Two classes of parameters are important in product quality control and process design: thermo-physical and rheological properties. Reliable estimates of thermal properties (thermal conductivity, diffusivity, density, specific heat, and glass transition temperature) are needed to model the rate of heat transfer during food processing. Measurements of rheological parameters like viscosity and elasticity have been recognized as important tools to provide fundamental insights on structural organization of the food. Small amplitude oscillatory testing is useful in evaluation of gel characteristics and texture development in different food products. Proper design of industrial plants, modeling and automation in food process industry require data on these properties for better quality control and improve the shelf life. Thermal processing has been a traditionally accepted method for developing safe and shelf-stable products. However, a disadvantage of thermal treatment is the reduced sensory and nutritional qualities. High pressure (HP) treatment, a novel non-thermal preservation technique, is used for producing high quality products. HP processing can also be used to achieve products with better textural properties and improved nutrition when supplemented with proteins. / This research was carried out in two parts. In first part, experiments with mango pulp were carried out at four temperatures (20, 40, 60 and 80°C) and total soluble solids concentrations (15, 20, 30 and 40°Brix) and their rheological and thermo-physical properties were evaluated and modeled. Thermal properties of mango puree were primarily dependent on the moisture content of the sample, and increased with temperature and decreased with concentration. Density showed a reverse trend. Glass transition temperatures increased with an increase in concentration indicating better stability. Separate models were developed for each thermal property as a function of temperature and concentration (R2 >0.90). Mango puree exhibited pseudoplaticity during steady shear measurements, and the power law model well described their flow behavior. Consistency coefficient increased with concentration and decreased with temperature. The flow behavior index decreased with concentration and generally increased with temperature beyond 40°C. Dynamic oscillation shear measurements revealed that mango puree behaved like a weak gel and demonstrated visco-elastic properties. / In the second part, experiments were divided in to two parts. In first part, the original soluble solids in mango puree (28°Brix) was lowered to 20, 23 and 26°Brix and each was supplemented with 2, 5 and 8% of whey protein. Effect of HP treatment at 425, 500, and 575 MPa with 0, 3 and 6 min holding times on rheological properties were evaluated. Pressure treatment resulted in a positive effect on elastic (G') and viscous modulii (G") as well as complex viscosity (eta*). Values of G' were higher than G" demonstrating the product to behave more and more like a gel. The changes in rheological parameters at 500 MPa were modeled based on soluble solids and protein content. In the second part of the experiments, the protein (P) and soluble solids concentrations (S) were simultaneously varied maintaining a total solids content at 28% (same as in the original mango puree) and their combined influence (P/S: 2/26, 3/25, 5/23, 7/21 and 8/20) on the rheology of the product after selected HP treatments (425-575 MPa, 0-6 min) were evaluated. The effects of holding time and pressure level were similar to those observed previously in first part of this study. However, the positive effect of added protein was over dominated by negative effect of the simultaneous decrease in the soluble solids concentration, resulting in an overall decreasing effect as protein content increased (with a same magnitude decrease in soluble solids content). Developed models well predicted the combined influence of protein and soluble solids concentration on rheological parameters (R2>0.85). / Sensory evaluation of mango puree supplemented with protein (2, 5 and 8%) was performed before and after high pressure treatment (500MPa/3min) using a nine point hedonic scale. The quality parameters chosen were color, sweetness, mouthfeel, flavor and acceptability. Sensory evaluation results indicated that protein enrichment up to 5% level did not adversely affect the sensory qualities.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.98717 |
| Date | January 2005 |
| Creators | Gundurao, Anuradha. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Food Science and Agricultural Chemistry.) |
| Rights | © Anuradha Gundurao, 2005 |
| Relation | alephsysno: 002479596, proquestno: AAIMR24686, Theses scanned by UMI/ProQuest. |
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