Brookfield LFRA Texture Analyzer - Manual (Page 19)

Brookfield Engineering Labs., Inc. Page 9 Manual No. M/05-370-B0507
V. APPLICATIONS
This applications section should be used as a guide to the development of techniques specific to
your own application and requirement. These notes are empirical in nature. Deviation from the
described test configurations (parameter settings, sample size, shape, formulation, etc.) will result
in deviations from the observations discussed in each application.
V. 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 influ-
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 flows 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 sufficient 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.