Alcoholic fermentation temperature control

A new method for the preparation of soy sauce has been developed. The new scaled-up method divides the moromi process into two processes autolysis and fermentation. Because of the utilization of high temperatures, the new process permits the production of a NaCl free autolyzate from koji. Division of the fermentation process into two separated processes permit better control of lactic acid fermentation and alcohol fermentation processed which used to require great skill. The new scale-up procedure for soy sauce production yields a product in half the time required by the traditional (conventional) method and still produces a soy sauce with high levels of the desirable Bavor component, glutamic acid. Utilization of this protocol by the soy sauce producing industry should have significant economic impact to bo producers and consumers. 

To show correlation between occurrence of malo-lactic fermentation and bacterial inoculation, and to show consistency of results among the control lots and inoculated lots, it is imperative that the division of lots be made before alcoholic fermentation. For red wines, great care must be taken to obtain equitable distribution of the crushed grapes in each of the lots. The inconsistency in the results mentioned above may have been caused by variation in amounts of grape skins during the alcoholic fermentation with the accompanying effect on fermentation temperature, sulfur dioxide concentration,. pH after pressing, and concentration of nutrients (55, 56). 

The growth of malo-lactic bacteria in wines is favored by moderate temperatures, low acidity, very low levels of S02, and the presence of small amounts of sugar undergoing fermentation by yeast. It is frequently possible to inoculate a wine with a pure culture of a desirable strain of bacteria and obtain the malo-lactic fermentation under controlled conditions. The pure-culture multiplication of the selected strain of bacteria is difficult, however. It is also difficult to control the time of the malo-lactic fermentation—sometimes it occurs when not wanted, and at other times will not go when very much desired. For the home winemaker it is probably most satisfactory to accept the malo-lactic fermentation if it occurs immediately following the alcoholic fermentation. The wines should then be siphoned away from deposits, stored in completely filled containers at cool temperatures, and have added to them about 50 ppm S02. If the malo-lactic fermentation does not take place spontaneously and the wine is reasonably tart, the above described regime of preservation will likely prevent its occurrence. When the malo-lactic transformation takes place in wines in bottles, the results are nearly always bad. The wine becomes slightly carbonated, and the spoiled sauerkraut flavors are emphasized. 

For the new wine to contain the desired 15-16 vol % alcohol, it is necessary to add some sugar to the juice or the partially fermented wine except in cases of unusually high sugar content in the grapes. In any event, it is necessary to have an accurate estimate of the sugar concentration in the juice before more sugar is added and before fermentation starts. It is better not to add the calculated amount of sucrose to the juice immediately but to make two or three smaller additions after the fermentation is actively under way. This technique is known as syruped fermentation and can yield wines of as much as 17 vol % alcohol under favorable conditions of yeast nutrients and temperature control. 

As for grape dehydration, the management of alcoholic fermentation is still linked to traditional practices, which provide very poor control of the fermentation parameters, such as microbial population and temperature. 

Variables in alcoholic fermentation, the yeast-enzyme conversion of grape sugar to ethanol and carbon dioxide, have a major impact on the character, composition, and quality of North Coast white table wines. Type of yeast, juice solids content, juice S02 content, juice protein content, fermentation temperature, and fermentation rate are factors the enologist may consider and control. 

Mannitol. Whereas mannitic fermentations are seldom a problem where sulfur dioxide, pure yeasts, and temperature control are employed, Martucci (1941) has reported them in Argentina. He recommended control of the must acidity, since a high pH also favored such spoilage. A complicated polaiimetric procedure for mannitol (a sugar alcohol) in wines was presented by Salani (1937). Formation of mannite during dialysis of musts at low temperatures (8° to 10° C. (46.4° to 50° F.)) in the presence of chloroform was reported by Barbera (1933b) (possibly owing to enzyme action). 

Another approach consists of creating a model of the alcoholic fermentation process. Different calculations concerning time, temperature, and alcohol and sugar concentrations are used to predict fermentation behavior—especially the risk of a stuck fermentation (Bov e et al., 1990). In this way, the need and moment of a certain operation (especially temperature control) could be anticipated. 

The duration of dry white wine fermentation depends on several parameters juice extraction conditions sugar and assimilable nitrogen concentrations turbidity yeast strain aeration and fermentation temperature. The winemaker can adjust and control all of them. A slow or stuck fermentation is most often the result of carelessness and always affects wine quality. The alcoholic fermentation of a white wine should not exceed 12 days. Longer fermentations should not be songht after except in the case of exceptionally high sngar concentrations. 

This gum was the first microbial gum to be used in the food industry. It is produced by the aerobic fermentation of Xanthomonas campestris. A specially selected culture is grown on a carbohydrate-containing nutrient medium with a nitrogen source and other essential elements. The pH, temperature and aeration are controlled carefully. The product is then sterilised and the gum is precipitated with propan-2-ol. Next, the precipitate is washed, then pressed to remove residual alcohol, followed by drying and grinding to the required size. 

Beer, on the other hand, is produced by more complex biochemical and technological processes, which all affect its flavor. Yeast amino acid metabolism, a key to the development of beer flavor as described earlier, is affected by process temperature and use of cell immobilization techniqnes. Therefore, technologies based on these features as well as other process conditions and strain selection have been developed to control beer flavor. The combination of immobilized yeast and low-temperature primary fermentation was found to produce beers with low diacetyl amounts, therefore indicating potential of low-cost industrial application since maturation is a high-energy-consuming process. Finally, Perpete and Collin showed that during alcohol-free beer production, the enzymatic reduction of worty flavor (caused by Strecker aldehydes) by brewer s yeast was improved by cold contact fermentation. 

Fermentation, an original chemical process that was discovered in ancient times, led to the production of wine and beer. With relatively crude techniques, a simple enzyme contained in yeast was found to catalyze the conversion of sugar into alcohol. Control of the ingredients in the fermentation broth would impact the flavor of the alcohol, and the effectiveness of the conversion was controlled by the length of time the fermentation was allowed to proceed and the temperature of the reaction. 

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