The gelatinization behaviour of potato starch in an excess of water or solutions of sugars, other organic hydroxy compounds, or various inorganic salts was studied. The distribution of water and solutes between the external phase and the starch granules was measured by refractometry and a dye exclusion technique. When the limited water uptake of native starch granules is taken into account, the cooperative nature of gelatinization and the effect of water content on gelatinization behaviour can be explained solely on the basis of the Flory theory of polymer melting. Following the same argument, the effect of many solutes can be approximately described by the derived relationship between initial gelatinization temperature, water activity of the system and volume fraction of water in the granules.

When starch powders are mixed with water and heated at or above the gelatinisation temperature, the granules absorb large quantities of water and form a viscous paste. The gelatinised pastes are shear‐thinning fluids, whose flow curves fit the expression n̈=kγm over a wide range of shear rates. Behaviour at very low shear rates indicates the existence of a yield stress. Under oscillatory shear the elastic moduli of the pastes considerably exceed the loss moduli, and both show only weak dependence on frequency over the range 0.002‐2.5 Hz. The apparent viscosities, pseudoplasticity constants, yield stresses and elastic moduli of the pastes are all concentration dependent, assuming significant values only when the starch level exceeds a minimum concentration. In many cases this threshold concentration corresponds closely to the point at which the volume of flocculated swollen starch granules just fills the total volume of the system.

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The digestion of gelatinised starch suspensions by salivary amylase was studied using a viscometric assay and also by measuring the mechanical properties of individual granules. Viscosity decay as a function of time was approximately exponential. A comparison with a reducing group assay showed that a 50% fall in viscosity corresponded to the scission of about 0.05% of the glycosidic bonds. The half-time for the reduction of viscosity by the enzyme was found to be proportional to enzyme concentration but independent of starch concentration over a wide concentration range. This result suggests that the starch concentrations used were well below the saturating point for the enzyme, which was thus largely in the free state, and that the enzyme attacked the gelatinised granules throughout their structure rather than just at the surface. Measurements of the forces required to deform individual granules supported this hypothesis by showing that the gelatinised granules lost nearly all their mechanical strength during initial contact with salivary amylase, without any apparent change in diameter.

Liposomes were prepared from a milk fat globule membrane (MFGM) phospholipid fraction and from soy phospholipid material using a high-pressure homogenizer (Microfluidizer). The liposomes were characterized in terms of general structure, phase transition temperature, lamellarity, bilayer thickness, and membrane permeability. The liposomes prepared from the MFGM fraction had a significantly higher phase transition temperature, thicker membrane, and lower membrane permeability. These differences were attributed to different phospholipid compositions of the MFGM and soy phospholipid fractions.

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Chromatographic examination has shown that the enzymic hydrolysis of amygdalin by an almond beta-glucosidase preparation proceeds consecutively: amygdalin was hydrolysed to prunasin and glucose; prunasin to mandelonitrile and glucose; mandelonitrile to benzaldehyde and hydrocyanic acid. Gentiobiose was not formed during the enzymic hydrolysis. The kinetics of the production of mandelonitrile and hydrocyanic acid from amygdalin by the action of the beta-glucosidase preparation favour the probability that three different enzymes are involved, each specific for one hydrolytic stage, namely, amygdalin lyase, prunasin lyase and hydroxynitrile lyase. Cellulose acetate electrophoresis of the enzyme preparation showed that it contained a number of enzymically active components.