EXPERTS IN FOOD TEXTURE MEASUREMENTS.

Transcription

1 EXPERTS IN FOOD TEXTURE MEASUREMENTS

2 OBJECTIVES Introduce the science of food texture analysis Discuss the relationship between sensory and instrumental measurements Highlight where and how we measure food texture Introduce the principles and equipment available for food texture measurement

3 HISTORICAL BACKGROUND Established brand in the international food texture market Founded in 1966 by creator of Kramer shear press Focus on cost-effective solutions Expertise in field and factory based measurements Specific range of instruments for R & D Specialists in food applications

4 28/02/2011 Texture Measurement

5 A Multi-Dimensional Attribute: + We see it + We feel it + We taste it + We hear it Relate human experience to perceived physical attributes Measurements are subjective and complex THE SENSORY DEFINITION OF TEXTURE IS... All the mechanical, geometrical and surface attributes of a product perceptible by means of mechanical, tactile and, where appropriate, visual and auditory receptors.

6 FOOD TEXTURE MEASUREMENT The science of Objectively measuring the Subjective SENSORY: INSTRUMENTAL: Human senses are used as measuring instruments Machines replicate human treatment

7 WHY MEASURE FOOD TEXTURE We measure things in order to quantify, control or optimize a variable or variables INPUT VARIABLE OUTPUT EFFECT FORMULATION PROCESS COND. NATURAL VARIATION FOODS PHYSICAL STRUCTURE CONSUMER SELECTION PROCESS HANDLING HARVEST/SECONDARY ENGINEERING PROCESS DESIGN OBJECTIVE TEXTURAL MARKERS SENSORY PREDICTION SUBJECTIVE TEXTURAL MARKERS

8 WHERE TO MEASURE TEXTURE Product texture is a critical characteristic during manufacture and development OBJECTIVE Texture is measured as a Critical Quality Point (CQP) SUBJECTIVE Textural properties identified and correlated to instrument PROCESS DEVELOPMENT QUALITY CONTROL RESEARCH & DEVELOPMENT NEW PRODUCT DEVELOPMENT

9 Food texture is a perception of human experience Representative of handling by consumer or process Evaluation encompasses more than behaviour in mouth Unrepresentative measures are of little value e.g cannot snap a yogurt or extrude a biscuit FOOD TEXTURE TESTING Evaluation is product specific: HARD/ BRITTLE SOFT/ LIQUID Cookies Carrots Apples Chocolate Wine Gums Tomatoes Marshmallows Bread Whips Puddings Sauces SNAPPING PUNCTURE DEFORMATION/ COMPRESSION VISCOSITY/ CONSISTENCY

10 WHAT IS TEXTURE ANALYSIS Instrumentation is used to replicate human evaluation and measure a samples mechanical characteristics Controlled mechanical stress input into sample Stress manipulated through fixtures and probes Calibrated to fundamental units (Mass, length & time) Deformation response to imposed stress is recorded and analysed

11 HOW A TEXTUTRE ANALYSER WORKS UNIAXIAL MOVEMENT Compression or extension of sample achieved through either UP or DOWN travel LOAD CELL Travelling cross-head fitted with load cell to record sample response to controlled stress and strain FORCE MANIPULATION Kinetic forces created within sample are manipulated to represent handling by consumer or process e.g. Shear, Extrusion, Snapping, Squeezing, Friction etc

12 TEST GRAPHICS Load, Displacement and Time information is collected DOWN STROKE UP STROKE Energy input during compression cycle Energy returned during decompression cycle TRIGGER Texture analyser detects sample surface ILS SQUASH Stress input on sample ILS RECOVER Stress removed and response recorded ILS

13 READING THE TRACE The force-deformation curve is interpreted for key events such as breaks, slopes, positive and negative areas, ratios, forces and deformations. Each event correlates to sensorial profile or treatment imposed ILS ELASTIC Return to original shape when stress removed memory Foods are visco-elastic Possess viscous and elastic properties Deformation dependant (elastic at small deformations) Force dependant (may rupture when penetrated) Compare ratio s of areas to assess sample properties ILS VISCOUS Retain shape at point stress was removed

14 Test Principles

15 PUNCTURE AND PENTRATION Small flat or round end cylinders are used to punch into sample Probes have surface area smaller than test sample Ideal for single point measurement Evaluate samples with dual structure (e.g. crispy shells) Results in rupture or breaking of sample No allowance for particulates Hardness Crispness Fracture Gel strength

16 SHEAR Blades cut through crosssection of sample creating combination of complex forces Use wires, blades and knife edges to manipulate forces Accommodates variation within sample Use parallel blades to obtain more accurate picture of product texture Shearing through base plate will introduce complex forces Hardness Shear force Bite strength Consistency

17 SNAPPING Brittle solids are supported either end and break or flexure force measured The sample must be selfsupporting Break characteristics are established Representative of treatment by consumer Distance between support jaws directly affects break properties Ideally use maximum test speed to cause massive fracture Brittleness Break point Crispness Fracture

18 COMPRESSION Large flat cylinders and platens are used to compress samples Probes have surface area greater than test sample Used extensively in Texture Profile Analysis Can use large diameter ball probes No rupture until sample fails or yields Surface interface can be variable Hardness TPA Modulus Rigidity

19 TEXTURE PROFILE ANALYSIS Technique developed within the food industry to bridge the gap between sensory and instrumental texture measures Primary Hardness Cohesiveness Springiness Adhesiveness Secondary Fracturability Gumminess Chewiness First Compression Cycle Second Compression Cycle I L S Down ward travel to detect sample surface I L S Continue down ward travel to target deformation I L S Upward travel to original starting height I L S Repeat downwar d travel to same target position as cycle 1 I L S Upward travel to original starting point

20 TEXTURE PROFILE ANALYSIS Originates from Szczesniak s 1963 classification of the textural characteristics of foods. TPA is used to form correlations between 7 sensorial parameters when following strictly defined test protocol. F Down FRACTURABILITY APPARENT MODULUS A1 A1 Up HARDNESS Adhesiveness = Negative area from first compression cycle Start of second compression cycle Adhesive Force Down A2 A2 D1 D2 Springiness Up t Uses Compression forces only Viscous element does not recover Characteristics established on 14 foods only Often misinterpreted due to incorrect use of terminology

21 EXTRUSION Forces are applied to viscous liquids and semi-solids causing them to flow Must standardise sample container and probe Distance between probe diameter and container is called annulus Particulates can be come trapped between annulus acting as piston Use shallow gradient cones to remove air at sample interface If decanting sample allow structure to recover (air pockets) Flow point Stiffness Consistency Adhesion

22 BULK ANALYSIS Used for particulate products where analysis of individual components is not practical Kramer shear cell uses parallel blades to shear, compress and extrude sample Ottawa cell uses bulk compression to create either forward or backward extrusion forces Accommodates variable texture Must standardise volume and weight of sample High forces are generated Hardness Consistency Compaction

23 TENSION Samples are stretched creating extension forces and break at weakest point Not always applicable to food analysis e.g mainly compression Must hold sample in a manner which limits creation of weak points or knocking Some time glues sample to probe and test bed Samples must break clearly and cleanly Modulus/Strength Break properties

24 Packaging Principles

25 PEEL TESTING Maintain seal integrity & easy open ability Maintain safety critical modified or controlled atmospheres Avoid moisture migration in or out Protect product and prevent tampering Validate seal strength & tear properties

26 TEAR TESTING Easy open ability e.g. children and elderly people Validate packaging design Maintain product integrity during storage and transport

27 TOP-LOAD TESTING Cost saving in packaging design Reduce environmental costs less material Maintain product integrity during storage and transport Meet environmental standards

28 Closing Considerations

29 CONTROL VARIABLES The empirical nature of texture measurements combined with the multi-functionality of Universal Testing Machines means that the Food Technologist must understand the effect of key test variables. INSTRUMENTAL VARIATION Compression v Tension Extent of deformation Cross-head speed Size of compressing unit versus sample SAMPLE VARIATION Isotropic v Anisotropic Uniformity of sample Sample temperature Sample size and shape Sample lubrication

30 CONSIDERATIONS TO ANALYSIS STANDARDIZATION is essential in all test investigations Be critical Record test conditions Establish application Be practical Standardize samples Identify characteristics TEST SELECTION: NATURE OF PRODUCT: Directly influences instrument or test procedure PURPOSE OF TEST: Application or test environment ACCURACY REQUIRED: Accuracy vs. Reproducibility, natural variability within sample. Use statistics to accommodate natural variation REPRESENTATIVE: How is the sample treated in the factory or by the consumer and what are the key characteristics of importance. Does the test method replicate these conditions?

31 Please contact: Drew Lambert or Michele Sink Corporation