Rheological And Microstructural Study Of Commercial Cheddar And Mozzarella Cheeses By Using Farinograph
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Publisher: 2012 Dissertation note: A series of five experiments were conducted using Brabender Farinograph-E to study rheological properties of different brands of cheeses. This is a computerized machine having data recording capacity. It was found that Farinograph was a use full machine for preparing cheese and studying its rheology. The data recorded in the form of Farinogram showed that torque (resistance against flow of farinograph paddles) depended on fat content, temperature employed and time given to cheese formation. Also, the texture of cheese was influenced by these factors.
Sensory tests are not capable of measuring results more accurately as compared to Instrumental tests. To study cheese properties and effects of many manufacturing factors the fundamental methods will help researchers to develop cheeses with required and persistent textural and rheological properties. The instrument most frequently used all over the world for determining water absorption and mixing characteristics of wheat and rye flour in baking industry is Brabender Farinograph®. The present study was conducted by using Farinograph-E as a major tool to measure rheology of cheeses. In this study cheeses of different ages, and kinds e.g., Mozzarella, medium Cheddar, mild Cheddar, old Cheddar, extra old Cheddar, Ricotta and Parmesan were included. The parameters for operating Farinograph-E were developed and initial trials were conducted in various directions to finalize the procedure. Farinograph-E (Brabender GmbH, Duisburg, Germany) was used in this study by using its bowl W-50.
The tests were performed by cutting whole cheese bars into small pieces and shifted into air tight containers. The grated cheese was loaded with the help of spatula into Farinograph bowl. Water bath was adjusted at various temperatures like 20, 30, 40, 50 and 60°C. The temperature was continuously monitored through a temperature probe, inserted into the bowl contained cheese sample. The speed of paddles/ spindles was fixed in Newton meters (Nm) and was kept as constant for all the trials. The lid was closed after filling the bowl and clamped in order to avoid any disturbance. The test was allowed to run for specified time for 35 and 60 minutes. After completion of time durations the test was stopped automatically. The readings were recorded in the form of a graph (torque, time and temperature) of cheese dough resistance over mixing time.
Besides Farinographic studies, the results of Mozzarella and medium Cheddar Farinographic samples of (brand No name) were examined through Cryo-scanning electron microscopy and Fluorescence microscopy to study their microstructure at different stages and their relationship with quality of cheeses. The present study revealed that temperature, time and different fat percentages of different cheese brands shows significant effects on torque values. The results indicated that by increasing fat percentage the torques value decreases.
Cryo-scanning electron microscopy revealed finer details of cheeses. Shape, size and distribution of fat globules were observed through fluorescence microscopy. The changes in globule sizes and their interaction with casein matrix was also observed. Size of globule was estimated using image analysis technique. Aggregation of globules and their rupture was also observed. These changes in fat globules shape and sizes affected flowability, meltability and viscosity of cheeses and thus affected production of torques which were observed in graphs produced by Farinographs.
By studying microstructure it was obvious from micrographs that Stage 1 showed smaller fat globules in large numbers. In Stage 2 the globules became larger in size and lesser in number and like bubbles in shape, as shown in plates. At stage 3, there was no particular change from Stage 2 texture, except slight change in colour. The same changes are depicted in the shape of curve, that moved up and downwards and then upwards.
Full fats at stage 1, showed smaller fat globules those enlarged at stage 2. In stage 3, only enlarged globules were observed, and the resistance increased against paddles of farinograph and sharp increase was seen in the slope of graph. Globules retained their features at next stage and slope in graph became horizontal to x-axis after reaching maximum value.
These results suggest that size distribution of fat globules tended to impose influence on Farinographic results. Overall it is indicated that Farinograph is a suitable instrument for measuring rheology of cheeses.
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