Starter culture fermentation process

Metabolic activity Storage stability Probiotic function 

Recently, a change from the traditional anaerobic fermentation to an aerobic respiration process has been intfoduced for Lactococcus spp. The lactic acid bacteria exhibit a respiratory lifestyle in the presence of oxygen and heme. Conseqnences of the respiration are the higher biomass and lower amount of lactic acid prodnced. However, the aeration and heme did not increase the biomass yield of Streptococcus thermophiles, L. delbrueckii subsp. bulgaricus, or L. helveticus (Pedersen, Iversen, Sorensen, Johansen, 2005). 

4 Freeze drying for the production of dried starter cuitures 

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The dried cell concentrate is typically produced by specialized suppliers and distributed worldwide. As the producers of fermented foods want to build up some stock, the cultures should be stable for at least one year. As the activity of the cultures after drying depends on the previous fermentation step (see Section 11.3), and the storage stability depends on the drying process as we will show in this section, the starter culture preparation process must be looked at in a holistic approach. This... 

The upstream processing element of the manufacture of a batch of biopharmaceutical product begins with the removal of a single ampoule of the working cell bank. This vial is used to inoculate a small volume of sterile media, with subsequent incubation under appropriate conditions. This describes the growth of laboratory-scale starter cultures of the producer cell line. This starter culture is, in turn, used to inoculate a production-scale starter culture that is used to inoculate the production-scale bioreactor (Figure 5.7). The media composition and fermentation conditions required to... 

Fermentation follows for several days subsequent to inoculation with the production-scale starter culture (Figure 5.7). During this process, biomass (i.e. cell mass) accumulates. In most cases, product accumulates intracellularly and cells are harvested when maximum biomass yields are achieved. This feed batch approach is the one normally taken during biopharmaceutical manufacture, although reactors can also be operated on a continuous basis, where fresh nutrient media is continually added and a fraction of the media/biomass continually removed and processed. During... 

Apart from public health impacts, residual antimicrobials in animal products can bring about technoeconomic losses in the food processing industry. It has long been known that the presence of some antimicrobial compounds in milk can dramatically affect the production of fermented dairy products such as yogurt, cheese, buttermilk and sour cream (72, 73). As shown in Table 10.2, even minute concentrations of antibiotics in milk can cause inhibition of the growth of commonly used dairy starter cultures (74). 

The most important fermentative reaction used in dairy processing is the homofermentative conversion of lactose to lactic acid. The efficient manufacture of high-quality cultured products, including most cheese varieties, yogurt, and cultured buttermilk, requires a rapid and consistent rate of lactic acid production. Lactic acid helps to preserve, contributes to the flavor, and modifies the texture of these products. Nearly all starter cultures used to produce acidified dairy products contain one or more strains of lactic streptococci, because these organisms can produce the desired acidity without causing detrimental changes in flavor or texture. Strains of lactic streptococci can be classified as... 

The fermentation is usually continuous it proceeds under sterile conditions, at constant temperature, and is started with a defined starter culture to avoid side products as far as possible. Several processes were developed Shell had originally introduced a process that used methane (natural gas) as the feedstock for SCP production. The microorganisms are cultured in an aqueous medium at temperatures of 42 to 45°C and at a pH value of 6.8 under semisterile conditions. The final fermentation broth contains protein at a concentration of 25 g/L. The biomass is concentrated in large sedimentation tanks and then spray-dried. The mass balance equation (Eq. 9.3) shows that large volumes of oxygen are needed and that carbon dioxide and heat must be removed from the reactor. 

In biotechnology man makes use of these multiple opportunities offered by nature for the synthesis of materials. In general, all biotechnical processes are based on the reaction of a living cell either directly with the raw material (fermentation with intact micro-organisms, e.g. mediated by starter cultures) or these reactions take place inside well controlled technical equipment, so-called bioreactors. 

Apart from these measures, the application of spontaneous and starter culture mediated fermentative generation of flavour active substances does not require any further technical equipment. This fact and the traditional experience with such processes are the reasons for the still considerably high amount of food produced by this technology. In 1990, such products exhibited a value of 23 billion compared to the total amount of 91 billion in the same year for all food products [3],... 

Foods that include the incorporation of microbial metabolites as part of their production are an intricate component of the world s food supply and for ethical and sensory-nutritional reasons it is essential for all the world s population to have access to this form of food. It is a process that has been in use since the early history of mankind. An Egyptian pot dating from 2300 BC (McGee, 1984) was found to contain residues of cheese and in passages in the Bible the use of some kind of fermentative starter culture is indicated. It is, therefore, possible that the use of bacteria such as the lactic acid bacteria (LAB) dates back at least four to five thousand years, although the exact principle behind the process may not have been known to the civilizations of those times (Davidson et al., 1995). Production of fermented foods, where organisms such as the LAB are involved, is a technological process that has been used for centuries at least (Herreros et al., 2005). 

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