Off-campus South Dakota State University users: To download campus access theses, please use the following link to log into our proxy server with your South Dakota State University ID and password.

Non-South Dakota State University users: Please talk to your librarian about requesting this thesis through interlibrary loan.

Document Type

Dissertation - University Access Only

Award Date

2003

Degree Name

Doctor of Philosophy (PhD)

Department / School

Dairy Science

First Advisor

K. Muthukumarappan

Abstract

Role of calcium on functional, rheological and structural characteristics of Mozzarella cheese was studied. Part skim and fat free Mozzarella cheeses were manufactured respectively from 1.8% fat and 0.05% fat milks by the direct acidification method. Calcium chloride was added into milk to study the effects of colloidal and soluble calcium. Milk was preacidified to four levels (no change in control, pH 6.2 in T1, pH 5.9 in T2 and pH 5.6 in T3). The cheeses were stored at 4°C until evaluation of various characteristics on d 1, 7, 15 and 30. Part skim Mozzarella cheeses were evaluated for chemical (moisture, fat, protein, salt, ash, calcium and soluble nitrogen), functional (softening time-temperature, melting time-temperature, melt area, flow rate, extent of flow and stretchability), rheological (viscoelasticity), and structural characteristics. Fat free cheeses were evaluated for chemical, functional ( except stretchability), and color characteristics. Regression models correlating calcium concentrations and various properties of cheeses were developed. The results revealed that soluble calcium did not affect the functional properties to a greater extent. Lowering of micellar calcium increased the melt area, flow rate and extent of flow but reduced the softening and melting time and softening temperature of part skim Mozzarella cheese. Lowering the amount of calcium bound to casein micelles

played an important role in deciding various properties of cheeses. Reducing 25, 35, and 45% levels of calcium increased the melt area of part skim Mozzarella cheese by 1.4, 2.1, and 2.6 times, respectively, on d I of manufacture. Low calcium cheeses (both, part skim and fat free) required less time to soften and melt, flowed faster and had greater extent of flow than control. Reduction of35 % of the calcium in fat free cheese increased the flow by 2.5 times and these cheeses required 19% less time to melt. Opacity decreased when calcium was lowered in fat free cheeses. Higher proteolysis at a faster rate was also observed in both (part skim as well as fat free) cheeses. Refrigerated storage also increased flow rate, extent of flow, and soluble nitrogen and lowered softening and melting times in all the cheeses. Storage also resulted in increase in melt area of part skim Mozzarella cheese. Reduced calcium part skim Mozzarella cheeses had 5 to 10 times higher elongation and required 33 to 45% less force to stretch as compared to control on d 1. Storage of 30 days resulted into 50% reduction in force required to stretch the cheese, however, no effect of storage on elongation of the cheeses was observed. Low calcium cheeses (0.35% in T3 vs. 0.65% in control) had lower values of elastic (0.83 MPa vs. 1.89 MPa) and viscous moduli (0.57 MPa vs. 1.43 MPa). After 30 days of storage, the elastic modulus (G') of the control and T3 cheese declined from 1.89MPa to 1.69 MPa and from 0.83 MPa to 0.55 MPa, respectively. Similar reduction in viscous modulus of control and lowest calcium cheeses (T3) was also noticed, i.e. the values of viscous modulus (G") declined from 1.43 to 1.25 MPa in control and from 0.57 to 0.27 MPa in T3. Reduced calcium cheeses had more hydrated protein matrix with greater number of fat particles (control = 125, T,=193, T2= 184 and T3= 215 with SEM and control= 86, T1=87, T2= 125 and T3= 140 with CLSM). Further, the area and perimeter of these fat particles were also greater in reduced calcium cheeses. Area, perimeter and size of fat particles increased and their roundness decreased upon storage of 30 days. Regression analysis revealed that 57, 52, 66, 74, 67 and 53% variation, respectively, in melt area, softening temperature, softening time, melting time, flow rate and extent of flow could be explained as a function of calcium concentration of part skim Mozzarella cheese. Calcium concentration also explained 50, 61 and 43% variation, respectively, in melting time, flow rate and extent of flow of fat free Mozzarella cheese. Calcium concentration was also one of the major predictor variables in regression models. The above characteristics of Mozzarella cheese were more affected by calcium reduction as compared to storage. Overall, it was concluded that Mozzarella cheeses with reduced calcium concentration had increased meltability and stretchability on d 1. Improved softening, melting, stretching and flow properties of low calcium Mozzarella cheeses is a clear advantage to cheese manufacturers and end users as they may not have to wait 15 to 20 days for proteolysis of cheese to obtain desired melt properties. Hydrated protein network and better emulsified fat in low calcium cheeses were attributed for improved properties of Mozzarella cheeses.

Library of Congress Subject Headings

Mozzarella cheese -- Composition
Calcium

Format

application/pdf

Publisher

South Dakota State University

Download

Share

COinS