How Starter Cultures are used in Industry

The food industry has changed in a very impressive manner in the past years and the average size of a typical production facility has increased several-fold. The fermented food industry is dominated by producers with large production capacity, although small (traditional-style) facilities still exist, as it is evident by the many breweries, wineries, bakery and artisanal dairies. Together with these modifications, the manner which fermented foods are produced has also changed. Nowadays, by commercial and financial pressure, fermented food production is strongly subject to time and scheduling demands. In a production operation, a slow fermentation may cause financial lost, problems with workers shift also affect the entire production schedule. The fermented food industry, as cited earlier, is the only food processing industry in which product success depends highly on the growth and activity of microorganisms.

There are two general ways that the cultures are used in fermented food and beverage industries. The first type, often referred to in the dairy industry as bulk cultures, is used to inoculate a bulk tank. The bulk SC is essentially the equivalent of several intermediate cultures that traditionally have been required to build up the culture. The dairy industry is by far the main user of bulk cultures routinely used to inoculate production vats throughout a manufacturing day. The dairies can buy the commercial SC in various forms: liquid, for propagation of mother culture; frozen concentrated and freeze-dried concentrated, for propagation of bulk starter; frozen superconcentrated in readily soluble form, for direct inoculation of the product.

Bulk culture can be prepared at the plant or from commercially available frozen concentrated or freeze-dried concentrated cultures. Preparing inoculum at the plant involves serial culturing, starting with a mother culture maintained in small amount of medium. The mother culture is used to inoculate successively larger amounts of medium until sufficient inoculum volume is obtained to prepare the bulk culture. Bulk culture handling at the plant carries an increased risk of phage contamination. In order to minimize this problem, bulk culture media used in the propagation may contain phosphate buffers and other agents that protect the cells from acid damage and from infection by lytic bacteriophages. Buffering activity supplied in the form of phosphate salts provides a phage-inhibitory function via calcium chelation (Hutkins 2006).

In contrast to the bulk cultures, some fermented foods are inoculated with a second type of culture. This type is usually most expensive and can simply be inoculated directly into the food substrate (direct-to-vat). Using the nominated direct-vat-set (DVS) cultures avoids the possibility that the starter will become contaminated with phage during preparation within the plant. Also, the use can reduce mixed strain compositional variability, assuring an appropriate strain balance. This is the normal means by which active bakers’ yeast, meat and several dairy SC are added directly to the dough, the meat mixture and milk, respectively. In the case of frozen concentrated

SC, the containers are first thawed in water prior to use. Freeze-dried pellets can be added directly, but may require mixing in the vat to facilitate solubility/hydration.

According to Hutkins (2006), the use of DVS cultures has advantages: eliminates the labour, equipment and by-products associated with the preparation and maintenance of bulk SC system. Although they were initially produced as frozen concentrates and packaged in cans, they are now available as pourable pellets or lyophilized powders, making it easy to dispense the exact amount necessary for inoculation. However, when DVS cultures are used in large industrial volume, the SC must be superconcentrated to deliver a sufficient inoculum into the raw material. The industrial production operations, discussed in the next section, may indirectly reduce SC viability, leading to slow-starting fermentations. Improvements in concentration technologies have minimized some of these problems.

 
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