Apple juice viscosity

Pulp from ripe Golden apple was pressed in a mortar and filtered, thus obtaining a cloudy and dense juice. Potassium metabisulphite was added as antioxidant at a final concentration of 0.15 mg/mL. The pH of the prepared apple juices was 4.1 4.3. Depectinisation experiments were carried out loading the juice in the packed bed reactor and recycling for 30 min at 25 "C. The reaction mixture was then collected and the percentage reduction of viscosity measured as above described. The y-alumina spheres were abundantly washed with distilled water before performing the successive batch reaction. 

The immobilised Pectolyase Y-23 was used to perform consecutive depectinisations of a cloudy apple juice in batch reactions. After five reaction cycles, the percentage reduction of viscosity was greater than 90%. The viscosity of the apple juice feed through a bed of inactive y-alumina spheres remains unchanged thus confirming that the viscosity loss attributable to pectin adsorption on the carrier is negligible. The alcohol tests, performed on the juices previously treated with the... 

Apple, pear, orange and grape juices are all clarified by ultrafiltration. Ultrafiltration of apple juice is a particularly successful application. Approximately 200 plants have been installed, and almost all US apple juice is clarified by this method. In the traditional process, crude filtration was performed directly after crushing the fruit. Pectinase was added to hydrolyze pectin, which reduced the viscosity of the juice before it was passed through a series of decantation and... 

This behaviour ean be quahtatively explained by Equation (12.7) since 4>m increases as the width of the size distribution increases. A good example of the ef-feets that particles and polymers have on the rheological behavior of liquids is cloudy apple juice (Genovese and Lozano, 2000). The aqueous milieu of the juice is a solution of sugar, acids and salts (i.e., the clarified juice) that contains charged particles (0.25-5 pm in size) and pectin as a colloidal dispersion. The viscosity of cloudy apple juice has been described by the expression ... 

Genovese, D.B., and Lozano, J.E. (2000). Effect of cloud particle characteristics on the viscosity of cloudy apple juice. J. FoodSci. 65, 641-645. 

Although pectic enzymes are used universally by the apple juice industry, the actual clarification mechanism has not been completely elucidated. Endo showed 186, 187) that hydrolysis of pectin, accompanied by a decrease in viscosity of the juice, is the principal step during clarification. Endo separated the clarification process into three phases a pectin fraction is solubilized viscosity decreases and previously col-... 

The effect of temperature and concentration on the viscosity of concentrated apple juice can be combined to obtain a single approximate equation that can be used for estimating viscosity as a function of both temperature and concentration (°Brix) ... 

Bayindirli, L. 1992. Mathematical analysis of variation of density and viscosity of apple juice with temperature and concentration. J. Food Proc. Preser. 16 23-28. 

Permeate flux decreases with an increase in feed concentration. This phenomenon can be attributed to the reduction of the driving force due to decrease of the vapor pressure of the feed solution and exponential increase of viscosity of the feed with increasing concentration. The DCMD flux gradually increases with an increase in temperature difference between feed and cooling water. Lagana et al. [63] reported that the viscosity of apple juice at high concentration induces severe temperature polarization. It may be noted that temperamre polarization is more important than concentration polarization, which is located mainly on the feed side. 

Enhancement of transmembrane flux has been shown in OMD of grape juice pretreated by UF [131]. The increase in flux has been attributed to a reduction in the viscosity of the concentrated juice-membrane boundary layer as the result of removal of high-molecular weight biopolymers present in juice. UF is a powerful method for removing natural polymers (polysaccharides, proteins) from fruit and vegetable juices. Lukanin et al. [12] have improved the concept of (UF + OMD), by enzymatic pretreatment of the apple juice prior to the UF step. Introduction of an additional enzymatic deproteinization step with the pectinase/amylase treatment of apple juice followed by UF has yielded minimal biopolymer content. Such a treatment is found to enhance transmembrane flux during concentration of clarified juice by MD. As in the case of grape juice this has been... 

Most of these products are fruit-flavored sugar syrups. For example, apple syrup is made by concentrating apple juice (by broiling or vacuum evaporation), then adding sugar until a syrup of the desired thickness (viscosity) is obtain. Syrups that have citrus fruit flavors may bre made in much the same way, except that they may also contain citrus peel and/or essential oil extracted from the peel. 

If we compare liquefaction to maceration, more activities are needed to liquefy the cell wall. Since 1991, new pectinases activities such as rhamnogalacturonase, pectin acetylesterase and xyloglucanases complex have been found to be important in the apple liquefaction by Henck Schols, Jean-Paul Vincken and Voragen [3]. The cellulose-xyloglucan complex accounts approximatively 57% of the apple cell-wall matrix. In a liquefaction process, an efficient enzymic degradation of this complex is crucial to increase the sugars extraction, to decrease the viscosity of the pulp then to be able to ultra-filtrate the juice without second depectinisation, at last to have negative alcohol tests required by some concentrate customers. 

Apples were chopped and mashed to a fine puree. Apple mash was treated with enzyme preparation and incubated for 2 hours at 55°C. Viscosity of mash was measured several times using a Brookfield DC3 viscometer with Helipath stand attachment and TD spindle. After two hours of incubation sanple was coitriftig for 20 minutes at 10.000 rpm. Volume, clarity, pH and brix of the juices were measured. The pectin level of the juices was assessed by a standard alcohol test. 

Apple application e)q)aiments for producing ple juice show a clear benificial effect liumnogalacturonase in combination with a pectinase was added to the process. As can be seen from figure 5 rhamnogalacturonase has a clear positive influence on viscosity-reduction. Rhamnogalacturonase also prevents formation of haze in juices and therefore gives a stable juice. 

The Arrhenius equation did not describe very well the influence of temperature on viscosity data of concentrated apple and grape juices in the range 60-68 °Brix (Rao et al., 1984, 1986). From non-linear regression analysis, it was determined that the empirical Fulcher equation (see Ferry, 1980 p. 289, Soesanto and Williams, 1981) described the viscosity versus temperature data on those juice samples better than the Arrhenius model (Rao et al., 1986) ... 

BecaiKe depectinized and filtered apple and grape Juices are Newtonian fluids, equations were derived by Bayindirli (1992,1993) that can be used to estimate their viscosities as a function of concentration and temperature. The equation for viscosity of both apple and grape Juices is of the form ... 

Rao et al. (1984) studied the role of concentration and temperature on the viscosity of concentrated depectinized and filtered apple and grape juices. At a constant temperature, the effect of concentration could be well described by an exponential relationship. For example, at 20°C, the effect of concentration ( 41-68 °Brix) on the viscosity of apple concentrates was described by the equation (7 = 0.947) ... 

Thus a more accurate estimate of the viscosities of concentrated apple and grape juices can be obtained by incorporating the value of calculated using either Equation 5.7 or 5.8 at a specific concentration in Equation 5.6. Although two separate equations were derived for the apple and grape juice concentrates, one could easily justify a single equation that would be reasonably applicable to both concentrates. 

The reduction in viscosity of the juice extracted from such mashes facilitates the concentration and significantly increases the juice yield from apple mash by over 10% [12]. Especially important is the enzyme support for juice extraction from fmit containing large amounts of pectins, e.g. black currants, certain grapes and other fmit. 

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