Brookfield LFRA Texture Analyzer - Manual (Page 19)

Brookfield Engineering Labs., Inc. Page 19 Manual No. M/05-370-A1205
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.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
influence 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 inter-
actions. Fat becomes trapped within this protein network where it imparts
a smooth creamy mouthfeel and spoonable glossy consistency characteris-
tic 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 applying a
force to a food until it flows through the outlets between the probe perim-
eter and the holding vessel. A wide range of complex forces are gener-
ated. 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)