Mashing

In the mashing step, the malt meal is made into a paste with brewing water (heatable mixing vessel) and partially degraded and solubilized with malt enzymes. 

In the case of poorly solubilized malt in which the starch-containing membranes have not ruptured, enzymatic degradation and the extract yield can be improved by stopping briefly at 47-50 °C before further temperature increase. This delays 

In infusion mashing, used mostly in England for brewing top fermented beer, the terminal mashing temperature is achieved not by stepwise increases, but by live steam injection or addition of hot water. As in the decoction method, the temperature program used can vary greatly. 

In modern processes, the classical brew kettle is replaced by a whirlpool kettle with external cooker. Shorter boiling times and a better quality of beer are achieved with this system. Moreover, separation from the spent hops can be conducted in the same vessel. 

Processes that use pressure boiling (high-temperature wort boiling up to 150 C) can produce beer with an unpleasant cooked taste. 

FIGURE 14.4 Flowchart of industrial processes for production of lager and ale beers. 

There are several conunercial mashing processes. Independent of the mashing procedure, the raw materials used are water, usually containing controlled levels 

During mashing with rice or maize adjuncts, about 80% of the grits are solubilized or extracted and become part of the sweet wort. The soluble solids are mainly dex-trins, maltose, maltotriose, glucose, and FAN. If starch is used, the extraction rates are usually 100 or more because the hydrolyzed starch gains water after conversion. 

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Mashing-in Mashing-off Masking of odors Masks Masonite Mason number Masonry... 

Another common system is the fixed knife mill. This consists of a chamber containing fixed knives and a rotating three-armed spider that shreds the fmit by forcing them against the fixed knives. Fmit are gravity fed into the chamber from an opening in the top. Small holes under the knives permit the mash to fall through to a conveyor. 

A rack and frame press uses heavy nylon cloth positioned in a wooden frame inside a rack. A measured amount of apple or other fmit mash is added from a hopper above the frame. The mash is leveled with a hand trowel and the edges of the nylon cloth are folded over the mash to encase it and create a cheese. The frame is removed, and a second rack is placed on top of the first cheese the process is repeated until a stack of cheeses is prepared. A hydrauhc ram then appHes gradually increa sing pressure on the stack and expresses the juice. A high yield of juice (80%) is obtained and no press aid is required. Because this process is labor intensive (17), it is mostly used for small farm and pilot-plant operations. 

The StoU press uses a horizontal hydrauhc ram and a chamber with screens on the sides that holds the mixture of fmit mash and press aid. 

Hydrauhc pressure is apphed to the mash first at 2750—3440 kPa (400—500 psi) and then at 17,200—20,600 kPa (2500—3000 psi) for preset times the pomace is removed after each cycle. One person can operate several presses at once, each with a 4—5 t/h throughput. 

A belt press commonly uses two belts of woven material. Fmit mash is deposited on, and spread out evenly between, the two belts which converge and press the mash between them. The belts wrap around a series of successively smaller cylinders or pass between rollers (less efficient) for the pressing action. Juice yield for the wraparound belt press is 72%, and increases to 92% with secondary water addition (15). 

Screw presses have been used extensively in North America, but are not popular in Europe. The mash is added at the top of a vertical rotating screw. As the mash moves down it is compressed in the taper and juice flows out through slatted conical walls. Compression of the pomace blocks channels for juice flow and iuhibits juice extraction. Extensive use of press aids is necessary for efficient operation. 

Fig. 1. Properties of foods near 2.45 GHz as a function of temperature, where A represents distilled water B, cooked carrots C, mashed potatoes D, cooked ham E, raw beef F, cooked beef and G, com oil (a) dielectric constants and (b) load factors, e = etan6 (32).

In 1973, a multistage surface-fermentation process was patented in Japan for the production of acetic acid (42) eight surface fermenters were connected in series and arranged in such a way that the mash passed slowly through the series without disturbing the film of yAcetobacter on the surface of the medium. This equipment is reported to produce vinegar of 5% acidity and 0.22% alcohol with a mean residency time in the tanks of 22 h. 

Fermentative Manufacture. Throughout the years, riboflavin yields obtained by fermentation have been improved to the point of commercial feasibiUty. Most of the riboflavin thus produced is consumed in the form of cmde concentrates for the enrichment of animal feeds. Riboflavin was first produced by fermentation in 1940 from the residue of butanol—acetone fermentation. Several methods were developed for large-scale production (41). A suitable carbohydrate-containing mash is prepared and sterilised, and the pH adjusted to 6—7. The mash is buffered with calcium carbonate, inoculated with Clostridium acetohutylicum and incubated at 37—40°C for 2—3 d. The yield is ca 70 mg riboflavin/L (42) (see Fermentation). 

The basic raw materials for the production of beer are sweet worts formed by en2ymatic hydrolysis of cereal starches. The principal cereal is barley which, after malting, is also the source of en2ymes that hydroly2e starches, glucans, and proteins. In some countries, eg, Germany, the mash biH consists... 

The most widely available yeast biomass is a by-product of the brewing industry, where the multiplication of yeast during brewing results in a surplus of ceUs. Eor every barrel (117 L) of beer brewed, 0.2—0.3 kg of yeast soHds may be recovered. In the U.S., a substantial fraction is recovered and made available about 40 x 10 kg of brewers yeast aimually. The yeast is recovered from beer by centrifuging and dried on roUer dmms or spray dryers and sold as animal feed or a pet-food supplement. It can be debittered by alkaline extraction to remove the bitter hop residues, and is then sold mainly by the health-food industry. It is available as tablets, powder, or flakes and is often fortified with additional vitamins. Distillers yeast caimot be readily separated from the fermented mash and the mixture is sold as an animal feed supplement. 

A beer with normal alcohol content, but much lower ia caloric coateat, can be made with the help of external, specific enzymes that ate added duriag mashing or fermentation to achieve further breakdowa of carbohydrates. 

Water. The character of the water has a great influence on the character of the beer and the hardness of water (alkalinity) manifests itself by the extent of its reaction with the weak acids of the mash. Certain ions are harm fill to brewing nitrates slow down fermentation, iron destroys the colloidal stabihty of beer, and calcium ions give beer a purer flavor than magnesium or sodium ions (Table 7). 

Fig. 3. Brewing (1 = mash turn 2 = mash kettle 3 = lauter tun 4 = wort kettle 5 = hop strainer 6 = wort tank 7 = wort separator and,...

The pH has a great influence on the en2ymatic processes during mashing. Through water treatment it is possible to bring about shifts in pH whereby the transformations are decisively induenced. ( -Amylase has a pH optimum at 5.4, a-amylase at 5.8, and the normal mash has a pH of about 5.4 during saccharification. The induence of the concentration of the mash is such that thin mash increases the yield of both extract and maltose (Table 9). 

Table 9. Effect of Mash Concentration on Yield of Extract and Maltose ...

Concentration of mash, malt water Extract yield, % Fermentable extract, %... 

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