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Immobilize cells to facilitate meat fermentation.

Using biotechnology to improve the fermentation of meat has been an ongoing effort over the years. Most research has been primarily focused on the genetic improvement or genetic engineering of meat fermentation starter culture strains. Traditionally, genetic research has focused on understanding bacterial species used as, or how they relate to, starter cultures. But only recently have investigators started exploring the potential for improving meat fermentations by genetically modifying starter cultures.

Immobilizing cells has made possible dramatic advancements in food fermentations. It has fostered the development of immobilizing processes that mimic natural growth conditions, making it possible for cells to grow on surfaces or within naturally occurring structures. The technique offers the advantages of continuous cell utilization, retention of specific plasmid-producing cell lines, protection of immobilized cells against inhibitory substances in the fermentation medium, the stimulation of production, protection from shear forces and increased fermentation rates.

Cell immobilization could potentially benefit the meat industry by decreasing starter culture costs, ensuring uniform distribution of bacteria, and simplifying recovery and recycling procedures. Immobilizing cells contributes to meat fermentation. The meat substrate's solid-semisolid nature restricts cell mobility. Immobilized cell technology can improve a starter culture's ecological competence.

Lyophilization is commonly utilized to preserve starter cultures and to increase storage times for subsequent use in food fermentations. Microbial cell survivability and viability during lyophilization and subsequent rehydration depend on numerous factors, such as the individual microbial strain, culture age, growth and storage conditions, and specific lyophilization and rehydration conditions. Immobilized cells are captive within a protective matrix, often reducing cell release. But immobilization matrices can protect the culture during lyophilization and rehydration, and from competition with indigenous microflora.

For example, the lyophilization and rehydration of Lactobacillus plantarum and Pediococcus pentosaceus cells immobilized within calcium alginate beads resulted in higher survival rates when researchers incorporated glycerol or adonitol with skim milk as a cryoprotectant. Immobilization also may decrease the rehydration rate and avoid the osmotic shock associated with instantaneous rehydration, which subsequently decreases the growth and acidification lag phase.

Using immobilized cells in meat starter cultures might make possible the production of a continuous cell line, which ensures retention of stable cell lines; the prevention of unpredictable genetic alterations associated with restarting culture broths; and the continuous release of microorganisms to a nonsterile meat product that cannot be pasteurized, like liquid food products. One disadvantage of incorporating immobilized cells into fermented meats might be a decrease in substrate availability compared with fluid products.

The survival, growth, and proliferation of standard bacterial inocula depend on the regulation of moisture content, temperature, pH, oxygen concentration and rate of diffusion, and nutrient availability. Immobilized cells may allow you to control or modify these variables so that you can optimize meat fermentations.

Further information. Steven Ricke, Department of Animal Science, Texas A&M University, College Station, TX 77843; phone: 409-862-1528; fax: 409-862-3075; email:
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Publication:Emerging Food R&D Report
Date:Jul 1, 2000
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