Physical Chemistry of Foods

of liquid fat, which often means a lower temperature. Recrystallization can involve change in polymorph, change in the compositi ...

the resultingcSis significantly biased: at the low temperature end of the melting rangecSis overestimated, at the high end under ...

Question 2 Milk fat as it occurs in milk, i.e., in globules of a fewmm in diameter, yields upon cooling always very small crysta ...

Monotropic polymorphism involves one or more unstable forms and a stable one; this occurs in fats. Compound crystals contain two ...

concentrated until the eutectic point (ce,Te) is reached, where also the solute will freeze. At high initial concentration, the ...

have a number of increasing ‘‘final’’ melting points (2 to 6), for each polymorph formed. In the third place, triglycerides of s ...

Introductory discussions related to foods are found in J. M. V. Blanshard, P. Lillford. Food Behaviour and Structure. Academic P ...

16 Glass Transitions and Freezing Many foods of low water content are wholly or partly in a glassy (vitreous) state. This is of ...

diffractogram of crystalline sugar shows many sharp peaks, that of amorphous sugar none. The glass transition phenomenon will be ...

FIGURE16.2 Illustration of the glass transition, as compared to a melting/ crystallizing transition, of a pure nonpolymeric subs ...

stronger upon approachingTg, where a sharp bend in the curve occurs. Notice thatZais given on a log scale. The decrease when goi ...

cooling, crystallites form again (retrogradation). In many foods, starch is in its gelatinized form. Figure 16.3a gives an examp ...

that at a given temperature the viscosity will markedly decrease with increasing water content. Such behavior is also observed f ...

of the system will become so high as to hinder greatly the diffusion of crystallizable components. Mixtures of a polymer, say st ...

whereZgis the viscosity atTg(Tis absolute temperature).C 1 andC 2 would be constants for each system, and often fixed values are ...

toTg, up to about 5 orders of magnitude. Nevertheless, the diffusivity is very much smaller than at high temperature. Figure 16. ...

Answer Provided that some conditions are fulfilled. The first is that the polymers are not intermingled on a scale much smaller ...

Processes. To obtain a food in a glassy state, water generally has to be removed without crystallization of solutes occurring. I ...

pieces of vegetables are dried, the cell walls can acquire a glassy state, leading to a hard and possibly brittle product. Bakin ...

made to agglomerate—a process applied to enhance the dispersibility of powders in water—by shaking the powder for a short while ...