Objective Methods of Food Analysis. Brookfield Viscometer. Brookfield viscometer

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Tiffany Grant
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of liquid dispersions such as salad dressings.

1 Objective Methods of Food Analysis Brookfield Viscometer Measures the thickness, or viscosity, of liquid dispersions such as salad dressings. A measure of liquid texture. Brookfield viscometer 1

Compensating Polar Planimeter Measures the area of irregularly shaped areas, for example the cross-sectional area of a loaf of bread, which may be related to loaf volume.

2 Compensating Polar Planimeter Measures the area of irregularly shaped areas, for example the cross-sectional area of a loaf of bread, which may be related to loaf volume. An indirect measure of texture. Compressometer/ penetrometer Measures compression of, or penetration into, a food sample. Direct texture measurement. Largely replaced by the texture analyzer in lab Compressometer/penetrometer 2

3 Hydrometer Measures solution density (specific gravity). Indirect texture measurement. Hydrometer Instron Materials Tester A very versatile machine that measures texture in many different ways. Can measure compression, withdrawal, extrusion, energy required to do a process, etc. Not as user friendly as the Texture Analyzer. 3

4 Jelmeter Measures the rate of flow of pectin dispersions through a pipette. As pectin concentration increases, rate of flow decreases. An indirect measure of texture. Linespread Apparatus Measures the amount of spread of a flowable liquid under the influence of gravity. A direct texture measurement. Linespread Apparatus 4

5 ph Meter Measures concentration of hydrogen ion in solution. A measure of sourness Also important to many chemical reactions that occur in food preparation, processing, or preservation. ph Meter Reflectance Meter Measures color, hue, and the like. A measure of appearance Replaced in the lab by the Hunter colorimeter 5

$Reflectance Meter Refractometer Measures the bending of light as it passes from$ Can be used to measure the concentration of dissolved solids, for example the

Can be used to measure the concentration of dissolved solids, for example the

6 Reflectance Meter Refractometer Measures the bending of light as it passes from air into another medium. Can be used to measure the concentration of dissolved solids, for example the sugar concentration in a syrup. This would be related to texture. May also be used to measure the degree of hydrogenation in fats. Refractometer 6

7 Seed Volume Apparatus Measures volume, typically for baked goods such as bread, muffins, and cakes. Related to texture. Seed Volume Apparatus Shear Press Measures the force needed to cut through a particular food, such as meat or vegetables. A direct texture measurement. 7

8 Shear Press Shortometer Measures the breaking strength of crisp baked goods such as cookies, pie crust, and crackers. A direct texture measure. Largely replaced by the texture analyzer in lab Shortometer 8

9 Spectrophotometer Measures the absorption of light by chemical compounds as a function of wavelength. Related to appearance and color. Spectrophotometer Vernier Caliper Provides an accurate measure of length. An example of it s use would be in measuring the percent sag of gels. In this case, the measurement provides an indirect measure of texture. 9

RapidViscoAnalyzer Measures the viscosity (thickness) as a function of time and temperature for dispersions of starch. Provides very useful information about starch cooking characteristics.

10 RapidViscoAnalyzer Measures the viscosity (thickness) as a function of time and temperature for dispersions of starch. Provides very useful information about starch cooking characteristics. A direct measure of texture. RapidViscoAnalyzer Texture Analyzer Essentially, a very user friendly Instrontype machine. Measures forces to cut, compress, puncture, etc. A direct texture measurement. 10

11 Texture Analyzer Hunter Colorimeter Measures the color of food samples Can report L, a, b values or other color parameters A direct measure of appearance/color Hunter Colorimeter 11

Brookfield texture analyzer Essentially, a very user friendly Instrontype machine. Measures forces to cut, compress, puncture, etc. A direct texture measurement.

12 Brookfield texture analyzer Essentially, a very user friendly Instrontype machine. Measures forces to cut, compress, puncture, etc. A direct texture measurement. Brookfield texture analyzer Brookfield computerized viscometer Measures the thickness, or viscosity, of liquid dispersions such as salad dressings. A measure of liquid texture. 12

HPLC utilizes a column that holds chromatographic packing material (stationary phase), a pump that moves the mobile phase(s)

13 Brookfield computerized viscometer Liquid chromatograph A form of column chromatography used in food chemistry to separate, identify, and quantify compounds. HPLC utilizes a column that holds chromatographic packing material (stationary phase), a pump that moves the mobile phase(s) through the column, and a detector that shows the retention times of the molecules. Retention time varies depending on the interactions between the stationary phase, molecules being analyzed, and the solvent(s) used. Liquid chromatograph 13

depending on their various chemical and physical properties and their interaction with a specific column material, called the stationary phase.

14 Gas chromatograph A gas chromatograph is an instrument for separating chemicals in a complex sample. A gas chromatograph uses a flow-through narrow tube known as the column, through which different chemical constituents of a sample pass in a gas stream (carrier gas, mobile phase) at different rates depending on their various chemical and physical properties and their interaction with a specific column material, called the stationary phase. As the chemicals exit the end of the column, they are detected and identified. The function of the stationary phase in the column is to separate different components, causing each one to exit the column at a different time (it's retention time). Gas chromatograph Chromatography simulation Differential scanning calorimeter (DSC ) This instrument measures heat flow during heating processes such as starch gelatinization, protein denaturation or fat crystal melting. Very useful for determining the thermal properties of various foods. 14

15 Food Rheology Rheology -- the science of the deformation and flow of matter. Rheos (Greek) -- to flow Viscosity Viscosity may be thought of as the internal friction of a fluid. Shear stress = force applied over an area/area = F/A. When stress is applied, this produces a shearing strain (movement). Viscosity Viscosity ( ) is defined as the ratio of shear stress to the rate of change of strain. If we let the rate of change of strain be represented by D, then = (F/A)/D, or, solving for F F = AD 15

16 Viscosity Graphical representations of flow behavior typically plot F vs. D (or D vs. F, more properly shearing stress vs rate of shearing strain) and vs. D. In experiments using the older model Brookfield viscometer, plot the spindle speed for D, plot the scale reading for F, and plot for. Newtonian Flow Scale reading Viscosity is independent of shear rate Spindle speed D Bingham Plastic Scale reading Yield Value Spindle speed (related to shear rate) Spindle speed 16

17 A ketchup poem You shake and shake the ketchup bottle. First, none will come; and then, a lot 'll. Some messy guy Pseudoplastic Scale reading Spindle speed Spindle speed These are called shear thinning fluids. Dilatant Scale reading Spindle speed Spindle speed These are known as shear thickening fluids. 17

18 Thixotropic Scale reading Spindle speed time Note the hysteresis loop -- a characteristic of thixotropic flow Rheopectic These are characterized by an increase in viscosity at constant shear rate. Examples: beaten egg white or whipping cream Food Rheology -- Examples 18

nm Lower energy Higher energy Munsell Color Notation Hue -- what the color

19 The electromagnetic spectrum RED ORANGE YELLOW GREEN BLUE VIOLET 700 nm 400 nm Lower energy Higher energy The electromagnetic spectrum 700 nm 400 nm Lower energy Higher energy Munsell Color Notation Hue -- what the color is Value -- lightness/darkness Chroma -- saturation of the color Color wheel 19

20 C. I. E. System X = amber filter measurement from the reflectance meter Y = green filter measurement from the reflectance meter Z = blue filter measurement from the reflectance meter Then these values are transformed. C. I. E. System x = X/(X + Y + Z) y = Y/(X + Y + Z) z = Z/(X + Y + Z) x is the dominant wavelength of the color (like Munsell hue) y is the purity of the color (degree of saturation) Y is used as the third parameter and represents lightness/darkness (value) C. I. E. System As an example, Blue lake green beans might have the following designations for x, y, and Y 0.376x 0.428y Y By reference to the C. I. E. color chart it is possible to see what this color is. 20

21 CIE Color Chart Green bean values: 0.376x 0.428y Green bean color Hunter Notation GREEN +b -a White a = red to green L b = yellow to blue YELLOW L= lightness +a RED -b BLUE Black Hunter Notation (another view) Image courtesy of Medallion Laboratories ( bernie.htm) 21

Chromatography & instrumentation in Organic Chemistry

Chromatography & instrumentation in Organic Chemistry What is Chromatography? Chromatography is a technique for separating mixtures into their components in order to analyze, identify, purify, and/or quantify