The heat-induced gelation properties of ultrafiltered (UF) whole milk concentrate were studied under different physical and chemical conditions. total solids concentration, homogenization pressures, heating temperatures, and heating times were found to have a positive correlation with gel strength. The addition of calcium chloride, sodium chloride, or trisodium citrate produced gels of higher strengths and textural properties than the gels obtained with non-salt-treated concentrate. Calcium chloride produced the strongest gels with a cheese-like texture and poor spreadability. Sodium chloride produced gels of intermediate strength with a firm, elastic texture and poor spreadability. Trisodium citrate produced the softest gels with a smooth, creamy texture and good spreadability.
A shelf stable 40% total solids UF concentrate was manufactured using ultra-high temperature (UHT) processing by direct steam injection. The pourable concentrate had a shelf life of 75 to 90 days at 23°C and did not have the ability to produce heat-induced gels after a second heating. Addition of calcium chloride, sodium chloride, or trisodium citrate restored the heat-induced gelation of the retentate. However, the gels were weaker and presented different characteristics than did the gels from non-UHT-treated concentrate.
Transmission electron microscopy (TEM) studies revealed a relationship between gel firmness and gel ultrastructure of the heat-induced gels. The gels consisted of a network of casein micelles connected with strands of a less dense protein material. The tighter the network the stronger the gel strength. High heating temperatures and calcium chloride addition caused fusion of the casein micelles int he network. Sensory evaluation of two prototype gelled desserts by a general consumer population showed a good potential for the use of the heat-induced gelation property of UF-concentrated whole milk in the development of new gelled dessert applications.
| Identifer | oai:union.ndltd.org:UTAHS/oai:digitalcommons.usu.edu:etd-6525 |
| Date | 01 May 1999 |
| Creators | Solorio, Hector Alejandro |
| Publisher | DigitalCommons@USU |
| Source Sets | Utah State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | All Graduate Theses and Dissertations |
| Rights | Copyright for this work is held by the author. Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user. For more information contact digitalcommons@usu.edu. |
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