Food Chemistry Laboratory report

The analysis of Lipids Determination of fat by Soxhlet Extraction and Determination of fat content in milk by Gerber method

Introduction
Lipids are molecular organic compounds, composed largely of carbon, oxygen and hydrogen and are essential for cell growth. Lipids are non-soluble in water and combine with carbohydrates and proteins to form the majority of all plant and animal cells. Lipids are transported through the body attached to protein and are an important element of food.
Lipids are the third major micronutrient required for the body after carbohydrates and protein. Lipids are also a medical term for ‘fat’ and though all fats are lipids, not all lipids are fats. Lipids have many roles within the body, one of its main duties is to transport, absorb and digest the fat soluble vitamins A,D,E and K. They provide the most energy to the body, are used for energy storage, cell membrane development, and they protect vital organs. Other major purposes are that they insulate layers under the skin, provide vitamins, essential nutrients and fatty acids in the body. Fatty acids cannot be made by the body and are therefore fat is essential in the diet. In many foods the lipid components add to flavor perception, texture, mouth feel and appearance. (Intro to food Nutrition handout, 15/02/11)
It is important to remember that although fat is essential, the body only requires 30% of daily calorie intake to come from fat. Over consumption of fats can lead to weight gain and health problems. There are many different types of fat some good and some bad. Polyunsaturated and Monounsaturated are good fats and raise healthy cholesterol levels. Saturated and Trans fat can lead to chronic disease and illnesses and lower cholesterol levels. . (www.health.learninginfo.org/22/2/2011)
The determination of lipid content in foods is very important within the food industry. Fat determination is one of the key analyses used for food labeling and quality control so the results of the lab experiments are very important. Manufacturers have a legal obligation to show accurate nutritional information on their products. Consumers are today extremely health conscious and are concerned with over-consumption of certain lipid components that can be damaging to their health, e.g. cholesterol and saturated fats. Consumers rely on food manufacturers that are currently developing low fat foods to indicate true fat content of their products on the wrapping to identify and show the nutritional information. (www.unix.oit.umass.edu, 17/2/2011)

Aims
This food chemistry report will look at the analysis of lipids to include the determination of fat content in 3g of sausage meat. The analysis will be carried out by Soxhlet Extraction. This report will also cover the determination of fat content in milk. This analysis will be carried out using the Gerber method.
Method
Test 1 the determination of fat content in 3g of sausage meat was carried out using Soxhlet Extraction. Test 2 the determination of fat content in milk was carried out using the Gerber Method. Methods carried out for both experiments are given on P7-12n in (BSc (Hons) Food Science Laboratory Manual. Dr A Calvert (2011). BSc (Hons) Food Science Lab Manuel. Loughry Campus: Dr A Calvert. P7-12)

Results
Table 1: Table indicating % of free fat in meat

Weight of Initial Sample (g) M0 | 2.9808g | Weight of Flask before extraction (g) M1 | 83.0703g | Weight of Flask after extraction (g) M2 | 83.6595g | % free fat in the sample | 19.77 % |

Table 2: Table showing calculation to determine % of free fat in meat M2– M1 X 100 M0 19.77% Free fat in Sausage |

Table 3: Table showing results of fat content in Milk

| Sample A | 1ST Reading | 3.4 % |

Discussion
In order to determine the free fat percentage in the sausage meat an apparatus called the Soxhlet Extraction was used to extract the lipids from the sausage meat. The result for the free fat in sausage meat was 19.77%. The class average for the sausage meat was 19.75%. 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.
The fat content found in milk using the Gerber method was 3.4% fat. Milk contains approximately 3.4% fat so this result was accurate. (www.milkfacts.info, 21/2/2011)
An accurate result is essential when testing fat in milk for e.g. a cheese manufacturer, as the greater the amount of fat and protein in milk the greater the yield of cheese, and milk with a high fat content gives more butter than milk 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 milk for displaying nutritional information for on labels of full, semi-skimmed and skimmed milk for consumers. Less fat in milk 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 sausage 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 sausage meat. (www.unix.oit.umass.edu,17/02/11)
The Gerber test was used to conduct the determination of fat content in milk 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 milk 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 organisation thousands. They are both the most common methods used to extract lipids from foods and widely recognised 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 off.

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 organisation. 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 sausage using the Soxhlet Extraction was 19.77%. The result for fat found in milk was 3.4 % using the Gerber Method.

References * http://health.learninginfo.org/fats-lipids.htm. Last accessed 22/02/2011

* BSc (Hons) Intro to Food Nutrition. N McClean (2011). Fats handout. Loughry Campus. 15/02/11)

* http://www-unix.oit.umass.edu/~mcclemen/581Lipids.html. Last accessed 17/02/11

* BSc (Hons) Food Science Laboratory Manual. Dr A Calvert (2011). BSc (Hons) Food Science Lab Manuel. Loughry Campus: Dr A Calvert. p7-12

* Agriculture and Consumer Protection. (2010). Milk Producer Group Resource Book.... Available: http://www.fao.org/docrep/007/y3548e/y3548e06.htm. Last accessed 20/02/2011.

* http://www-unix.oit.umass.edu/~mcclemen/581Lipids.html. Last accessed 17/02/11

* http://www.milkfacts.info/Milk%20Composition/fat.htm, last accessed 21/2/2011

* http://www.bbc.co.uk/health/treatments/healthy_living/nutrition/healthy_dairy.shtml