Jorge F. Toro-Vazquez

Effect of triacylglycerols in formulated diets on growth and fatty acid composition in tissue of green abalone (Haliotis fulgens)

Abstract Isocaloric formulated diets containing four different sources of triacylglycerols (olive, corn, linseed and cod liver oils) at three levels (1.5%, 3.0% and 5.0%, total added dietary lipid=5.0%) and a crude protein content of 37.5% to 39.9% were fed to juvenile green abalone ( Haliotis fulgens ). Growth and fatty acid composition of the muscle tissue were compared to that of abalone fed a reference diet that contained no added lipids (0.25% total lipids). After 75 days of culture in a flow-through system, no significant differences in growth were found among abalone fed the different oil types. Responses to different dietary levels of lipid were significantly different but not to sources of oils. Maximum growth was achieved at a 1.5% inclusion of oil sources. It appears that abalone have a great capacity to synthesize lipid from carbohydrate sources. Results also suggest that abalone are capable of desaturation and elongation of 18 C polyunsaturated fatty acids (PUFAs) of the n −3 and n −6 family to 20:5 n −3 and 20:4 n −6. Synthesis of 22:6 n −3 from 20:5 n −3 is not reflected in the results. The lack of a growth response to the different levels of highly unsaturated fatty acids (HUFA) provided by the different oils included in the experimental diets may be due to an insufficient duration of the experiment to achieve an essential fatty acid deficiency. The relationship between fatty acid profiles of tissue and the diets fed to the abalone suggests that metabolic activity of the gut microflora is not a source of essential fatty acids.

The Freundlich Isotherm in Studying Adsorption in Oil Processing

The objective of this review is to discuss the history of the use of the Freundlich isotherm in investigating adsorption processing of vegetable oils and to evaluate its current value in adsorption studies. The Freundlich isotherm was originally developed to explain the adsorption of a single solute from solution. However, a similar adsorption pattern has been observed when studying a more complex system of adsorption of vegetable oil pigments onto bleaching clay during commercial bleaching of vegetable oils. The Freundlich isotherm has been useful for decades in finding the commercial value of adsorbents as long as a narrow experimental interval of adsorbate is used. More recent studies have shown that a complex series of interactions controls the adsorption process. While the isotherm summarizes these interactions, investigating them is vital to understand the physicochemical factors involved during adsorption. Statistical modeling and spectroscopy are useful in understanding the vegetable oil bleaching/refining process as a multiple-component adsorption system.

Regressional models that describe oil absolute viscosity

Equations that describe the temperature dependence (298–338°K) of absolute viscosity (μ) of 21 oils and oil-liquid fat mixtures were obtained based on two different approaches. Fitting each particular viscosity profile to a quadratic extension of the Andrade equation provided the best predictive models (R2>0.96). However, the coefficients associated with temperature effect did not have a physical-chemical meaning. In contrast, the multiple variable regressional approach fitted, in just one equation, the μ of all 21 oil systems (R2≈0.93). This equation included terms associated with structural parameters of acylglycerides, namely the degree of unsaturation (i.e., iodine value) and chainlength (i.e., saponification value) of the fatty acids. The models described effects of thecis double bonds and fatty acid chainlength on the acylglycerides’ interactions that determine both the μ of the system and its capability to crystallize. Therefore, multiple variable regressional analysis might be an excellent tool to better understand the quantitative structure-functional property relationships in lipids systems.

Viscosity and its relationship to crystallization in a binary system of saturated triacylglycerides and sesame seed oil

This paper describes the relationship of viscosity with the crystallization process in a binary system formed by sasame oil and different concentrations of tripalmitin (TP) and tristerian (TS) (0.0, 0.032, 0.098, 0.18, 0.26, 0.344 g/dL). The behavior of the reduced viscosity (ηred) indicated that TP and TS affected the native bilayer lamellar organization of sesame oil triacylglycerides. The behaviour of ηred at TP or TS concentrations ≤0.098 g/dL suggested that, as a result of intermolecular interactions between the saturated triacylglyceride and the unsaturated triacylglycerides of sesame oil, the oil solution developed lamellar structures with a smaller size than the native structures in sesame oil. At TP or TS concentrations >0.098 g/dL, the behavior of ηred indicated that TP or TS segregated out of the lamellar structure as the temperature was decreased. The kinetics of the segregation phenomenon was a function of the concentration of saturated triacylglyceride and the type of triacylglyceride (i.e., TP or TS), and was favored by an increase in the shear rate. In all situations, the temperature of nucleation was achieved when ηred=0, which may represent the point at which the interfacial energy between sesame oil and the developing nuclei achieved its maximum value. The higher the intermolecular interaction between the TP or TS and the triacylglyceride structure of the sesame oil, the lower the temperature at which ηred=0 in the oil solutions. As a result, the diffusion term (i.e., viscosity of the liquid phase) became a limiting factor for crystal growth rate, especially at TP and TS concentrations ≤0.18 g/dL.

Interaction of granular maize starch with lysophosphatidylcholine evaluated by calorimetry, mechanical and microscopy analysis

In this study we evaluated the thermo-mechanical properties of maize starch pastes (80% wt/wt) under the effect of exogenous lysophosphatidylcholine (LPC) using differential scanning calorimetry (DSC), dynamic mechanical spectrometry (DMS), and scanning electron microscopy (SEM). Particular attention was paid to the development of the amylose-LPC inclusion complex. Results from SEM and DSC showed that with no exogenous LPC, granular maize starch developed the amylose network structure for starch gelling at 80 – 95 8C. In comparison, at 1.86 and 3.35% of LPC, heating up to 130 8C was needed to develop the three-dimensional network required for starch gelling. Results showed that at these LPC concentrations LPC interacted mainly with amylose within the starch granule. At concentrations

Adsorption isotherms of sesame oil in a concentrated miscella system

8.26% the LPC interacted with amylose both inside the granule and on the granule’s surface. At such LPC concentrations heating to 130 8C did not fully develop the starch network structure for gelling. These results suggested that a higher thermal stability was achieved by starch granules because of LPC inclusion complex formation. DSC or DMS did not detect the development of this complex, probably because its formation took place below the onset of gelatinization under conditions of limited molecular mobility. Subsequently, a lower level of organization (i.e. complex in form I) was achieved than in the complex developed at high temperature and water excess (i.e. complex in form II). On the other hand, the changes in the starch granule structure observed by SEM as a function of the time – temperature variable were well described by the phase shift angle ðdÞ rheograms for starch pastes with and without addition of LPC. q 2003 Elsevier Ltd. All rights reserved.

Chemical and Physicochemical Properties of Maize Starch After Industrial Nixtamalization

The adsorption of peroxides, unsaturated carbonyls, free fatty acids and carotenoids from unrefined sesame oil on vegetable carbon (5%, w/w) in a miscella system was studied. Three different solvent conditions (hexane/ethanol, 100:0, 95:5 and 75:25, vol/vol), combined in a factorial design with five levels of solvent (0, 10, 20, 30 and 40%, w/w), were used to develop the miscella. Equilibrium adsorption was not achieved during the 100 min of adsorption, mainly because the oil components were involved in oxidation reactions during the adsorption process. However, for a given solvent concentration, adsorption of the oil components showed a significant linear regression on their respective initial concentration in the miscella (Ci). Peroxides and carbonyls showed, at all solvent levels investigated, an affinity for the carbon more independent of their Ci than free fatty acids and carotenoids. In general, at the same Ci, a higher adsorption was achieved as solvent concentration increased. The results indicated that free fatty acid adsorption may depend on competitive adsorption based on molecule hydrophobicity. However, in spite of the higher hydrophobicity of carotenoids, compared with free fatty acids, they might not be competing for the same adsorbing sites. Ethanol showed a prooxidant effect that increased peroxide production during adsorption but did not affect the reaction involved in carbonyl production.

Adsorption isotherms of squash (Cucurbita moschata) seed oil on activated carbon

ABSTRACT Processing conditions similar to traditional nixtamalization are now used by the industry in the production of dry maize flours (DMF). The objective of this investigation was to evaluate the effect of industrial nixtamalization on maize starch. Thus, dent maize grains were sampled from storage silos and the starch isolated (S). From the same batch of maize, DMF was obtained and the starch isolated (S-DMF). The amylose content in the starches was quite similar (21.5–23.4%) and characteristic of a dent maize. However, nixtamalization increased the calcium content in S-DMF. The starches investigated exhibited the typical A-type diffraction pattern after 40 days of storage at 11–84.1% rh. However, the differential scanning calorimetry (DSC) results showed that annealing of maize starch occurred during storage at 30°C. On the other hand, industrial nixtamalization has both a melting and annealing effect on maize starch. Thus, the operative glass transition temperature (Tg), and the DSC parameters that...

Modification of Solubility and Heat-Induced Gelation of Amaranth 11S Globulin by Protein Engineering

With vegetal carbon as adsorbent (5% w/w), the effects of temperature (30°C and 50°C), concentration of H2O (0% and 25%) and adsorption time (0 hr, 1 hr, 2 hr, 3 hr) on the chemical characteristics of unrefinedCucurbita moschata seed oil were studied in a batch adsorption system by using a “split-plot” experimental design. With the exception of the iodine value, the chemical properties of the oil (saponification and peroxide value, carotenoid, and free fatty acids concentration) were affected significantly by interactions among the adsorption time, temperature and concentration of H2O in the adsorption system. The results suggest that the physicochemical characteristics of the oil, and therefore its functional properties, may be modified and controlled by the conditions utilized during the adsorption process.

Competitive adsorption among sesame oil components in a concentrated miscella system

The primary structure of amaranth 11S globulin (Ah11S) was engineered with the aim to improve its functional properties. Four continuous methionines were inserted in variable region V, obtaining the Ah11Sr+4M construction. Changes on protein structure and surface characteristics were analyzed in silico. Solubility and heat-induced gelation of recombinant amaranth 11S proglobulin (Ah11Sr and Ah11Sr+4M) were compared with the native protein (Ah11Sn) purified from amaranth seed flour. The Ah11Sr+4 M showed the highest surface hydrophobicity, but as consequence the solubility was reduced. At low ionic strength (μ = 0.2) and acidic pH (<4.1), the recombinant proteins Ah11Sr and Ah11Sr+4 M had the highest and lowest solubility values, respectively. All globulins samples formed gels at 90 °C and low ionic strength, but Ah11Sn produced the weakest and Ah11Sr the strongest gels. Differential scanning calorimetry analysis under gel forming conditions revealed only exothermic transitions for all amaranth 11S globulins analyzed. In conclusion, the 3D structure analysis has revealed interesting molecular features that could explain the thermal resistance and gel forming ability of amaranth 11S globulins. The incorporation of four continuous methionines in amaranth increased the hydrophobicity, and self-supporting gels formed had intermediate hardness between Ah11Sn and Ah11Sr. These functional properties could be used in the food industry for the development of new products based on amaranth proteins.