Sensory, compositional and texture profile analysis of high-pressure treated fresh renneted cheese - Queso Fresco style Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/6108vf214

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  • 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.
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