Apple juice, clarification

Figure 6.24 Ultrafiltration flux in apple juice clarification as a function of the volumetric feed-to-residue concentration factor. Tubular polysulfone membranes at 55 °C [27]. Reprinted from R.G. Blanck and W. Eykamp, Fruit Juice Ultrafiltration, in Recent Advances in Separation Techniques-III, N.N. Li (ed.), AIChE Symposium Series Number 250, 82 (1986). Reproduced by permission of the American Institute of Chemical Engineers. Copyright 1986 AIChE. All rights reserved...

Riedl K., Girard B., and Lencki W., Influence of membrane stmeture on fouUng layer morphology during apple juice clarification. Journal of Membrane Science 139 1998 155-166. 

Bissessur, J., Permaul, K., and Odhav, B. 2001. Reduction of patulin during apple juice clarification. J. FoodProt. 64, 1216-1219. 

FIGURE 18,1-4 Schematic diagram of process using UF for apple juice clarification. 

Abcor (now a division of Koch Industries) installed the first industrial ultrafiltration plant to recover electrocoat paint from automobile paint shop rinse water in 1969. Shortly afterwards, systems were installed in the food industry for protein separation from milk whey and for apple juice clarification. The separation of oil emulsions from effluent wastewaters has also become a significant application. The current ultrafiltration market is approximately US 200 million/ year, but because the market is very fragmented no individual end-use segment is more than US 10-30 million/year. In the chemical and refining industries, the principal application of ultrafiltration is the treatment of oily wastewater. 

Gravity and centrifugal sedimentation can be combined for the same sample in order to directly determine Stokes diameter for a wide range of particle sizes. In such a way conversion are avoided and a mass distributions, applicable to processes where gravimetric efficiencies are relevant, can be properly derived. Ortega-Rivas and Svarovsky (1994) determined particle sizes distributions of fines powders using a combined Andreasen Pipette-pipette centrifuge method. They derive relations useful to model hydrocyclone separations, which were later employed to describe apple juice clarification. 

Veleirinho and Lopes-da-Silva produced self-supporting nanoflbrous PET membranes with good mechanical strength and applied them in the apple juice clarification process [86]. The experimental findings demonstrated that the ENM had a higher throughput, resulting in more economical operations than traditional processes. The same approach could be transferred to other applications in the food industry. 

Veleiiinho B, Lopes-da-Silva JA (2009) Application of electrospun poly(ethylene terephtha-late) nanofiber mat to apple juice clarification. Process Biochem 44 353-356... 

Use of ultrafiltration (UF) membranes is becoming increasingly popular for clarification of apple juice. AH particulate matter and cloud is removed, but enzymes pass through the membrane as part of the clarified juice. Thus pasteurization before UF treatment to inactivate enzymes prevents haze formation from enzymatic activity. Retention of flavor volatiles is lower than that using a rack-and-frame press, but higher than that using rotary vacuum precoat-filtration (21). 

Rhamnogalacturonase may be useful in the prevention of haze formation in apple Juice concentrates. In combination with other enzymes it mi t improve liquefaction, resulting in increase juice yield and clarification. 

Limitations Some applications which seem ideal for MF, for example the clarification of apple juice, are done with UF instead. The reason is the presence of deformable solids which easily plug and blind an MF membrane. The pores of an ultrafiltration membrane are so small that this plugging does not occur, and high fluxes are maintained. UF can be used because there is no soluble macromolecule in the juice that is desired in the filtrate. There are a few other significant applications where MF seems obvious, but is not used because of deformable particle plugging. 

Cloud stability in citrus juices Pectin manufacture from citrus pomace Distillates from fermented fruit pulps Enzymatic maceration of fruits and vegetables Self-clarification of lemon/lime and apple juices Pressing characteristics of citrus pomace Ca2 -firming of fruits and vegetables... 

Clarification (apple juice, pear juice, grape musts or wines)... 

Clarification apple juice Enzymic juice extraction... 

Versteeg et al. (50) have isolated various multiple forms of pectin esterases in oranges and shown that they differ in affinity to pectins and pectates and in heat stability and therefore may play different roles in cloud loss phenomena. One form (about 5% of the total PE activity) was found to be much more heat stable than the other forms it was also active at low pH (2.5) and at low temperatures. Another form did not cause self-clarification for this enzyme a similar mode of attack was proposed as for fungal pectin esterases which produce low-ester pectins less sensitive to calcium. Multiple forms of pectin esterases are present in the fruits of all of the orange varieties and citrus species tested. The two isoenzymes known to be responsible for cloud loss and gelation in citrus products were found to occur in all of the component parts of the orange fruit (51). In the French cider industry the endogenous PE of apple is used for the self-clarification of apple juice (52). 

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-... 

Recently Ishii and Yokotsuka 170, 171,172) reported that a purified pectin lyase from AspergiUus sojae initiated the clarification reaction in apple juice. This enzyme has a molecular weight of 32,000 and a pH optimum of 5.5 for 68% esterified pectin (pH 7.0 for 98% esterified pectin). Divalent cations stimulated activity and shifted the pH optimum towards neutrality. The enzyme was stable between pH 4 and 7. One mg of purified pectin lyase (76.5 units of activity) could clarify 30-40 liters of apple juice within one hour at 40°C [0.018-0.024 units needed to clarify 10 ml (172)]. At the point of complete clarification 50% of the pectin in the juice had been converted to a form soluble in 75% ethanol. 

Clarification of apple juice. Inorganic membranes have been utilized in two ways in the production of apple juice. One is to clarify pressed or prefiltered apple juice and the other is to extract clarified apple juice directly from apple puree or pomace. Microfiltration of apple juice has been one of the most successful commercial applications of inorganic membranes. 

Venkataraman, K., M.T. Giles and P.K. Silverberg, 1988, Ceramic membrane applications in juice clarification a case study, presented at 2nd Annual Meeting of North Am. Membr. Soc., Syracuse, N.Y., USA (details given in Inorganic Membr. Synth., Charact. Appl., RR. Bhave, Ed., p. 239). 

All the above mentioned evaporators can be equipped with aroma recovery units which for better heat balance can be integrated directly into the evaporator stages. Apple juice evaporators are designed in such a way that the de-aromatised juice can be taken out of the evaporator with approx. 50°C for clarification. The clarified juice is fed back to the next evaporator stage at the same temperature. The evaporation process is not interrupted and the evaporator can operate smoothly and uniformly. 

Ultrafiltration and microfiltrafion are employed successfully on an industrial scale for the clarification of juices (e.g. apple juice, pear juice, etc.). Ultrafiltration saves filter aids and fining aids which have to be used when operating conventionally with rotating vacuum filters or plate filters and precoat filters. On the other hand, the power consumption of an ultrafiltration system is high and so is the replacement cost of membranes. 

In this regard, a study in the USA is of interest which investigates the loss of the aroma of apple juice when using various filtration methods for clarification (M.F. Sancho u. M.A. Rao, Department of Food Science and Technology, New York State Agricultural Experiment Station, Cornell University Geneva, New York) [17]. 

The application of ceramic membranes in the production of fruit juices is a well established technique [3,6,12,14,44-50]. A very wide range of fruit juices is designated (apple, pear, peach, orange, grapefruit, pineapple, kiwi fruit, strawberry, cranberry, carrot, beet) the clarification of apple juice seems to be the main application [6,14,44r-49]. 

Endo, A. Studies on the enzymatic clarification of apple juice, Agric. Biol. Chem., 2,25, 1965. Beveridge, T. Haze and cloud in apple juices, Crit. Rev. Food Sci. Nutr., 37, 75, 1997. 

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