Non-enzymatic browning in an 11 °Brix apple juice during thermal treatment was studied through ch... more Non-enzymatic browning in an 11 °Brix apple juice during thermal treatment was studied through changes in colour by colorimetric parameters (A 420 , colour difference and index of browning), and HMF and sugars (fructose, glucose and sucrose) evolution. Zero and first order kinetics were applied to describe evolution of colorimetric parameters. The formation of HMF was fitted to auto-catalytical and first order equations. Sucrose tends to disappear according to a first order kinetics giving fructose and glucose. For the reducing sugars (fructose and glucose), no clear tendency was observed. The effect of temperature can be described by an Arrhenius-type equation.
espanolEn este trabajo se presenta un estudio sobre el comportamiento tixotropico de leches conde... more espanolEn este trabajo se presenta un estudio sobre el comportamiento tixotropico de leches condensadas, asi como de su evolucion a lo largo de un proceso de almacenamiento. Para cuantificar dicho comportamiento tixotropico se han utilizado los modelos de Hahn et al. y de Weltman. EnglishThis work shows a research on the rheologic behaviour of milk samples with different content in their components. Having a commercial sample of concentrated milk, different samples diluted in distilled water can be prepared. To begin with, the effect of the temperature on the rheologic behaviour of the sample of concentrated milk is studied, adjusting the variation of the viscosity to an equation of the exponential type. For a fixed 25oC temperature it is studied the rheologic of the different samples which have been obtained by dilution and therefore an expression that describes the variation of the rheologic behaviour with the concentration is obtained. It has been observed that the sample of conc...
In this paper is reported a study of rheological caracterization of blackcurrant juices and a new... more In this paper is reported a study of rheological caracterization of blackcurrant juices and a newtonian behaviour is described. The effect of the temperature on a 66,5o Brix concentrate is studied and an equation of Arrhenius type to describe this influence is found. The influence of the soluble solids contents on the viscosity of the blackcurrant juices at 25oC was also studied and two models of expressions (potential and exponential) were tried to describe this effects.
In this paper is reported a study of rheological caracterization of blackcurrant juices and a new... more In this paper is reported a study of rheological caracterization of blackcurrant juices and a newtonian behaviour is described. The effect of the temperature on a 66,5o Brix concentrate is studied and an equation of Arrhenius type to describe this influence is found. The influence of the soluble solids contents on the viscosity of the blackcurrant juices at 25oC was also studied and two models of expressions (potential and exponential) were tried to describe this effects.
... de distinto grado. El oscurecimiento se debe principal-mente al pardeamiento no enzimàtico, p... more ... de distinto grado. El oscurecimiento se debe principal-mente al pardeamiento no enzimàtico, producido por la reacción de Maillard entre los azúcares reductores y grupos amino libres (Ibarz et al., 1989). El par-deamiento ...
Alimentaria Revista De Tecnologia E Higiene De Los Alimentos, 2001
In the fruit juices and purees industrial manufacturing, there are some steps where the fruit pul... more In the fruit juices and purees industrial manufacturing, there are some steps where the fruit pulp is ground and other steps where treatments at high temperature are applied. In these steps dark colors called browning can appear, causing deterioration on the final products. There are two important browning groups: enzymatic, due to the polyphenoloxidase enzyme present in the fruit tissue which acts on phenolic substrates also present in the fruit pulp starting a reactions sequence producing a compounds named melanins, causing the dark colors on the final products. There are influence of the fruit degree maturation on the enzymatic browning in such a way that the more immature the fruit the more rapid the browning is observed. The second browning group is non-enzymatic. This deterioration is due to the polymers called melanoidins formed from three principal chemical reactions: Maillard, caramellisation and ascorbic acid decomposition. Studies carried out to establish a kinetic model on the color evolution lead to a model based on a two-stage mechanism applied to the color evolution. The first stage, color formation, is zero order and the second stage, pigment destruction, is first-order. The most important factors influencing on the reaction rate are: temperature, monosaccharides and aminoacids concentration, water activity and pH.
Because of the non-enzymatic browning reactions are the main factor in the browning of fruit juic... more Because of the non-enzymatic browning reactions are the main factor in the browning of fruit juices and concentrates, this paper presents a review and a theoretical study of the use of the cinetic models to these reactions. Simple cinetic models, used in the determination of the color generation rate, and the variables, which have influence in the non-enzymatic browning rate, are described and analyzed.
In the present work the cinetics of formation of Hidroxymethylfurfural (HMF) on concentrate pear ... more In the present work the cinetics of formation of Hidroxymethylfurfural (HMF) on concentrate pear juice of 70,4o Brix stored at different temperatures are studied. Two cinetical models of reaction, autocatalitics of second orden one of them and first order, are essayed, reaching similar results applying both models. At low temperatures (4oC) the formation of HMF is almost inappreciable during all time of storing.
The rheological characterization of food is important for efficient product and process design. A... more The rheological characterization of food is important for efficient product and process design. Although its importance in semi-arid regions, there are only a few studies regarding the rheological properties of cactus pear products in the literature. The present work has used the Mitschka-Briggs-Steffe method for evaluation of the rheological behavior of cactus pear concentrated pulps. The pulps have shown pseudoplastic behavior. The flow behavior index (n) shows a constant value in the evaluated conditions, and its average value was considered in the evaluated temperature and concentration range. The consistency index (k) has shown dependency of concentration and temperature, being well modeled by a modified Arrhenius equation. Thus, the rheological parameters of cactus pear concentrated pulps can be obtained using a single equation, related with temperature, concentration and shear rate. The obtained data are potentially useful for future studies on product development, food prope...
Non-enzymatic browning in an 11 °Brix apple juice during thermal treatment was studied through ch... more Non-enzymatic browning in an 11 °Brix apple juice during thermal treatment was studied through changes in colour by colorimetric parameters (A 420 , colour difference and index of browning), and HMF and sugars (fructose, glucose and sucrose) evolution. Zero and first order kinetics were applied to describe evolution of colorimetric parameters. The formation of HMF was fitted to auto-catalytical and first order equations. Sucrose tends to disappear according to a first order kinetics giving fructose and glucose. For the reducing sugars (fructose and glucose), no clear tendency was observed. The effect of temperature can be described by an Arrhenius-type equation.
espanolEn este trabajo se presenta un estudio sobre el comportamiento tixotropico de leches conde... more espanolEn este trabajo se presenta un estudio sobre el comportamiento tixotropico de leches condensadas, asi como de su evolucion a lo largo de un proceso de almacenamiento. Para cuantificar dicho comportamiento tixotropico se han utilizado los modelos de Hahn et al. y de Weltman. EnglishThis work shows a research on the rheologic behaviour of milk samples with different content in their components. Having a commercial sample of concentrated milk, different samples diluted in distilled water can be prepared. To begin with, the effect of the temperature on the rheologic behaviour of the sample of concentrated milk is studied, adjusting the variation of the viscosity to an equation of the exponential type. For a fixed 25oC temperature it is studied the rheologic of the different samples which have been obtained by dilution and therefore an expression that describes the variation of the rheologic behaviour with the concentration is obtained. It has been observed that the sample of conc...
In this paper is reported a study of rheological caracterization of blackcurrant juices and a new... more In this paper is reported a study of rheological caracterization of blackcurrant juices and a newtonian behaviour is described. The effect of the temperature on a 66,5o Brix concentrate is studied and an equation of Arrhenius type to describe this influence is found. The influence of the soluble solids contents on the viscosity of the blackcurrant juices at 25oC was also studied and two models of expressions (potential and exponential) were tried to describe this effects.
In this paper is reported a study of rheological caracterization of blackcurrant juices and a new... more In this paper is reported a study of rheological caracterization of blackcurrant juices and a newtonian behaviour is described. The effect of the temperature on a 66,5o Brix concentrate is studied and an equation of Arrhenius type to describe this influence is found. The influence of the soluble solids contents on the viscosity of the blackcurrant juices at 25oC was also studied and two models of expressions (potential and exponential) were tried to describe this effects.
... de distinto grado. El oscurecimiento se debe principal-mente al pardeamiento no enzimàtico, p... more ... de distinto grado. El oscurecimiento se debe principal-mente al pardeamiento no enzimàtico, producido por la reacción de Maillard entre los azúcares reductores y grupos amino libres (Ibarz et al., 1989). El par-deamiento ...
Alimentaria Revista De Tecnologia E Higiene De Los Alimentos, 2001
In the fruit juices and purees industrial manufacturing, there are some steps where the fruit pul... more In the fruit juices and purees industrial manufacturing, there are some steps where the fruit pulp is ground and other steps where treatments at high temperature are applied. In these steps dark colors called browning can appear, causing deterioration on the final products. There are two important browning groups: enzymatic, due to the polyphenoloxidase enzyme present in the fruit tissue which acts on phenolic substrates also present in the fruit pulp starting a reactions sequence producing a compounds named melanins, causing the dark colors on the final products. There are influence of the fruit degree maturation on the enzymatic browning in such a way that the more immature the fruit the more rapid the browning is observed. The second browning group is non-enzymatic. This deterioration is due to the polymers called melanoidins formed from three principal chemical reactions: Maillard, caramellisation and ascorbic acid decomposition. Studies carried out to establish a kinetic model on the color evolution lead to a model based on a two-stage mechanism applied to the color evolution. The first stage, color formation, is zero order and the second stage, pigment destruction, is first-order. The most important factors influencing on the reaction rate are: temperature, monosaccharides and aminoacids concentration, water activity and pH.
Because of the non-enzymatic browning reactions are the main factor in the browning of fruit juic... more Because of the non-enzymatic browning reactions are the main factor in the browning of fruit juices and concentrates, this paper presents a review and a theoretical study of the use of the cinetic models to these reactions. Simple cinetic models, used in the determination of the color generation rate, and the variables, which have influence in the non-enzymatic browning rate, are described and analyzed.
In the present work the cinetics of formation of Hidroxymethylfurfural (HMF) on concentrate pear ... more In the present work the cinetics of formation of Hidroxymethylfurfural (HMF) on concentrate pear juice of 70,4o Brix stored at different temperatures are studied. Two cinetical models of reaction, autocatalitics of second orden one of them and first order, are essayed, reaching similar results applying both models. At low temperatures (4oC) the formation of HMF is almost inappreciable during all time of storing.
The rheological characterization of food is important for efficient product and process design. A... more The rheological characterization of food is important for efficient product and process design. Although its importance in semi-arid regions, there are only a few studies regarding the rheological properties of cactus pear products in the literature. The present work has used the Mitschka-Briggs-Steffe method for evaluation of the rheological behavior of cactus pear concentrated pulps. The pulps have shown pseudoplastic behavior. The flow behavior index (n) shows a constant value in the evaluated conditions, and its average value was considered in the evaluated temperature and concentration range. The consistency index (k) has shown dependency of concentration and temperature, being well modeled by a modified Arrhenius equation. Thus, the rheological parameters of cactus pear concentrated pulps can be obtained using a single equation, related with temperature, concentration and shear rate. The obtained data are potentially useful for future studies on product development, food prope...
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