Characterization of chemical and physical changes in soft cheese during ripening
Schlesser, Joseph Edward
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Permalink
https://hdl.handle.net/2142/23269
Description
Title
Characterization of chemical and physical changes in soft cheese during ripening
Author(s)
Schlesser, Joseph Edward
Issue Date
1990
Doctoral Committee Chair(s)
Schmidt, Shelly J.
Department of Study
Food Science and Human Nutrition
Discipline
Food Science and Human Nutrition
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Chemistry, Biochemistry
Language
eng
Abstract
In Camembert cheese, as the paracasein was proteolyzed and the pH value increased, there was an increase in water sorption, while a decrease of water activity and water mobility. The texture of the cheese changed from curd-like to a semi-liquid.
A model soft cheese system was developed to investigate the various stages and factors that contribute to soft cheese ripening. The model system was based on the enzymatic hydrolysis of paracasein. The model system was comprised of five components, paracasein, water, lactic acid, salt and Neutrase. In preliminary pilot studies, Neutrase level and temperature were investigated and subsequently fixed at levels of 0.1% and 30$\sp\circ$C, respectively. A Central Composite Design was used to determine the magnitude and the direction that the experimental treatment conditions of water/non fat dry matter (W/NFDM) ratio, pH sodium chloride/water (NaCl/W) ratio and days of ripening had on the desired responses. The responses measured included: total solids, pH, nitrogen solubility, water sorption, water activity (a$\sb{\rm w}$), water mobility and rheology.
As the NaCl/W ratio or W/NFDM ratio increased, water sorption increased. As the cheese ripened, the increase in soluble nitrogen levels increased the water sorption. The pH for the minimum amount of water held shifted downward as the cheese aged.
As NaCl/W ratio or days of ripening increased, a$\sb{\rm w}$ decreased. As the model cheese ripened, proteolysis of paracasein may have contributed to the decrease in the a$\sb{\rm w}$. With an increase in the W/NFDM ratio or pH, a$\sb{\rm w}$ increased.
Spin-spin (R$\sb2$) relaxation rate was a better indicator of water mobility than Spin-lattice (R$\sb1$). The R$\sb2$ relaxation rate decreased with an increase in W/NFDM ratio and days of ripening, indicating an increase in water mobility as the cheese ripened. As pH increased, water mobility decreased.
The increase of W/NFDM ratio decreased the firmness of the protein matrix. At the higher pH values, the texture became more firm. The proteolysis of paracasein softened the cheese texture. At low pH values, an increase of texture was noted due to syneresis of the sample. The texture of the cheese was firmer at the higher NaCl/W ratios.
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