Brookfield LFRA Texture Analyzer Manual de usuario descargar pdf (Pagina 19)

Brookeld Engineering Labs., Inc. Page 19 Manual No. M/05-370-B0507

V. APPLICATIONS

Thisapplicationssectionshouldbeusedasaguidetothedevelopmentoftechniquesspecicto

your own application and requirement. These notes are empirical in nature. Deviation from the

describedtestcongurations(parametersettings,samplesize,shape,formulation,etc.)willresult

in deviations from the observations discussed in each application.

V.1 Comparison of Low Fat and Virtually Fat Free Yogurt Consistencies

PRODUCT: Low-fat(1%)andvirtuallyfat-free(0.05%)naturalyogurt

OBJECTIVE: Comparison of textural properties in order to identify differences between

protein networks formed as an indication of product creaminess.

BACKGROUND: The textural properties of yogurts are critical in determining consumer

preferencewherevariationinfatcontentofformulationhasadirectinu-

ence on the sensory characteristics of the product. The elevated Solids

Not Fat (SNF) content of low-fat yogurts forms strong casein-casein bonds

uncharacteristicinafull-fatyogurt,wherehomogenizedfatglobulesare

partly covered with casein, facilitating protein-protein interactions. Fat

becomes trapped within this protein network where it imparts a smooth

creamy mouthfeel and spoonable glossy consistency characteristic of full-

fat yogurts.

Back Extrusion is an ideal method for the assessment of yogurts and other

semi-solid foods. This compression extrusion test consists of apply-

ingaforcetoafooduntilitowsthroughtheoutletsbetweentheprobe

perimeter and the holding vessel. A wide range of complex forces are

generated. However, the test gives good measures of peak force and area

of work to attain deformation of sample indicative of yogurt consistency.

These forces may also be recorded in reverse on the negative portion of

the force-time curve where they are indicative of sample viscosity.

LFRA SETTINGS: MODE: Measureforceincompression

  PLOT: Peak

  OPTION: Normal

  TRIGGER: Auto4gTrigger

  DISTANCE: 30mm

  SPEED: 1mm/s

PROBE REF: TA 4 38.1mm Ø Perspex Cylinder

METHOD: Samples were removed from refrigerated conditions of 5°C and centrally

positioned beneath the probe within the container in which they were

packed. Tests were conducted at ambient conditions of 18.2°C while the

average temperature of the low-fat yogurt was 8.7°C and the virtually fat-

freewas7.9°C.Itwasessentialthatasufcientdistance(circa20mm)

was left between the sample surface and the base of the probe. This was

left to ensure that a break between probe/sample interface was made and

that true adhesiveness characteristics could be calculated.

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Brookfield LFRA Texture Analyzer Manual de usuario Pagina 19