Haze and sediment

A second effect of a raised extraction temperature may be to increase the solubility of some of the less soluble plant components. This could lead to hazing and sedimentation since these components slowly come out of solution again on standing during storage. This may not be a problem if the extract is to be used in a cloudy drink. 

Grape and wine proteins have been of interest to winemakers for many years. This interest is primarily due to the ability of these proteins to aggregate together in finished white wines and form unattractive hazes and sediments. Proteins are significant in wine because they are a nuisance Endogenous wine proteins, of course, also have other roles in wine and have been examined for their impact on the aroma and... 

Although proteins and peptides are minor constituents of wine, they make a significant contribution to the quality of product and play an important role in the wine quality as they affect taste, clarity, and stability. Chitinases and TLP persist through the vinification process and may cause hazes and sediments in bottled wines during the storage due to protein denaturing and aggregating with mechanisms not fully... 

The formol index (total free amino acids) was the best predictor of browning rate of concentrates during storage for a given commodity. While haze and sediment formation were quality factors of major interest in this study, none of the juices or concentrates produced were particularly troublesome in this regard. The phenolic and protein profiles should still provide a reference with which unstable experimental or commercial samples can be compared in the future, however. In addition to color and appearance, quality factors of flavor, astringency, bitterness, viscosity and mouthfeel warrant investigation. 

In some cases, however, the formation of salts and complexes is an unwanted phenomenon, as protein salts and complexes with polyphenols form hazes and sediments in preserved fruit, fruit juices and beer. Protein hazes can also form in white wines after bottling, where the main factor is inorganic sulfate ions. Protein complexes with transition metals are often coloured, and their formation in processed foods is generally undesirable. An example is the protein conalbumin occurring in egg white, which readily forms coloured complexes with metal ions (pink with Fe +, yellow with Cu + and Mn +) in media of pH > 6 through tyrosine and histidine residues of the polypeptide chain. Complexes with iron ions often cause discoloration of egg products, but in media with pH < 4, these complexes dissociate to the original colourless compounds. 

The samples to be measured should be clear and contain no haze or sediments however, some colloidal materials may be suspended in the sample, causing scattering of light and a cloudy appearance (haze). This scattering of light needs to be corrected for by reading at a wavelength where no absorbance of the sample occurs, i. e., 700 nm. 

Appearance Clear to slight haze free from suspended matter and sediment Color Colorless to straw yellow Viscosity at 25C (77F), cst 1300 Specific Gravity at 25C (77F) 0.96 Refractive Index at 25C (77F) 1.407 Flash Point, Closed Cup, C (F) 141 (285)... 

Appearance Clear to slight haze free from suspended matter and sediment... 

Table III gives the protein content and percent haze readings for the single-strength apple juice and reconstituted apple juice concentrate samples. All of the samples showed high clarity as evidenced by the low haze readings, none having a propensity towards haze or sediment formation. A decrease in total soluble proteins was observed with increased storage time of apple fruit. Fining resulted in ca. 25-50% reduction in total soluble protein.

None of the bottled pear juices or reconstituted pear juice samples showed particular problems of haze or sediment formation (Table IV). SO2 addition, which protected phenolics from oxidation, had no influence on the clarity of these samples. Juice from ripened d Anjou and Cornice fruit had slightly higher % haze readings than juice from unripe fruit. All of these samples were subjected to standard fining procedures which may account for their stability and clarity (6). 

Interpretation Haze and/or sediment suggests the likelihood of future instability. If the test tube receiving citric acid and H2O2 shows no sign of haze, use of the acid should be considered. 

Examination of storage temperature and sediment concentration on haze formation in canola oil showed if the sediment concentration was <50 ppm more than 24 h was required to observe a sediment irrespective of the temperature (0-32°C). At 25°C, canola oil samples containing 50 ppm required 2 days before it became cloudy. Oil samples containing 25 ppm sediment, however, remained clear for a month. The optimum temperature for sediment formation appeared to be 5 C (Table 1.5). 

The dramatic changes in haze particle size seen with alterations in protein-to-polyphenol ratio in a model system, would, if this also occurs in real beverages, have profound effects on both sedimentation (e.g., cold maturation in a tank or centrifugation) and filtration operations. 

In procedure 2, approximately 900 mL of fuel is placed into a 1-L clear glass jar and examined visually for clarity. Fuel clarity is rated by placing a standard bar chart behind the sample and comparing its visual appearance with the standard haze rating photos. The sample is then swirled and examined for visual sediment or water drops below the vortex. 

The cloudy juice contains colloids which increase the viscosity of the juice (and prevent sedimentation) while at the same time binding suspended particles by virtue of electric charges. These colloids which are responsible for the haze stability of a juice are mainly pectins and starch. It is therefore a key priority in processing to retain these colloidal substances. The unripe fruit contains a lot of starch but little soluble pectin, whereas the fully ripe fruit contains little starch and a lot of soluble pectin. This means that it is possible to influence the haze stability of the juice by selection of the raw material. 

After the fermentation and aging steps the beer is cloudy, despite the fact that after aging the beer is separated from most of the sedimented yeast and tank bottoms. This cloudiness results from the remaining yeast cells—yeast concentrations of approximately 200,000 ceUs/mL are common for beer after separation from the tank bottoms—and from the haze-forming components of beer. 

Emit juice clarification is the oldest and largest use of pectinase. The traditional way to prepare juices is by cmshing and pressing fruit pulp. The raw juice is a viscous liquid with a persistent cloud of cell wall fragments and protein complexes. Addition of pectinase lowers the viscosity of the juice and modifies the haze particles. These sediment and can be removed by centrifugation or (ultra)filtration. Pectin lyase or the combination of polygalacturonase with pectin esterase are found optimal for this application. 

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