF LAB REPORT IS SUBMITTED: 15th DECEMBER 2020 LECTURER’S NAME:

INTRODUCTION Ash refers to the inorganic residue remaining after either ignition or complete oxidation of organic matter in a food sample. The total mineral content in foods represents the ash content. Although minerals, often less than 7% of the total, represent a small proportion of dry matter, they play an important role from a physicochemical, technological and nutritional perspective. Determining the ash content of a food is part of proximate analysis for nutritional evaluation and it is an important quality attribute for some food ingredients. Ashing is also the first step in preparing a sample for particular elemental analysis (Ismail, 2017). The dry ashing technique with a muffle furnace is used to assess the ash content of a range of food items. In order to convey ash content data on both a wet weight basis and a dry weight basis, moisture content determination is also included. Dry ashing refers to the use of a muffle furnace that is capable of sustaining 500-600 C temperatures. Water and volatiles are vaporized and organic compounds are combusted with CO2 and N2 oxides in the presence of oxygen in the air. Oxides, sulfates, phosphates, chlorides, and silicates are converted into most minerals (Patil, 2017). Thus, the aim of this experiment is to determine the total ash content of food sample using dry ashing method and to determine the acid soluble ash content using acid-insoluble ash method.

OBJECTIVE The objective of this experiment is to determine the total ash content of food sample using dry ashing method and to determine the acid soluble ash content using acid-insoluble ash method.

DRY ASHING METHOD MATERIALS The materials used for this method are porcelain dish, analytical balance, Bunsen burner, oven, muffle furnace and tongs.

PROCEDURE First, the bottom of each porcelain dish was labelled clearly using carbon pencil. The shallow porcelain dish was dried in oven at 105 oC for 3 hour and cooled in dessicator and weighed soon after has attained room temperature. After that, 5 g of the homogenised food sample was weighed accurately into the porcelain dish and dried in oven at 105oC for one day if the samples contain high moisture. Next, the dried sample was burned gently over a Bunsen burner until smoke was no longer evolved when heated strongly. The dish placed in muffle furnace and heated at 550oC for 3 hours until a whitish or greyish ash was obtained. Lastly, the dish was removed, cooled in dessicator and weighed soon after attaining room temperature.

ACID – INSOLUBLE ASH METHOD MATERIALS The materials used in this method are hydrochloric acid, porcelain dish, watch glass, filter paper, analytical balance and Bunsen burner.

PROCEDURE First, the ash obtained from above was boiled with 25ml diluted HCL for 5 minutes and the dish was covered with watch glass to prevent spattering. After that, the insoluble matter was collected by filtering through an ashless filter paper and washed with hot water until washing are acid-free. Next, the filter paper was ignited in the original dish. Lastly, the original dish was cooled and weighed.

RESULTS Table 1.1: Data for ash analysis using dry ashing method Sample: Tea Sample (Brand)

Replicate

Weight of crucible (g)

1 2 3 1 2 3

63.0046 67.1132 65.2875 66.6936 64.2457 63.2913

Boh

Lipton

Weight of crucible + sample (g) 68.0379 72.1430 70.3187 71.7037 69.2554 68.3019

Weight of sample (g) 5.0333 5.0298 5.0312 5.0101 5.0097 5.0106

Weight of crucible + ash (g) 63.2915 67.3929 65.5709 66.9624 64.5137 63.5582

Weight of ash (g)

% ash content

0.2869 0.2797 0.2834 0.2688 0.268 0.2669

5.70 5.56 5.63 5.37 5.35 5.33

Table 1.2: Data for acid-insoluble ash analysis using dry ashing method Sample: Tea Sample (Brand)

Replicate

Boh

Lipton

1 2 3 1 2 3

Weight of crucible + acidinsoluble ash (g) 63.0102 67.1181 65.2926 66.6974 64.2490 63.2948

Weight of acidinsoluble ash (g)

g Acidinsoluble ash/ 100 g sample

g Acidinsoluble ash/ 100 g total ash

% acid soluble ash

0.0056 0.0049 0.0051 0.0038 0.0033 0.0035

0.11 0.10 0.10 0.08 0.07 0.07

1.95 1.75 1.80 1.41 1.23 1.31

3.75 3.81 3.83 3.96 4.12 4.02

Table 1.3: Average value of ash content in tea sample Replicate

% total ash

g Acid-insoluble ash/ 100 g sample

Boh Lipton

5.63 5.35

0.10 0.07

g Acid-insoluble ash/ 100 g total ash 1.83 1.32

% acid soluble ash 3.80 4.03

CALCULATION Dry Ashing Method: g ash 100g the total sample a) Boh

=

Weight of ash(g) Weight of sample(g)

X

100

g ash 100g the total sample

= =

g ash 100g the total sample

= =

g ash 100g the total sample

= =

0.2869 g 5.0333 g 5.70 % 0.2797 g 5.0298 g 5.56 % 0.2834 g 5.0312 g 5.63 %

X

100

X

100

X

100

X

100

X

100

X

100

b) Lipton g ash 100g the total sample

= =

g ash 100g the total sample

= =

g ash 100g the total sample

= =

0.2688 g 5.0101 g 5.37 % 0.268 g 5.0097 g 5.35 % 0.2669 g 5.0106 g 5.33 %

Acid-insoluble method: g acid-insoluble ash/ 100g the total sample =

Weight of acid−insoluble ash(g) Weight of sample (g)

X 100 g acid-insoluble ash/ 100g the total ash

=

Weight of acid−insoluble ash( g) Weight of ash (g)

X 100 Acid soluble ash (%) =

% Total ash - % Acid-insoluble ash

a) Boh g acid-insoluble ash/ 100g the total sample = = g acid-insoluble ash/ 100g the total ash

= =

Acid soluble ash (%) = =

0.0056 g 5.0333 g 0.11 0.0056 g 0.2869 g 1.95

X 100

X 100

5.70 – 1.95 3.75 %

g acid-insoluble ash/ 100g the total sample =

0.0049 g 5.0298 g

X 100

= g acid-insoluble ash/ 100g the total ash

= =

Acid soluble ash (%) = =

= g acid-insoluble ash/ 100g the total ash

= =

= g acid-insoluble ash/ 100g the total ash

= =

= g acid-insoluble ash/ 100g the total ash

= =

= g acid-insoluble ash/ 100g the total ash

= =

DISCUSSION

X 100

0.0038 g 5.0101 g 0.08 0.0038 g 0.2688 g 1.41

X 100

X 100

0.0033 g 5.0097 g 0.07 0.0033 g 0.268 g 1.23

X 100

X 100

5.35 – 1.23 4.12 %

g acid-insoluble ash/ 100g the total sample =

Acid soluble ash (%) = =

X 100

5.37 – 1.41 3.96 %

g acid-insoluble ash/ 100g the total sample =

Acid soluble ash (%) = =

0.0051 g 5.0312 g 0.10 0.0051 g 0.2834 g 1.80

5.63 – 1.80 3.83 %

g acid-insoluble ash/ 100g the total sample =

Acid soluble ash (%) = =

X 100

5.56 – 1.75 3.81 %

g acid-insoluble ash/ 100g the total sample =

Acid soluble ash (%) = = b) Lipton

0.10 0.0049 g 0.2797 g 1.75

5.33 – 1.31 4.02 %

0.0035 g 5.0106 g 0.07 0.0035 g 0.2669 g 1.31

X 100

X 100

In this experiment, Boh and Lipton was used as a food sample. As shown in table 1.3, the percent of total ash and percent acid-insoluble ash obtained for Boh are 5.63% and 3.80% respectively while the percent of total ash and percent acid-insoluble ash obtained for Lipton are 5.35% and 4.03% respectively. On the other hand, the amount of acid insoluble ash per 100 g sample is 0.10 g for Boh and 0.07 for Lipton whereas acid-insoluble ash per 100 g total ash for Boh is 1.83 g and 1.32 g for Lipton. According to Adnan (2013), in many teas the ash content varies from 5 to 6 percent. The proportion of ash can be as high as 10 percent in fresh tea. A tea must contain 4 to 8 percent (by mass) of total ash and at least 40 percent of it must be below 3 percent and the ash itself is high in calcium, as per BIS requirements. Around 50 percent of the ash is water soluble ash in genuine tea and is contained in the range of 3 to 3.5 percent, whereas it decreases to around 0.5 percent in depleted teas (spent). Thus, it shows that Boh have higher content of total ash compared to Lipton. Based on the result, the weight of the crucible and the sample being ignited using the muffle furnace forming the ash resulted a decreased in weight. This is because the crucibles containing the tea sample was subjected to a very hot temperature which cause to decomposes and produces oxygen and the water vapor was loosed. Dry ashing method was used in this experiment where the tea samples was incinerated at high temperature 550oC. The water and volatile materials from the tea samples were vaporized and organic substances burned in the presence of oxygen (O2) in air producing Carbon dioxide (CO2), water (H2O) and nitrogen (N2). Most of the minerals converted to oxides, sulfates, phosphate, chloride and silicates. The crucible used was porcelain because porcelain able to resemble quartz properties, can withstand 1200oC, easy to clean, cheap and susceptible to alkali. Moreover, dry ashing method also a safe method, applicable in determination of most common metals and resultant ash can be used for other analyses such as water-soluble, water-insoluble, and acid-insoluble ash.

QUESTIONS

1. How do you know when the ash is free from carbon? The ash is free from carbon when the ash become whitish or greyish after being heated in muffle furnace. 2. Why is the sample needed to be heated over a Bunsen burner before heating in a muffle furnace? The sample need to be heated over Bunsen burner before heating in a muffle furnace because to accelerate the heating process and to eliminate water, volatile compounds and substances easily thermodegradable before the calcining in a muffle furnace.

CONCLUSION The experiment was achieved because able to determine the total ash content of food sample using dry ashing method and to determine the acid soluble ash content using acidinsoluble ash method. The total ash and acid-insoluble ash obtained for Boh are 5.63% and 3.80% respectively while the total ash and acid-insoluble ash obtained for Lipton are 5.35% and 4.03% respectively. Calculating and weighing the tea samples before and after the changes occurred shows that the weights decreased after it was subjected to heat and cooled down.

REFERENCES Adnan, M., Ahmad, A., Ahmed, A., Khalid, N., Hayat, I., & Ahmed, I. (2013). Chemical composition and sensory evaluation of tea (Camellia sinensis) commercialized in Pakistan. Pak. J. Bot, 45(3), 901-907. Retrieved from http://www.pakbs.org/pjbot/PDFs/45%283%29/24.pdf Ismail, B. P. (2017). Ash content determination. Food Analysis Laboratory Manual, 117-119. Retrieved from https://link.springer.com/chapter/10.1007/978-3-319-44127-6_11 Patil, H. (2017, August 8). Discover Food Technology. Retrieved from Estimation of Ash Content in Food: https://discoverfoodtech.com/estimation-of-ash-content-infood/#:~:text=Dry%20ashing%20refers%20to%20the,phosphates%2C%20chlorides%2C %20and%20silicates....