Cloud stability

Apples (Red Belle de Boskoop, Jonagold or Mutzu) were cut and milled (1.5 mm) and 5% (w/w) of a 2% ascorbic acid solution was added immediately. Enzyme preparations (25 mg enzyme protein / kg mash) were added and the mash was incubated for 2 hours at 20°C whereafter it was pressed. The resulting apple juice was pasteurised at 85°C to discontinue further enzyme degradation. The cloud was measured as turbidity in EF/F units [15]. The cloud stability was determined by a centrifugation test as the amount of turbidity remaining after centrifugation at 4,200 x g for 15 minutes [15]. 

Enzyme Turbidity before centrifugation Increase in turbidity relative to untreated control % Cloud stability %... 

The chromatogram of the serum from juice with poor cloud stability obtained after mash treatment with the enzyme mixture including the pectin depolymerisation enzyme combination of polygalacturonase and pectin methyl esterase is seen to be lacking the A-peak. High molecular pectin is therefore considered to be a prerequisite for a cloud stable juice. 

Figure 8. Size distribution corrections as a function of particle size for samples taken at 15,000 meters altitude at various times after cloud stabilization...

Protein-fortified soft drinks have been developed and marketed but there are no mainstream brands currently successful in the world. Generally the protein source used is dairy based usually whey or skimmed milk. Great care must be taken to prevent precipitation as the protein is acidified through its isoelectric point to a microbiologically safe pH and it is necessary to use stabilisers for long-term cloud stability. 

Even at these levels, pectin influences juice quality, both positively and negatively, by its contribution to viscosity, gelation, and cloud stability. 

Since PL cannot attack deesterified pectin, cloud stabilization of PE active juice requires relatively large quantities of PL to compete with PE for esterified pectin. 

Cloud loss may also be prevented by enzymic destruction of low ester pectins prior to their precipitation as pectates. Commercial fungal PG preparations (AO, Al) or PG derived from yeast (A2) have been used successfully to stabilize cloud of unpasteurized PE active juice. As only the low ester pectins need be destroyed to prevent cloud loss, considerably less PG is required than PL (30). Cloud stabilization with pectinases permits production of cloud stable juices with lower pasteurization temperatures (AO). 

Qin, L., Xu, S., and Zhang, W. 2005. Effect of enzymatic hydrolysis on the yield of cloudy carrot juice and the effects of hydrocolloids on color and cloud stability during ambient storage. J. Sci. Food... 

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... 

To maintain cloud stability in fruit juices, high-temperature-short-time (HTST) pasteurization is used to deactivate pectolytic enzymes. Pectin is a protective colloid that helps to keep insoluble particles in suspension. Cloudiness is required in commercial products to provide a desirable appearance. The destruction of the high levels of pectin-esterase during the production of tomato juice and puree is of vital importance. The pectinesterase will act quite rapidly once the tomato is broken. In the so-called hot-break method, the tomatoes are broken up at high temperature so that the pectic enzymes are destroyed instantaneously. 

The taste of these products is usually clean but flat and less aromatic than normal juice. A result of the higher pectin content, pulp wash products usually have an extremely good turbidity and cloud stability which makes them well suited for the production of drinks with low juice content. 

In order to produce clear juice the cloudy product is treated with pectolytic enzymes to degrade the pectic substances which are responsible for the cloud stability of the cloudy juice. The treatment time depends on the activity of the enzymes and the temperature respectively. Several years ago the industry had no enzymes which were able to work in very acid juice environments (e.g. lemon juice). However, in the meantime new types were developed which are capable of treating acid juices satisfactorily. Some fruit juices contain substances which cannot be removed with pectolytic enzymes and which require other specific enzymatic products to eliminate turbidity, e.g. starch in apple juice requires a suitable amylase. 

Particle-size distribution and zeta-potential measurements of CAJ and CAJ - - CR were performed on a Malvern Zetasizer 3000 (Malvern Instruments Inc., London). Both CAJ and CAJ - - CR were centrifuged at 4200 X g during 15 min to remove unstable particles (Stahle-Hamatschek, 1989 Genovese et al., 1997). Cloud stability (S%) was calculated with the expression (Genovese and Lozano, 2001 Mensah-Wilson et al., 2002) ... 

Genovese, D.B., Elustondo, M.P., and Lozano, J.E. Color and cloud stabilization in cloudy apple juice by steam heating during crushing, /. Food Sci., 62,1171,1997. 

Mensah-Wilson, M., Reiter, M., Bail, R., Neidhart, S., and Carle, R. Cloud stabilizing potential of pectin on pulp-containing fruit beverages. Fruit Process., 2,47,2002. 

Stahle-Hamatschek, S. Cloud composition and its effect on cloud stability in natural cloudy apple juices, Flussiges Obst., 56, 543,1989. 

Pectinases, cellulases and hemicellulases are used for clarification of fruit juices, juice extraction, improvement of cloud stability of vegetable and fruit juices and nectars, liquefaction and maceration of fruits and vegetables, reduction of cooking time of pulses and improvement of rehydration characteristics of dried vegetables. The chemical basis of these treatments and of the consequential changes in sensory and nutritional quality are discussed. 

Goodner, J.K., Braddock, R.J., Parish, M.E., and Sims, C.A. 1999. Cloud stabilization of orange juice by high pressure processing. Journal of Food Science 64 699-700. 

Effect of pure and technical enzyme preparations on cloud stability... 

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