|Abstract or Summary
- A sensory method was developed to determine cheese texture by hand
evaluation. Cheese sensory evaluation was conducted by panelists (n=8) on four
commercial samples in duplicates. Standards, descriptors, methods of each
attribute evaluation, sample size, and ballot were developed based on panelists'
consensus. Fifteen total attributes, divided into five groups, were tested.
Crumbliness was defined as the ease of the sample to break apart during
manipulation using the thumb and two fingers for five times. Using Principal
Component Analysis (PCA), four components were extracted with the first two
explaining most of the variability (60.4%). PCA showed that moistness,
crumbliness, color, cohesiveness, irregularity, and oiliness were the main attributes
describing the samples. Irregularity and cohesiveness had 83.6% and -88.1%
correlations with crumbliness, respectively. Panelists' performances were not
significantly different (p≤0.05) and each subject used the method consistently for
crumbliness. This method was then applied to evaluate and compare the sensory
attributes of Queso Fresco.
Three types of Queso Fresco cheese were made: raw cheese (RC), High
Hydrostatic Pressure (HHP) treated raw cheese (HP), and cheese made from HHP
treated milk (HPM). Sensory attributes, compositions, microstructures and protein
profile were compared. Sensory attributes were examined by ten trained panelists
using hand evaluation method developed and instrumental methods (Texture Profile Analysis (TPA) and 80% compression test). Protein, fat, and moisture
contents were valuated by Micro Kjeldahl, Babcock, and Forced air draft oven
respectively. Microstructure was examined by light microscopy using Acid
Fuschin protein staining, while native and SDS PAGE were carried out to show
the protein profile. One and eight days storage times were studied. HHP treatment
of cheese or cheese milk (400 MPa, 20 min, ambient temperature) were shown to
reduce microbial loads. HP and RC had similar microstructure, compositional (p-value≤0.05), and sensory attributes, except color (p-value≤0.05). HP and RC had
distinct protein network, while HPM had a very diffuse network. HPM was
different from both RC and HP. HPM was the least firm, least crumbly, most
sticky and oily. HPM day one was firmer, less oily, less springy than day eight.
HPM had higher moisture and yield, due to incorporation of denatured whey
proteins, than RC and HP cheese.
The hand evaluation method developed was proven to be able to
differentiate cheese textural attributes. Overall, HHP treatment of Queso Fresco
produced cheese with similar characteristics as traditionally made Queso Fresco,
while HHP treatment of cheese milk created cheese with weak texture
characteristics. HHP treatment of cheese might be an alternative way to produce
Queso Fresco with acceptable attributes and reduced microbial load.