Browsing by Author "AGUILERA, JM"

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    A KINETIC INTERPRETATION OF TEXTURAL CHANGES IN BLACK BEANS DURING PROLONGED STORAGE
    (1987) AGUILERA, JM; BALLIVIAN, A
    Control and roasted (80.degree.C), dry black beans (Phaseolus vulgaris) were stored for 9 months at 8, 10, 12, and/or 14% moisture content and 8.5.degree., 25.degree., and 40.degree.C. Similarly, beans heated in a solid-to-solid roaster to 51.degree., 61.degree., 72.3.degree., 80.degree., 85.5.degree., 89.5.degree., 101.degree., and 111.degree.C were maintained at 8% moisture and 25.degree.C. Final hardness increased with moisture content and temperature. Hardening at 8.5.degree. and 25.degree.C proceeded initially almost linearly reaching a constant value after 4 to 6 months while at 40.degree.C it was sigma-shaped. A pseudo-zero order kinetic model fitted for initial rates had an activation energy of 6-11.8 kcal/mol. The hardening rate at 25.degree.C paralleled the shape of the sorption isotherm.
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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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    CATALYZED FLASH PRETREATMENTS IMPROVE SACCHARIFICATION OF PINE (PINUS-RADIATA) SAWDUST
    (1989) HOHLBERG, AI; AGUILERA, JM; AGOSIN, E; SANMARTIN, R
    Physico-chemical pretreatments with steam explosion were used to improve digestion in vitro of pine sawdust. Maximum reducing sugar yields (g/100 g substrate) obtained after hydrolysis of pretreated samples were: 14 g for steam-exploded sawdust, 26 g for SO2 impregnated steam-exploded samples and 32.5 g for CO2 steam-exploded samples. Increase in digestibility is related to the catalytic effect of cooking at high temperatures with dissolved acids formed from the gases, as well as to the physical effect of the discharge during the explosion. Pretreatment with SO2 was the most efficient process for hydrolyzing hemicelluloses, as determined by the high content of soluble reducing sugars present in the washing liquor.
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    CHARACTERISTICS OF GUINDILLA (VALENZUELA-TRINERVIS BERT) OIL
    (1986) AGUILERA, JM; FRETES, A; SANMARTIN, R
    Seed of Guindilla (Valenzuela trinervis Bert.) and its oil were characterized. On a dry weight basis, the seed consists of 56% hull and seed coat and 44% cotyledon, containing about 67.0% lipids. The main fatty acids are: 62.3% oleic, 12.9% gadoleic, 10.1% linoleic and 9.6% palmitic. Physical properties of oil, expressed by hand press, include: melting point, -6 to -2 C; iodine value, 75.1; saponification value, 192; and unsaponifiable matter, 0.8%.
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    CHEMICAL-COMPONENTS OF GUINDILLA SEEDS (VALENZUELIA-TRINERVIS)
    (1987) SEIGLER, DS; CORTES, M; AGUILERA, JM
    A cyanolipid has been isolated and characterized from Valenzuelia trinervis (guindilla, Sapindaceae). The seed oil contains primarily oleic (62.3%), gadoleic (12.4%), linoleic (10.1%), and palmitic (9.6%) acids. The leaves of this plant contain approximately 25% saponins of which one predominates. The genin appears to be of triterpenoid origin. The seed meal contains ample lysine, leucine and phenylalanine, but is deficient in methionine. The seed meal is toxic to rats.
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    COMPRESSION STRENGTH OF DAIRY GELS AND MICROSTRUCTURAL INTERPRETATION
    (1991) AGUILERA, JM; KINSELLA, JE
    Contour plots were developed for the compression stress (at 20% deformation) of single-component, mixed and filled protein gels. Samples were made by heating and acidification from skim milk powder, SMP (0-20% TS), whey protein isolate, WPI (0-10% TS), and recombined cream, within pH 3.6-3.9, 4.6-4.8 and 5.1-5.3. At higher pH, WPI gels were stronger than SMP gels. WPI had a reinforcing effect on SMP gels, while small additions of SMP to WPI gels resulted in weaker mixed gels. Filled gels containing cream had higher compression strengths than mixed gels. Micrographs showed linking of casein chains by WPI strands in mixed gels and compatibility of fat globules with casein micelles in the protein network of filled gels.
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    EFFECT OF CELLULASE PRETREATMENTS ON RED ALGAE AGAR EXTRACTABILITY
    (1988) SANMARTIN, R; AGUILERA, JM; HOHLBERG, AI
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    EFFECT OF ROASTING ON THE NUTRITIONAL-VALUE OF DRY BEANS (PHASEOLUS-VULGARIS)
    (1984) STEINSAPIR, A; AGUILERA, JM; YANEZ, E
    Dry beans (Phaseolus vulgaris cv. Tortola Diana) slightly roasted by solid-to-solid heat transfer to 105.degree. C in 3 min were stored at 20.degree. C for 10 mo. After soaking and cooking in boiling water roasted beans achieved eating texture 30 min before the control. There were no major differences in proximate composition. Roasted and unroasted samples prepared at 3 cooking times (for proper texture and plus and minus 30 min) showed no significant differences in net protein ratio (NPR). The NPR values ranged from 3.46 to 3.60 for the 6 samples. Consequently, controlled high temperature-short time roasting inhibits the enzymatic system partly responsible of hardening without impairing the nutritional value of the beans.
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    EMULSIFIED MILKFAT EFFECTS ON RHEOLOGY OF ACID-INDUCED MILK GELS
    (INST FOOD TECHNOLOGISTS, 1991) XIONG, YL; AGUILERA, JM; KINSELLA, JE
    Reconstituted skim milk formed by a gel by acidification to < pH 5.2 and heating to 60-degrees-C. The gel compressive stress (sigma-c) was influenced by the heating process, increased with milk-nonfat-solids (MNFS) and reached a maximum at pH 4.0. The addition of emulsified fat facilitated gelation, increase gel sigma-c and shear modulus, and decreased gel deformability. At an equal fat concentration, emulsions containing small-sized fat globules (i.e., more globules) reinforced the gels more markedly than emulsions comprised of large globules reflecting the importance of number of globules in the gels. Electron micrographs revealed crosslinkages between fat globules and casein particles in the gel network, which may have caused reinforcement of milk gels by milkfat.
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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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    FOOD, AGRICULTURAL AND MARINE BIOTECHNOLOGY IN CHILE
    (ELSEVIER SCIENCE BV, 1993) AGUILERA, JM; AGOSIN, E; MARTIN, RS
    Economic segments with highest growth rates in Chile are those based on renewable resources like agriculture (fruits and vegetables), marine and forest products. Opportunities for biotechnology are based on a sound scientific base at universities, adequate funding and incipient industry-academia relationships. However, there is an urgent need to develop the engineering capabilities required to scale-up processes and to design, build and operate industrial biotechnology plants.
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    HARD-TO-COOK DEFECT IN BLACK BEANS - HARDENING RATES, WATER IMBIBITION AND MULTIPLE MECHANISM HYPOTHESIS
    (ELSEVIER SCIENCE BV, 1992) AGUILERA, JM; RIVERA, R
    The existence of a slower initial hardening period during storage of dry black beans, independent of cooking time and heat pretreatment, was corroborated. Water vapor production during storage for 1 year at 25 and 35-degrees-C did not change appreciably the moisture in dry beans stored at 10 and 12% moisture content. Further support to the hypothesis that water in soaked hard beans is held differently from that in soft beans was based on differences in the rate of drying and microstructural evidence. A dual contribution to the hardening mechanism, one reversible and another irreversible, was postulated based on soaking experiments with monovalent salts and chelating agents. Cell separation was not changed by salt treatment although the cell wall morphology was modified.
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    HARD-TO-COOK DEFECT IN BLACK BEANS - PEROXIDASE CHARACTERIZATION AND EFFECT OF HEAT PRETREATMENT AND STORAGE-CONDITIONS ON ENZYME INACTIVATION
    (1989) RIVERA, JA; HOHLBERG, AI; AGUILERA, JM; PLHAK, LC; STANLEY, DW
    Black beans (Phaseolus vulgaris) were studied in order to characterize the soluble peroxidase (POD) activity and to determine the effect of heat pretreatment and storage conditions on hardening and enzyme inactivation. Bean POD activity demonstrated a pH optimum from 6.4 to 6.8, an optimum temperature between 40 and 45.degree.C, an activation energy of 1.19 kJ/mol, a strong dependence on water activity and little sensitivity to added calcium ions. Beans stored at 30.degree.C/85%RH exhibited a 30-50% reduction in POD activity compared to samples kept at 15.degree.C/35%RH but this may not reflect in vivo rates. Thermal inactivation of POD activity in bean flour was facilitated at increasing moisture levels. A heat pretreatment of beans at moisture contents not exceeding 13% failed to control hardening in beans subsequently stored at temperatures of 27.degree.C or above and moisture levels of 13%. While no POD activity was found at heat pretreatment equilibrium temperatures above 102.degree.C and none of the samples that had acceptable hardening values demonstrated POD activity, increasing equilibrium temperature above 105.degree.C continued to reduce hardness. Thus, heating to only inactivate POD was not sufficient and higher temperatures were required to inactivate the hardening mechanism.
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    KINETICS OF BROWNING OF SULTANA GRAPES
    (1987) AGUILERA, JM; OPPERMANN, K; SANCHEZ, F
    Heat inactivation of polyphenoloxidase (PPO) in sultana grapes between 83.degree. and 98.degree. C followed zero order kinetics with an activation energy of 13.7-16.7 kcal/mol. A high correlation (r = 0.973) was found between the residual PPO activity and darkness of the raisins (Hunterlab L value) after drying at 50.degree. C. Reaction rate for enzymatic browning increased with higher water activities while non-enzymatic browning showed the typical bell-shaped curve with a maximum around 0.8. Light-colored raisins were obtained without the use of SO2 by pretreating the grapes with a 2 min dip in 93.degree. C water that inactivated PPO and improved mass transfer through the skin. This latter effect was compared to that of other treatments such as ethyl oleate and caustic soda by drying studies and scanning electron microscopy.
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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.