Robert W. Lencki

Lipid modification strategies in the production of nutritionally functional fats and oils.

Rapid improvements in the understanding of the nutritional requirements of both infants and adults has led to new developments in the modification of fats and oils. Specific targets include the improvement in growth and development of infants, treatment of disease in adults, and disease prevention. Efforts have been focussed on the production of structured lipids using medium-chain acids and long-chain polyunsaturated fatty acids (PUFAs), as well as the concentration of long-chain PUFAs from new and existing sources. Short- and medium-chain fatty acids are metabolized differently than long-chain fatty acids and have been used as a source of rapid energy for preterm infants and patients with fat malabsorption-related diseases. Long-chain PUFAs, specifically docosahexaenoic acid and arachidonic acid, are important both in the growth and development of infants, while n-3 PUFAs have been associated with reduced risk of cardiovascular disease in adults. Based on the requirements for individual fat components by different segments of the population, including infants, adults, and patients, ideal fats can be formulated to meet their needs. By using specific novel fat sources and lipid modification techniques, the concentrations of medium-chain, long-chain saturated, and long-chain polyunsaturated fatty acids as well as cholesterol can be varied to meet the individual needs of each of these groups. While genetic modification of oilseeds and other novel sources of specific lipid components are still being developed, chemical and lipase-catalyzed interesterification reactions have moved to the forefront of lipid modification technology. Fractionation of fats and oils to provide fractions with different nutritional properties has potential, but little work has been performed on the nutritional applications of this method. The choice of suitable lipid modification technologies will depend on the target lipid structure, production costs, and consumer demand. A combination of some or all of the present lipid modification techniques may be required for this purpose.

Influence of membrane structure on fouling layer morphology during apple juice clarification

The flux behavior of 0.2 μm nylon, polysulfone (PS), polyvinylidene fluoride (PVDF) and polyethersulfone (PES) membranes was examined during dead-end microfiltration of commercial apple juice. On nylon membranes, a 0.1 μm thick surface fouling layer rapidly formed that acted as a secondary membrane. The colloidal particles retained by this surface layer aggregated to form a thick loose gel structure, producing an anisotropic fouling structure. In contrast, the 4 μm thick surface fouling layer of PES was slower to form and had a more open structure with a lower flux resistance per unit thickness. The morphology of the PES surface layer also did not differ dramatically from the loose gel structure that subsequently formed on top of this secondary membrane. The PS surface fouling layer was similar in structure to nylon whereas the PVDF layer more closely resembled that found with PES. The density of the surface fouling layer did not directly correlate to membrane surface hydrophobicity or pure water flux. Atomic force microscopy (AFM) indicated that surface roughness strongly influenced surface fouling layer morphology. The membrane surface appears to act as a template for the fouling process; therefore, smooth membranes (nylon and PS) produce a dense surface fouling layer whereas this same layer on rough membranes (PES and PVDF) is much more open. Consequently, the fluxes of PES and PVDF membranes are less affected by fouling formation.

Effect of nonaqueous solvents on the flux behavior of ultrafiltration membranes

Abstract Flux experiments were conducted to determine the effect of aqueous methanol, resistance behavior of 10 and 30 kDa molecular weight cutoff cellulose and polysulfone membranes. The resistance of the 10 kDa cellulose membrane increased as the solubility parameter of the aqueous solvent solution (δS) approached that of the membrane (δP). The opposite effect was observed with the 30 kDa cellulose membrane: a resistance minimum was observed when δS ≅ δP. Differences in flux behavior are believed to be a consequence of the 10 kDa membrane having a much more anisotropic structure as compared to the 30 kDa membrane. Basically the same flux maxima and minima trends were observed with the flow of solvent solutions throgh 10 and 30 kDa polysulfone membranes. However, acetonitrile, because of its low hydrogen bonding capabilities, dramatically reduces the glass transition temperature of polysulfone. As a result, the presence of this solvent at high concentrations disrupted the integrity of the 10 kDa polysulfone membrane, leading to an over ten fold decrease in flow resistance.

Protein ternary phase diagrams. 2. Effect of ethanol, ammonium sulfate, and temperature on the phase behavior of (S)-ovalbumin

The phase behavior of (S)-ovalbumin in aqueous ethanol and (NH4)2SO4 solutions (pH 7.0) was investigated for temperatures ranging from 20 to 90 °C. The various morphologies observed were presented on ternary phase diagrams. At 20 °C, three morphologies were observed in aqueous ethanol:  one-phase liquid, one-phase solid, and two-phase liquid and aggregate. Differential scanning calorimetry indicated that the (S)-ovalbumin denaturation temperature in buffer solution of 89.45 °C significantly decreased with ethanol addition and increased in the presence of (NH4)2SO4. As a result, a pastelike morphology was observed at moderate protein (3−30 wt %) and ethanol (20−40 wt %) concentrations when (S)-ovalbumin solutions were heated above 50 °C. In contrast, (NH4)2SO4 had a stabilizing effect on (S)-ovalbumin ternary structure and thus had little effect on (S)-ovalbumin phase behavior below the denaturation transition temperature. However, this salt encouraged solid phase formation once the denaturation transition...

Effect of fractal flocculation behavior on fouling layer resistance during apple juice microfiltration

The colloidal material in juice obtained from Red Delicious apples held in cold storage for over 6 months was observed to spontaneously aggregate to form ordered flocculation patterns. These flocculation patterns could be altered by heat treatment and by gelatin or antioxidant addition. The specific resistance of the fouling layer produced by each juice during microfiltration could be qualitatively predicted by examining the structure of macroscopic flocculation patterns. Environmental scanning electron microscopy (ESEM) photos of the various hydrated fouling layers indicated that loose flocs appeared to compress and rearrange on the membrane surface, producing smooth, low porosity secondary membranes. Densely packed cross-linked aggregate networks also formed low porosity structures, once again creating a fouling layer with high resistance. The lowest resistance fouling layers were produced when the flocs were dense enough to resist compression but porous enough to provide pathways for permeate flow. Field emission scanning electron microscopy (FESEM) and ESEM images indicated that, in many cases, the spacial distribution of solids in the microscopic aggregates were reminiscent of those in the macroscopic flocs. Such scaling relationships are typical of fractal systems.

Protein ultrafiltration concentration polarization layer flux resistance: II. Importance of protein layer morphology on flux decline with ovalbumin

Abstract The effect of added ethanol and (NH4)2SO4 on the morphology of the gelatin concentration polarization (CP) layer during ultrafiltration (UF) was analyzed using protein ternary phase diagrams, as well as turbidity and intrinsic viscosity measurements. CP layer resistance was characterized by measuring the flux decline index (FDI) of a 0.10 wt% gelatin solution in a dead-end UF system at 40°C. Ethanol concentrations up to 30 wt% produced an aggregated CP layer morphology with a moderate FDI. However, above 30 wt%, a swollen macromolecular gel formed on the membrane surface, resulting in a lower FDI. Low salt levels led to the formation of compact protein particles in the CP layer that had a moderate FDI. In contrast, a concentration of 8 wt% produced a high FDI coacervate structure. The highest FDI was observed at salt concentrations above 12 wt%, where the surface morphology consisted of a dense particulate gel. Overall, the FDI could be altered by a factor of ∼3 by manipulating the concentration of solute in the solution.

Increasing Short-Chain Fatty Acid Yield During Lipase Hydrolysis of a Butterfat Fraction with Periodic Aqueous Extraction

Factors affecting the release of short-chain fatty acids during hydrolysis of a butterfat fraction with a 1,3-positional and short-chain-specific Penicillium roqueforti lipase were investigated. When a short-chain triglyceride fraction was used as substrate, as opposed to whole butterfat, the ratio of desirable flavor short-chain free fatty acids (FFA) to undesirable medium-chain FFA in the FFA fraction increased from 0.75 to 1.80. However, with both substrates, FFA accumulation eventually led to lipase inhibition and limited the total amount of triglyceride hydrolysis. This inhibition phenomenon was principally due to product inhibition. Periodically extracting the FFA with a buffer solution minimized this inhibition phenomenon, thereby significantly increasing lipase activity and the degree of triglyceride hydrolysis. Thus, on-line extraction of FFA in lipase reactors has the potential of greatly increasing system productivity.

Methodology for determining the appropriate selectivity of mass transfer devices for modified atmosphere packaging of fresh produce

Perforations or polymeric membranes are not capable of simultaneously providing optimum O 2 and CO 2 levels for many fruits and vegetables contained in modified atmosphere packaging. However, combining these two gas transfer devices, either in series or in parallel, can provide the required gas selectivities to create optimal modified atmosphere conditions. A methodology for determining the perforation and membrane surface areas for individual and combined systems is described. Gradient diagrams are used to calculate the optimum system selectivity, ΔpO 2 and ΔpCO 2 . These values can be used to select the appropriate gas exchange devices and to determine the appropriate perforation and membrane surface area.

Solubility of milk fat triglycerides in supercritical carbon dioxide

Abstract Five fractions of milk fat triglycerides were obtained by extraction with supercritical carbon dioxide in the pressure range of 12–33 MPa and at temperatures of 50 and 80°C. The results showed that increasing the solubility parameter or density of supercritical CO 2 under these conditions increased the solubility of milk fat triglycerides, but with this increase the supercritical fluid became less selective for the extraction of short-, medium- or long-chain triglycerides. The differences in solubility of individual milk fat triglycerides in supercritical CO 2 can be explained by solute-solvent interactions (extraction) and vapour pressure enhancement (distillation).

Effect of ethanol, ammonium sulfate, fatty acids, and temperature on the solution behavior of bovine serum albumin.

Ternary phase diagrams (TPDs) for aqueous bovine serum albumin (BSA) solutions containing ethanol or (NH4) 2SO4 were determined for temperatures ranging from 20 to 70 °C. At 20 °C, ethanol destabilized BSA, resulting in gel formation at moderate solute concentrations. In contrast, (NH4) 2SO4 concentrations above 20 wt % precipitated BSA from solution. Raising the temperature led to gel formation at increasingly lower BSA and solute concentrations. The removal of adsorbed fatty acids from BSA had little effect on the ethanol TPDs but reduced protein solubility in (NH4) 2SO4. Moreover, the salt TPDs of fatty‐acid‐poor BSA were similar to those previously observed with S‐ovalbumin.