Industrial Production of Starter Cultures

Commercial SC industrial production requires specialized knowledge of microbiology, molecular biology and biotechnology. Furthermore, SC development, maintenance and distribution demand special logistic and economic considerations. Since the fermented food industry depends on the use of selected strains with known metabolic and technological properties, the introduction of commercial SC has undoubtedly improved the quality of the products and the overall process of standardization discussed in the section above.

The limited number of available strains with specific technological performance and the constant risk of bacteriophage attacks justify the continuous need to search for new commercial strains for industrial product diversification. Nowadays, the organisms present in modern commercial SC preparations are very well defined. They are carefully selected based on the precise phenotypic criteria relevant for the particular fermented product.

For the preparation of fermented products, Latin American industries acquire imported SC that sometimes have inadequate performance in local food matrix, mainly due to differences in the quality of raw materials, for example, in raw milk. The SC global market in 2014 was around 2.5 million tons and Latin America represented a small share of this with 100,000 tons (4%) and an annual growth of 2%.

Commercial SC are currently available for direct addition to production vats contain > 109 viable microorganisms, preserved in a form that could be readily and quickly activated in the matrix to perform the technological functions necessary to transform the raw food into the desired fermented product. To achieve that, the selected microorganism needs to be grown in a suitable media to high biomass volume and to concentrate the cells.

The amenable manufacturing processes for large-scale SC fundamentally follow four steps: (1) preparation of the growth medium; (2) biomass production; (3) biomass concentration; and (4) biomass preservation. All steps will contribute to the quality of the product. SC need to be tolerant of the stresses of concentration, packaging, storage and reactivation processes (Soubeyrand 2005). These requirements need to be reached without loss of the desirable fermentation properties.

Many of the manufacturing processes are considered stressful for microorganisms. Adverse environmental conditions include extreme temperatures, osmotic stress, mechanical stress, acidity of the medium, as well as nutrient-deficit stress at the end of culture. These hostile conditions for culture require selection of resistant strains, which should retain adequate viability, metabolic activity and genetic stability.

SC quality control is required to prepare the user for the importance of sanitization and strict adherence to use protocols. Quality control tests for commercial SC include the assessment of viable cell numbers, presence of pathogens and extraneous matter, technological performance as acid-producing and other functional activities, package integrity, accuracy of label information on the package, and shelf life of the product according to specification (Vedamuthu 2006).

Sip and Grajek (2010) described the production of probiotic cultures on commercial scale in a strongly concentrated form for introducing to the food as DVS preparations. Cultures of probiotic microorganisms are commercialized in the form of frozen concentrates, either freeze- or spray-dried. Probiotic cultures may be composed of single strain or a mixture of strains. Due to differences in growth requirements, they may not be cultured in the food together with commercial LAB SC, but in practice, this occurs. For example, in mixed SC for fermented milk containing Lactobacillus acidophilus, Bifidobacterium and S. thermophilus. They need to be added to the food in sufficient CFU per gram to provide a probiotic effect. Production technology for probiotic cultures is identical to that cited for SC and comprises the same basic stages (Lacroix and Yildirim 2007).

 
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