Due to technological improves in the temperatures controllers and you will operating handle process, it has become it is possible to in order to integrate drying sky temperature control actions (nonisothermal drying out), enabling you to go after sinusoidal wave users (Shape 1a), square wave or container means pages (Contour 1b), increasing and you may p users, saw-enamel revolution users, and you may trapezoidal trend pages (Profile 1c), yet others. Nonisothermal drying out makes it you can to locate affairs out of high high quality and even less drying moments as opposed to those gotten with lingering convective drying out ( Chua while others 2002 ). No matter if individuals quality services was indeed learnt inside material published to nonisothermal drying out, architectural characteristics haven’t been claimed, nor provides equations become suggested to describe the choices ( Chua while some 2000 ; Chua and others 2002 ). So far, zero equations was recommended so you can connect alterations in brand new structural features of materials confronted by changeable external requirements.
It’s been noticed there is no significant difference ranging from this new choices out of true occurrence according to X away from the information presented during convective drying out and you may after being rehydrated to several dampness articles; but not, differences had been observed anywhere between noticeable density with regards to the X of your own material through the lyophilization and you may next rehydration to several water content material ( Krokida and you will ).
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.
Density Activities
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 thickness (?p) activities
Individuals writers enjoys recommended correlations obtained courtesy nonlinear regression getting predicting real thickness and apparent occurrence since the site de rencontres célibataires religieux seulement a function of dampness blogs. But not, the outcomes perhaps not become widespread and are generally simply good towards the point, geometry, and you will drying out conditions found in the individuals works (Table step 3).
They noticed linear behavior away from density for several suspensions away from natural ingredients, such as for instance proteins, oils, carbohydrates, fibers, and ash. These article authors compared the designs having fresh occurrence philosophy for milk, lime liquid, and you will bratwurst sausage, obtaining a max mistake of just one.45%, and you can looking a quadratic effectiveness having h2o.
