Instrumental sensory analysis of food quality

Instrumental testing methods for sensory qualities of food

1. FOOD QUALITY AND STANDARDS FT- 507 “ INSTRUMENTAL METHODS FOR TESTING SENSORY QUALITIES ”- ( SIGHT, HEAR & TOUCH ) SUBMITTED BY: KRATIKA SINGHAM INT.FOOD TECHNOLOGY

2. TYPES OF ANALYSIS SUBJECTIVE ANALYSIS / ORGANOLEPTIC People oriented- uses individual Three divisions- (Effective testing, Affective testing , perception) Involves human sensory organs- appearance, flavour , color, texture Result may vary Determines human sensitivity to changes in ingredients, processing or packaging Determine consumer acceptance Time consuming and expensive Must for product development and for good marketing of new products

3. OBJECTIVE ANALYSIS Product oriented Uses equipment(Analytical) Use physical and chemical technique. Results are repeatable. Need to find a technique appropriate for the food being tested Cannot determine consumer acceptance unless correlated with sensory testing. Generally faster and cheaper and more efficient. Essential for routine quality control. Measures- density maturity moisture content oil content tenderness ,etc.

4. FOOD SENSES TOUCH - TEXTURE , VISCOSITY & CONSISTENCY (SMOOTH , GRITTY, GRAINY, CHALKY, FIBROUS, LUMPY, BRITTLE, CREAMY, VISCOUS, ELASTIC, STICKY, SPONGY, SLIPPERY) SIGHT - COLOR, &APPEARANCE (GLOSSY, OILY, TRANSPARENT, CLOUDY, OPAQUE, TRANSLUCENT ) HEAR - SOUND (CRUNCHY, CRISPY, POPPY, CRACKLY, FIZZ, SQUEAK)

5. TYPES OF TEXTURE MEASUREMENT Empirical - method measure often ill-defined variables that are indicated through practical experience to be related to some aspect of textural quality, and are frequently dedicated to a specific product type. Eg : penetrometer I mitative - Imitative methods mimic conditions that the product is subjected to during eating . Eg:TPA Fundamental - Fundamental methods measure well-defined physical properties of the product which can be independent of the measurement method. Eg : UTM

6. SENSORY- TOUCH Consistency and Texture& viscosity Texture - ( for solids or semisolids ) eg : apple, curd, butter Viscosity - ( for homogeneous Newtonian liquids) eg : ketchup, honey Consistency - ( for non-Newtonian or heterogeneous liquids and semisolids ) eg : mayonnaise, pudding

7. TEXTURE MEASUREMENT Universal testing Machine(UTM) Snapping –Bending test( 3 point bending test) Tenderometer Puncture test Penetrometer Texture profile analysis(TPA) Dough testing instruments Farinograph & Mixgraph Extensograph & alveograph Amylograph

8. UNIVERSAL TESTING MACHINE (UTM) A Universal testing machine ( UTM ) is used to test the mechanical properties (tension, compression etc ) of a given test specimen by exerting tensile, compressive or transverse stresses . The machine has been named so because of the wide range of tests it can perform over different kind of materials.

9. COMPONENTS A universal testing machine consists of two main parts : ( i ) Loading unit :- 1 . Load Frame 2. Upper Crosshead and Lower Crosshead 3 . Elongation Scale. (ii) Control Unit:- 1. Hydraulic Power Unit 2. Load Measuring Unit 3 .  Control Devices PERMORMS :- Tensile Test Compression Test Adhesion Tests Pull-Out Tests Bending Test Hysteresis Test Friction Test Flexural Test Spring Test APPLICATIONS: Firmness Crunchiness Hardness Extendibility Brittleness Gumminess Cohesiveness Stickiness

10. 3- POINT BENDING TEST Working/Mechanism First deforms food elastically and then plastically If the sample is sufficiently brittle the force required within the limit of the load cell, fracture will occur Unstretched / uncompressed plane is called “neutral surface”

11. During the test, the force applied, the distance moved by the probe and the time are all recorded in  Exponent . The force-distance graph usually begins with a straight section that corresponds to elastic (reversible) deformation , then most samples show a curved section that shows plastic (irreversible) deformation

12. TENDEROMETER Instrument to measure the stage of maturity( harvest) of mostly peas and tenderness of foods to determine whether they are ready for cropping. Measures the force required to effect a shearing action . APPLICATION Most pea processors pay their growers based on the Tenderometer value of the peas delivered to the processing plant. A Tenderometer Unit is a direct measure of the maturity and quality of the raw product being supplied, analyzed in bulk.

13. PENETROMETER A penetrometer is a device to test the strength of a material  Penetrometers, equipped with a plunger and a needle or cone, penetrate food samples through gravitational force for a selected period of time. The distance the test device penetrates into the sample is measured to determine the relative tenderness of the samples APPLICATIONS baked products ( pizza bases, bread cakes) Gels ( jellies)

14. FARINOGRAPH The farinograph is a tool used for measuring the  shear  and viscosity  of a mixture of  flour and water Uses- 1) milling (flours) 2) bakery( buiscuits , breads cakes ,tortillas) Used to determine wheat flour’s (used by bakers mostly) Water absorption Dough viscosity, including peak water to gluten ratio prior to gluten breakdown Peak mixing time to arrive at desired water/gluten ratio The stability of flour under mixing The tolerance of a flour's gluten WORKING Farinographs measure and record the resistance to deformation of a flour/water dough against the  mixing action of blades over time and at a specific speed (rpm) and temperature. Dough resistance is expressed as motor torque, in dimensionless units known as Farinograph or Brabender Units (FU or BU). During the test, the dough is developed and further broken down. Resistance has traditionally been known as “consistency.” The maximum consistency of the dough is adjusted to a fixed value (500 FU) by altering the quantity of water added (i.e. % absorption).

15. MIXOGRAPH It measures and records resistance of a dough to mixing. It consists of small dough mixer constructed in such a manner that the force required (torque) to turn a head over a static bowl containing dough is measured and recorded as a graphical curve called “ mixogram ”. The wider the curve, the stronger the flour, and the more elastic and less extensible the dough will be. The steeper or the more pronounced the angle after peak, the less mixing tolerance .

16. EXTENSOGRAPH An extensograph is a tool used for measuring the flour quality and stretching behavior of dough. Extensional properties, which determine the course of dough expansion during proofing and baking, have a direct effect on: Loaf volume Quality of texture of bread crumb 1 Information on the extensional properties of bread dough is read directly from the diagram of the extensograph curve, also referred to as the “ extensogram ” The extensogram represents changes in resistance, also called the strength, of the dough to extension (R) as a function of the extension distance. APPLICATIONS: extensograph are useful in determining the gluten strength and bread-making characteristics of flour .

17. ALVEOGRAPH An alveograph is a rheological tool used to assess the baking performance of flours used in baked products (bread, noodles, tortillas, biscuits, etc.). WORKING It is based on injecting air into a thinly stretched sheet of dough to form a bubble, simulating gas/carbon dioxide release and retention during dough fermentation and oven spring during baking . APPLICATIONS Bakers use alveograph data to gain understanding of fluctuations in dough rheological changes by assessing: Tenacity Elasticity Baking strength Resistance of dough to deformation Extensibility

18. PUNCTURE TEST Puncture and penetration tests are commonly used in the testing of the ripeness and bio yield point of fresh fruits and vegetables USES R ipeness of cheese, H ardness of confectionery S preadability of butter and margarine. rigidity of gels Firmness , gel strength, dipping consistency, product toughness, fracture force, 'cake' breaking strength, semi-solid consistency, actuation force Penetration tests usually employ cylinders (2mm – 10mm diameter), cones, ball probes or needles. Small probes are particularly recommended for the assessment of rupture force or for the testing of multiple structure products e.g. measuring skin/crust/coatings and continuing to test the underlying material. Ball probes are recommended where the surface of the sample is not flat or the sample is extremely thin. Hemispherical probes are recommended for imitating a finger when assessing actuation force. APPLICATIONS: Texture of fish gels

19. TEXTURE PROFILE ANALYSIS (TPA)/ TEXTUROMETER Texture profile analysis(TPA) compresses a bite-sized piece of food usually (1cm cube) twice to stimulate the chewing action of the teeth. Compression is usually 80% of the original length of sample. Texture analyzer are used to obtain” texture profile analysis” The force curve generated as a function of time is called “Texture profile ” PRINCIPLE T exture measurement system is physically deforming a test sample in a controlled manner and measuring its response . WORKING A  Texture  Analyzer is a  texture measurement  system that moves up or down to compress and stretch a sample. In a simple  test , the analyzer's traveling arm is fitted with a load cell. It records the force response of the sample to the deformation that it is undergoing. Since the instrument compresses the sample twice , two positive and two negative curve are obtained . Peak forces and areas under the curves are used to Determine various properties of foods like – Fracturability (brittleness) Hardness Cohesiveness Adhesiveness Springiness(elasticity) Gumminess Chewiness

20. Fracturability - defined as the force at the first significant break in the first positive bite area Hardness - defined as the peak force during the first compression cycle Cohesiveness - is defined as the ratio of the second positive bite area to the first positive bite area Adhesivenss - is defined as the negative force area for the first bite representing the work required to pull the plunger away from the food Springiness (elasticity) - is defined as the height to which the food recovers during the time that elapses between the end of the first bite and start of the second bite ( distance or length of the compression cycle during the second bite) Gumminess - defined as the product of hardness and cohesivess . In sensory terms, it is the energy required to disintegrate the semi solid food so that it is ready for swallowing. Chewiness - is defined as the product of gumminess and springiness. In sensory terms it is known as the energy required for chewing a solid food until it is ready for swallowing

21. TPA CURVE ADAVNTAGES A texture analyzer has the capacity to replace human sensory evaluation by providing a numerical value that can serve as a quality assurance standard when evaluation products. Additionally an instrumental method of assessing texture can be carried out under strictly defined and controlled conditions that are repeatable. Your texture measurement test method or application will call for different levels of technology, accuracy, load capacity and budget.

22. Cone probes Cylinder probes Round end probe Puncture probe Knife/shear probes Grisp + clamp probes Extrusion fixtures Food fixtures

23. SENSE - SIGHT SIGHT The human eye has an important role in the perception of colour , and this influences our idea of food flavour . Research shows that we associate specific colour perception of food with certain flavours (although tastes like bitter and sweet are not associated with a particular colour ). The stronger the flavour / colour link, the greater the impact of food colour . As colour levels increase our perception of taste and intensity of flavour do also. COLOR A   phenomenon that involves both physical and psychological components: the perception by the visual system of light of wavelengths 400 to 500 nm (blue), 500 to 600 nm (green and yellow), and 600 to 800 nm (red), commonly expressed in terms of the hue, value, and chroma of the Munsell color system. Deterioration of food is often accompanied by a color change.

24. COLOR MEASURING INSTRUMENTS Spectrophotometer Colorimeter Hunter lab Color order system Munsell color system CIE color system CIE l*a*b (CIE LAB) color spaces Hunterlab color space Lovibond system Color differences

25. SPECTROPHOTOMETER The spectrometer is to produce light of any wavelength, while the photometer is to measure the intensity of light. The spectrophotometer is designed in a way that the liquid or a sample is placed between spectrometer and photometer . photometer measures the amount of light that passes through the sample and delivers a voltage signal to the display. If the absorbing of light change, the voltage signal also changes. PRINCIPLE Spectrometer- produce light from any selected wave length Photometer- measures the intensity of light, and the analyte is put between them Beer’s Law This law states that the amount of light absorbed is directly proportional to the concentration of the solute in the solution. Log 10  I /I t  = a s c where,           a s  = Absorbency index             c = Concentration of Solution Lambert’s Law The Lambert’s law states that the amount of light absorbed is directly proportional to the length and thickness of the solution under analysis. A = log 10  I /I t  = a s b Where,             A = Absorbance of test            a s  = Absorbance of standard             b = length / thickness of the solution

26. COMPONENTS Light source  Monochromator   . Sample holder  Beam splitter  Mirror   Photodetector system  Measuring device  APPLICATIONS The spectrophotometer is commonly used for the determination of the concentration of colored as well as colorless compounds by measuring the optical density or its absorbance . Eg : fruit juices, beverages It can also be used for the determination of the course of the reaction by measuring the rate of formation and disappearance of the light absorbing compound in the range of the visible & UV region of electromagnetic spectrum . A compound can be identified by determining the absorption spectrum in the visible region of the light spectrum as well as the UV region of the electromagnetic spectrum.

27. TYPES OF SPECTROPHOTOMETER

28. COLORIMETER Colorimeter is the instrument which is used in the measuremnent of the luminous intensity of light It is the most common analytical technique used in biochemical estimation Involves quantitative estimation of color A substance to be estimated must be colored or capable of forming chromogens through the addition of reagent. The color of light is the function of its wavelength PRINCIPLE When a monochromatic light passes through a colored solution , some specific wavelengths of light are absorbed which is related to color intensity. The amount of light absorbed or transmitted by a color solution is in the accordance with two laws beer’s and lambert’s law according to which the absorption of light transmitted through the medium is directly proportional to the medium concentration

29. COMPONENTS Tungsten lamp Slit Condensing lens Cuvette Filter Photocell Galvanometer

30. APPLICATIONS For the Estimation of: Glucose Urea Creatinine Water quality Uric acid Bilirubin Lipids Total protein Enzymes ( ALT, AST, ALP) Minerals( calcium, phosphorous) ADVANTAGES It is an inexpensive method , widely used in the quantitative analysis of coloured samples, easy to carry and transport . DISADVANTAGES Analysis of colourless compounds is not possible D oes not work in IR and UV regions . We cannot set specific wavelength as we have to set a range as a parameter Similar colors from interfering substances can produce errors in result.

31. HUNTER LAB Based on the basic of the opponent-color theory which assumes that the receptors in the human eye perceive  color  as the following pairs of opposites: Light-dark , Red-green , Yellow-blue. All three values are required to completely describe an object's  color . T he Hunter L, a, b color space is a three dimensional rectangular, where: L (lightness) varies from 0 (black) to 100 (white), a which represent red-green axis with positive (redness) and negative (greenness) values b which represent yellow-blue axis with positive (yellowness) and negative (blueness) values. The values of 0 for the a* and b* always represent neutral. Once the L, a, b position of a standard color is determined, a rectangular tolerance box can be drawn around the standard. T here are two popular L, a, b color scales which are Hunter L, a, b and CIE L*, a*, b *. Hunter L, a, b is over expanded in the blue region of color space whereas CIE L*, a* and b* is over expanded in the yellow region.

32. MUNSELL- COLOR ORDER SYSTEM The Munsell color-order system is a way of specifying colors and showing the relationships among them. Every color has three qualities or attributes: hue , value , and chroma . Munsell established numeric scales with visually uniform steps for each of these attributes. The color of any surface can be identified by comparing it to the chips under proper illumination and viewing conditions. The color is then identified by its hue, value, and chroma

33. SENSE- HEAR Being able to hear the sounds of food contributes to the enjoyment of eating – not just the crackle and crunch as we eat but also the sizzle and spit of the cooking process. Hearing sounds contributes to the experience of eating crisp and crunchy foods like potato chips and biscuits. 

34. SOUND – A HIDDEN SENSORY ATTRIBUTE When a crisp food is broken or crushed characteristic sounds are produced due to the brittle fracture of the cell walls. Since cracks propagate at very high speeds (too high for even high speed cameras) the sound is produced in a very short space of time – i.e. as a pulse. Slowed down and plotted onto a graph, the pulses can be seen as a series of tall peaks, but actually last only for milliseconds. The more peaks, the crispier it is – it's as simple as that. These sounds (acoustic emission) have been used to try to quantify sensory crispness . Crisper products would produce louder noise A mplitude is one of the variables that distinguishes more crisp from less crisp sounds. This is used in combination with the number of sounds (frequency) produced within a given distance or time.

35. COMMON NOISE CHARACTERSTICS OF FOODS PITCH   - frequency of sound, Crispy, Crunchy, Squeak LOUDNESS -   intensity of sound PERSISTENCE -   endurance of sound over time, Perceived sounds (pitch, loudness, persistence) and auditory measurement MEASURING OTHER SOUNDS The ‘Crack’ of a chocolate coating (whilst measuring the force to crack ) The ‘Snap’ of spaghetti (whilst measuring the break) The ‘Squeak’ of Halloumi cheese (whilst measuring the bite force)    The ‘Bite’ of an apple (whilst measuring the force to puncture its skin)

36. TEXTURE ANALYSER Texture Analyser using an appropriate fixture – eg : for a biscuit, use a three-point-bending rig. They would then position the microphone 1 centimetre from where the biscuits were going to fracture. The acoustic data would then be captured throughout the breaking of the biscuit and would be presented graphically, as a jagged line with some taller peaks. 

37. ISO STANDARDS FOR SENSORY ANALYSIS ISO 3591-1977 Sensory analysis - Apparatus - Wine-tasting glass ISO 3972-1991 Sensory analysis - Methodology - Method of investigating sensitivity of taste ISO 4120-1983 Sensory analysis - Methodology - Triangular test ISO 4121-1987 Sensory analysis - Methodology - Evaluation of food products by methods using scales ISO 5495-1983 Sensory analysis - Methodology - Paired comparison test ISO 6564-1985 Sensory analysis - Methodology - Flavour profile methods ISO 10399-1991 Sensory analysis - Methodology - Duo-trio test ISO 11036-1994 Sensory analysis - Methodology - Texture profile ISO 11037-1999 Sensory analysis - General guidance and test method for assessment of the colour of foods ISO 11056-1999 Sensory analysis - Methodology - Magnitude estimation method