ONPS2143 2010 Literature Review Assignment

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ONPS2143 -Lipids in Food Science

2012 Literature Review Assignment

Introduction

In Food lipids are one of the major constituents and also a most important part for our diet and

that has been proven in the number of researches. There have been a number of reasons for

which lipids are very useful for our body and important to the diet. Lipids are considered as the

one of the most important or major sources of energy and consists of the essential lipid nutrients.

It is not always that there are benefits from the lipids but also there is problem because of this too

if the lipid are consumed over the limit. (Laurence M. Harwood et al, 1989) Not all lipids but

few specific lipids if consumed over the certain limit then it might be harmful for the health. For

example cholesterol and saturated fats are harmful if consumed more than the limit. The physical

characteristics of the food mainly determine by the amount of the lipid in the food. This is the

reason the low fat alternatives of the number of food are very difficult to develop because with

the reduction or removal of fat the physical characteristics of the food get lost. Some of the

important properties of the foods include as the amount of total lipid concentration, which type

of lipid present, physicochemical properties and structural organization of lipids within a food

etc.

Lipids are generally defined as the components that are soluble in the organic solvents. The

Lipids are insoluble in water. In the lipid fraction of the food there is high complex mixture of

the different molecules. The analysis of the lipids can be done with the different methods such as

soxhlet extractor (William B. Jensen, 2007) and solvent extraction. Both methods are used to

analyses the lipids in the food and both are very specific methods for the acids which are mainly

soluble in organic solvent only. How much lipid concentration is available can be analyzed

through the use of these mentioned methods. (Nielsen, S, 1994) The analysis can easily separate

lipid components in food from water soluble components. This report analyze about the two

different methods of lipid analysis based on the previous literature.

Two different methods of Lipid Analysis

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There are many methods available for the analysis of the lipids. The two methods soxhlet

extractor and solvent or liquid - liquid extraction methods are analyzed based on the earlier

literature. The analysis is done such as:

Soxhlet extractor – This analysis is done to analyze the concentration of the lipids in the food

and also used for extracting the lipids from the solid material. (Soxhlet, F, 1879) The lipids are

not dissolved in the water and other liquid solvent except the organic solvent so it is very use

using the soxhlet extractor. Laurence M. Harwood states in his research that soxhlet extractor is

very useful to separate the lipids from the food. Not only for food but also in other activities it

can be used perfectly. (P. Giridhar et al, 2006) This methodology only works where there is the

compound which has the limited solubility in the solvent. In this method the solid material or

food which contains the desired component or lipids inside a thimble which is made of the thick

filter paper. That thick filter paper made thimble is loaded in to the main chamber of the soxhlet

extractor. Then this soxhlet extractor is placed on the above of the flask which contains the

extraction solvent. And then the condenser is used in the soxhlet extractor for extracting the

desired components as lipids from the material. The solvent is heated then and the vapor travels

to the condense part and the desired components is separated from the solid material. Soxhlet

extractor is generally used for the fast –food or can say as commercial foods to extract the fats

from the food. Nielsen, S (1994) describes that the chemical process used for the extraction of

the lipids from the food as using the soxhlet extractor for the fast foods because these foods have

the highest amount of the lipids.

This soxhlet extractor is not good for the foods where there is poor extraction of polar lipids,

long time involved, large volumes of solvents, and hazards of boiling solvents. The accuracy of

getting the concentration of the lipids or amounts of the lipids in the food is almost 95-98 percent

because as the method use the condense process so in that case there is some chances of not

getting the condense lipids from the food perfectly as there might be some components of the

extracted material too. (William B. Jensen, 2007) As from the previous literature it can be

explains that the precision of the extracted lipids have some issues as lipids are not 100 percent

pure lipids extracted from the foods. As this method is totally equipment based in the laboratory

so there is need to follow the instructions to carry out the extraction process and also there is

need to maintain safety issues because the equipment is made of the glass and thick paper as well

it uses the high temperature. (Laurence M. Harwood et al, 1989) Chemicals are harmful for the

ONPS2143 2010 Literature Review Assignment

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body so keep safe while working with this soxhlet extractor. Soxhlet, F (1879) itself explains in

his research that safety is more important in this analysis. This method is suitable for both

routine use and for the research too because this instrument also works automatically so very

useful for the industry too. It signifies that soxhlet extractor is very useful for extracting the

lipids concentration from the foods which have high amount of the lipids.

Solvent or Liquid- Liquid extraction – The purpose of this analysis is to extract the compounds

or separate the compounds which have the relative solubility in two different immiscible liquids.

The immiscible liquids are water and organic solvent. It is generally used for separating the

lipids from the water in the food. (Yoshinari Baba et al, 2002) It is an extraction of a substance

from one liquid phase into another liquid phase. Liquid–liquid extraction is a basic technique in

chemical laboratories, where it is performed using a separatory funnel. This type of process is

commonly performed after a chemical reaction as part of the work-up. There are few processes

used in the solvent extraction for different kind of lipid extraction in many ways such as Batch

wise single stage extractions, multistage countercurrent continuous processes, extraction without

chemical change, Ion pair extraction, (Danil de Namor et al, 1983) solvation mechanism and ion

exchange mechanism etc. This method is applicable for the foods such as meat, milk, margarine,

cookie, dairy cream which has highest fats inside it.

The lipids concentration can be determine form the solvent extraction process from these foods.

This method is most suitable for these kinds of foods because there is high amount of the water

and the lipids are not soluble in the water easily so can be extracted easily. The accuracy issues

in this method as the lipids are separated from the immiscible liquids and it might happen that

the not all the lipids are separated from the liquid so the concentration of the lipids in the food

can’t be tested accurately but it is 97-99 percent accurate. J. M. Sánchez explains that the

accuracy is more than the other methods in this method lipid concentration measurement. There

is not much issues in case of the precision of the measurement of the lipids in the foods

mentioned above. (M. Filiz et al, 2006) As this method does not use the equipments so the safety

problems are less but as because it uses the chemicals so the person who is doing the process

should be keep safe with the chemicals. It is a method that is suitable for routine use in industry

and also applicable to research too because this is very general process and can be used to extract

the lipids in larger amount too.

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Conclusion

The above discussion analyze that lipids are soluble in organic solvent but not in the water so

easily separated from the water solvent in the food. The important methods are used for the lipid

analysis such as soxhlet extractor and solvent extraction. Solvent extraction method is generally

used method for isolating lipids from the foods and also determines the amount or concentration

of lipids in the food. (J. M. Sánchez et al, 1999) Soxhlet extractor is used for isolating the lipids

from the solid material and is a kind of laboratory apparatus. The previous literature states that

lipids can be analyses with these methods and these lipids are very important for the health if are

taken within the limit as required. This concludes that the lipids are important for health and the

concentration of the lipids in the food can be analyzed using the different methods.

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References:

1. Laurence M. Harwood, Christopher J. Moody. Experimental organic chemistry: Principles and

Practice (Illustrated edition ed.). 1989 pp. 122–125

2. Soxhlet, F. Die gewichtsanalytische Bestimmung des Milchfettes, Polytechnisches J.

(Dingler's) 1879, 232, 461

3. The Origin of the Soxhlet Extractor, William B. Jensen Vol. 84 No. 12 December 2007 •

Journal of Chemical Education.

4. Nielsen, S. Introduction to the Chemical Analysis of Foods; Jones and Bartlett: Boston, 1994;

pp 183–191.

5. Danil de Namor, A.F.; T. Hill (1983). Journal of the Chemical Society, Faraday Transactions:

2713.

6. M. Filiz, N.A. Sayar and A.A. Sayar, Hydrometallurgy, 2006, 81, 167–173

7. Yoshinari Baba, Minako Iwakuma and Hideto Nagami, Ind. Eng. Chem. Res, 2002, 41, 5835–

5841

8. J. M. Sánchez, M. Hidalgo, M. Valiente and V. Salvadó, Solvent Extraction and Ion Exchange,

1999, 17, 455–474.

9. P. Giridhar, K.A. Venkatesan, T.G. Srinivasan and P.R. Vasudeva Rao, Hydrometallurgy,

2006, 81, 30–39.

10. K. Takeshita, K. Watanabe, Y. Nakano, M. Watanabe (2003). "Solvent extraction separation of

Cd(II) and Zn(II) with the organophosphorus extractant D2EHPA and the aqueous nitrogen-

donor ligand TPEN". Hydrometallurgy 70: 63–71.