Opaque beers

Fonio (Figure 1.4, Digitaria exilis) is an important subsistence crop in the savannas of West Africa, where it has been planted because of its short growing cycle (2 months), resistance to arid conditions, scarce rainfalls, and poor soils. Fonio also yields very small kernels that are milled into flours which are mainly used for preparation of porridges, couscous, traditional breads, and opaque beers (see Chapter 16 Dendy 1995, McDonough et al. 2000, National Research Council 1996, Belton and Taylor 2002). 

Sorghum has long been malted for the production of opaque Kaffir beers and weaning foods. Today it is considered the second most popular source of malt. It is both traditionally and industrially produced in Africa and India instead of barley malt. In these regions, barley cannot be successfully planted because it adapts to cold temperatures. Sorghum malt is mainly used for the production of opaque beers, although it is utilized alone or supplemented with enzymes in Nigeria to produce European... 

Malts produced from sorghum grain that is stepped and germinated at temperatures higher than 25°C and are usually solar-dried or artificially kilned at low temperature. Sorghum malts are used for the production of opaque beers and weaning foods in Africa. Sorghum malt contains lower P-amylase activity compared to barley malt. 

FIGURE 14.5 Flowchart of the industrial process for production of sorghum opaque beer (photograph courtesy of Dr. John Taylor, University of Pretoria, South Africa). 

What are the main differences between a lager and opaque beers in terms of processing and product characteristics ... 

Daiber, K.H., and Taylor, J.R.N. 1995. Opaque beers. Chapter 10 in Sorghum and Millets Chemistry and Technology. D.A.V. Dendy (ed.). American Association of Cereal Chemists, St. Paul, MN. 

FIGURE 16.10 The traditional process for the production of sorghum opaque beer.561... 

Due to the high absorbency in the MIR region and to comply with the Beer-Lambert law, the path-length of the cuvette must be about 10 pm. The development of the attenuated total reflectance (ATR) device allows the sampling problems encountered when collecting spectra from opaque and viscous samples to be overcome (Figure 20.1). 

There are two fundamental laws to consider when we discuss absorption Beer s law and Lambert s law. Lambert s law states that equal thickness of materials cause equal amounts of absorption. Beer s law states that equal amounts of absorbing material cause equal absorption. Figure 2.5 illustrates these laws (Billmeyer and Saltzman, 1981). Both laws will only work in the absence of scattering and are not applicable in opaque or translucent materials. They are very useful in transparent materials, where the scattering due to the colorants and the polymers themselves (low refractive indices) is very low. 

Because the incident monochromatic light is absorbed, reflected, and scattered by the opaque layer material, the theoretical relationship between amount of absorption and amount of substance does not follow the simple Beer-Lambert law that is valid for solutions. The Kubelka-Munk equation is the most accepted theoretical relationship for TLC, but its use is not necessary because of the ability of densitometer software to handle empirical nonlinear regression functions. 

PORTERS ARE MALTY DARK BROWN BEERS. They are typically brewed with about 25% of the grain bill being darker grains, including crystal, chocolate, and perhaps some black patent malt. The color will start at a very dark brown (about 30 SRM) and go as dark as opaque black, Traditional English hops are preferred by many homebrewers, though quite a few people swear by American hybrids, such as Clusters and Cascade. 

This is a very clear beer, but still totally opaque — just very clean looking. The head is long-lasting, cream-colored and consists of fine bubbles. The taste is rich, creamy, milky, yet firm. A must for stout-heads ... 

Cultural characteristics of Pectimtus species have been studied in peptone yeast extract fructose (PYF) medium (http //culturecollection.vtt.fi) and MRS medium. The beer-spoilage species form circular, entire, glistening and opaque colonies on PYF... 

Cultural characteristics have been determined on modified MRS agar medium in which the beer-spoilage Propionispira species form circular, smooth, opaque and slightly yellow colonies with a diameter of 1-2 mm after 3 days of incubation (Schleifer et al., 1990). The colonies of S. lacticifex are also smooth, circular, opaque and yellowish with a diameter of 2-3 mm after 3 days of incubation. 

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