Browsing by Author "KAREL, M"

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    CAKING PHENOMENA IN AMORPHOUS FOOD POWDERS
    (ELSEVIER SCI LTD, 1995) AGUILERA, JM; DELVALLE, JM; KAREL, M
    Caking of free-flowing powders during storage is a deleterious phenomenon that is ubiquitous in the feed, fertilizer and pharmaceutical industries, and of economical importance for low-moisture foods. Among other subjects related to caking of amorphous powders, the following aspects are reviewed in this article: (1) physical and morphological changes, and quantitative procedures to assess caking; (2) proposed mechanisms of caking phenomena; (3) examples of caking in food materials; (4) the relationships between storage-induced caking and other phenomena and the glass transition of amorphous powders; (5) methods for estimating the evolution of caking with lime from the physical properties of powder samples and environmental conditions; and (6) measures to minimize the occurrence of caking phenomena.
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    EFFECT OF WATER-CONTENT ON THE GLASS-TRANSITION AND CAKING OF FISH-PROTEIN HYDROLYZATES
    (AMER CHEMICAL SOC, 1993) AGUILIERA, JM; LEVI, G; KAREL, M
    The glass transition temperature (T(g)) and structure collapse (volumetric shrinkage) of a freeze-dried fish protein hydrolyzate (HFP) were studied. An increase in the water activity from 0 to 0.64 reduced the T(g) of HFP from 79.1 to -42.8-degrees-C. The Gordon-Taylor equation was a good predictor for the plasticizing effect of water on T(g). At room temperature (19-degrees-C), collapse was initiated at a(W)= 0.44 corresponding to a T - T(g) value of 35.8-degrees-C, and browning was evident above a(W) = 0.55. Above these critical values several structural changes occurred: shrinkage, collapse, browning, and setting into a sticky, high-viscosity brown liquid. The viscosity of the matrix at the onset of collapse was 10(5)-10(7) Pa.s, as estimated using the Williams-Landel-Ferry equation.