Call number: LD2668 .T4 1932 M32

It has been reported recently that extracts of filbert nuts demonstrate considerable proteolytic activity on a non-fat milk solids substrate. The addition of these extracts to cheddar cheese, in an attempt to enhance the rate of ripening, has been suggested. In these experiments, the extracts of two varieties of filbert nuts, i.e. Du Chilly and Barcelona, were added to cheddar cheese samples at the milling stage of manufacture. The rate of proteolysis, in the cheese samples, was determined quantitatively by the increase in soluble protein content over a three month period. At the termination of these experiments a taste evaluation was performed on all cheese samples. A statistical analysis on the results of the soluble protein analyses showed that the proteolysis in the treated cheese samples was significantly greater than the proteolytic breakdown in the control samples. A defatted extract of Barcelona variety of filbert nuts was the most effective treatment of enhancing the proteolysis in the cheese samples. The results of the taste tests showed that no significant improvement in the flavor of the cheese resulted from the addition of filbert extracts. / Graduation date: 1951

The effect of reducing sodium chloride in Cheddar cheese was studied. Milled curd from a split-lot was salted at selected NaCl concentrations and analyzed through aging by sensory and rheological tests. Estimation of differences in compositional analysis, lactic acid populations, degree of proteolysis, water activity, and pH were also determined. Consumer panel analysis of the cheese on a hedonic scale over seven months aging showed no significant differences in overall desirability between cheese containing 1.75 - 0.88% NaCl. At 0.75% NaCl in cheese, ratings were lower, but flavor and texture scores were considered acceptable. Addition of even a small amount of salt (0.38 - 0.44%) significantly improved sensory characteristics relative to an unsalted cheese. Regression analysis of trained panel evaluations to predict consumer response showed that "firmness" and "adhesiveness" were the most important attributes for favorable consumer ratings of texture. Trained panel determination of "Cheddar intensity" and "unpleasant aftertaste" were found to be the two most important factors for determining consumer panel flavor scores. These four attributes, as rated by the trained panel, correlated with salt concentration in cheese. Instron evaluation of reduced sodium Cheddar cheese showed a decrease in firmness, chewiness, and gumminess and an increase in determinations showed an increase in proteolysis and water activity and a decrease in pH of the finished cheese. Lactic acid bacterial populations were significantly higher in the cheese containing reduced NaCl concentrations with the highest population differences observed through one month of age. / Graduation date: 1984

The tendency for certain single- and mixed-strain lactic starter cultures to develop a fruity and/or fermented off-flavor in ripening Cheddar cheese was traced to certain strains of Streptococcus lactis in the starter. A very intense fruity and/or fermented flavor developed in experimental cheeses when one particular S. lactis strain was used as a component microorganism in the starter culture. Contrary to previous implications, strains of Streptococcus diacetilactis did not produce a fruity and/or fermented flavor in experimental cheeses made with starter cultures containing these organisms. Mixed-strain cultures of Streptococcus cremoris were used to produce control cheeses, which did not develop the fruity and/or fermented flavor defect. The starter culture and treatment of the cheese milk were the only variables used in the cheesemaking trials. Results obtained indicate that the specific species and/or strain of lactic streptococci contained in the starter culture affect the flavor score and type of flavor in the resultant cheese, independent of the temperature of the heat treatment or hydrogen peroxide-catalase treatment of cheese milk. There were no apparent correlations between "normal" and "defective" starter cultures for the level of proteolytic activity or production of acetaldehyde or diacetyl to the development of fruity and/or fermented off-flavor in cheeses. Existing procedures for the quantification of acetaldehyde, diacetyl and volatile esters were adapted and modified for determining the concentration of these compounds in cheese curd and ripened cheese. The method of slurry preparation, type of diluent and the pH were factors found to affect the recovery rate for acetaldehyde from cheese. The relative flavor preference for typical experimental cheeses was determined with the aid of a flavor panel. A sample of fermented- unclean cheese received the lowest hedonic flavor score, whereas the flavor score of a slight fruity and/or fermented sample compared favorably with that of the reference sample. / Graduation date: 1967

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Digitized by Kansas Correctional Industries

Strains of Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris with potential use in the food industry which had been previously isolated from nature using 16S rRNA probes were characterized for unique identifying traits and for attributes important for potential use in cheese manufacture. Strains of Lc. cremoris which showed desirable characteristics for cheesemaking were selected for Cheddar cheese making trials where they were used first as single strains then in combination. Biochemical testing included lithium chloride sensitivity using Alsan medium. Strains of Lc. cremoris showed greater sensitivity to lithium chloride than Lc. lactis. strains. however sensitivity was generally indicated by reduced colony size rather than absence of growth as predicted for Lc. cremoris. strains. Strains of both Lc. lactis and Lc. cremoris produced blue colonies on Alsan medium indicating citrate utilization. Citrate utilization could not be confirmed by other traditional methods. Carbohydrate utilization using API 50 test kits revealed no pattern which could definitively differentiate strains of Lc. lactis from Lc. cremoris. It was found that all strains fermented galactose, D-glucose. D-fructose. D-mannose. N-acetyl glucosamine and lactose. Regardless of genotype. strains which were shown to be phenotypically Lc. lactis generally fermented additional carbohydrates. whereas Lc. cremoris phenotype strains did not. Only one probe-isolated strain of Lc. lactis fermented D-xylose. Tests to identify potential Cheddar cheese starter strains were performed on all environmental isolates. All strains which were phenotypically identified as Lc. lactis were rejected as potential starters because they railed to coagulate milk after 15 to 18 hours or they developed undesirable flavors in milk. Nine of twenty strains that were both phenotypically and genotypically Lc. cremoris were identified as having good potential for use as Cheddar cheese starter cultures. Four strains (MS-9, MS-23, MS-24, MS-51) were selected for Cheddar cheesemaking trials. Twenty small vats of cheese were made using each of the four strains individually then in every possible combination. In each case the experimental strains showed good functional characteristics with no sensitivity to bacteriophage present in the manufacturing environment. Five commercial scale cheese trials (53,500 lbs of milk) with automated equipment were also undertaken. Each strain was used first individually then in combination. Starter activity in the automated system using the experimental strains was sufficient to allow a 14% reduction in starter usage and still obtain good acid development. Flavor development of the cheese was monitored for one year of aging. Single strains varied in flavor development, with bitter notes being the most prominent off flavor detected. For some strains the bitter flavor was transitory and varied in intensity. Cheese produced from the four combined strains never developed the bitter defect, indicating that proteolysis of the combined strains was sufficient to degrade the bitter peptides as they were produced. / Graduation date: 1999