FST Lab 6 (Determination of crude fat by Soxhlet Extraction Method)

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OBJECTIVE

Determination of crude fat content in food sample through a soxhlet extraction method

REQUIREMENTS: 

  • Soxhlet apparatus 

  • Extraction thimbles 

  • Hot plate

  • Petri dishes 

  • Round bottom flask

  • Beaker 

  • Sample 

Chemicals: 

Solvent (n-hexane)

THEORY:

The fat content of food is an essential parameter in food analysis as it is one of the key components affecting the nutritional value, quality, and sensory properties of food. The fat content in food is usually determined through various methods, including extraction, gravimetric analysis, and chromatography. Soxhlet extraction is a commonly used method for determining crude fat in food samples.

Soxhlet apparatus

Soxhlet apparatus is a laboratory apparatus invented by Franz von Soxhlet in 1879. It is used for the extraction of compounds from a solid material. 

It consists of three main parts.

  • Thimble: A solid sample is placed in a thimble which is then placed in an extraction chamber 

  • A boiling flask: it is filled with the solvent, which is heated to boiling.

  • Water-cooled condenser: the vapors from boiling solvent rise into the condenser, which is cooled and condensed back into a liquid. The condensed solvent drops into the thimble, extracting the organic compounds from the solid sample. The solvent and the extracted compounds then drop back into the boiling flask, and the cycle is repeated.

PROCEDURE: 

  • Weight the food sample accurately using an analytical balance and transfer it into an extraction thimble.

  • Place the extraction thimble into the soxhlet apparatus 

  • Add n-hexane to the flask of the apparatus

  • Heat the flask, allow the solvent to boil, and repeatedly condense for several hours. 

  • After extraction, remove the thimble from the apparatus and allow it to dry.

  • Remove the receiving flask and evaporate the ether on a hotplate at 60-70◦C. 

  • After evaporation, weigh the fat content and calculate the % crude fat. 

OBSERVATION: 

Weight of thimble: ____5g_______

Weight of thimble + sample: ____25g_______

Weight of sample: __20g_________

Weight of empty flask: ___84g________

Weight of flask containing ether extract: ___92.05g______

CALCULATION: 

% CRUDE FAT= Weight of flask containing ether extract-weight of empty flaskweight of sample x 100

% CRUDE FAT=  92.05-84 / 20 x 100

%CRUDE FAT= 40.25%

RESULT: 

The crude fat oil present in peanuts according to our experiment is 40.25%.

DISCUSSION:

The experiment aims to determine the crude fat content in a food sample using the Soxhlet extraction method. Fat analysis is essential for understanding the nutritional content of foods, aiding in health management, ensuring product quality in industries, and facilitating research advancements across various fields. The standard value of crude fat in peanuts ranges from 50.45% to 52.12%. However, our measured value is 40.25%, indicating a potential machine error.

STUDY QUESTIONS 

Q1) What is the purpose of using n-hexane as a solvent in determining crude fat through soxhlet extraction?

Ans: N-hexane is used as a solvent in Soxhlet extraction to effectively dissolve fats and oils from solid samples due to its non-polar nature and high extraction efficiency.


Q2) What is the difference between crude fat and total fat in food analysis?

Ans: Crude fat refers to the total fat content determined by extraction methods, while total fat encompasses all types of fats and fatty substances, including those that may be lost during processing or analysis.


Q3) What are some potential sources of error in determining crude fat through soxhlet extraction? 

Ans: Potential sources of error in determining crude fat through Soxhlet extraction include incomplete extraction due to insufficient solvent volume or inadequate extraction time, loss of volatile compounds, and contamination from non-fat substances.


Q4)What other applications of soxhlet extraction in food analysis besides determining crude fat?

Ans: Soxhlet extraction is also used in food analysis for extracting various compounds such as pesticides, flavors, and aromas for qualitative and quantitative analysis.

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