Spreadability

Gaines [13] has reported on dimethylsiloxane-containing block copolymers. Interestingly, if the organic block would not in itself spread, the area of the block polymer was simply proportional to the siloxane content, indicating that the organic blocks did not occupy any surface area. If the organic block was separately spreadable, then it contributed, but nonadditively, to the surface area of the block copolymer. 

Gels with a low dynamic WeiBenberg number that means with large elastic and increasing viscous shares are soft and show better spreadability. They are more stable against mechanical treatment and have less syneresis. 

The jellies (20 sets) were submitted to a sensory panel (ten panellists from the laboratory staff with some experience in sensory evaluation) requested to give a score (from low to high in a non-structured 10 cm scale) to each of the following characteristics aroma (intensity), taste (sweet, acid and intensity), texture (hardness, spreadability) and overall acceptance. 

Had= Hardness Spr.= Springiness Che= Chewiness Gum= Gumminess Coe= Cohesiveness HS= Sensory hardness SP= Spreadability Ac= Acid Sw= Sweet Fia= Fiavour Ti= Taste intensity OA= Overall acceptance. 

The data from sensory evaluation and texture profile analysis of the jellies made with amidated pectin and sunflower pectin were subjected to Principal component analysis (PC) using the statistical software based on Jacobi method (Univac, 1973). The results of PC analysis are shown in figure 7. The plane of two principal components (F1,F2) explain 89,75 % of the variance contained in the original data. The attributes related with textural evaluation are highly correlated with the first principal component (Had.=0.95, Spr.=0.97, Che.=0.98, Gum.=0.95, Coe=0.98, HS=0.82 and SP=-0.93). As it could be expected, spreadability increases along the negative side of the axis unlike other textural parameters. 

Except in certain specialized areas, it is seldom practical to place an equality constraint on a continuous response-, it is usually not possible to achieve an exact value for an output. For example, a purchasing agent for a restaurant might specify that the margarine it buys from a producer have a spreadability index of 0.50. When questioned further, however, the buyer will probably admit that if the spreadability index is between 0.45 and 0.55 the product will be considered acceptable. In general, if an equality constraint is requested for a continuous response, an inequality constraint is usually preferable. 

Artificial surfactant, which contains dipalmitoylphosphati-dyl choline and some palmitic acid to provide for spreadability, is now commercially available for instillation into the lung. Adminishation of steroids to the mother prior to birth of the premature infant is also carried out. 

For mashed potato texture, profile analysis (TPA) and cone penetration tests are performed with a TA HDi Texture Analyser (Stable Micro Systems Ltd, Godaiming, UK). During the tests, the mashed potatoes are kept at 55° C by means of a temperature-controlled Peltier cabinet (XT/PC) coupled to a separate heat exchanger and PID control unit. For the cone penetration tests, a spreadability rig is used, consisting of a 45° conical perspex probe (P/45°C) that penetrates a conical sample holder containing 7 0.1 g of mashed potatoes (Alvarez et al., 2005 Canet et al., 2005b Fernandez et al, 2006). 

One of the major advantages of processed cheese is the flexibility of the finished form, which facilitates usage. The texture may vary from firm and sliceable to soft and spreadable. These cheeses may be presented as large blocks (5-10kg), suitable for industrial catering, smaller blocks, e.g. 0.5kg,... 

Next let us consider those difficulties associated with the determination of the amount of material deposited on the surface. We have already noted that the method of depositing insoluble monolayers by spreading permits the accurate determination of n. Since the spreading technique requires solvent volatility, care must be exercised to prevent the stock solutions from changing concentration due to evaporation prior to their application to the surface. Also, precise microvolumetric methods must be used to dispense the solution on the aqueous surface since the quantity used is small. The solvent (as well as the solute) must be free from contaminants. There is also the possibility that the solvent will extract spreadable contaminants from the waxed surfaces of the float, barriers, and tray. Some workers advocate addition and evaporation of one drop at a time to minimize this. Oily contaminants may also reach the water surface from the fingers and from the atmosphere. These last sources are particularly hard to control Tests for reproducibility and blank compressions (i.e., moving the barrier toward the float on a clean surface) are the best evidence of their absence. 

Examination of Cast Film. The film can now be examined both before and after stripping from foil. A simple test was devised to determined the transition point from liquid to nonliquid state. A palette knife was drawn along the foil from the end where some of the plastisol was still liquid. Plastisol flowed easily in front of the knife until it came to a point where the plastisol was no longer spreadable. At this point, which was sharply defined, it was impossible to push the blade further. The temperature at which this occurs has been called the liquid/solid transition point (Figure 5). 

Schaap, J. E., Hagedoorn, H. G. and Rutten, G. A. M. 1981. Effect of storage time, temperature and working on the firmness and spreadability of butter. Zuivelzicht 73, 38-40. (Dutch)... 

Puncture probes are commonly used for fruits and vegetables, and allow for the determination of force at rupture of the cellular structure. The procedure outlined below is adapted from the method of Bourne (1979). Cone penetrometers are commonly employed for determining firmness and yield value for foods such as margarine and butter, which may be a reflection of the product s spreadability. Quite often it is desirable to use a testing system that provides a constant deformation rate. Additionally, a mechanical testing machine allows for production of a force/deformation curve to further analyze the data. 

Butter has a limited plastic range. At refrigerator temperature ( 1-0°C), butter behaves essentially as a solid and lacks spreadability, whereas at room temperature (21-25°C), it oils off and exhibits moisture exudation. 

---