Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 96-98).

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

The effect of time that processed cheese was held ex- posed to heat alone or with agitation, the level of rework cheese, and the type and level of emulsifying salt were evaluated by determining finess of emulsion based on scanning electron microscopy measurements, meltability, and rheological measurements using a Universal Testing Machine. Process cheese held in the cooker at 82°C for up to 4o minutes became less meltable and more firm and the emulsion became finer while that held at 82°C outside of the cooker without agitation was only slightly affected. Loss of meltability and increased firmness associated with pro-longed cooking of process cheese is associated with the state of the fat emulsion and not with the effect of heat on the proteins per se. The level of rework cheese had a great influence on the cheese rheological properties as well as on the microstructure of process cheese. There was a poor emulsion when no emulsifying salt was used regardless of the percent rework cheese added. The emulsion became finer as the per- cent rework cheese was increased if emulsifying salt was also present except after 20% rework cheese addition where the emulsion became coarse again. Process cheese lost meltability during storage at 4°C after 53 days when 1.0 or 0.0% emulsifying salt is used or when rework cheese is present at 0.0 or 5%, but no effect was noticed in meltability values if the 2.5% emulsifying salt was used with no rework cheese.

Call number: LD2668 .T4 1979 D66 / Master of Science

Four batches of pasteurized process cheese were prepared from the same Cheddar cheese by cooking to 82C in the presence of sodium citrate, disodium phosphate, tetrasodium pyrophosphate or sodium aluminum phosphate. Each batch contained the same moisture (40.6%) and emulsifying salt concentration (2.5%). The process cheese was sampled for microstructural and rheological examination after 0, 5, 10, 20 and 40 min in the cooker at 82C. Even though each emulsifying salt affected the physical properties of the process cheese differently, the cheese generally became firmer, stiffer, more elastic and less meltable as cooking time increased from 0 to 40 min. These changes were accompanied by a decrease in the dimension of fat masses and an increase in the degree of emulsification as evidenced by scanning electron microscopy and transmission electron microscopy. The degree of emulsification (fineness of fat particles) seemed directly related to firmness, poor meltability, toughness, breaking force, apparent stiffness modulus, degree of elasticity , apparent ultimate stress and inversely related to hysteresis and apparent ultimate strain. Tetrasodium pyrophosphate produced the most rapid emulsification of the fat in the cheese and sodium aluminum phosphate the slowest. The effect of the other salts was intermediate. The softest most meltable cheese was poorly emulsified while the firmest most sliceable was well emulsified. Sodium citrate and tetrasodium pyrophosphate crystals remained undissolved in the cheese after 40 min in the cooker while sodium aluminum phosphate crystals were still undissolved after 10 min. There was a close statistical relationship among several of the rheological measurements viz. meltability and firmness, toughness and breaking force, and meltability and breaking force. Future rheological studies on process cheese should not require all of the above measurements. An increase in the fineness of the fat emulsion as determined by scanning electron microscopy was generally accompanied by increased firmness, poorer meltability and increased toughness.

Process cheese models were prepared by blending acid or rennet casein, milk fat, sodium chloride, 2.5% emulsifying salt and water and heating to 80 C. Acid casein cheese models were subjected to sodium hydroxide conditioning at 65 C in the cooker. Model process cheeses were acidified with lactic acid and treated by addition of undenatured and heat-denatured whey protein, four different emulsifying salts and sodium oxalate. Meltability and toughness of the model cheese increased to a maximum with increased sodium hydroxide conditioning of acid casein to pH 7.20. These same properties decreased with addition of undenatured and heat-denatured whey protein to both casein cheese models. Loss of emulsion occurred during the meltability test of rennet casein cheese models with 3.0 and 4.5% added whey protein. Emulsifying salts affected the models differently. Disodium phosphate and tetrasodium pyrophosphate in rennet casein models eliminated the melting property. These same salts in acid casein models produced excellent meltability. Trisodium citrate produced cheeses with good meltability in both acid and rennet casein cheese models. Acid casein cheese models prepared with sodium aluminum phosphate had fair meltability and were very tender (no rupture upon compression). Chelation of calcium by sodium oxalate in rennet casein cheese emulsified with disodium phosphate or tetrasodium pyrophosphate improved meltability with a corresponding increase in toughness. Scanning electron micrographs of model process cheeses indicated a direct relationship between extent of emulsification and poor meltability of rennet and pH conditioned acid casein model cheeses. Acid casein model cheeses prepared with different emulsifying salts did not exhibit this same relationship. Addition of whey protein concentrate to rennet case~n model cheese produced fibrous structures around the fat globules. No structural abnormalities were noted in the acid casein cheeses prepared with whey protein concentrate.