Haze particle

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. 

Figure 8.12 shows the projected conversion of S02 to sulfate as a function of the volume of water per cubic meter of air available for conversion in the aqueous phase, covering a range typical of haze particles, fogs, and clouds for atmospheric lifetimes which are typical for each (Lamb et al., 1987). As expected from Eq. (M), the conversion increases with the water available in the atmosphere. As we shall see, the aqueous-phase oxidation does indeed predominate in the atmosphere under many circumstances. Equations (G) and (M) apply as long as the partial pressure of SOz in the gas phase, so,, is measured simultaneously with the solution concentration of S(IV). 

FIGURE 8.12 Percentage of S02 converted to sulfate after a time interval At in small haze particles, fogs, and clouds as a function of the aqueous reaction volume note that the time intervals for each one are different, reflecting how long they typically last in the atmosphere (adapted from Lamb et al., 1987). 

FIGURE 9.57 Electron micrographs of haze aerosol collected in Pasadena in 1973 (A) and of (B) unheated and (C) heated haze particle (adapted from Husar and Shu, 1975). 

In short, particles to the left of the peak in Fig. 14.38a do not tend to shrink or grow. Because they are generally in the 0.1- to 1-jum size range which scatters light efficiently (see Chapter 9.A.4), these particles are known as haze particles or droplets. These often occur at relative humidities below 100%. 

Aerosols are ubiquitous in our environment. Haze particles are formed over vegetation dust clouds are blown up by the wind volcanoes erupt, spewing dense smoke into the atmosphere and, of course, in their many activities people mark their way by the particles they discharge into the air. This book is about aerosol particles, their physical properties, and the scientific basis that has been developed for predicting their behavior. 

Haze Particles with some water vapor incorporated into them or around them, as observed in the atmosphere. 

Research into the isoelectric point of wine proteins has often been concurrent with smdies of wine protein size. Proteins with low isoelectric points (pi) were found to be significant contributors to total wine protein (Moretti and Berg 1965) and to wine haze (Bayly and Berg 1967). Hsu and Heatherbell (1987a) confirmed this observation and suggested that the majority of wine proteins had a pi of 4.1-5.8, whilst Lee (1986) suggested the major protein fractions of wine had a pi of 4.8-5.7. Dawes et al. (1994) fractionated wine proteins on the basis of their pi and found that the five different fractions all produced haze after heat treatment. Haze particle formation was found to differ between the fractions however, leading to a statement that other wine components, such as phenolic compounds, need to be considered to understand fully protein haze. 

Goetz (5), writing about maritime haze particles, said that the degrading of particles by ultraviolet radiation appears to be definite proof for the significant, if not occasional dominant, presence of various hydrocarbons in the aerocolloidal matter. ... 

Other enzymes are required to obtain good quality beer with good shelf-life. The major use of non-malt enzymes is an enzyme that is added to fermented beer to chillproof the beer. Beer is fermented and aged under chilled conditions. Almost all packed beer is filtered while cold to achieve clarity. In spite of the filtration steps beer becomes cloudy after it is packed, distributed and chilled again for serving. The cloudiness that develops is caused by formation of haze particles called chill haze which are the result of the interaction between peptides and polyphenol compounds. 

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. 

The PSI in Singapore exceeded 100 for 12 days during the 1997 haze episode, reaching a maximum of 138. About 94% of haze particles were found to have a diameter less than 2.5 microns, and thus easily breathed in. Hospital visits for all haze-related illness increased by about 30%. 

Ground-based polarimetric observations of some features on the planetary disk indicated the existence of a haze layer overlying the main cloud (especially in subauroral regions). This was confirmed by the results of photopolarimetric observations from Pioneer Venus [24]. The value of the effective radius of the haze particles was about 0.23 micrometers the value of the real part of the refractive index was the same as for the cloud particles. 

Inconsistency of the published estimates of the haze-particle effective radius are discussed in [24, 29, 51]. The cause of the differences is discussed in [53]. Using the assumption that the haze (for heights greater than 66 km) is a continuation of the underlying cloud layer [30], it was shown that stratification of particles should take place due to turbulent intermixing. 

Omura, R, Nakao, Y., Teranishi, T., Fujita, A. (2009). High expression levels of cell wall protein Cwp2p decreases the turbidity of fresh lager beer by reducing the size of haze particles. Journal of the American Society of Brewing Chemists, 67, 135-140. http //dx.doi.Org/10.1094/ASBCJ-2009-0602-01. 

Colloidal instability due to interactions between polyphenols and proteins limits the shelf life of beer. A lag phase is usually observed in lager beers before chUl-haze development [23-25]. The time needed to form critical amounts of tanning polyphenols leading to visible chiU-haze particles corresponds to the lag phase. As described by Leemans et al. [25] for different batches, the longer the lag phase, the better the colloidal stability. 

Fig. 3.8.2 Single scattering functions for a water cloud and an aerosol haze, each associated with a real refractive index n = 1.33. The cloud and haze particle size distributions peak at particle radii a 4.0 and a 0.05 pm, respectively. Computations were made for a wavelength k = 0.8189 pm (after Hansen, 1969).

---