On account of technological advances inside the heat controllers and you can running manage procedure, it has become you’ll so you’re able to put drying out heavens temperature manage methods (nonisothermal drying), where you are able to follow sinusoidal wave profiles (Contour 1a), square-wave or box form pages (Shape 1b), expanding and you will p users, saw-enamel trend profiles, and you will trapezoidal trend profiles (Shape 1c), and others. Nonisothermal drying makes it it is possible to to find factors from large top quality and also smaller drying moments than others obtained having constant convective drying ( Chua while some 2002 ). Even if various high quality services was indeed studied within the information published to nonisothermal drying, architectural services haven’t been claimed, neither has actually equations become proposed to explain the behavior ( Chua and others 2000 ; Chua while others 2002 ). At this point, no equations was indeed recommended to associate alterations in the newest structural services regarding material met with adjustable external requirements.

It has been observed that there is zero factor anywhere between the brand new conclusion out of genuine thickness according to the X out of the materials while in the convective drying out and you can just after getting rehydrated to several moisture contents; not, differences was basically observed anywhere between apparent occurrence depending on the X of procedure throughout the lyophilization and you will further rehydration to several water articles ( Krokida and you may ).

Three possible tendencies of ?_p as a function of X have been found (Figure 2), both linear and nonlinear (concave-down and concave-up). _p and X, which considers reduction in volume to be equal to the volume of the water eliminated from the material ( Madamba and others 1994 ). In tendency of Figure 2b, it can be observed how ?_p increases slowly up to a critical point, followed by an exponential decay. This change has been explained by water loss in the material during drying ( Lozano and others 1983 ; Zogzas and others 1994 ). In tendency in Figure 2c, it is assumed that the increase in ?_p to a critical point is due to the fact that the reduction in volume is greater than the reduction in mass; after this critical point, the pores in the material are considered to be closed, and measured volume is greater than true volume ( Lozano and others 1983 ). In the above-described tendencies, it is merely assumed that volume and solid dry mass are constant. However, when materials are heated, they may expand or contract; in such cases, volume is not constant.

Thickness Designs

Several efforts have been made to predict different tendencies of ? as a function of X. Generally in these models, the foodstuff is considered to be a binary compound (water–solid). Table 3 shows models for true and apparent density proposed for foodstuffs. The models for predicting ?_b and ?_p are based on the development of pores during the lyophilization process, as the formation of pores is considered to be a function of ideal conditions, since there is no reduction in the volume of the solid as a result of water sublimation ( Karathanos and others 1996 ).

True density (?p) habits

Certain authors features proposed correlations received as a result of nonlinear regression getting forecasting real thickness and you will noticeable occurrence once the a purpose of dampness posts. Although not, the outcome maybe not become common and they are simply appropriate with the point, geometry, and drying out criteria found in people functions (Table step three).

It seen linear choices from thickness for different suspensions off absolute ingredients, such proteins, oils, carbohydrates, materials, and ash. These writers opposed their designs having fresh occurrence beliefs for dairy, orange fruit juice, and you can bratwurst sausage, obtaining a max error of just one.45%, and you will in search of a beneficial quadratic features to have h2o.