Fermentation selected products

One important class of foods possessing natural flavors that arise via enzymatic and microbial action are "fermented" dairy products. This important food group, consisting of cheeses, yoghurt, buttermilk, sour cream and similar products is very interesting and illustrates the importance of taste and odor in food selection. 

We consume them directly, combine them with other foods directly or through cooking, convert them into sauces, etc. There seems to be no end to the creative way we utilize and consume fermented dairy products. The lesson is clear, we use these products because we enjoy their odor and taste. In the selection process, their nutritional value is secondary when compared to their flavor. Since food consumption is a necessary part of life, and in most societies food selection is primarily based on hedonics, then a priori, the biological origin of aromas is an important subject. 

Mandal, C., Gudi, R. D. and Shuraishk, G. K. (2005). Multi-objective optimization in Aspergillus niger fermentation for selective product enhancement. Bioprocess Biosyst. Eng., 28, pp. 149-164. 

One of the objectives of a biochemical separation system design is to minimize the number of steps (Figure 1) One way of accomplishing this is to perform the separation and concentration in situ that is directly with the whole fermentation broth using solids phase adsorbents. This type of separation requires the design of an affinity bead that provides for selective product removal from the fermentation broth. 

Phenoloxidase (monophenol monooxygenase, E.C. 1.14.18.1) introduces one atom of molecular oxygen into the substrate and was used in alginate-entrapped cells or in partially purified form. The pharmaceutical 7,8-dihydroxy-N-(di-n-propyl)-2-aminotetralin was produced continuously using a phenol oxidase suspension in dialysis tubing in an airlift fermenter coupled to an aluminium oxide column for selective product isolation (Figure 16.3-13)[6S1. A product concentration of 130 mg/L and a yield of 25 % were reached. 

The bacterial surface is also involved in the formation of texture in fermented dairy products such as yogurt. Consumers today prefer products that have a mild flavor and a high level of texture. Mutants of S. thermophilus andL. delbrueckii subsp. bulgaricus resistant to D-cycloserine were selected and tested for their ability to grow in milk. It was observed that several of the mutants produce more texture and less whey than the parent strain and combining mutants of each species produced yogurt with properties satisfying the current consumer preference (Kibenich, Sprensen, Johansen, 2012). 

One promising approach might be the application of defined starter cultures that are capable of growing rapidly and that are highly competitive in the environmental conditions under which the product is kept Therefore, numerous attempts have made especially to ferment cabbage to sauerkraut, but also to ferment cucumbers and olives by defined starter cultures. Especially in the case of sauerkraut, most of the experiments performed with pure cultures or mixtures of pure cultures led indeed to the desired uniform, sufficient and rapid acidification of the products. But they lacked the typical rounded sauerkraut flavour, which essentially is due to the lack of certain fermentation by-products or the insufficient decomposition of compounds characteristic for the respective raw material (Kandler, 1981). Sauerkraut with perfect sensorial characteristics was obtained with selected strains of L. mesenteroides, which simultaneously improved the uniformity of sauerkraut from different batches. However, even in this case, so far no such benefits could be achieved compared to spontaneous fermentation that would economically justify the cost of the production of starter cultures (Buckenhueskes Hammes, 1990). 

In practice, not all requirements for an ideal model organism can be fulfilled by one single species, but E. coli is the first choice in most cases. This bacterium occurs universally in feces of warm-blooded animals (including humans) and can be detected to a fairly high degree of selectivity by simple, rapid procedures. Lactose fermentation, indole production, growth at 44 C, and -glucuronidase activity are the key properties for detection and confirmation of this species. In practice, many routine methods aim... 

Measurement of the fermentation and maturation parameters allows the fermentation performance, as weU as any problems or any other developments that may arise, to be monitored and rectified if necessary. Table 5.9 shows a list of analysis methods for monitoring the principal fermentation parameters and also for selected fermentation by-products approved by the ASBC, MEBAK, and EBC. 

Table 5.9 Approved analysis methods for fermentation main parameters and selected fermentation by-products of the analysis commissions of ASBC, MEBAK, and EBC...

Figure 5.11 Interpretation of selected fermentation by-products of two beers in terms of process errors.

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