Experiment to determine the fat content of a sample ( corn-soy flour) PDF

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Proximate analysis of the fat content of a sample ( corn-soy flour). This experiment uses the soxhlet apparatus in conjunction with a solvent called petroleum ether to extract the fat...

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KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY, KUMASI

COLLEGE OF SCIENCE DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY (FST 2) LAB REPORT NAME: OWUSU SAMUEL KWANING INDEX NUMBER: 9314819 FOOD ANALYSIS DATE:20thJULY, 2021.

TITLE DETERMINATION OF THE CRUDE FAT CONTENT OF FOOD SAMPLES

AIM: TO DETERMINE THE CONTENT OF CRUDE FAT IN CERTAIN FOOD SAMPLES

ABSTRACT; The purposes of this lab were to: demonstrate a fat extraction procedure, determine fat contents of different food products, and to calculate and compare the fat contents of the test foods.1The two most common lipid extraction methods are Soxhelt and Goldfish extraction methods.1The Soxhlet Method is a semi-continuous extraction method, while the Goldfish is a continuous extraction.1Each of these extractions normally use anhydrous petroleum ether, or diethyl ether (ether), or hexane as their non-polar solvents for the lipid extraction

INTRODUCTION The basic function of food is to keep us alive and healthy. Therefore, there is the need to understand the natural composition and behavior of food materials during both processing and storage. One of the most essential natural composition of food is crude fat. Crude fat is the term used to refer to the crude mixture of fat-soluble material present in a food. It is also known as the free lipid content. It is the traditional measure of fat in food products (Maxwell et al, 1980). The lipid materials comprising crude fat may include triglycerides, diglycerides, monoglycerides, steroids and free fatty acids. The little difference between crude fat and total fat content is that the total fat content also known as the net fat takes into account lipid components that remain unchanged and not converted to triacylglycerol (Hyvonen et al, 1993). Therefore, most of the labelling on food products are with respect to crude fat. The crude fat is determined based on the phenomenon of the solubility of lipids in non- polar organic solvents such as hexanes or petroleum ether. There are several methods for the extraction of crude fat. These methods include acid or alkaline hydrolysis, microwave accelerated extraction, Babcock method, mid-infrared spectroscopic method, rapid specific gravity method and mojonnier method. However, the two main methods most commonly used to determine crude fat are wet extraction and dry extraction. The wet extraction is performed with water remaining in the sample. Examples include the Babcock and Mojonnier methods which are used for milk and milk products (Perez-palacios et al, 2008). In this experiment, the soxhlet method of extraction was used. It was invented by Franz Soxhlet in 1879. The soxhlet method is the most commonly used example of semi-

continuous method applied to extraction of lipids from food. According to its procedure, oil and fat from solid material are extracted by repeated washing with an organic solvent usually hexane or pet ether under reflux in a glassware. It works based on the principle that, lipid is soluble in organic solvents and insoluble in water, hence organic solvents have the ability to solubilize fat and fat is extracted from the food in combination with the solvent. Besides lipid extraction, soxhlet method is normally required where the desired compounds have limited solubility in a solvent. The samples mainly used in the soxhlet method are dried. This is because, the presence of moisture affects the effectiveness of the organic solvents. Soxhlet method has its advantages and disadvantages. Its advantages include the fact that, instead of many portions of warm solvent being passed through the food sample, just one batch of solvent is recycled. Also, the solvent used is being recovered back and can be changed. Furthermore, it is straight-forward and an inexpensive method. Its disadvantages include its poor extraction of polar lipids, long time being required for extraction, possibility of thermal decomposition of certain compounds, exposure to hazards of boiling solvents and impossibility of agitation (Xu and Chang, 2007). In this experiment, the solvent used was petroleum ether. The petroleum ether was used over other solvents like hexane and alcohol because of its distribution coefficient, insolubility of solvent, recoverability, density, chemical reactivity being inert and stable and its non-toxicity. Crude fat analysis is widely done in the food industries. It is important to analyze fat in food in food industries since fat contribute to the flavour, texture and mouthfeel of the products. Fat analysis also enables the consumer to make an informed choice about a particular food product due to diet management.

METHODOLOGY SOXHLET EXTRATION METHOD About 2g of dried sample was weighed into an extraction thimble or a piece of filter paper. The opening of the thimble was plugged loosely with cotton, the thimble or paper was placed and contented into a Soxhlet extractor. A dried round bottom flask was weighed accurately and 150ml of petroleum ether was added, the apparatus was connected to the condenser, the water was turned on and extracted for a minimum of 4-6 hours on an electrothermal extraction unit. Flask containing the petroleum ether extract was removed after the extraction was completed. The petroleum ether was evaporated on a boiling water bath. The flask was transferred into an oven to dry the extract for one hour at 105 degrees Celsius. The flask was transferred immediately into a desiccator to cool and weigh

%FAT (dry basis) = Fat/oil collected * 100

Weight of sample

%FAT (dry basis) = (wt of flask + oil) – wt of flask *100 Weight of sample

RESULTS AND DISCUSSION TABLE 2.0: RESULTS SHOWING THE % CRUDE FAT CONTENT OF SAMPLE B CRUDE

% CRUDE

PAPER+SAMP E

FAT

FAT

LE WEIGHT/g

WEIGH

CONTENT

CONTENT(X1

T

T

(g)

00)

BEFORE

AFTER

DRYING

DRYING 0.3773 0.3764

37.73 37.64

SAMP

FILTER

SAMPL

FILTER

LE B

PAPER

E

WEIGH

WEIGH

T/g

2A1 2A2

0.5889 0.5685

/g 2.0844 2.0372

2.6733 2.6057

SAMPL

/g 1.8868 1.8389

In order to determine the free fat percentage in the sample B namely 2A1 and 2A2 an apparatus called the Soxhlet Extraction was used to extract the lipids from the sample B. The result for the free fat in sample B (2A1) was 37.73%. and sample B (2A2) was 37.64%. which was lower than the sample 2A1. High similarity between the results shows that the experiment went according to plan. A high result would have suggested that there was an error made during the experiment such as the dish not spending long enough drying in the oven. A low result would have suggested that some of the dried food had been lost during the experiment through personal error. An accurate result is essential when testing fat in sample B (2A1 and 2A2) In the food industry certain food like, cheese manufacturer, as the greater amount of fat and protein in sample 2A1, the high fat content gives more butter than 2A2 with a low-fat content. (www.fao.org, 20/02/2011). It is also very important to have an accurate result when testing the fat content in sample B (2A1 and 2A2) for displaying nutritional information for on labels of full, food product. Less fat in sample B (2A1 and A2) contains less energy and lower amounts of fat-soluble vitamins so consumers need to be correctly informed as to make a decision. (www.bbc.co.uk,22/2/2011) The Soxhlet method was used to conduct the analysis of free fat in sample B because it is efficient and accurate. As lipids are soluble in organic solvents, but insoluble in water, this is a convenient method of separating the lipid using the extraction method to isolate the lipids from foods and determining the total lipid content of the sample. (www.unix.oit.umass.edu,17/02/11)

The Gerber test was used to conduct the determination of fat content in sample B as it very popular in the food industry and is an extremely accurate standard method for determining the content of milk lipids. As seen in the method the test was used to separate the sample from the proteins by adding sulfuric acid. The advantages of the Gerber test and the Soxhlet analysis are they are simple to use and cheap, new equipment can cost the organization thousands. They are both the most common methods used to extract lipids from foods and widely recognized worldwide to produce excellent results that meet international standards. The disadvantages of the Gerber test and the Soxhlet analysis are that they are both time consuming, outdated and not environmentally friendly. The solvents used are costly and emit toxic emissions during extraction; the sulphuric acid can also be harmful if not properly disposed of.

The Gerber test and the Soxhlet Extraction although very accurate are very time consuming are not very practical for industry but play a very important role. It is very important and beneficial for the company to get the results as accurate as possible as the success of a company depends on the accuracy of its products conforming to specification and to fulfill legal obligations. It is extremely important for fat-free products that the nutritional information is correct. Also having accurate tests can prevent wastage and save the company money. New technology is available for testing fat in foods but is very expensive. A company would need to look at long terms costs and decide would it be more cost effective in the long run before investing in expensive equipment.

CONCLUSION Fat analysis testing is very importance within any food organization. Testing must be carried out in order to determine accurate results and provide by law the nutritional information of a product to a consumer through labeling. The result for free fat found in sample B using the Soxhlet Extraction was 37.74%. The result for fat found in sample 2A2 was 37.76 % using the Gerber Method.

APPENDIX.

% CRUDE FAT CONTENT DETERMINATION: % FAT (dry basis) = (wt of filter +weight of sample before extraction) – (weight of sample after extraction) x 100 Wight of sample

For 2A1;wt of filter paper-0.5889g,weight of sample +filter paper-2.0844g(before extraction) ,wt of sample after extraction -1.8868g % FAT (dry basis) = (2.0844) – (1.8868) x 100 1.4955 =13.21%

For 2A2;wt of filter paper-0.5685g,weight of sample +filter paper-2.0372g(before extraction) ,wt of sample after extraction -1.8389g % FAT (dry basis) = (2.0372) – (1.8389) x 100 1.4687 =13.50%

REFERENCE 1. Maxwell, R.J., Manner, W.N., Zubillaga, M.P. and Dalickas, G.A. (1980). Determination of total fat and crude fat in meat and meat products by a rapid, dry column method. Journal-Association of Official Analytical Chemists, 63(3), pp 600-603. 2. Hyvonen, L., Lampi, A.M., Varo, P. and Koivistoinen, P. (1993). Fatty acid analysis, TAG equivalents as net fat value and nutritional attributes of commercial fats and oils. Journal of Food Composition and Analysis, 6(1), pp. 24-40. 3. Perez-palacoius, T., Ruiz, J., Martin, D., Muriel, E. and Antequera, T. (2008). Comparison of different methods for total lipid quantification in meat and meat products. Food Chemistry, 110(11), pp. 1025-1029. 4. Xu, B.J and Chang, S.K. (2007). A comparative study on phenolic profiles and antioxidant activities of legumes as affected by extraction solvents. Journal of Food Science, 72(2), pp. 55-60....