Effect of water content, temperature and storage on the glass transition, moisture sorption characteristics and stickiness of β-casein

L. J. Mauer, D. E. Smith, T. P. Labuza

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Moisture sorption isotherms at +4 °C and +22.5 °C were obtained for β-casein after isolation and after 9 months of storage at -29 °C and +22.5 °C. Glass transition state diagrams (Tg vs. moisture) were determined for β-casein after storage. The results showed that effects of storage temperature on moisture sorption isotherms were varied; however, at any aw differences in moisture content were small (<0.03g H2O/g solids at high aw). β-Casein stored at -29°C had lower mo and Tg values than that of β-casein stored at +22.5°C. The glass transition temperatures for β-casein were above room temperature, even at aw = 0.76. Onset of stickiness occurred above aw = 0.76.

Original languageEnglish (US)
Pages (from-to)233-248
Number of pages16
JournalInternational Journal of Food Properties
Volume3
Issue number2
DOIs
StatePublished - Jul 2000

Bibliographical note

Funding Information:
In the ongoing effort to improve and expand the supply of nutritional and functional food ingredients, the unique properties of casein and individual casein proteins are attractive for many applications. The majority of caseins exist in milk as micelles. Individual caseins are relatively small (20,000-24,000 Daltons), amphipathic, conjugated, randomly coiled, hydrophobic, open molecules that are insoluble around their isoelectric points (pH 4.5-4.9) and have an uneven distribution of polar and hydrophobic residues (Fox, 1989). Caseinates, water soluble derivatives of casein, are 1 Published as paper number 99-1-18-0017 of the contribution series of the Minnesota Agricultural Experiment Station based on research conducted under project 18-24 and supported by the National Dairy and Promotion Board and the USDA National Needs Fellowship Program.

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