Gain of Moisture

The flavour is obviously an important component of chewing gum, and common flavours are normally compounded from essential oils. Essential oils give good flavours but they also affect the texture of the chewing gum since they act as plasticisers. The other component of fruit flavours is fruit acids. This of course precludes using calcium carbonate as a texturiser. 

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Precautions may also have to be taken to prevent loss or gain of moisture, and to prevent photochemical degradation. Light-sensitive samples should be stored in the dark, in amber glass containers or in glass containers protected by aluminium foil. Samples containing volatile constituents should be kept in well-sealed containers and preferably stored in the cold to reduce the vapour pressure of such compounds. 

Thus, under ideal conditions, ERH is the % relative humidity of an atmosphere in which a foodstuff may be stored without a net loss or gain of moisture. Water activity, together with temperature and pH, is one of the most important parameters which determine the rates of chemical, biochemical and microbiological changes which occur in foods. However, since aw presupposes equilibrium conditions, its usefulness is limited to foods in which these conditions exist. 

The change in the laminates mass describes the loss/gain of moisture and this varies from the higher water absorbency of aramid composites to lower capacities of glass and carbon composites (Figure 9.5). Saturation of a composite is achieved far more easily in boiling water than in a humid atmosphere at room temperature. 

Carefully mix the grab sample and reduce it in size to a convenient laboratory sample by the quartering procedure described in Practice D 346. Perform the quartering operation on a hard, clean surface, free from cracks, and protected from rain, snow, wind, and sun. Avoid contamination with cinders, sand, chips from the floor, or any other material. Protect the sample from loss or gain of moisture or dust. Mix and spread ffie sample in a circular layer, and divide it into quadrants. Combine two opposite quadrants to form a representative reduced sample. If this sample is still too large for laboratory purposes, repeat the quartering operation. In this manner, the sample will finally... 

In a study (206) of the moisture gain of foamed plastic roof insulations under controlled thermal gradients the apparent permeabiUty values were greater than those predicted by regular wet-cup permeabiUty measurements. The moisture gains found in polyurethane are greater than those of bead polystyrene and much greater than those of extmded polystyrene. 

Heat gains from internal loads normally are sensible beat. Nevertheless, many processes release a significant amount of moisture. Also, occupants produce relevant amounts of latent heat, especially at high metabolic rates and at high air temperatures. 

The objective of the immersion test is to determine the moisture content (percent weight gain) of a material as a function of its immersion time. To interpret immersion test data, moisture diffusion through the thickness of a test specimen can be described using a one-dimensional Fickian equation... 

Thermogravimetry (TG) is a measure of the thermally induced weight loss of a material as a function of the applied temperature [39], Thermogravimetric analysis is restricted to studies involving either a mass gain or loss, and it is most commonly used to study desolvation processes and compound decomposition. Thermogravimetric analysis is a very useful method for the quantitative determination of the total volatile content of a solid, and it can be used as an adjunct to Karl Fischer titrations for the determination of moisture. 

For a food system in equilibrium with a gaseous atmosphere (i.e. no net gain or loss of moisture to or from the system caused by differences in the vapour pressure of water), the equilibrium relative humidity (ERH) is related to aw by ... 

The relative amounts of sample and standard material have to be different because the moisture transferred from the food sample to the standard (characterized by the mass gain of the standard) must not result in a significant change in the vapor pressure maintained by the sample. Essentially, the sample replaces the salt solution in the Basic Protocol to create constant aw in the closed chamber. 

As an alternative, centrifugation can be used. The major issue in this approach is how to collect the expressed moisture. One way, as presented in this unit, is to collect the moisture on filter paper and measure either the weight gain of the filter paper or the weight loss of the sample. The material can be put into a few pieces of filter paper and centrifuged. As a practical matter, the author has found that a piece of nylon mesh placed between the meat sample and the filter paper make it easier to remove the meat sample after centrifugation... 

RCTs it is therefore possible to gain information about the efficacy of moisturizers as monotherapy. The effect of the cream base varies. In a stable, dry, and scaly dermatosis such as psoriasis, active treatment with calcipotriol reduces disease severity as assessed by PASI scores by 56%, whereas the use of the cream base reduces it 35%.1 Dry skin is also a key diagnostic element in atopic dermatitis and moisturizers are therefore extensively used in this disease. Looking at the placebo-arm in RCTs of topical treatment of atopic dermatitis the placebo effect appears to be in the range of 20%.2 6 The disease is however also more dynamic, and it waxes and wanes more frequently than psoriasis, which may explain the difference seen between the two disseases. 

A hygroscopic material absorbs moisture from its surrounding atmosphere, while a humectant material is one that resists changes in relative moisture content. The gain or loss of moisture in a com syrup is dependent on the relative humidity of the atmosphere surrounding the syrup. Moisture absorption values for several sweeteners are shown in Table 21.16.79... 

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