Topic outline

  • Introduction


    Introduction

    Analytical chemistry/Instrumental methods studies and uses instruments and methods used to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separation isolates analytes. Qualitative analysis identifies analytes, while quantitative analysis determines the numerical amount or concentration.

    Analytical chemistry consists of classical, wet chemical methods and modern, instrumental methods. Classical qualitative methods use separations such as precipitation, extraction, and distillation. Identification may be based on differences in color, odor, melting point, boiling point, radioactivity or reactivity. Classical quantitative analysis uses mass or volume changes to quantify amount. Instrumental methods may be used to separate samples using chromatography, electrophoresis or field flow fractionation. Then qualitative and quantitative analysis can be performed, often with the same instrument and may use light interaction, heat interaction, electric fields or magnetic fields. Often the same instrument can separate, identify and quantify an analyte.

    Analytical chemistry is also focused on improvements in experimental design, chemometrics, and the creation of new measurement tools. Analytical chemistry has broad applications to medicine, science and engineering.

    Rationale


    This course is designed to provide practical knowledge of using instrumentation in food analysis. It covers qualitative and quantitative analysis of different food stuffs so that students will be able to know independently using their own hands to drive instruments to learn with hand to do analysis of foods.

    Objectives

    The specific objectives of the course are:


    1. to make apprehend the principles of methods and analytical instruments used in analysis of food products.

    2. To provide necessary knowledge in application of these principles including analytical instrument operation to analysis of sample in the laboratory situation.

    3. To develop necessary skills on proximate analysis of foods.

    4. To afford students with an opportunity to identify different types of analytical instruments in their respective laboratories.

    5. To enlighten interaction of food by using different analytical techniques

    6. To provide essential knowledge on how to design, carry out, record and analyse the results in experiment

    7. To develop skills for the assessment of physico-chemical properties.

    Outcomes

    Students will be able to determine the techniques/procedures for Fat test, protein test, moisture, ash, viscosity, extraction, UV graph etc.

    Text Books & References

    • Instrumental Methods in Food Analysis, J.R.J. Paré J.M.R. Bélanger, Elsevier.
    • Analytical Electrochemistry. Joseph Wang. Weilly.VCh
    • Chromatography Booklet. GE Healthcare
    • Vogel’s Textbook of Quantitative Chemical Analysis, J Mendham, RC Denny, JD Barnes, MJK Thomas

    Course Assessment Strategy


    Assessment Strategy

    Marks

    Lab Final

    40

    Lab Performance

    25

    Lab Report Book

    25

    Class Attendance

    10

    Total =

    100


    Course Outline & Semester Schedule


    • Introductory class of instrumental methods of food analyses practical
    • Determination of Moisture Content/Water Content
    • Determination of Ash Content/Mineral Content
    • Determination of Protein by Kjeldhal Methods
    • Determination of Viscosity by Digital Viscometer

    Lab Performance Exam

    • Extraction of Caffeine from Tea
    • Making a calibration curve with starch concentrations by UV-visible Spectrophotometer
    • Determination of Fat by Soxhlet Apparatus

    Lab Final Exam

     


    • Determination of Ash of supplied sample

      Ash refers to the inorganic residue remaining after either ignition or complete oxidation of organic matter
      in a food sample. 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. Also, ashing is the first step
      in the preparation of a sample for specific elemental analysis. This laboratory exercise uses the dry ashing
      technique with a muffle furnace to determine the ash content of a variety of food products. Moisture
      content determination is also included so ash content data can be expressed on both a wet weight basis
      and a dry weight basis.
    • Making a calibration curve with starch concentrations by UV-visible spectrophotometry

      In analytical chemistry, a calibration curve, also known as a standard curve, is a general
      method for determining the concentration of a substance in an unknown sample by comparing
      the unknown to a set of standard samples of known concentration.

    • Fat Test by Soxhlet Method

      Lipid in food present in various forms like monoglycerides, diglycerides, triglycerides and sterol
      and free fatty acid and phospholipid and carotenoids and fat-soluble vitamins. Lipid is soluble in
      organic solvent and insoluble in water, because of this, organic solvents like hexane, petroleum
      ether have the ability to solubilize fat and fat is extracted from food in combination with the
      solvent. Later the fat is collected by evaporating the solvent.Almost all the solvent is distilled off
      and can be reused.

    • Protein determination using Kjeldahl Apparatus

      The Kjeldahl method or Kjeldahl digestion in analytical chemistry is a method for the
      quantitative determination of nitrogen contained in organic substances plus the nitrogen
      contained in the inorganic compounds ammonia and ammonium (NH3/NH4+). Without
      modification, other forms of inorganic nitrogen, for instance nitrate, are not included in this
      measurement.

    • Determination of Moisture Content or Water Content

      Principle

      Water content or moisture contentis the quantity of water contained in a material, such assoil (calledsoil moisture), rock, ceramics,crops, orwood. Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 (completely dry) to the value of the materials'porosityat saturation. It can be given on a volumetric or mass (gravimetric) basis.

      Link: https://elearn.daffodilvarsity.edu.bd/pluginfile.php/377926/mod_resource/content/3/Experiment%20No-01%20of%20NFE%20428.pdf

    • Determination of Viscosity by Digital Viscometer

      Viscometer:

      Viscometer. A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid. For liquids with viscosities which vary with flow conditions, an instrument called a rheometer is used. Thus, a rheometer can be considered as a special type of viscometer.

      Viscosity

      The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water

      Viscosity can be conceptualized as quantifying the internal frictional force that arises between adjacent layers of fluid that are in relative motion. For instance, when a fluid is forced through a tube, it flows more quickly near the tube's axis than near its walls. In such a case, experiments show that some stress (such as a pressure difference between the two ends of the tube) is needed to sustain the flow through the tube. This is because a force is required to overcome the friction between the layers of the fluid which are in relative motion: the strength of this force is proportional to the viscosity.


    • Extraction Process of Caffeine from Tea (Classic DCM Method)

      Objective:

      To extract caffeine from tea powder using polar - nonpolar solvent extraction technique.

      Theory:

      The technique used to separate an organic compound from a mixture of compounds is called Extraction. Extraction process selectively dissolves one or more of the mixture compounds into a suitable solvent. The solution of these dissolved compounds is referred to as the Extract. Here the organic solvent dichloromethane is used to extract caffeine from an aqueous extract of tea leaves because caffeine is more soluble in dichloromethane (140 mg/ml) than it is in water (22 mg/ml). However, the tannins that are slightly soluble in dichloromethane can be eliminated by converting it to their salts (phenolic anions by adding sodium carbonate) (tannins are phenolic compounds of high molecular weight and being acidic in nature can be converted to salts by deprotonation of the -OH group) which remain in the water.

      Bevarages cover a vast variety of addictive drinks out of which Tea and Coffee are the most popular acceptable drinks. Tea powder is extracted from tea leaves which contain tannins, which are acidic in nature,  a number of colored compounds and a small amount of unrecompensed chlorophyll and an important stimulant called Caffeine. Because of the presence of Caffeine, tea and coffee are gaining popularity as an addictive stimulant. An average 30g of tea can contain 20-ll0 mg of caffeine thereby making  tea  a significant source of caffeine compared to other beverages. Caffeine can stimulate nervous system and can cause relaxation of respiratory and cardiac muscles.  Caffeine is well known to increase both the alertness level and attention span. But like all other addictives, tea also shows withdrawal symptoms like headache, nervousness and insomnia for a regular consuming person.


      Caffeine, 1,3,7 - trimethylxanthine, belongs to a wide  class of compounds known as alkaloids. These are plant derived compounds with complex structure containing nitrogen, and usually have roles in physiological activity. The melting point of Caffeine is 238°C.

       

      Principle:

       

      Extraction is a method used for the separation of organic compound from a mixture of compound. This technique selectively dissolves one or more compounds into an appropriate solvent. The solution of these dissolved compounds is referred to as the extract. In the case of Caffeine extraction from tea powder, the solubility of caffeine in water is 22mg/ml at 25°C, 180mg/ml at 80°C, and 670mg/ml at 100°C. Here the organic solvent Dichloromethane is used to extract caffeine from aqueous extract of tea powder because caffeine is more soluble in dichloromethane (140mg/ml) than it is in water (22mg/ml).The dichloromethane - caffeine mixture can then be separated on the basis of the different densities of dichloromethane and water because dichloromethane is much denser than water and insoluble in it. Residual water is separated from dichloromethane by drain out the dichloromethane through separating funnel, thus dichloromethane passed through the funnel while polar solvents such as water is still remains in the funnel. Water and dichloromethane is slightly soluble in each other. So, after separating the solvents, residual water will remain the organic layer. Mainly anhydrous sodium sulfite is used for the removal of water from organic layer. Anhydrous sodium sulfite is an insoluble inorganic solid which will absorb water, thus drying it.


    • Determination of Moisture

      Water content or moisture content is the quantity of water contained in a material, such as soil (called soil moisture), rock, ceramics, crops, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 (completely dry) to the value of the materials' porosity at saturation. It can be given on a volumetric or mass (gravimetric) basis.