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Influence of drying method on qualit...

Contreras Monzon, Carolina.

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Influence of drying method on quality parameters related to the structure and color of dried apple and strawberry.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Influence of drying method on quality parameters related to the structure and color of dried apple and strawberry./
Author:	Contreras Monzon, Carolina.
Description:	233 p.
Notes:	Source: Dissertation Abstracts International, Volume: 67-03, Section: B, page: 1215.
Contained By:	Dissertation Abstracts International67-03B.
Subject:	Agriculture, Food Science and Technology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3211734
ISBN:	9780542601675

Influence of drying method on quality parameters related to the structure and color of dried apple and strawberry.
Contreras Monzon, Carolina.

Influence of drying method on quality parameters related to the structure and color of dried apple and strawberry. - 233 p.

Source: Dissertation Abstracts International, Volume: 67-03, Section: B, page: 1215.

Thesis (Dr.)--Universidad Politecnica de Valencia (Spain), 2006.

The influence of air temperature, microwave application and vacuum impregnation or pulsed vacuum osmotic dehydration as pre-treatments on convective drying and rehydration kinetics of apple and strawberry and also on some characteristics of the dried and rehydrated samples has been studied. It was observed that air drying at 50°C was faster than this at 30°C, which implies a lower degree of sample's browning. Also, the higher air temperature induces a greater change on the pectin solubility, as a result of an increase on the water soluble fraction and a decrease on both the oxalate soluble fraction and the residual pectins, which implies a higher mechanical resistance of the dried samples. Microwave application to hot air drying provokes a great reduction on process time and changes on pectin solubility similar but greater than those observed when increasing the air temperature on the convective drying. Hence, when applying microwaves, dried strawberry and apple showed a higher mechanical resistance and moreover, strawberry kept better the initial shape. However, the structural damage associated to dehydration is reflected on the lower mechanical resistance of the corresponding rehydrated samples and also in a lower capacity to retain the liquid phase. On the other hand, microwave application induces an increase in luminosity of the strawberry, which shows an anthocyanin content loss. Related to pre-treatments, vacuum impregnation of apple increases translucency and remarks the colour changes that take place during drying, although the osmotic pre-treatment did not affect significantly its colour. Both kinds of pre-treatments implied higher process times when using convective drying but no significant differences were found when applying microwaves. Nevertheless, both promoted pectic solubilization which, together with the higher sugar content when dried, could explain the higher mechanical resistance observed on the pre-treated samples. At the same time, the sugar added during the osmotic pre-treatment contributes to a better mechanical response of the tissue when rehydrated and to a lower decrease on the sample volume after drying. Taking into account all these considerations, it is recommended to use these pre-treatments and microwave application to hot air drying in order to obtain dried apple or strawberry with a high mechanical resistance, although colour changes would be greater in these cases, especially in apple. The higher the sugar introduced on the product with the pre-treatment, the higher the resistance of the dried fruit to fracture, but there is also a higher probability for obtaining a product at rubbery state. If the objective of the process is mainly to obtain a product with good response to further rehydration, osmotic pre-treatment is recommended as well, but not microwave application to convective drying.

ISBN: 9780542601675Subjects--Topical Terms:

1017813
Agriculture, Food Science and Technology.

Influence of drying method on quality parameters related to the structure and color of dried apple and strawberry.
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245 1 0 $a Influence of drying method on quality parameters related to the structure and color of dried apple and strawberry.
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500 $a Advisers: Nuria Martinez Navarrete; Eugenia Martin Esparza.
502 $a Thesis (Dr.)--Universidad Politecnica de Valencia (Spain), 2006.
520 $a The influence of air temperature, microwave application and vacuum impregnation or pulsed vacuum osmotic dehydration as pre-treatments on convective drying and rehydration kinetics of apple and strawberry and also on some characteristics of the dried and rehydrated samples has been studied. It was observed that air drying at 50°C was faster than this at 30°C, which implies a lower degree of sample's browning. Also, the higher air temperature induces a greater change on the pectin solubility, as a result of an increase on the water soluble fraction and a decrease on both the oxalate soluble fraction and the residual pectins, which implies a higher mechanical resistance of the dried samples. Microwave application to hot air drying provokes a great reduction on process time and changes on pectin solubility similar but greater than those observed when increasing the air temperature on the convective drying. Hence, when applying microwaves, dried strawberry and apple showed a higher mechanical resistance and moreover, strawberry kept better the initial shape. However, the structural damage associated to dehydration is reflected on the lower mechanical resistance of the corresponding rehydrated samples and also in a lower capacity to retain the liquid phase. On the other hand, microwave application induces an increase in luminosity of the strawberry, which shows an anthocyanin content loss. Related to pre-treatments, vacuum impregnation of apple increases translucency and remarks the colour changes that take place during drying, although the osmotic pre-treatment did not affect significantly its colour. Both kinds of pre-treatments implied higher process times when using convective drying but no significant differences were found when applying microwaves. Nevertheless, both promoted pectic solubilization which, together with the higher sugar content when dried, could explain the higher mechanical resistance observed on the pre-treated samples. At the same time, the sugar added during the osmotic pre-treatment contributes to a better mechanical response of the tissue when rehydrated and to a lower decrease on the sample volume after drying. Taking into account all these considerations, it is recommended to use these pre-treatments and microwave application to hot air drying in order to obtain dried apple or strawberry with a high mechanical resistance, although colour changes would be greater in these cases, especially in apple. The higher the sugar introduced on the product with the pre-treatment, the higher the resistance of the dried fruit to fracture, but there is also a higher probability for obtaining a product at rubbery state. If the objective of the process is mainly to obtain a product with good response to further rehydration, osmotic pre-treatment is recommended as well, but not microwave application to convective drying.
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