Browsing by Author "DELVALLE, JM"

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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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    ETHANOL EXTRACTION OF RED-PEPPER - 3 KINETIC-STUDIES AND MICROSTRUCTURE
    (1987) AGUILERA, JM; ESCOBAR, GA; DELVALLE, JM; MARTIN, RS
    A three-parameter kinetic equation was developed for ethanol extraction of oleoresin from dry red peppers under different solute to solvent ratios, particle sizes and condition of structural damage. The model distinguished two main mechanisms of extraction: a fast, washing step and a diffusion-controlled process. Flaking and, to a lesser extent, blanching induced significant cellular damage resulting in more oleoresin being washed, a faster extraction rate and a higher final concentration in the solvent, compared to untreated material. The activation energy for extraction derived from the study was 6.1 kcal/mol, typical of diffusion-controlled processes. Light micrographs related microstructure to variations in extraction parameters.
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    MODELING OF BEAN HARDENING KINETICS DURING STORAGE
    (FOOD NUTRITION PRESS INC, 1993) DELVALLE, JM; AGUILERA, JM; HOHLBERG, AI; RICHARDSON, JC; STANLEY, DW
    Two kinetic models ('empirical' and 'logistic') were adapted to predict storage-induced hardening of black and white beans, A database consisting of 451 observations gathered using black bean samples at 38 different storage conditions and 155 experimental data points corresponding to white beans stored at 12 different conditions was utilized to validate the proposed equations. Compared to other published models, the ones developed in this study were not limited to mild storage conditions or short storage times. Hardening showed an initial lag period, followed by a period of fast hardening, and ending in a period of declining hardening rate as hardness plateaued to equilibrium values at adverse storage conditions. Hardening rates increased with either the water activity of beans or storage temperature, whereas equilibrium values were only determined by sample water activity, for black beans, or temperature, for white beans. Both models used the activation energy and equilibrium constant of the hardening reaction as parameters, which could be assumed to be independent of the sample storage conditions and still allow an adequate fit between experimental and predicted values.
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    PHYSICOCHEMICAL CHARACTERIZATION OF RAW FISH AND STICKWATER FROM FISH-MEAL PRODUCTION
    (1991) DELVALLE, JM; AGUILERA, JM
    Chemical and microbiological properties of raw fish (RF) and chemical properties of stickwater (SW) samples were studied as a function of the staleness level of the fish. As time elapsed from fish capture increased, the microbial count in RF, volatile nitrogen content in RF and SW, and dissolved solids and dissolved protein in SW, increased. The apparent viscosity of SW increased as the temperature decreased and as the dry solids or suspended matter content increased. The size distribution of suspended particles in SW depended on the sample preparation technique, method used to measure particle size and whether the size distribution was expressed in terms of the weight or population of fractions. The average size (by weight) of suspended solids in SW was 2.5-mu-m as estimated by electronic counting. The solubility of protein in SW decreased when acid or alkali were added or thermal treatment (1 h at 90-degrees-C) applied. A minimal solubility point occurred near pH 5. The molecular weight of most dissolved proteins in SF was 3 kD. SF also contained a small proportion of 67 kD proteins. The significance of this basic characterisation study for the selection of improved processes for stickwater recovery is discussed.
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    RECOVERY OF LIQUID BY-PRODUCTS FROM FISH-MEAL FACTORIES - A REVIEW
    (ELSEVIER SCI LTD, 1990) DELVALLE, JM; AGUILERA, JM