Ryuichi Matsuno

Lipid encapsulation technology - techniques and applications to food

Abstract Encapsulation is a means of isolating a substance from the reactions of the surrounding matter. After encapsulation, the entropy of the isolate decreases; the potency increases and, in some cases, the isolate gains new functions. A variety of methods have been developed to encapsulate various substances, and most are applicable to the encapsulation of lipids. This review focuses on lipid encapsulation in dried polysaccharide and protein matrices, covering why and how to encapsulate lipids, how to evaluate potential wall materials, and how to asses the retardation of lipid oxidation.

Oxidation of linoleic acid encapsulated with gum arabic or maltodextrin by spray-drying

Linoleic acid was emulsified with gum arabic or maltodextrin at various weight ratios of the acid to the polysaccharide in the presence or absence of a small-molecule emulsifier. The emulsions were spray-dried to produce microcapsules. Emulsions prepared with gum arabic were smaller in droplet size and more stable than those prepared with maltodextrin, and linoleic acid in a gum arabic-based microcapsule was also most resistant to oxidation than that in a maltodextrin-based microcapsule. Although the oil droplet size in the emulsion with maltodextrin decreased and the emulsion stability was improved by addition of a small-molecule emulsifier to linoleic acid, the oxidative stability of the encapsulated linoleic acid was not significantly improved. Encapsulated linoleic acid of small droplet size oxidized more slowly than that of large droplet size.

On the specific resistance of cakes of microorganisms

The mean specific resistance of the cakes of various microorganisms was evaluated by measurement of either a change in the amount of permeate with time or of steady-state flux under constant pressure. The mean specific resistance was different with different shapes and sizes of microorganisms. The large differences arose from different packing structures of the cake. The effect of a filter aid on the filtration rate and cake structure was studied experimentally and theoretically. The effects of a filter aid were best explained by a series model, in which a cake layer composed of microbial cells and a layer of randomly distributed microbial cells and filter aid are packed on the membrane surface in series with respect to the directions of permeation.

Autoxidation Kinetics for Fatty Acids and Their Esters

The autoxidation kinetics for n-3 and n-6 polyunsaturated fatty acids and their esters, which are collectively referred to as polyunsaturated fatty acids (PUFA), were investigated. Changes in the amounts of unreacted n-6 PUFA during the entire period of autoxidation could be expressed by dY/dt−k1Y(1 −Y), wereY was the fraction of unreacted PUFA,t was the time, andk1 was the rate constant. For n-3 PUFA, autoxidation had to be separated into two parts. The first half of autoxidation (Y ≥ 0.5) was expressed by the same equation as above, while the latter half (Y<0.5) relates to dY/dt=−k2Y, wherek2 was the rate constant. The apparent activation energies and the frequency factors ofk1 andk2 were evaluated. The apparent activation energies were in a range of 50 to 60 kJ/mol for bothk1 andk2. The frequency factor became large as the number of double bonds of PUFA increased.

Equilibrium yield of n-alkyl-β-d-glucoside through condensation of glucose and n-alcohol by β-glucosidase in a biphasic system

The β-glucosidase-catalyzed synthesis of n-alkyl-β-d-glucosides through the condensation of glucose and n-alcohols with alkyl chain lengths of 6 to 12 was carried out in a biphasic system, where the organic phase consisted only of an alcohol substrate. All the alcohols tested were condensed with glucose to give the corresponding n-alkyl-β-d-glucosides. An equation was formulated to predict the equilibrium yields of n-alkyl-β-d-glucosides under various conditions, and its validity was experimentally verified. The equilibrium constant for the formation of n-alkyl-β-d-glucosides was independent of the alkyl chain length and was 1.90 at 60°C. The volume ratio of the organic to the aqueous phase was a factor significantly affecting the equilibrium yield. It was also shown that the synthesis at lower initial glucose concentrations effectively yielded alkylglucosides with less β-glucobiose formation.

Solubility of Saturated Fatty Acids in Water at Elevated Temperatures

The solubility in water of saturated fatty acids with even carbon numbers from 8 to 18 was measured in the temperature range of 60 to 230°C and at a pressure of 5 or 15 MPa. The pressure had no significant effect on the solubility. The solubility of the fatty acids increased with increasing temperature. At temperatures higher than about 160°C, the logarithm of the solubility in mole fraction was linearly related to the reciprocal of the absolute temperature for each fatty acid, indicating that the water containing solubilized fatty acid molecules formed a regular solution at the higher temperatures. The enthalpy of a solution of the fatty acids in water, which was evaluated from the linear relationship at the given temperatures, increased linearly with the carbon number of the fatty acid.

Properties of immobilized β-d-galactosidase from Bacillus circulans

Partially purified β-d-galactosidase (β-d-galactoside galactohydrolase, EC 3.2.1.23) from Bacillus circulans showed high activity towards both pure lactose and lactose in skim milk, and a better thermal stability than the enzyme from yeast or Escherichia coli. During the course of hydrolysis of lactose catalysed by the enzyme, considerable amounts of oligosaccharides were produced. β-d-Galactosidase from B. circulans was immobilized onto Duolite ES-762, Dowex MWA-1 and sintered alumina by adsorption with glutaraldehyde treatment. The highest activity for hydrolysis of lactose was obtained with immobilization onto Duolite ES-762. During a continuous hydrolysis of lactose, the immobilized enzyme was reversibly inactivated, probably due to oligosaccharides accumulating in the gel. The inactivation was reduced when a continuous reaction was operated at a high percent conversion of lactose in a continuous stirred tank reactor (CSTR). The half-life of the immobilized enzyme was estimated to be 50 and 15 days at 50 and 55°C, respectively, when the reaction was carried out in a CSTR with a percent conversion of lactose >70%.

Preparation of fine W/O/W emulsion through membrane filtration of coarse W/O/W emulsion and disappearance of the inclusion of outer phase solution

Abstract A water-in-oil-in-water (W/O/W) emulsion was prepared as a carrier system for the daily uptake of a bioactive compound using decaglycerol monolaurate and hexaglyceryl condensed ricinolate as hydrophilic and lipophilic surfactants, respectively. 1,3,6,8-Pyrenetetrasulfonic acid tetrasodium salt (PTSA) was used as a hydrophilic model compound of a bioactive substance. Membrane filtration of a coarse W/O/W emulsion prepared with a rotor/stator homogenizer produced a fine emulsion which had a mean oil-droplet diameter of 90%. Microscopic observations revealed that the fluorescent material in the outer-phase solution was included into the oil phase during rotor/stator homogenization. It was suggested that because the rotor/stator homogenizer was used to produce both O/W and W/O/W emulsions, some part of the outer phase solution would be included in the oil phase during the second homogenization. The fluorescence shown in the oil droplets of the coarse W/O/W emulsion was diminished after membrane emulsification. This phenomenon suggested that the included outer-phase solution was released to the outer-phase solution from the interior of the W/O/W oil droplets during the membrane emulsification.

An extracellular D(-)-3-hydroxybutyrate oligomer hydrolase from Alcaligenes faecalis.

A strain of Alcaligenes faecalis secretes an extracellular D(-)-3-hydroxybutyrate oligomer hydrolase, in addition to poly(3-hydroxybutyrate) depolymerase, when it is grown in a medium containing poly(3-hydroxybutyrate) as the sole carbon source. The oligomer hydrolase (EC 3.1.1.22), which has been purified to electrophoretic homogeneity, has a molecular weight of 68 000, as estimated by Sephadex G-100 gel filtration, and of 74 000, by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The isoelectric point of the enzyme is approx. 6.0 and the pH optimum for the enzyme reaction is 8.5. The purified oligomer hydrolase has high affinity for oligomeric esters (apparent Km for the D(-)-3-hydroxybutyrate dimer = 32.8 microM; for the dodecamer = 1.3 microM), but does not attack poly(3-hydroxybutyrate) (average molecular weight, 32 500) at all. Analysis of hydrolysates of the oligomeric esters suggests that the enzyme hydrolyzes these substrates from the carboxyl terminus, releasing D(-)-3-hydroxybutyrate units one by one.

Continuous production of galacto-oligosaccharides from lactose using immobilized β-galactosidase from Bacillus circulans

Summaryβ-Galactosidase-2 (β-d-galactoside galactohydrolase, EC 3.2.1.23) from Bacillus circulans was purified using hydroxyapatite gel chromatography and immobilized onto Duolite ES-762 (phenolformaldehyde resin) and Merckogel (controlled pore silica gel) for continuous production of galacto-oligosaccharides using lactose as the substrate. The maximum amount of ologosaccharides produced by the immobilized enzyme was 35–40% of the total sugar during hydrolysis of 4.56% lactose. Partially purified β-galactosidase from B. circulans was also immobilized onto various supports for the same purpose. The stability of the immobilized β-galactosidase-2 or partially purified enzyme during a continuous reaction depended on their supports and specific activity. Of the supports tested, Merckogel was best for operational stability. With this support, the enzyme was quite stable with specific activity up to 15 units/g of wet gel; it was reversibly inactivated with more.